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| 6. |
- Ahmed, Tamer A. E., et al.
(författare)
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Characterization and inhibition of fibrin hydrogel-degrading enzymes during development of tissue engineering scaffolds
- 2007
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Ingår i: Tissue engineering. - : Mary Ann Liebert. - 1076-3279 .- 1557-8690. ; 13:7, s. 1469-1477
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Tidskriftsartikel (refereegranskat)abstract
- The goal of articular cartilage tissue engineering is to provide cartilaginous constructs to replace abnormal cartilage. We have evaluated the chondroprogenitor clonal cell line RCJ3.1C5.18 (C5.18) as a model to guide the development of appropriate scaffolds for tissue engineering. Rapid degradation of fibrin hydrogels was observed after encapsulation of C5.18 cells. The enzymes responsible for this fibrin gel breakdown were characterized to control their activity and regulate gel stability. Western blotting, confirming zymography, revealed bands due to matrix metalloproteinases (MMP-2, MMP-3) that are secreted concomitantly with fibrin hydrogels breakdown. High plasmin activity was detected in conditioned media during hydrogel breakdown but not in the confluent cells before encapsulation. Reverse transcriptase polymerase chain reaction indicated the expression of MMP-2, -3, and -9 and plasminogen in the cells. MMP-9 was 100 times higher at day 1, whereas MMP-2 started to increase and reached its maximum level by day 7. Aprotinin, a known serine protease inhibitor, and galardin (GM6001), a potent MMP inhibitor, in combination or separately, prevented the breakdown of fibrin-C5.18 hydrogels, whereas only the combination of both promoted the accumulation of extracellular matrix. These findings suggest that plasmin and MMPs contribute independently to fibrin hydrogel breakdown, but that either enzyme can achieve extracellular matrix breakdown.
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| 7. |
- Ahmed, Tamer A. E., et al.
(författare)
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Fibrin Glues in Combination with Mesenchymal Stem Cells to Develop a Tissue-Engineered Cartilage Substitute
- 2011
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Ingår i: Tissue Engineering. Parts A, B and C. - : Mary Ann Liebert Inc. - 2152-4947 .- 2152-4955. ; 17:3-4, s. 323-335
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Tidskriftsartikel (refereegranskat)abstract
- Damage of cartilage due to traumatic or pathological conditions results in disability and severe pain. Regenerative medicine, using tissue engineering-based constructs to enhance cartilage repair by mobilizing chondrogenic cells, is a promising approach for restoration of structure and function. Fresh fibrin (FG) and platelet-rich fibrin (PR-FG) glues produced by the CryoSeal (R) FS System, in combination with human bone marrow-derived mesenchymal stem cells (BM-hMSCs), were evaluated in this study. We additionally tested the incorporation of heparin-based delivery system (HBDS) into these scaffolds to immobilize endogenous growth factors as well as exogenous transforming growth factor-beta(2). Strongly, CD90+ and CD105+ hMSCs were encapsulated into FG and PR-FG with and without HBDS. Encapsulation of hMSCs in PR-FG led to increased expression of collagen II gene at 2.5 weeks; however, no difference was observed between FG and PR-FG at 5 weeks. The incorporation of HBDS prevented the enhancement of collagen II gene expression. BM-hMSCs in FG initially displayed enhanced aggrecan gene expression and increased accumulation of Alcian blue-positive extracellular matrix; incorporation of HBDS into these glues did not improve aggrecan gene expression and extracellular matrix accumulation. The most significant effect on cartilage marker gene expression and accumulation was observed after encapsulation of hMSCs in FG. We conclude that FG is more promising than PR-FG as a scaffold for chondrogenic differentiation of hMSCs; however, immobilization of growth factors inside these fibrin scaffolds with the HBDS system has a negative impact on this process. In addition, BM-hMSCs are valid and potentially superior alternatives to chondrocytes for tissue engineering of articular cartilage.
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| 8. |
- Ahn, Jae-Il, et al.
(författare)
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Crosslinked collagen hydrogels as corneal implants: Effects of sterically bulky vs. non-bulky carbodiimides as crosslinkers
- 2013
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Ingår i: Acta Biomaterialia. - : Elsevier. - 1742-7061 .- 1878-7568. ; 9:8, s. 7796-7805
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that recombinant human collagen can be crosslinked with N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDC) to fabricate transparent hydrogels possessing the shape and dimensions of the human cornea. These corneal implants have been tested in a Phase I human clinical study. Although these hydrogels successfully promoted corneal tissue and nerve regeneration, the gelling kinetics were difficult to control during the manufacture of the implants. An alternative carbodiimide capable of producing hydrogels of similar characteristics as EDC in terms of strength and biocompatibility, but with a longer gelation time would be a desirable alternative. Here, we compared the crosslinking kinetics and properties of hydrogels crosslinked with a sterically bulky carbodiimide, N-Cyclohexyl-N-(2-morpholinoethyl) carbodiimide metho-p-toluenesulfonate (CMC), with that of EDC. CMC crosslinking was possible at ambient temperature whereas the EDC reaction was too rapid to control and had to be carried out at low temperatures. The highest tensile strength obtained using optimized formulations were equivalent, although CMC crosslinked hydrogels were found to be stiffer. The collagenase resistance of CMC crosslinked hydrogels was superior to that of EDC crosslinked hydrogels while biocompatibility was similar. We are also able to substitute porcine collagen with recombinant human collagen and show that the in vivo performance of both resulting hydrogels as full-thickness corneal implants is comparable in a mouse model of an orthotopic corneal graft. In conclusion, CMC is a viable alternative to EDC as a crosslinker for collagen-based biomaterials for use as corneal implants, and potentially for use in other tissue engineering applications.
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| 9. |
- Alarcon, E I, et al.
(författare)
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Coloured cornea replacements with anti-infective properties : expanding the safe use of silver nanoparticles in regenerative medicine.
- 2016
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 8:12, s. 6484-6489
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Tidskriftsartikel (refereegranskat)abstract
- Despite the broad anti-microbial and anti-inflammatory properties of silver nanoparticles (AgNPs), their use in bioengineered corneal replacements or bandage contact lenses has been hindered due to their intense yellow coloration. In this communication, we report the development of a new strategy to pre-stabilize and incorporate AgNPs with different colours into collagen matrices for fabrication of corneal implants and lenses, and assessed their in vitro and in vivo activity.
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| 10. |
- Alarcon, Emilio I., et al.
(författare)
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Safety and efficacy of composite collagen-silver nanoparticle hydrogels as tissue engineering scaffolds
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 7:44, s. 18789-18798
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Tidskriftsartikel (refereegranskat)abstract
- The increasing number of multidrug resistant bacteria has revitalized interest in seeking alternative sources for controlling bacterial infection. Silver nanoparticles (AgNPs), are amongst the most promising candidates due to their wide microbial spectrum of action. In this work, we report on the safety and efficacy of the incorporation of collagen coated AgNPs into collagen hydrogels for tissue engineering. The resulting hybrid materials at [AgNPs] less than0.4 mu M retained the mechanical properties and biocompatibility for primary human skin fibroblasts and keratinocytes of collagen hydrogels; they also displayed remarkable anti-infective properties against S. aureus, S. epidermidis, E. coli and P. aeruginosa at considerably lower concentrations than silver nitrate. Further, subcutaneous implants of materials containing 0.2 mu M AgNPs in mice showed a reduction in the levels of IL-6 and other inflammation markers (CCL24, sTNFR-2, and TIMP1). Finally, an analysis of silver contents in implanted mice showed that silver accumulation primarily occurred within the tissue surrounding the implant.
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| 11. |
- Alarcon, Emilio I, et al.
(författare)
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The biocompatibility and antibacterial properties of collagen-stabilized, photochemically prepared silver nanoparticles
- 2012
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 33:19, s. 4947-4956
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Tidskriftsartikel (refereegranskat)abstract
- Spherical 3.5 nm diameter silver nanoparticles (AgNP) stabilized in type I collagen (AgNP@collagen) were prepared in minutes (5-15 min) at room temperature by a photochemical method initiated by UVA irradiation of a water-soluble non-toxic benzoin. This biocomposite was examined to evaluate its biocompatibility and its anti-bacterial properties and showed remarkable properties. Thus, while keratinocytes and fibroblasts were not affected by AgNP@collagen, it was bactericidal against Bacillus megaterium and E. coli but only bacteriostatic against S. epidermidis. In particular, the bactericidal properties displayed by AgNP@collagen were proven to be due to AgNP in AgNP@collagen, rather than to released silver ions, since equimolar concentrations of Ag are about four times less active than AgNP@collagen based on total Ag content. This new biocomposite was stable over a remarkable range of NaCl, phosphate, and 2-(N-morpholino)ethanesulfonic acid concentrations and for over one month at 4 degrees C. Circular dichroism studies show that the conformation of collagen in AgNP@collagen remains intact. Finally, we have compared the properties of AgNP@collagen with a similar biocomposite prepared using alpha-poly-L-Lysine and also with citrate stabilized AgNP; neither of these materials showed comparable biocompatibility, stability, or anti-bacterial activity.
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| 12. |
- Bentley, E, et al.
(författare)
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Biosynthetic Corneal Substitute Implantation in Dogs
- 2010
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Ingår i: Cornea. - : LWW. - 0277-3740 .- 1536-4798. ; 29:8, s. 910-916
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To assess integration of a biosynthetic corneal implant in dogs. Methods: Three normal adult laboratory Beagles underwent ophthalmic examinations, including slit-lamp biomicroscopy, indirect ophthalmoscopy, applanation tonometry, and Cochet-Bonnet aesthesiometry. Biosynthetic corneas fabricated from glutaraldehyde crosslinked collagen and copolymers of collagen and poly (N-isopropylacrylamide-co-acrylic acid-co-acryloxysuccinimide, denoted as TERP) were implanted into dogs by a modified epikeratoplasty technique. Ophthalmic examinations and aesthesiometry were performed daily for 5 days and then weekly thereafter for 16 weeks. Corneal samples underwent histopathological and transmission electron microscopy examination at 16 weeks. Results: Implants were epithelialized by 7 days. Intraocular pressure was within normal range throughout the study. Aesthesiometry values dropped from an average of 3.67 cm preoperatively to less than 1 mm for all dogs for the first postoperative weeks. By week 16, the average Cochet-Bonnet value was 1.67 cm, demonstrating partial recovery of functional innervation of the implant. No inflammation or rejection of the implant occurred, and minimal haze formation was noted. Light microscopy revealed thickened but normal epithelium over the implant with fibroblast migration into the scaffold. On transmission electron microscopy, the basement membrane was irregular but present and adhesion complexes were noted. Conclusion: Biosynthetic corneal implantation is well tolerated in dogs, and the collagen-polymer hybrid construct holds promise for clinical application in animals and humans.
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| 13. |
- Blais, David R., et al.
(författare)
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LBP and CD14 secreted in tears by the lacrimal glands modulate the LPS response of corneal epithelial cells
- 2005
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Ingår i: Investigative Ophthalmology and Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 0146-0404 .- 1552-5783. ; 46:11, s. 4235-4244
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. Lipopolysaccharide (LPS) is one of the most powerful bacterial virulence factors in terms of proinflammatory properties and is likely to contribute to corneal bacterial keratitis. Better understanding of the spatial expression of the LPS receptor components at the tear - corneal interface might facilitate enhanced functions of the LPS receptor complex in ocular defense against Gram-negative infections. METHODS. The expression of LPS-binding protein (LBP), CD14, toll-like receptor (TLR)-4, and MD-2 in human lacrimal glands, reflex tears, and corneal epithelia was examined by ELISA, RT-PCR, Western blot analysis, and immunofluorescence. The release of proinflammatory cytokines after the activation of primary and immortalized corneal epithelial cells with LPS and human tears was measured by ELISA. RESULTS. LBP and CD14 proteins were detected in reflex human tears. Human lacrimal glands and corneal epithelia expressed LBP, CD14, TLR4, and MD-2 mRNAs and proteins. In the corneal epithelium, LBP was mainly expressed by superficial and basal epithelial cells, whereas CD14, TLR4, and MD-2 expression were limited to the wing and basal epithelial cells. In a dose-dependant manner, tear CD14 and LBP mediated the secretion of interleukin (IL)-6 and IL-8 by corneal epithelia cells when challenged with LPS. CONCLUSIONS. Tear CD14 and LBP complemented the LPS receptor complex expressed by the corneal epithelia to trigger an immune response in the presence of LPS. The complementation of these tear and corneal immune proteins could play an important role in LPS recognition and signaling and, therefore, could modulate ocular innate immunity.
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| 14. |
- Blake, Jessie A, et al.
(författare)
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Design of xanthone propionate photolabile protecting group releasing acyclovir for the treatment of ocular herpes simplex virus
- 2012
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Ingår i: Photochemical and Photobiological Sciences. - : Royal Society of Chemistry. - 1474-905X .- 1474-9092. ; 11:3, s. 539-547
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Tidskriftsartikel (refereegranskat)abstract
- We have attached the antiviral drug acyclovir (ACV) to a xanthone photolabile protecting group (or photocage) through the O6 position of acyclovir, a procedure designed for the treatment of ocular herpes simplex virus infections. Acyclovir is photoreleased from the photocage, under physiological conditions, with a quantum yield (Phi(ACV release)) of 0.1-0.3 and an uncaging cross section (Phi.epsilon) of 450-1350 M cm(-1). We demonstrate that this photorelease method outcompetes alternative reaction pathways, such as protonation. Furthermore, complete release of the drug is theoretically possible given a sufficient dose of light. Surprisingly the acyclovir photocage, also showed some antiviral activity towards HSV-1.
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| 15. |
- Brunette, Isabelle, et al.
(författare)
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Cornea Regeneration as an Alternative to Human Donor Transplantation
- 2015
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Ingår i: European Ophthalmic Review. - : touchOPHTHALMOLOGY.com. - 1756-1795. ; 9:2, s. 111-114
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for an alternative to human donor corneas as the availability of good-quality tissues remains limited, with this situation potentially worsening as the population in many countries is progressively ageing. There have been numerous attempts to develop corneal equivalent as alternatives to donated human corneas as well as prostheses. In this short review, we focus on the efforts in bioengineering implants that promote regeneration by Canadian researchers, including our current team of authors. The examples of technologies developed that we describe include biomaterials that allow for partial regeneration of corneal tissue, self-assembled cornea constructs and cell-free corneal implants that promoted regeneration when evaluated in clinical trials in Europe.
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| 16. |
- Buznyk, Oleksiy, et al.
(författare)
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Bioengineered Corneas Grafted as Alternatives to Human Donor Corneas in Three High-Risk Patients
- 2015
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Ingår i: Clinical and Translational Science. - : WILEY-BLACKWELL. - 1752-8054 .- 1752-8062. ; 8:5, s. 558-562
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Tidskriftsartikel (refereegranskat)abstract
- Corneas with severe pathologies have a high risk of rejection when conventionally grafted with human donor tissues. In this early observational study, we grafted bioengineered corneal implants made from recombinant human collagen and synthetic phosphorylcholine polymer into three patients for whom donor cornea transplantation carried a high risk of transplant failure. These patients suffered from corneal ulcers and recurrent erosions preoperatively. The implants provided relief from pain and discomfort, restored corneal integrity by promoting endogenous regeneration of corneal tissues, and improved vision in two of three patients. Such implants could in the future be alternatives to donor corneas for high-risk patients, and therefore, merits further testing in a clinical trial.
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| 17. |
- Cheung Mak, Wing, et al.
(författare)
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Surface-Engineered Contact Lens as an Advanced Theranostic Platform for Modulation and Detection of Viral Infection
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:45, s. 25487-25494
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated an entirely new concept of a wearable theranostic device in the form of a contact lens (theranostic lens) with a dual-functional hybrid surface to modulate and detect a pathogenic attack, using a the corneal HSV serotype-1 (HSV-1) model. The theranostic lenses were constructed using a facile layer-by-layer surface engineering technique, keeping the theranostic lenses with good surface wettability, optically transparency, and nontoxic toward human corneal epithelial cells. The theranostic lenses were used to capture and concentrate inflammatory cytokines such as interleukin-1 alpha (IL-1 alpha), which is upregulated during HSV-1 reactivation, for sensitive, noninvasive diagnostics. The theranostic lens also incorporated an antiviral coating to serve as a first line of defense to protect patients against disease. Our strategy tackles major problems in tear diagnostics that are mainly associated with the sampling of a relatively small volume of fluid and the low concentration of biomarkers. The theranostic lenses show effective anti-HSV-1 activity and good analytical performance for the detection of IL-1a, with a limit of detection of 1.43 pg mL(-1) and a wide linear range covering the clinically relevant region. This work offers a new paradigm for wearable noninvasive healthcare devices combining diagnosis and protection against disease, while supporting patient compliance. We believe that this approach holds immense promise as a next-generation point-of-care and decentralized diagnostic/theranostic platform for a range of biomarkers.
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| 18. |
- Coutu, Daniel L, et al.
(författare)
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Hierarchical scaffold design for mesenchymal stem cell-based gene therapy of hemophilia B
- 2011
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 32:1, s. 295-305
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Tidskriftsartikel (refereegranskat)abstract
- Gene therapy for hemophilia B and other hereditary plasma protein deficiencies showed great promise in pre-clinical and early clinical trials. However, safety concerns about in vivo delivery of viral vectors and poor post-transplant survival of ex vivo modified cells remain key hurdles for clinical translation of gene therapy. We here describe a 3D scaffold system based on porous hydroxyapatite PLGA composites coated with biomineralized collagen 1. When combined with autologous gene-engineered factor IX (hFIX) positive mesenchymal stem cells (MSCs) and implanted in hemophilic mice, these scaffolds supported long-term engraftment and systemic protein delivery by MSCs in vivo. Optimization of the scaffolds at the macro-, micro- and nanoscales provided efficient cell delivery capacity, MSC self-renewal and osteogenesis respectively, concurrent with sustained delivery of hFIX. In conclusion, the use of gene-enhanced MSC-seeded scaffolds may be of practical use for treatment of hemophilia B and other plasma protein deficiencies.
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| 19. |
- Dare, Emma V., et al.
(författare)
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Fibrin Sealants from Fresh or Fresh/Frozen Plasma as Scaffolds for In Vitro Articular Cartilage Regeneration
- 2009
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Ingår i: TISSUE ENGINEERING PART A. - : Mary Ann Leibert Inc. - 1937-3341 .- 1937-335X. ; 15:8, s. 2285-2297
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Tidskriftsartikel (refereegranskat)abstract
- Our objective was to evaluate human CryoSeal (R) fibrin glue derived from single units of plasma as scaffolds for articular cartilage tissue engineering. Human articular chondrocytes were encapsulated into genipin cross-linked fibrin glue derived from individual units of fresh or frozen plasma using the CryoSeal (R) fibrin sealant (FS) system. The constructs were cultured for up to 7 weeks in vitro under low (5%) or normal (21%) oxygen. Chondrocyte viability was greater than90% within the fibrin gels. Hypoxia induced significant increases in collagen II and Sox9 gene expression and a significant decrease in collagen I. A significant increase in collagen II was detected in fresh plasma-derived cultures, while only collagen I was significantly increased in frozen plasma cultures. Significant increases in total glycosaminoglycan and collagen were detected in the extracellular matrix secreted by the encapsulated chondrocytes. A significant increase in compression modulus was only observed for fresh plasma-derived gels, which is likely explained by a greater amount of collagen type I detected after 7 weeks in frozen compared to fresh plasma gels. Our results indicate that CryoSeal (R) fibrin glue derived from fresh plasma is suitable as a tissue engineering scaffold for human articular chondrocytes, and therefore should be evaluated for autologous articular cartilage regeneration.
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| 20. |
- Dare, Emma V., et al.
(författare)
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Genipin Cross-Linked Fibrin Hydrogels for in vitro Human Articular Cartilage Tissue-Engineered Regeneration
- 2009
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Ingår i: Cells Tissues Organs. - : Karger. - 1422-6405 .- 1422-6421. ; 190:6, s. 313-325
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Tidskriftsartikel (refereegranskat)abstract
- Our objective was to examine the potential of a genipin cross-linked human fibrin hydrogel system as a scaffold for articular cartilage tissue engineering. Human articular chondrocytes were incorporated into modified human fibrin gels and evaluated for mechanical properties, cell viability, gene expression, extracellular matrix production and subcutaneous biodegradation. Genipin, a naturally occurring compound used in the treatment of inflammation, was used as a cross-linker. Genipin cross-linking did not significantly affect cell viability, but significantly increased the dynamic compression and shear moduli of the hydrogel. The ratio of the change in collagen II versus collagen I expression increased more than 8-fold over 5 weeks as detected with real-time RT-PCR. Accumulation of collagen II and aggrecan in hydrogel extracellular matrix was observed after 5 weeks in cell culture. Overall, our results indicate that genipin appeared to inhibit the inflammatory reaction observed 3 weeks after subcutaneous implantation of the fibrin into rats. Therefore, genipin cross-linked fibrin hydrogels can be used as cell-compatible tissue engineering scaffolds for articular cartilage regeneration, for utility in autologous treatments that eliminate the risk of tissue rejection and viral infection.
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| 21. |
- Deng, C, et al.
(författare)
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A Collagen-Chitosan Hydrogel for Endothelial Differentiation and Angiogenesis
- 2010
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Ingår i: TISSUE ENGINEERING PART A. - : Mary Ann Liebert. - 1937-3341 .- 1937-335X. ; 16:10, s. 3099-3109
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Tidskriftsartikel (refereegranskat)abstract
- Cell therapy for the treatment of cardiovascular disease has been hindered by low cell engraftment, poor survival, and inadequate phenotype and function. In this study, we added chitosan to a previously developed injectable collagen matrix, with the aim of improving its properties for cell therapy and neovascularization. Different ratios of collagen and chitosan were mixed and chemically crosslinked to produce hydrogels. Swell and degradation assays showed that chitosan improved the stability of the collagen hydrogel. In culture, endothelial cells formed significantly more vascular-like structures on collagen-chitosan than collagen-only matrix. While the differentiation of circulating progenitor cells to CD31(+) cells was equal on all matrices, vascular endothelial-cadherin expression was increased on the collagen-chitosan matrix, suggesting greater maturation of the endothelial cells. In addition, the collagen-chitosan matrix supported a significantly greater number of CD133(+) progenitor cells than the collagen-only matrix. In vivo, subcutaneously implanted collagen-chitosan matrices stimulated greater vascular growth and recruited more von Willebrand factor (vWF(+)) and CXCR4(+) endothelial/angiogenic cells than the collagen-only matrix. These results indicate that the addition of chitosan can improve the physical properties of collagen matrices, and enhance their ability to support endothelial cells and angiogenesis for use in cardiovascular tissue engineering applications.
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| 22. |
- Deng, C, et al.
(författare)
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Collagen and glycopolymer based hydrogel for potential corneal application
- 2010
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Ingår i: ACTA BIOMATERIALIA. - : Elsevier. - 1742-7061. ; 6:1, s. 187-194
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Tidskriftsartikel (refereegranskat)abstract
- 6-Methacryloyl-alpha-D-galactopyranose (MG) was synthesized, and characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectrometry, and single-crystal X-ray diffraction. A series of interpenetrating polymer network (IPN) hydrogels was fabricated by simultaneously photo-curing MG crosslinked by poly(ethylene glycol) diacrylate and chemically crosslinking type I collagen with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The successful incorporation of the glycopolymer, polymer MG, into collagen hydrogel was confirmed by FTIR and solid-state C-13 NMR. The optical characteristics of the IPN hydrogels are comparable to those of human corneas. The tensile strength and modulus of the hydrogels are enhanced by incorporation of polymer MG in comparison to that of the control collagen hydrogel. Biodegradation results indicated that polymer MG enhanced the stability of the composite hydrogels against collagenase. In vitro results demonstrated that the IPN hydrogel supported the adhesion and proliferation of human corneal epithelial cells and outperformed human cornea in blocking bacteria adhesion. Taken together, the IPN hydrogel might be a promising material for use in corneal lamellar keratoplasty. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 23. |
- Dilip Deb, Kaushik, et al.
(författare)
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Nanotechnology in stem cells research: advances and applications
- 2012
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Ingår i: Frontiers in Bioscience. - : Frontiers in Bioscience. - 1093-9946 .- 1093-4715. ; 17, s. 1747-1760
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Tidskriftsartikel (refereegranskat)abstract
- Human beings suffer from a myriad of disorders caused by biochemical or biophysical alteration of physiological systems leading to organ failure. For a number of these conditions, stem cells and their enormous reparative potential may be the last hope for restoring function to these failing organ or tissue systems. To harness the potential of stem cells for biotherapeutic applications, we need to work at the size scale of molecules and processes that govern stem cells fate. Nanotechnology provides us with such capacity. Therefore, effective amalgamation of nanotechnology and stem cells - medical nanoscience or nanomedicine - offers immense benefits to the human race. The aim of this paper is to discuss the role and importance of nanotechnology in stem cell research by focusing on several important areas such as stem cell visualization and imaging, genetic modifications and reprogramming by gene delivery systems, creating stem cell niche, and similar therapeutic applications.
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| 24. |
- Dravida, Subhadra, et al.
(författare)
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A biomimetic scaffold for culturing limbal stem cells: a promising alternative for clinical transplantation
- 2008
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Ingår i: JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE. - : John Wiley and Sons. - 1932-6254 .- 1932-7005. ; 2:5, s. 263-271
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Tidskriftsartikel (refereegranskat)abstract
- Limbal tissues can be cultured on various types of scaffolds to create a sheet of limbal-corneal epithelium for research as well as clinical transplantation. An optically clear, biocompatible, biomimetic scaffold would be an ideal replacement graft for transplanting limbal stem cells. in this study, we evaluated the physical and culture characteristics of the recombinant human cross-linked collagen scaffold (RHC-III scaffold) and compared it with denuded human amniotic membrane (HAM). Optical/mechanical properties and microbial susceptibility were measured for the scaffolds. With the approval of the institutional review board, 2 mm. fresh human limbal tissues were cultured on 2.5 x 2.5 cm(2) scaffolds in a medium containing autologous serum in a feeder cell-free submerged system. The cultured cell systems were characterized by morphology and immunohistochemistry for putative stem cells and differentiated cell markers. The refractive index (RI) and tensile strength of the RHC-III scaffold were comparable to human cornea, with delayed in vitro degradation compared to HAM. RHC-III scaffolds were 10-fold less susceptible to microbial growth. Cultures were initiated on day 1, expanded to form a monolayer by day 3 and covered the entire growth surface in 10 days. Stratified epithelium on the scaffolds was visualized by transmission electron microscopy. The cultured cells showed p63 and ABCG2 positivity in the basal layer and were immunoreactive for cytokeratin K3 and K12 in the suprabasal layers. RHC-III scaffold supports and retains the growth and stemness of limbal stem cells, in addition to resembling human cornea; thus, it could be a good replacement scaffold for growing cells for clinical transplantation.
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| 25. |
- Duan, Xiaodong, et al.
(författare)
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Biofunctionalization of collagen for improved biological response: Scaffolds for corneal tissue engineering
- 2007
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 28:1, s. 78-88
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Tidskriftsartikel (refereegranskat)abstract
- Residual dendrimer amine groups were modified with incorporate COOH group containing biomolecules such as cell adhesion peptides into collagen scaffolds. YIGSR, as a model cell adhesion peptide, was incorporated into both the bulk structure of the gels and onto the gel surface. The effects of the peptide modified collagen gets on corneal epithelial cell behavior were examined with an aim of improving the potential of these materials as tissue-engineering scaffolds. YIGSR was first chemically attached to dendrimers and the YIGSR attached dendrimers were then used as collagen crosslinkers, incorporating the peptide into the bulk structure of the collagen gels. YIGSR was also attached to the surface of dendrimer crosslinked collagen gels through reaction with excess amine groups. The YIGSR modified dendrimers were characterized by H-NMR and MALDI mass spectra. The amount of YIGSR incorporated into collagen gels was determined by (125)1 radiolabelling at maximum to be 3.1-3.4 x 10(-2)mg/mg collagen when reacted with the bulk and 88.9-95.6 mu g/cm(2) when attached to the surface. The amount of YIGSR could be tuned by varying the amount of peptide reacted with the dendrimer or the amount of modified dendrimer used in the crosslinking reaction. It was found that YIGSR incorporation into the bulk and YIGSR modification of surface promoted the adhesion and proliferation of human corneal epithelial cells as well as neurite extension from dorsal root ganglia. (c) 2006 Elsevier Ltd. All rights reserved.
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| 26. |
- Edin, Elle, 1986-
(författare)
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Composite Regenerative Scaffolds
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Regenerative medicine and tissue engineering solutions of heavily innervated tissues are at this point lacklustre. This thesis expands our knowledge of appropriate acellular scaffolds for tissue repair in general and nerve regeneration in particular. The optimal surgical procedure for the implantation of artificial extracellular matrix (ECM) was evaluated for recombinant human collagen (RHCIII) implants. Suturing techniques, as well as the usage of human amniotic membrane “bandages” were evaluated. While complete regeneration of corneal tissues occurred, only slight differences in effects of surgical technique could be found.The safety and efficacy of clinical trials using mesenchymal stromal cells (MSCs) was evaluated by conducting a systematic review and meta-analysis. MSC therapy was shown to be safe, with no increases mortality, rehospitalization or adverse events. There was also an indication of efficacy, as the overall mortality in the studies included was significantly smaller in the MSC treated group.Multicomponent hydrogel capsules encapsulating single cells were developed. Capsules manufactured from gelatin, agarose and fibrinogen were compared to pure gelatin capsules. The composite capsules successfully delayed cell release and prolonged cell survival.Surface patterning of collagen based biomimetic corneas was performed by microcontact printing. The ability of different sizes of fibronectin stripes to stimulate cell adhesion and proliferation was compared. The patterned surfaces improved cell adhesion, as well as proliferation markers.Conductive polymer composites were manufactured for use as nerve guides. The guides were created from electrospun polycaprolactone fibers coated with a series of different poly(3,4-ethylenedioxythiophene) films. A comparison of nerve progenitor growth and differentiation on the composite fibers was performed. Both the effects of fiber composition and MSC co-culture was investigated, with or without electrostimulation. MSC treatments and polymer coating was both important for nerve cell differentiation and growth.
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| 27. |
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| 28. |
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| 29. |
- Fagerholm, Per, et al.
(författare)
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A biosynthetic alternative to human donor tissue for inducing corneal regeneration : 24-month follow-up of a phase 1 clinical study
- 2010
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Ingår i: Science translational medicine. - : American Association for the Advancement of Science (AAAS). - 1946-6234 .- 1946-6242. ; 2:46, s. 46-61
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Tidskriftsartikel (refereegranskat)abstract
- Corneas from human donors are used to replace damaged tissue and treat corneal blindness, but there is a severe worldwide shortage of donor corneas. We conducted a phase 1 clinical study in which biosynthetic mimics of corneal extracellular matrix were implanted to replace the pathologic anterior cornea of 10 patients who had significant vision loss, with the aim of facilitating endogenous tissue regeneration without the use of human donor tissue. The biosynthetic implants remained stably integrated and avascular for 24 months after surgery, without the need for long-term use of the steroid immunosuppression that is required for traditional allotransplantation. Corneal reepithelialization occurred in all patients, although a delay in epithelial closure as a result of the overlying retaining sutures led to early, localized implant thinning and fibrosis in some patients. The tear film was restored, and stromal cells were recruited into the implant in all patients. Nerve regeneration was also observed and touch sensitivity was restored, both to an equal or to a greater degree than is seen with human donor tissue. Vision at 24 months improved from preoperative values in six patients. With further optimization, biosynthetic corneal implants could offer a safe and effective alternative to the implantation of human tissue to help address the current donor cornea shortage.
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| 30. |
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| 31. |
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| 32. |
- Fagerholm, Per, et al.
(författare)
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Stable corneal regeneration four years after implantation of a cell-free recombinant human collagen scaffold
- 2014
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 35:8, s. 2420-2427
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Tidskriftsartikel (refereegranskat)abstract
- We developed cell-free implants, comprising carbodiimide crosslinked recombinant human collagen (RHC), to enable corneal regeneration by endogenous cell recruitment, to address the worldwide shortage of donor corneas. Patients were grafted with RHC implants. Over four years, the regenerated neo-corneas were stably integrated without rejection, without the long immunosuppression regime needed by donor cornea patients. There was no recruitment of inflammatory dendritic cells into the implant area, whereas, even with immunosuppression, donor cornea recipients showed dendritic cell migration into the central cornea and a rejection episode was observed. Regeneration as evidenced by continued nerve and stromal cell repopulation occurred over the four years to approximate the micro-architecture of healthy corneas. Histopathology of a regenerated, clear cornea from a regrafted patient showed normal corneal architecture. Donor human cornea grafted eyes had abnormally tortuous nerves and stromal cell death was found. Implanted patients had a 4-year average corrected visual acuity of 20/54 and gained more than 5 Snellen lines of vision on an eye chart. The visual acuity can be improved with more robust materials for better shape retention. Nevertheless, these RHC implants can achieve stable regeneration and therefore, represent a potentially safe alternative to donor organ transplantation.
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| 33. |
- Ghani, Mozhdeh, et al.
(författare)
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Cross-linked superfine electrospun tragacanth-based biomaterial as scaffolds for tissue engineering
- 2016
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Ingår i: European Cells & Materials. - Davos, Switzerland : AO Research Institute Davos. - 1473-2262. ; 31:Suppl. 1, s. 204-204
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Tidskriftsartikel (refereegranskat)abstract
- Natural polymer-based nanofibrous structures promote cell adhesion and proliferation due to their high surface area/volume ratio, high porosity, and similarity to native extracellular matrix in terms of both chemical composition and physical structure. Gum tragacanth (Tg) is a natural polysaccharides obtained from plants. It is a biocompatible, biodegradable and anionic polysaccharides that has been used extensively as an emulsifier in food and pharmaceutical industries. Despite, its good rheological properties and compatibility, the potential biomedical applications of Tg have not been fully investigated. The objective of the present study was to explore the feasibility of combining Tg with gelatin to fabricate a scaffold that serves as a simple collagen-glycosaminoglycans analog for tissue engineering applications, e.g. as a scaffold for human skin epithelial cells.
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| 34. |
- Gian Vascotto, Sandy, et al.
(författare)
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Localization of candidate stem and progenitor cell markers within the human cornea, limbus, and bulbar conjunctiva in vivo and in cell culture
- 2006
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Ingår i: Anatomical Record Part A-discoveries in Molecular Cellular and Evolutionary Biology. - : John Wiley and Sons, Ltd. - 1552-4884 .- 1932-8494 .- 1552-4892. ; 288A:8, s. 921-931
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Tidskriftsartikel (refereegranskat)abstract
- Corneal diseases are some of the most prevalent causes of blindness worldwide. While the most common treatment for corneal blindness is the transplantation of cadaver corneas, expanded limbal stem cells are finding recent application. Unknown, however, is the identity of the actual repopulating stem cell fraction utilized in both treatments and the critical factors governing successful engraftment and repopulation. In order to localize potential stem cell populations in vivo, we have immunohistochemically mapped a battery of candidate stem and progenitor cell markers including c-Kit and other growth factor receptors, nuclear markers including Delta Np63, as well as adhesion factors across the cornea and distal sclera. Cell populations that differentially and specifically stained for some of these markers include the basal and superficial limbal/conjunctival epithelium and scattered cells within the substantia propria of the bulbar conjunctiva. We have also determined that the culture of differentiated cornea epithelial cells as dissociated and explant cultures induces the expression of several markers previously characterized as candidate limbal stem cell markers. This study provides a foundation to explore candidate corneal stem cell populations. As well, we show that expression of traditional stem cell markers may not be reliable indicator of stem cell content during limbal stem cell expansion in vitro and could contribute to the variable success rates of corneal stem cell transplantation.
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| 35. |
- Griffith, May, et al.
(författare)
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Artificial corneas : a regenerative medicine approach
- 2009
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Ingår i: EYE. - : Springer Science and Business Media LLC. - 0950-222X .- 1476-5454. ; 23:10, s. 1985-1989
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Tidskriftsartikel (refereegranskat)abstract
- Corneal substitutes are being developed to address the shortage of human donor tissues as well as the current disadvantages in some clinical indications, which include immune rejection. In the past few years, there have been significant developments in bioengineered corneas that are designed to replace part or the full thickness of damaged or diseased corneas that range from keratoprostheses that solely address the replacement of the corneas function, through tissue-engineered hydrogels that permit regeneration of host tissues. We describe examples of corneal substitutes that encourage regeneration of the host tissue. We also contend that it is unlikely that there will be a single "one-size-fits-all corneal substitute for all indications. Instead, there will most likely be a small range of corneal substitutes ranging from prostheses to tissue-engineered matrix substitutes that are tailored to different clusters of clinical indications. The tissue-engineered matrices can either be produced as sterile acellular matrices, or complete with functional cells, ready for implantation.
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| 36. |
- Griffith, May, et al.
(författare)
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Artificial Corneas, and Reinforced Composite Implants for High Risk Donor Cornea Transplantation
- 2017
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Ingår i: The Stem Cell Microenvironment and its Role in Regenerative Medicine and Cancer Pathogenesis. - : RIVER PUBLISHERS. - 9788793519008 - 9788793379930 ; , s. 93-102
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Konferensbidrag (refereegranskat)abstract
- Here, we review examples of artificial corneas that have been developed as alternatives to donor cornea transplantation. These consist of artificial corneas developed as prostheses and regenerative scaffolds. Examples of reinforced and composite implants developed within our group are profiled.
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| 37. |
- Griffith, May, et al.
(författare)
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Artificial human corneas - Scaffolds for transplantation and host regeneration
- 2002
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Ingår i: Cornea. - : Lippincott, Williams andamp; Wilkins. - 0277-3740 .- 1536-4798. ; 21:7, s. S54-S61
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. To review the development of artificial corneas (prostheses and tissue equivalents) for transplantation, and to provide recent updates on our tissue-engineered replacement corneas. Methods. Modified natural polymers and synthetic polymers were screened for their potential to replace damaged portions of the human cornea or the entire corneal thickness. These polymers, combined with cells derived from each of the three main corneal layers or stem cells, were used to develop artificial corneas. Functional testing was performed in vitro. Trials of biocompatibility and immune and inflammatory reactions were performed by implanting the most promising polymers into rabbit corneas. Results. Collagen-based biopolymers, combined with synthetic crosslinkers or copolymers, formed effective scaffolds for developing prototype artificial corneas that could be used as tissue replacements in the future. We have previously developed an artificial cornea that mimicked key morphologic and functional properties of the human cornea. The addition of synthetic polymers increased its toughness as it retained transparency and low light scattering, making the matrix scaffold more suitable for transplantation. These new composites were implanted into rabbits without causing any acute inflammation or immune response. We have also fabricated full-thickness composites that can be fully sutured. However, the long-term effects of these artificial corneas need to be evaluated. Conclusions. Novel tissue-engineered corneas that comprise composites of natural and synthetic biopolymers together with corneal cell lines or stem cells will, in the future, replace portions of the cornea that are damaged. Our results provide a basis for the development of both implantable temporary and permanent corneal replacements.
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| 38. |
- Griffith, May, et al.
(författare)
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COLLAGEN AND COLLAGEN LIKE PEPTIDE BASED HYDROGELS, CORNEAL IMPLANTS, FILLER GLUE AND USES THEREOF
- 2018
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Patent (populärvet., debatt m.m.)abstract
- The present invention provides for collagen and collagen like peptide based hydrogels, corneal implants, filler glue 00 and uses thereof. The invention represents an advancement in the field of hydrogels, corneal implants, filler glue based on collagen o and collagen like peptides. The invention discloses collagen and novel collagen like peptides crosslinked with DMTMM and their use in preparation of hydrogel, corneal implant and filler glue which are highly efficacious and robust as compared to existing corneal implants. Further, the invention relates to method of treating corneal defects and diseases.
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| 39. |
- Griffith, May, et al.
(författare)
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Corneal stromal mesenchymal stem cells for corneal stroma reconstruction
- 2011
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Ingår i: Acta Ophthalmologica; Special Issue: Abstracts from the 2011 European Association for Vision and Eye Research ConferenceVolume 89, Issue Supplement s248, page 0, September 2011. - : Wiley.
-
Konferensbidrag (refereegranskat)abstract
- PurposeTo date, corneal epithelial reconstruction has been very successful. However, in a number of cases of injury or disease, the stromal layer is affected. Our goal is to develop biomaterials that will enable the regeneration of the corneal stroma. In this study, we compare endogenous vs exogenous stem cell courses for corneal stromal regeneration.MethodsWe have previously developed collagen-based corneal stromal extracellular matrix substitutes based on EDC crosslinked collagen, and have shown that they promote ingrowth of stromal cells from the host cornea (Merrett et al. 2009; Fagerholm et al. 2010). For cases where stromal progenitors are depleted, we developed a non-toxic collagen-based hydrogel system where a macromolecular photoinitiator (Dex-BBA)was used to form the hydrogel around cells. The feasibility of Dex-BBA as a photoinitiator to initiate the gelation of aminoethylmethacylate-modified collagen (Coll-AEMA) was examined with or without the presence of stroma cells.ResultsThe Dex-BBA crosslinked hydrogels were weaker than the EDC crosslinked constructs. However, they were fairly robust and no apparent toxicity of the hydrogel system to mesenchymal stroma (or stem) cells (MSCs)were observed during the culture of 7 days, which indicated that Dex-BBA based macrophotoinitiator and our collagen-based hydrogel system may have potential in corneal stromal regeneration applications.ConclusionsWe show that corneal stromal regeneration can be achieved by endogenous stimulation of existing corneal progenitor cells. Where the host cells may be depleted, our results show that hydrogel encapsulated stem cells may be used in the future.
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| 40. |
- Griffith, May, et al.
(författare)
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Interpenetrating Networks, and Related Methods and Compositions
- 2007
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Patent (populärvet., debatt m.m.)abstract
- The present invention provides interpenetrating polymeric networks (IPNs), and related methods and compositions. The hydrogel material of this invention comprises an interpenetrating network of two or more polymer networks, wherein at least one of the polymer networks is based on a biopolymer. Also provided is a method of producing the hydrogel material comprising, combining a first polymeric network with a second polymeric network, wherein the first polymeric network or the second polymeric network is based on a biopolymer. The present application also discloses devices manufactured from the IPN hydrogel material and uses thereof.
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| 41. |
- Griffith, May, et al.
(författare)
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Recent advances in the design of artificial corneas
- 2014
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Ingår i: Current Opinion in Ophthalmology. - : Lippincott Williams & Wilkins. - 1040-8738 .- 1531-7021. ; 25:3, s. 240-247
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Forskningsöversikt (refereegranskat)abstract
- PURPOSE OF REVIEW:Artificial corneas are being developed to meet a shortage of donor corneas and to address cases in which allografting is contraindicated. A range of artificial corneas has been developed. Here we review several newer designs and especially those inspired by naturally occurring biomaterials found with the human body and elsewhere.RECENT FINDINGS:Recent trends in the development of artificial corneas indicate a move towards the use of materials derived from native sources including decellularized corneal tissue and tissue substitutes synthesized by corneal cells in vitro when grown either on their own or in conjunction with novel protein-based scaffolds. Biologically inspired materials are also being considered for implantation on their own with the view to promoting endogenous corneal tissue.SUMMARY:More recent attempts at making artificial corneas have taken a more nature-based or nature-inspired approach. Several will in the near future be likely to be available clinically.
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| 42. |
- Griffith, May, et al.
(författare)
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Regenerative Approaches as Alternatives to Donor Allografting for Restoration of Corneal Function
- 2012
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Ingår i: The Ocular Surface. - : Elsevier. - 1542-0124. ; 10:3, s. 170-183
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Tidskriftsartikel (refereegranskat)abstract
- A range of alternatives to human donor tissue for corneal transplantation are being developed to address the shortfall of good quality tissues as well as the clinical conditions for which allografting is contraindicated. Classical keratoprostheses, commonly referred to as artificial corneas, are being used clinically to replace minimal corneal function. However, they are used only as last resorts, as they are associated with significant complications, such as extrusion/rejection, glaucoma, and retinal detachment. The past few years have seen significant developments in technologies designed to replace part or the full thickness of damaged or diseased corneas with materials that encourage regeneration to different extents. This review describes selected examples of these corneal substitutes, which range from cell-based regenerative strategies to keratoprostheses with regenerative capabilities via tissue-engineered scaffolds pre-seeded with stem cells. It is unlikely that one corneal substitute will be best for all indications, but taken together, the various approaches may soon be able to supplement the supply of human donor corneas for transplantation or allow restoration of diseased or damaged corneas that cannot be treated by currently available techniques.
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| 43. |
- Griffith, May, et al.
(författare)
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Regenerative approaches for the cornea
- 2016
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Ingår i: Journal of Internal Medicine. - : WILEY-BLACKWELL. - 0954-6820 .- 1365-2796. ; 280:3, s. 276-286
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Forskningsöversikt (refereegranskat)abstract
- The cornea is the transparent front part of the eye that transmits light to the back of the eye to generate vision. Loss of corneal transparency, if irreversible, leads to severe vision loss or blindness. For decades, corneal transplantation using human donor corneas has been the only option for treating corneal blindness. Despite recent improvement in surgical techniques, donor cornea transplantation remains plagued by risks of suboptimal optical results and visual acuity, immune rejection and eventually graft failure. Furthermore, the demand for suitable donor corneas is increasing faster than the number of donors, leaving thousands of curable patients untreated worldwide. Here, we critically review the state of the art of biomaterials for corneal regeneration. However, the lessons learned from the use of the cornea as a disease model will allow for extension of the biomaterials and techniques for regeneration of more complex organs such as the heart.
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| 44. |
- Griffith, May, et al.
(författare)
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Vision Enhancing Ophthalmic Devices and Related Methods and Compositions
- 2005
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Patent (populärvet., debatt m.m.)abstract
- Devices, methods, and compositions for improving vision or treating diseases, disorders or injury of the eye are described. Ophthalmic devices, such as corneal onlays, corneal inlays, and full-thickness corneal implants, are made of a material that is effective in facilitating nerve growth through or over the device. The material may include an amount of collagen greater than 1% (w/w), such as between about 10% (w/w) and about 30% (w/w). The material may include collagen polymers and/or a second biopolymer or water-soluble synthetic polymer cross-linked using EDC/NHS chemistry. The material may additionally comprise a synthetic polymer. The devices are placed into an eye to correct or improve the vision of an individual or to treat a disease, disorder or injury of an eye of an individual.
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| 45. |
- Haagdorens, Michel, et al.
(författare)
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Plant Recombinant Human Collagen Type I Hydrogels for Corneal Regeneration
- 2022
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Ingår i: REGENERATIVE ENGINEERING AND TRANSLATIONAL MEDICINE. - : Springer Berlin/Heidelberg. - 2364-4133 .- 2364-4141. ; 8:2, s. 269-283
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Tidskriftsartikel (refereegranskat)abstract
- Purpose To determine feasibility of plant-derived recombinant human collagen type I (RHCI) for use in corneal regenerative implantsMethods RHCI was crosslinked with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to form hydrogels. Application of shear force to liquid crystalline RHCI aligned the collagen fibrils. Both aligned and random hydrogels were evaluated for mechanical and optical properties, as well as in vitro biocompatibility. Further evaluation was performed in vivo by subcutaneous implantation in rats and corneal implantation in Gottingen minipigs.Results Spontaneous crosslinking of randomly aligned RHCI (rRHCI) formed robust, transparent hydrogels that were sufficient for implantation. Aligning the RHCI (aRHCI) resulted in thicker collagen fibrils forming an opaque hydrogel with insufficient transverse mechanical strength for surgical manipulation. rRHCI showed minimal inflammation when implanted subcutaneously in rats. The corneal implants in minipigs showed that rRHCI hydrogels promoted regeneration of corneal epithelium, stroma, and nerves; some myofibroblasts were seen in the regenerated neo-corneas.Conclusion Plant-derived RHCI was used to fabricate a hydrogel that is transparent, mechanically stable, and biocompatible when grafted as corneal implants in minipigs. Plant-derived collagen is determined to be a safe alternative to allografts, animal collagens, or yeast-derived recombinant human collagen for tissue engineering applications. The main advantage is that unlike donor corneas or yeast-produced collagen, the RHCI supply is potentially unlimited due to the high yields of this production method. Lay Summary A severe shortage of human-donor corneas for transplantation has led scientists to develop synthetic alternatives. Here, recombinant human collagen type I made of tobacco plants through genetic engineering was tested for use in making corneal implants. We made strong, transparent hydrogels that were tested by implanting subcutaneously in rats and in the corneas of minipigs. We showed that the plant collagen was biocompatible and was able to stably regenerate the corneas of minipigs comparable to yeast-produced recombinant collagen that we previously tested in clinical trials. The advantage of the plant collagen is that the supply is potentially limitless.
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| 46. |
- Hackett, Joanne M., et al.
(författare)
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Biosynthetic corneal implants for replacement of pathologic corneal tissue : performance in a controlled rabbit alkali burn model
- 2011
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Ingår i: Investigative Ophthalmology and Visual Science. - : Research in Vision and Opthalmology. - 0146-0404 .- 1552-5783. ; 52:2, s. 651-657
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate the performance of structurally reinforced, stabilized recombinant human collagen-phosphorylcholine (RHCIII-MPC) hydrogels as corneal substitutes in a rabbit model of severe corneal damage. Methods: One eye each of 12 rabbits received a deep corneal alkali wound. Four corneas were implanted with RHCIII-MPC hydrogels. The other eight control corneas were implanted with either allografts or a simple crosslinked RHCIII hydrogel. In all cases, 6.25 mm diameter, 350 µm thick buttons were implanted by anterior lamellar keratoplasty to replace damaged corneal tissue. Implants were followed for nine months by clinical examination and in vivo confocal microscopy, after which implanted corneas were removed and processed for histopathological and ultrastructural examination. Results: Alkali exposure induced extensive central corneal scarring, ocular surface irregularity, and neovascularization in one case. All implants showed complete epithelial coverage by four weeks post-operative, but with accompanying suture-induced vascularization in 6/12 cases. A stable, stratified epithelium with hemidesmosomal adhesion complexes regenerated over all implants, and subbasal nerve regeneration was observed in allograft and RHCIII-MPC implants. Initially acellular biosynthetic implants were populated with host-derived keratocytes as stromal haze subsided and stromal collagen was remodeled. Notably, RHCIII-MPC implants exhibited resistance to vascular ingrowth while supporting endogenous cell and nerve repopulation. Conclusion: Biosynthetic implants based on RHC promoted cell and nerve repopulation in alkali burned rabbit eyes. In RHCIII-MPC implants, evidence of an enhanced resistance to neovascularization was additionally noted.
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| 47. |
- Hackett, JM, et al.
(författare)
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Optimal neural differentiation and extension of hybrid neuroblastoma cells (NDC) for nerve-target evaluations using a multifactorial approach
- 2010
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Ingår i: Toxicology in Vitro. - : Elsevier BV. - 0887-2333 .- 1879-3177. ; 24:2, s. 567-577
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Tidskriftsartikel (refereegranskat)abstract
- In vitro models of tissues, such as the cornea, represent systems for modeling cell-to-cell interactions and tissue function. The objective of this study was to develop an optimized nerve differentiation medium to incorporate into a 3D in vitro model to study innervation and cell targeting. A hybrid neuroblastoma cell line (NDC) was examined for its ability to differentiate into neurons, produce neurites, and functionally contact target cells. Neuronal differentiation of NDCs was optimized through a combinatorial approach which involved culturing cells in the presence of various extracellular matrices and soluble factors. A serum-free medium containing nerve growth factor (NGF), dimethyl sulfoxide (DMSO), or dexamethasone resulted in the greatest proportion of NDCs demonstrating a neuronal morphology. Similarly, with supplementation of cyclic AMP (cAMP) or NGF, neurite extension was optimized. Combining these factors generated an optimized differentiation and extension medium, relative to the individual components alone. In co-culture with epithelial cells, NDC neurites generated in the optimized medium formed contacts with epithelial targets and produced substance P. Similarly, NDCs seeded into a collagen matrix produced neurites that projected through the matrix to target epithelial cells, promoted epithelial stratification, and increased the rate of epithelial wound healing. As well, differentiated NDCs could target and alter acetylcholine receptor clustering in mouse C2C12 myotubes, demonstrating synaptic plasticity. Our data supports the use of NDCs, in combination with optimized medium, for generating an innervated in vitro model. (C) 2009 Elsevier Ltd. All rights reserved.
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| 48. |
- Hayes, Sally, et al.
(författare)
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The structural and optical properties of type III human collagen biosynthetic corneal substitutes
- 2015
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Ingår i: Acta Biomaterialia. - : ELSEVIER SCI LTD. - 1742-7061 .- 1878-7568. ; 25, s. 121-130
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Tidskriftsartikel (refereegranskat)abstract
- The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2-9 nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd.
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| 49. |
- He, Min, et al.
(författare)
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Artificial Polymeric Scaffolds as Extracellular Matrix Substitutes for Autologous Conjunctival Goblet Cell Expansion
- 2016
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Ingår i: Investigative Ophthalmology and Visual Science. - : ASSOC RESEARCH VISION OPHTHALMOLOGY INC. - 0146-0404 .- 1552-5783. ; 57:14, s. 6134-6146
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. We fabricated and investigated polymeric scaffolds that can substitute for the conjunctival extracellular matrix to provide a substrate for autologous expansion of human conjunctival goblet cells in culture. METHODS. We fabricated two hydrogels and two silk films: (1) recombinant human collagen (RHC) hydrogel, (2) recombinant human collagen 2-methacryloylxyethyl phosphorylcholine (RHC-MPC) hydrogel, (3) arginine-glycine-aspartic acid (RGD) modified silk, and (4) poly-D-lysine (PDL) coated silk, and four electrospun scaffolds: (1) collagen, (2) poly(acrylic acid) (PAA), (3) poly(caprolactone) (PCL), and (4) poly(vinyl alcohol) (PVA). Coverslips and polyethylene terephthalate (PET) were used for comparison. Human conjunctival explants were cultured on scaffolds for 9 to 15 days. Cell viability, outgrowth area, and the percentage of cells expressing markers for stratified squamous epithelial cells (cytokeratin 4) and goblet cells (cytokeratin 7) were determined. RESULTS. Most of cells grown on all scaffolds were viable except for PCL in which only 3.6 +/- 2.2% of the cells were viable. No cells attached to PVA scaffold. The outgrowth was greatest on PDL-silk and PET. Outgrowth was smallest on PCL. All cells were CK7-positive on RHCMPC while 84.7 +/- 6.9% of cells expressed CK7 on PDL-silk. For PCL, 87.10 +/- 3.17% of cells were CK7-positive compared to PET where 67.10 +/- 12.08% of cells were CK7-positive cells. CONCLUSIONS. Biopolymer substrates in the form of hydrogels and silk films provided for better adherence, proliferation, and differentiation than the electrospun scaffolds and could be used for conjunctival goblet cell expansion for eventual transplantation once undifferentiated and stratified squamous cells are included. Useful polymer scaffold design characteristics have emerged from this study.
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| 50. |
- Hyde, K. D., et al.
(författare)
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Global consortium for the classification of fungi and fungus-like taxa
- 2023
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Ingår i: MYCOSPHERE. - : Mushroom Research Foundation. - 2077-7000 .- 2077-7019. ; 14:1, s. 1960-2012
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Tidskriftsartikel (refereegranskat)abstract
- The Global Consortium for the Classification of Fungi and fungus-like taxa is an international initiative of more than 550 mycologists to develop an electronic structure for the classification of these organisms. The members of the Consortium originate from 55 countries/regions worldwide, from a wide range of disciplines, and include senior, mid-career and early-career mycologists and plant pathologists. The Consortium will publish a biannual update of the Outline of Fungi and fungus-like taxa, to act as an international scheme for other scientists. Notes on all newly published taxa at or above the level of species will be prepared and published online on the Outline of Fungi website (https://www.outlineoffungi.org/), and these will be finally published in the biannual edition of the Outline of Fungi and fungus-like taxa. Comments on recent important taxonomic opinions on controversial topics will be included in the biannual outline. For example, 'to promote a more stable taxonomy in Fusarium given the divergences over its generic delimitation', or 'are there too many genera in the Boletales?' and even more importantly, 'what should be done with the tremendously diverse 'dark fungal taxa?' There are undeniable differences in mycologists' perceptions and opinions regarding species classification as well as the establishment of new species. Given the pluralistic nature of fungal taxonomy and its implications for species concepts and the nature of species, this consortium aims to provide a platform to better refine and stabilise fungal classification, taking into consideration views from different parties. In the future, a confidential voting system will be set up to gauge the opinions of all mycologists in the Consortium on important topics. The results of such surveys will be presented to the International Commission on the Taxonomy of Fungi (ICTF) and the Nomenclature Committee for Fungi (NCF) with opinions and percentages of votes for and against. Criticisms based on scientific evidence with regards to nomenclature, classifications, and taxonomic concepts will be welcomed, and any recommendations on specific taxonomic issues will also be encouraged; however, we will encourage professionally and ethically responsible criticisms of others' work. This biannual ongoing project will provide an outlet for advances in various topics of fungal classification, nomenclature, and taxonomic concepts and lead to a community-agreed classification scheme for the fungi and fungus-like taxa. Interested parties should contact the lead author if they would like to be involved in future outlines.
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