| 1. |
- 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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| 2. |
- 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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| 3. |
- Lee, Chyan-Jang, et al.
(författare)
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Cathelicidin LL-37 and HSV-1 Corneal Infection : Peptide Versus Gene Therapy
- 2014
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Ingår i: Translational Vision Science & Technology. - : Association for Research in Vision and Ophthalmology. - 2164-2591. ; 3:3, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate the potential utility of collagen-based corneal implants with anti?Herpes Simplex Virus (HSV)-1 activity achieved through sustained release of LL-37, from incorporated nanoparticles, as compared with cell-based delivery from model human corneal epithelial cells (HCECs) transfected to produce endogenous LL-37. Methods: We tested the ability of collagen-phosphorylcholine implants to tolerate the adverse microenvironment of herpetic murine corneas. Then, we investigated the efficacy of LL-37 peptides delivered through nanoparticles incorporated within the corneal implants to block HSV-1 viral activity. In addition, LL-37 complementary DNA (cDNA) was transferred into HCECs to confer viral resistance, and their response to HSV-1 infection was examined. Results: Our implants remained in herpetic murine corneas 7 days longer than allografts. LL-37 released from the implants blocked HSV-1 infection of HCECs by interfering with viral binding. However, in pre-infected HCECs, LL-37 delayed but could not prevent viral spreading nor clear viruses from the infected cells. HCECs transfected with the LL-37 expressed and secreted the peptide. Secreted LL-37 inhibited viral binding in vitro but was insufficient to protect cells completely from HSV-1 infection. Nevertheless, secreted LL-37 reduced both the incidence of plaque formation and plaque size. Conclusion: LL-37 released from composite nanoparticle-hydrogel corneal implants and HCEC-produced peptide, both showed anti?HSV-1 activity by blocking binding. However, while both slowed down virus spread, neither was able on its own to completely inhibit the viruses. Translational Relevance: LL-37 releasing hydrogels may have potential utility as corneal substitutes for grafting in HSV-1 infected corneas, possibly in combination with LL-37 producing therapeutic cells.
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| 4. |
- Liu, Lei, et al.
(författare)
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Immunological responses in mice to full-thickness corneal grafts engineered from porcine collagen
- 2007
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 28:26, s. 3807-3814
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Tidskriftsartikel (refereegranskat)abstract
- Tissue-engineered (TE) corneas were fabricated from porcine collagen cross-linked with 1-ethyl-3-(3-dimethyl aminoproplyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS), and were transplanted into BALB/c mice orthotopically using a full-thickness penetrating keratoplasty (PKP) procedure. The biocompatibility was evaluated by assessing both local and systemic immune responses. Myeloid cells including granulocytes and macrophages were the main infiltrating cells in recipient cornea and in retro-TE corneal membrane which developed 7-10 days post surgery. Sodium citrate was found to be effective in reducing fibrin accumulation in anterior chamber post grafting at early time points, but it did not prevent formation of the retro-TE corneal membrane. No significant T cell activation was observed in the submandibular draining lymph nodes (SMDLN) by flow cytometry. Anti-porcine type I collagen IgG antibodies were detected in the serum of grafted mice from 2 weeks post grafting and the concentration of antibodies increased with time. Overall, porcine collagen-EDC/NHS TE corneas were tolerated well in murine recipients, causing mainly a self-limiting local innate immune response and a low-grade humoral response with little evidence of sustained T cell activation. Retro-TE corneal membrane formation was the main complication and barrier to clarity.
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| 5. |
- McLaughlin, Christopher, et al.
(författare)
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Regeneration of Corneal Cells and Nerves in an Implanted Collagen Corneal Substitute
- 2008
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Ingår i: Cornea. - 0277-3740 .- 1536-4798. ; 27:5, s. 580-589
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Our objective was to evaluate promotion of tissue regeneration by extracellular matrix (ECM) mimics, by using corneal implantation as a model system.METHODS: Carbodiimide cross-linked porcine type I collagen was molded into appropriate corneal dimensions to serve as substitutes for natural corneal ECM. These were implanted into corneas of mini-pigs after removal of the host tissue, and tracked over 12 months, by clinical examination, slit-lamp biomicroscopy, in vivo confocal microscopy, topography, and esthesiometry. Histopathology and tensile strength testing were performed at the end of 12 months. Other samples were biotin labeled and implanted into mice to evaluate matrix remodeling.RESULTS: The implants promoted regeneration of corneal cells, nerves, and the tear film while retaining optical clarity. Mechanical testing data were consistent with stable, seamless host-graft integration in regenerated corneas, which were as robust as the untreated fellow corneas. Biotin conjugation is an effective method for tracking the implant within the host tissue.CONCLUSIONS: We show that a simple ECM mimetic can promote regeneration of corneal cells and nerves. Gradual turnover of matrix material as part of the natural remodeling process allowed for stable integration with host tissue and restoration of mechanical properties of the organ. The simplicity in fabrication and shown functionality shows potential for ECM
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| 6. |
- Moelzer, Christine, et al.
(författare)
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Activation of dendritic cells by crosslinked collagen hydrogels (artificial corneas) varies with their composition
- 2019
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Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : WILEY. - 1932-6254 .- 1932-7005. ; 13:9, s. 1528-1543
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Tidskriftsartikel (refereegranskat)abstract
- Activated T cells are known to promote fibrosis, a major complication limiting the range of polymeric hydrogels as artificial corneal implants. As T cells are activated by dendritic cells (DC), minimally activating hydrogels would be optimal. In this study, we evaluated the ability of a series of engineered (manufactured/fabricated) and natural collagen matrices to either activate DC or conversely induce DC apoptosis in vitro. Bone marrow DC were cultured on a series of singly and doubly crosslinked hydrogels (made from recombinant human collagen III [RHCIII] or collagen mimetic peptide [CMP]) or on natural collagen-containing matrices, Matrigel(TM) and de-cellularised mouse corneal stroma. DC surface expression of major histocompatibility complex Class II and CD86 as well as apoptosis markers were examined. Natural matrices induced low levels of DC activation and maintained a "tolerogenic" phenotype. The same applied to singly crosslinked CMP-PEG gels. RHCIII gels singly crosslinked using either N-(3-dimethylaminopropyl)-N -ethylcarbodiimide with the coinitiator N-hydroxy succinimide (EDC-NHS) or N-cyclohexyl-N-(2-morpholinoethyl)carbodiimide metho-p-toulenesulfonate with NHS (CMC-NHS) induced varying levels of DC activation. In contrast, however, RHCIII hydrogels incorporating an additional polymeric network of 2-methacryloyloxyethyl phosphorylcholine did not activate DC but instead induced DC apoptosis, a phenomenon observed in natural matrices. This correlated with increased DC expression of leukocyte-associated immunoglobulin-like receptor-1. Despite low immunogenic potential, viable tolerogenic DC migrated into and through both natural and manufactured RHCIII gels. These data show that the immunogenic potential of RHCIII gels varies with the nature and composition of the gel. Preclinical evaluation of hydrogel immunogenic/fibrogenic potential is recommended.
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| 7. |
- Molzer, Christine, et al.
(författare)
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TGF-beta 1-activated type 2 dendritic cells promote wound healing and induce fibroblasts to express tenascin c following corneal full-thickness hydrogel transplantation
- 2019
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Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : WILEY. - 1932-6254 .- 1932-7005. ; 13:9, s. 1507-1517
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Tidskriftsartikel (refereegranskat)abstract
- We showed previously that 1-ethyl-3-(3-dimethylamino-propyl)-carbodiimide hydrochloride (EDC) cross-linked recombinant human collagen III hydrogels promoted stable regeneration of the human cornea (continued nerve and stromal cell repopulation) for over 4 years. However, as EDC cross linking kinetics were difficult to control, we additionally tested a sterically bulky carbodiimide. Here, we compared the effects of two carbodiimide cross linkers-bulky, aromatic N-cyclohexyl-N0-(2-morpholinoethyl)-carbodiimide (CMC), and nonbulky EDC-in a mouse corneal graft model. Murine corneas undergoing full-thickness implantation with these gels became opaque due to dense retro-corneal membranes (RCM). Corneal epithelial cytokeratin 12 and alpha smooth muscle actin indicative of functional tissue regeneration and wound contraction were observed in RCM surrounding both hydrogel types. However, quantitatively different levels of infiltrating CD11c(+) dendritic cells (DC) were found, suggesting a hydrogel-specific innate immune response. More DC infiltrated the stroma surrounding EDC-N-hydroxysuccinimide (NHS) hydrogels concurrently with higher fibrosis-associated tenascin c expression. The opposite was true for CMC-NHS gels that had previously been shown to be more tolerising to DC. In vitro studies showed that DC cultured with transforming growth factor beta 1 (TGF-beta 1) induced fibroblasts to secrete more tenascin c than those cultured with lipopolysaccharide and this effect was blocked by TGF-beta 1 neutralisation. Furthermore, tenascin c staining was found in 40- to 50 mu m long membrane nanotubes formed in fibroblast/DC cocultures. We suggest that TGF-beta 1 alternatively activated (tolerising) DC regulate fibroblast-mediated tenascin c secretion, possibly via local production of TGF-beta 1 in early wound contraction, and that this is indirectly modulated by different hydrogel chemistries.
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| 8. |
- Rajendran, Vijayalakshmi, et al.
(författare)
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Mesenchymal stem cell therapy for retro-corneal membrane - A clinical challenge in full-thickness transplantation of biosynthetic corneal equivalents
- 2017
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Ingår i: Acta Biomaterialia. - : ELSEVIER SCI LTD. - 1742-7061 .- 1878-7568. ; 64, s. 346-356
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Tidskriftsartikel (refereegranskat)abstract
- Artificial corneas (keratoprostheses) and biosynthetic collagen-based corneal equivalents are surgical implants designed to ease the global burden of corneal blindness. However, keratoprostheses in many cases fail due to development of fibrous retro-corneal membranes (RCM). Fibrous membranes which develop in the anterior chamber after prosthesis implantation do so on a matrix of fibrin. This study investigated fibrin deposition and RCM formation after full-thickness collagen-based hydrogel implants and compared them with syngeneic and allogeneic corneal grafts in mice. Fibrin cleared from the anterior chamber within 14 days in both allo- and syn-grafts but, persisted in hydrogel implants and developed into dense retro-corneal membrane (RCM) which were heavily infiltrated by activated myofibroblasts. In contrast, the number of CD11 b(+) macrophages infiltrating the initial deposition of fibrin in the anterior chamber (AC) after hydrogel implantation was markedly reduced compared to syn- and allo-grafts. Inoculation of mesenchymal stem cells prior to collagen gel implant promoted clearance of gel associated fibrin from the anterior chamber. We propose that a failure of macrophage-mediated clearance of fibrin may be the cause of RCM formation after collagen-based hydrogel implants and that mesenchymal stem cell therapy promotes clearance of fibrin and prevents RCM formation. Statement of Significance The manuscript addresses the potential value of bone marrow-derived mesenchymal stem cell therapy for retro-corneal membrane (RCM) formation in full-thickness transplantation of biosynthetic corneal equivalents. This work reports the pathophysiological changes in the anterior chamber of the mouse eye following full-thickness recombinant human cross-linked collagen-based hydrogel implants in which persistent fibrin promotes the development of dense RCM. Furthermore, pre-treatment with mesenchymal stem cells reduces RCM formation and enhances corneal transparency. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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