| 1. |
- Allardyce, Benjamin J., et al.
(författare)
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Comparative acoustic performance and mechanical properties of silk membranes for the repair of chronic tympanic membrane perforations
- 2016
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 64, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100 mu m) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative pressures in the middle ear. Part of this strength can be explained by the substantially higher modulus of silk films compared with cartilage. This allows for the production of films that are much thinner than cartilage, with superior acoustic properties, but that still provide the same level of mechanical support as thicker cartilage. Together, these in vitro results suggest that silk membranes may provide good hearing outcomes while offering similar levels of mechanical support to the reconstructed middle ear.
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| 2. |
- Liew, Lawrence J., et al.
(författare)
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Tympanic Membrane Derived Stem Cell-Like Cultures for Tissue Regeneration
- 2018
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Ingår i: Stem Cells and Development. - : Mary Ann Liebert Inc. - 1547-3287 .- 1557-8534. ; 27:10, s. 649-657
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Tidskriftsartikel (refereegranskat)abstract
- Epidermal cells with stem cell-like characteristics have been identified in the tympanic membrane (TM) and localized specifically to the umbo and annulus regions. While they have been proposed to play a role in the regeneration of both acute and chronic TM perforations, evidence for the mechanism and regulation of their contribution is not yet described. Indeed, the behavior of these putative stem cells is largely unknown, in part due to a lack of refined methods for efficient cell isolation. In this study, we compared different explant techniques using normal and perforated rat TM tissues and investigated their ex vivo characteristics. TM after perforation in vivo showed increased staining for epidermal stem cell markers integrin 1 and cytokeratin (CK) 19, and for proliferation Ki-67, indicating activation of the proliferative centers. A mixed population of fibroblasts and epithelial cells were isolated from explant cultures. Excised TM umbo implanted on a culture well insert was the most effective technique. Explants made from perforated TM produced cells before those from unperforated TM. More importantly, the implanted TM umbo organoid was capable of producing cells in a continuous manner, allowing subsequent harvest using trypsin. Primary rat TM epithelial cell cultures positive for pancytokeratin had colony forming activity and could be enriched for CK 19-positive cells that were capable of culture expansion by proliferation and cell migration when subject to a wound assay. Taken together, trauma to the TM activated the proliferative centers and prompted early cell production from TM umbo organoid cultures, which produced TM stem cell-like cultures that proved suitable for tissue engineering of the TM.
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| 3. |
- Ong, Huan Ting, et al.
(författare)
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Paracrine Activity from Adipose-Derived Stem Cells on In Vitro Wound Healing in Human Tympanic Membrane Keratinocytes
- 2017
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Ingår i: Stem Cells and Development. - : MARY ANN LIEBERT, INC. - 1547-3287 .- 1557-8534. ; 26:6, s. 405-418
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Tidskriftsartikel (refereegranskat)abstract
- Stem cell therapies for tympanic membrane repair have shown initial experimental success using mesenchymal stem cells in rat models to promote healing; however, the mechanisms providing this benefit are not known. We investigated in vitro the paracrine effects of human adipose-derived stem cells (ADSCs) on wound healing mechanisms for human tympanic membrane-derived keratinocytes (hTM) and immortalized human keratinocytes (HaCaT). ADSC conditioned media (CMADSC) were assessed for paracrine activity on keratinocyte proliferation and migration, with hypoxic conditions for ADSC culture used to generate contrasting effects on cytokine gene expression. Keratinocytes cultured in CMADSC showed a significant increase in cell number compared to serum-free cultures and further significant increases in hypoxic CMADSC. Assessment of ADSC gene expression on a cytokine array showed a range of wound healing cytokines expressed and under stringent hypoxic and serum-free conditions was upregulated (VEGF A, MMP9, Tissue Factor, PAI-1) or downregulated (CXCL5, CCL7, TNF-). Several of these may contribute to the activity of conditioned media on the keratinocytes with potential applications in TM perforation repair. VEGFA protein was confirmed by immunoassay to be increased in conditioned media. Together with gene regulation associated with hypoxia in ADSCs, this study has provided several strong leads for a stem cell-derived approach to TM wound healing.
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| 4. |
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| 5. |
- Wang, Allen Y., et al.
(författare)
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Rat model of chronic tympanic membrane perforation : A longitudinal histological evaluation of underlying mechanisms
- 2017
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Ingår i: International Journal of Pediatric Otorhinolaryngology. - : Elsevier BV. - 0165-5876 .- 1872-8464. ; 93, s. 88-96
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To evaluate histologically the progressive development and underlying mechanisms of chronic tympanic membrane perforation (TMP) in a rat model using a two-weeks ventilation tube (VT) treatment combined with topical application of mitomycin Cidexamethasone (VT-MID), compared with normal tympanic membrane and acute TMPs. Methods: Fifty male Sprague-Dawley rats were divided into three experimental groups: a normal control group (n = 5), an acute TMP group (n = 5) (i.e. 3 days post-myringotomy) and a VT-M/D group (n = 40). The TMs were regularly assessed by otoscopy. The normal control animals were sacrificed on day 0 and the acute TMP group was sacrificed 3 days post-myringotomy for histological and immunohistochemical evaluations. The VT-M/D group was sacrificed at various time points - 14 and 17 days, 3, 4, 6, 8 and 10 weeks. Results: On longitudinal histological examination, compared with normal TM and acute TMP, the perforation edges at the later time points illustrated thickened stratified squamous epithelium rimming around the edges, significant increase in keratin and collagen deposition, increased macrophage infiltration as well as reduced cellular proliferation. Three phases of TMP healing process were identified the acute healing phase (3-17 days), the transition phase (3-4 weeks) and the chronic phase (6-10 weeks). Conclusion: Based on the histological results of this study, the progressive development of chronic TMPs appeared to be associated with increased epidermal thickening, collagen and keratin deposition, macrophage infiltration and reduced cellular proliferation. After the 3-4 weeks of transition phase, the TMPs seemed to have transformed into a non-healing chronic TMP between 6 and 10 weeks. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
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| 6. |
- Wang, Allen Y., et al.
(författare)
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Rat model of chronic tympanic membrane perforation : Ventilation tube with mitomycin C and dexamethasone
- 2016
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Ingår i: International Journal of Pediatric Otorhinolaryngology. - : Elsevier BV. - 0165-5876 .- 1872-8464. ; 80:1, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Chronic tympanic membrane perforation (TMP) in a clinical setting may attract surgical intervention. With the advent of modern biomaterials, new options are available for myringoplasty but safety and efficacy need evaluation in a chronic TMP animal model. The aim of this study was to evaluate the efficacy of ventilation tube (VT) insertion in conjunction with topical application of mitomycin Cl dexamethasone (M/D) for the creation of chronic TMP in rats. Methods: Thirty male Sprague-Dawley rats underwent myringotomy of the right tympanic membrane (TM) and were divided into three experimental groups: spontaneous healing (myringotomy control), VT insertion for 2 weeks and VT insertion for 2 weeks in conjunction with topical application of M/D (VT-M/D). All TMs were regularly assessed by otoscopy for 10 weeks and then animals were sacrificed for histological evaluation. Results: In the VT-M/D group, seven out of ten (70%) perforations were patent at 10 weeks (mean patency, 57.9 days; P < 0.01). The VT group had two out of ten (20%) perforations patent at 10 weeks (mean patency, 26.5 days; P < 0.01), while all TMPs from the myringotomy control group were closed by day 9 (mean patency, 7.2 days). Histologically, the TMPs patent at week 10 had a stratified squamous epithelialized rim, keratinocyte layer thickening around the perforation edge as well as increased collagen deposition and macrophage infiltration. Conclusion: Chronic TMP in a rat model was successfully created by VT insertion and the efficacy was increased in combination with topical application of M/D.
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| 7. |
- Wang, Allen Y., et al.
(författare)
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Searching for a rat model of chronic tympanic membrane perforation : Healing delayed by mitomycin C/dexamethasone but not paper implantation or iterative myringotomy
- 2015
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Ingår i: International Journal of Pediatric Otorhinolaryngology. - : Elsevier BV. - 0165-5876 .- 1872-8464. ; 79:8, s. 1240-1247
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Surgical intervention such as myringoplasty or tympanoplasty is an option in the current clinical management of chronic tympanic membrane perforation (TMP). Animal models of chronic TMP are needed for pre-clinical testing of new materials and to improve existing techniques. We evaluated several reported animal model techniques from the literature for the creation of chronic TMPs. The aim of this study was to evaluate production of chronic TMPs in a rat model using topical mitomycin C/dexamethasone, paper insertion into middle ear cavity (MEC) or re-myringotomy. Methods: Forty male Sprague-Dawley rats underwent myringotomy of the right tympanic membrane (TM) and were randomly divided into 3 experimental groups: application of topical mitomycin C/dexamethasone, paper insertion into middle ear cavity, or re-myringotomy. Control perforations were allowed to close spontaneously. TMs were assessed regularly with otoscopy for 8 weeks. At the end of 8 weeks, animals were sacrificed for histology. Results: The closure of TMPs was significantly delayed by mitomycin C/dexamethasone (mean patency, 18.9 days; P <= 0.01) compared with the control (mean patency, 7 days), but was not significantly delayed in the paper insertion group (mean patency, 9.4 days; P = 0.74). Repeated myringotomy of closed perforations (mean number of myringotomies, 8.9 per ear) stimulated acceleration of closure rather than delay. Histologically, the mitomycin C/dexamethasone group had almost normal TM morphology, while the paper insertion group revealed inflammatory and granulomatous responses. The re-myringotomy group had a thickened TM fibrous layer with collagen deposition. Conclusions: Mitomycin C/dexamethasone delayed TMP closure in rats but the effect was not sufficiently long-lasting to be defined as a chronic TMP. Neither paper insertion into middle ear cavity nor re-myringotomy created chronic TMP in rats. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
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