Biopolymer-Based Hydrogel Carriers as Multifunctional Delivery System in Corneal Endothelial Cell Sheet Engineering

• Main Authors: Pei-Lin Lu, 盧佩琳
• Other Authors: Ging-Ho Hsiue
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/61945481128087403007

博士 === 國立清華大學 === 化學工程學系 === 95 === Human corneal endothelium in vivo demonstrates an age-related decrease in cell density and cannot be compensated due to its limited regenerative capacity. When the cell density is less than a critical level of 1000 cells/mm2, the endothelial monolayer no longer functions, causing corneal edema and loss of visual acuity. Penetrating keratoplasty (PK) is currently the common way to treat corneas that are opacified due to endothelial dysfunction. However, insufficient supplies of donor corneas and several complications associated with PK remain a worldwide problem. Therefore, transplantation of tissue-engineered human corneal endothelial cell (HCEC) sheets to replace damaged corneal endothelium alone is a promising alternative to PK. This work is devoted to overcome the limitations of cell sheet transplantation. Because of the soft and fragile nature of bioengineered HCEC sheets, we have designed and developed a multifunctional hydrogel carrier system for intraocular delivery of these sheet grafts. The functionality of gamma-sterilized cell carriers made from raw gelatins with a different isoelectric point (IEP = 5.0 and 9.0) and a molecular weight (MW) range from 3 to 100 kDa, was investigated by the determination of mechanical properties, water content, dissolution degree, and cytocompatibility. The results of our study indicate that the gamma-sterilized hydrogel discs consisting of raw gelatins (IEP = 5.0, MW = 100 kDa) are promising candidates as cell sheet carriers for effective corneal endothelial cell transplantation and therapy. Development of alternative biomaterials to bovine-based gelatin vehicles can potentially eliminate the risk of bovine spongiform encephalopathy. To investigate whether it was appropriate for use as cell sheet delivery vehicles, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) cross-linked hyaluronic acid (HA) hydrogels were studied by determinations of morphological characteristic, mechanical and thermal property, water content, in vitro degradability, and cytocompatibility. Glutaraldehyde (GTA) cross-linked HA samples were used for comparison. It is concluded that EDC can be successfully applied for HA cross-linking to fabricate structurally stable, mechanically reinforced, readily deformable, transparent, and cytocompatible HA hydrogel discs with the potential to be applied as delivery vehicles for corneal endothelial cell therapy. On the other hand, intraocular implantation in the anterior chamber has received much attention for the determination of the interactions between the immune privileged tissues and biomaterial implants. A novel methodology based on the anterior chamber of rabbit eyes model was developed to evaluate the in vivo biocompatibility of biomaterials in an immune privileged site. The 7-mm-diameter membrane implants made from either a biological tissue material (amniotic membrane, AM group) or a biomedical polymeric material (gelatin, GM group) were inserted in rabbit anterior chamber for 36 months and characterized by biomicroscopic examinations, intraocular pressure measurements, and corneal thickness measurements. The noninvasive ophthalmic parameters were scored to provide a quantitative grading system. Our data suggest that the anterior chamber of rabbit eyes model is an efficient method for noninvasively determining the immune privileged tissue/biomaterial interactions. In the present study, we have demonstrated that the multifunctional carrier system is beneficial for transportation and surgical handling of bioengineered human corneal endothelium. Cell sheet transplantation with biopolymer-based hydrogels can potentially offer a new therapeutic strategy for corneal endothelial cell loss. In addition, a novel methodology based on the anterior chamber of rabbit eyes model has great potential for evaluating the ocular biocompatibility and safety of biomaterial carriers. We hope this work will lead to insights into cell sheet-based therapy for ocular regenerative medicine and will open an exciting new door to the future.