| Articular cartilage is a very resilient tissue; however, it has a very limited healing capacity after damage due to osteoarthritis or injury. The objective of this project is to determine the suitability of modified fibrin hydrogels as scaffolds for articular cartilage regeneration. The chondrogenic precursor cell line, RCJ 3.105.18 (C5.18), was initially chosen as a test system for evaluating the effect of fibrin gel encapsulation on articular chondrogenic differentiation. Fibrin-encapsulated C5.18 cells elaborated an ECM containing type II collagen and aggrecan and exhibited increases in collagen II and aggrecan gene expression. From these experiments, it was concluded that the fibrin hydrogel scaffold had potential for articular cartilage tissue engineering. To develop the system further towards a more implantable construct, fibrin gels, derived from commercially available human fibrinogen and thrombin, were seeded with primary human articular chondrocytes. The gels were stabilized with genipin, a naturally occurring cross-linker. Genipin cross-linking significantly increased hydrogel dynamic compression and shear moduli and led to enhanced accumulation of collagen II and aggrecan within the ECM secreted by the encapsulated chondrocytes after 5 weeks. Three weeks after subcutaneous implantation of acellular fibrin into Sprague-Dawley rats, less inflammation was observed with genipin cross-linking and when the material origin was allogeneic. As a result, it was necessary to identify an autologous source of fibrin in order to avoid the issues associated with disease transmission. The CryoSealRTM FS System was used, which can rapidly and reliably produce autologous fibrin glue from single units of plasma. Using the CryoSealRTM fibrin glue, we found that chondrocyte viability was >90%. Gene expression analysis revealed significant increases in collagen II and Sox9, and a significant decrease in collagen I, under hypoxic culture. When we compared fresh and frozen plasma-derived fibrin there was only a significant difference in mechanical properties after 7 weeks for the material derived from fresh plasma. This may be because greater amounts of collagen type I were detected in frozen compared to fresh plasma gels. Our results indicate that CryoSealRTM fibrin glue derived from fresh plasma shows potential for the development of an autologous human articular cartilage tissue engineering system. |
