Aims: This study investigates the use of novel autologous bone marrow plugs as a biological ÒmatrixÒ to support transgene expression following genetic modiþcation in vitro, and to deliver gene vectors to cartilage defects in vivo. Methods: Adenoviral vectors encoding marker genes (luciferase, green ßuorescent protein (GFP)) and bioactive genes (TGF-?) as well as genetically modiþed mesenchymalstem cells were used to characterize an autologous delivery system using clots of bone marrow aspirates in vitro, and within rabbit osteochondral defects in vivo. Results: Bone marrow clots were able to support expression of luciferase and TGF-? transgenes for up to 21d. In addition incubation of bone marrow clots with rTGF-? demonstrated, that the clots have chondrogenic potential, as evidenced by type II collagen and proteogly-can staining. Bone marrow clots seeded with cells genetically modiþed to express luciferase were able to support transgene expression following implantation into rabbit osteochondral defects for up to 14 days. Implanted clots were able to remain within the defects without þxation, and considerable integration with surrounding tissue was observed after 3 days. The bone marrow clots were also able to effectively localize transgene expression within the defects without leakage to surrounding tissue. Conclusion: These results demonstrate that genetically modiþed bone marrow plugs can support persistent transgene expression in vitro and within osteochondral defects in vivo. They provide an effective delivery system with chondrogenic potential.

Aims: This in vitro study investigates the use of Collagen/PRP Hydrogels as a biological matrix for containing genetically modified human ACL cells, and supporting transgene expression. Methods: Adenoviral vectors encoding marker genes (green fluorescent protein (GFP)) and bioactive) where used to infect cultured human ACL cells?genes (TGF- ex vivo. The cells were seeded in Collagen/PRP Hydrogels and maintained in culture. To expression over time, ELISA was performed at days 4, 8, 15, 23,?measure TGFand 29. GFP positive cells within the gel were viewed by fluorescence microscopy at the same time points. After 29 days, the cultures were fixed, sectioned and various sections were stained with H& E, toluidine blue to detect proteoglycans and by immunhistocemistry for collagen type I and II. Results: Collagen/PRP Hydrogels were transgenes for up to 29 days.?able to support expression of GFP and TGF- expressing gel/cell constructs produced an abundant?Compared to controls, TGF- amount of type I collagen, consistent with the ligament phenotype and appeared more cellular. Little or no proteoglycan staining was observed in either group. Conclusion: These results demonstrate that genetically modified human ACL cells can support persistent transgene expression in vitro, sufficient to stimulate growth of ligamentlike tissue within a Collagen/PRP Hydrogel. The high levels of transgene expression suggest that the Collagen/PRP Hydrogel can function as an effective gene delivery system for tendon repair in vivo.