Gelatin-based resorbable sponge as a carrier matrix for human mesenchymal stem cells in cartilage regeneration therapy

Adult mesenchymal stem cells (MSCs), found in the bone marrow, have the potential to differentiate into multiple connective tissue types, including cartilage. In this study, we examined the potential of a porous gelatin sponge, Gelfoam, for use as a delivery vehicle for MSCs in cartilage regeneration therapy. Adult human MSCs (hMSCs) were seeded throughout the gelatin sponge after a 2-h incubation period. When cultured for 21 days in vitro in a defined medium supplemented with 10 ng/mL of TGF-beta 3, hMSC/Gelfoam constructs produced a cartilage-like extracellular matrix containing sulfated glycosaminoglycans (s-GAGs) and type-II collagen, as evident upon histologic evaluation. Constructs loaded with a cell suspension of 12 x 10(6) cells/mL produced an extracellular matrix containing 21 microg of s-GAG/microg of DNA after 21 days of culture. This production was more efficient than constructs loaded at higher or lower cell densities, indicating that the initial seeding density influences the ability of cells to produce extracellular matrix. When implanted in an osteochondral defect in the rabbit femoral condyle, Gelfoam cylinders were observed to be very biocompatible, with no evidence of immune response or lymphocytic infiltration at the site. Based on these observations we conclude that Gelfoam resorbable gelatin sponge is a promising candidate as a carrier matrix for MSC-based cartilage regeneration therapies.