Adenoviral-mediated transfer of TGF-β1 but not IGF-1 induces chondrogenic differentiation of human mesenchymal stem cells in pellet cultures

Objective. The objective of the present study was to investigate the potential of application of growth factor genes to induce chondrogenic differentiation of human-derived mesenchymal stem cells (MSCs). The growth factor genes evaluated in the present study were transforming growth factor 1 (TGF-β1) and insulin-like growth factor 1 (IGF-1). Methods. Human MSCs were transduced with the adenoviral vectors carrying either TGF-β1 or IGF-1 (AdTGF-β1 and AdIGF-1 respectively) or a combination of both growth factor genes at different multiplicities of infection (MOI) and were then made into pellets. Pellets were also made from nontransduced cells and maintained in culture medium supplemented with 10 ng/mL of TGF-β1. At specified time points, histological analysis, cartilage matrix gene expression, and immunofluorescence were performed to determine the extent of chondrogenic differentiation. Results. MSCs transduced with the AdTGF-β1 demonstrated robust chondrogenic differentiation, while those made from AdIGF-1 did not. AdTGF-β1 pellets demonstrated aggrecan gene expression as early as day 3 of pellet culture, while type II collagen gene expression was detected by day 10 of culture. The AdIGF-1, alone or in combination with TGF-β1 pellets, did not show any type II collagen gene expression at any time point. By immunofluoresecence, type X collagen was distributed throughout the matrix in TGF-β1 protein pellets while the growth factor gene pellets displayed scant staining. Conclusion. The results suggest that sustained administration of TGF-β1 may be more effective in suppressing terminal differentiation than intermittent dosing and thus effective for cartilage repair.