TGF-?1, GDF-5, and BMP-2 stimulation induces chondrogenesis in expanded human articular chondrocytes and marrow-derived stromal cells.
Replacement of degenerated cartilage with cell-based cartilage products may offer a long-term solution to halt arthritis' degenerative progression. Chondrocytes are frequently employed in cell-based FDA-approved cartilage products, yet human marrow-derived stromal cells (hMSCs) show significant translational potential, reducing donor site morbidity and maintaining their undifferentiated phenotype with expansion. This study sought to investigate the effects of transforming growth factor ?1 (TGF-?1), growth/differentiation factor 5 (GDF-5), and bone morphogenetic protein 2 (BMP-2) during post-expansion chondrogenesis in human articular chondrocytes (hACs) and to compare chondrogenesis in passaged hACs with that of passaged hMSCs. Through serial expansion, chondrocytes dedifferentiated, decreasing expression of chondrogenic genes while increasing expression of fibroblastic genes. However, following expansion, 10 ng/mL TGF-?1, 100 ng/mL GDF-5, or 100 ng/mL BMP-2 supplementation during three-dimensional aggregate culture each upregulated one or more markers of chondrogenic gene expression in both hACs and hMSCs. Additionally, in both cell types, the combination of TGF-?1, GDF-5, and BMP-2 induced the greatest upregulation of chondrogenic genes, i.e., Col2A1, Col2A1/Col1A1 ratio, SOX9, and ACAN, and synthesis of cartilage-specific matrix, i.e., glycosaminoglycans (GAGs) and ratio of collagen II/I. Finally, TGF-?1, GDF-5, and BMP-2 stimulation yielded mechanically robust cartilage rich in collagen II and GAGs in both cell types, following 4 wks maturation. The present study illustrates notable success in employing the self-assembling method to generate robust, scaffold-free neocartilage constructs using expanded human ACs and MSCs. Stem Cells 2014.