TGF-β3-induced chondrogenesis in co-cultures of chondrocytes and mesenchymal stem cells on biodegradable scaffolds

In this work, it was hypothesized that co-cultures of articular chondrocytes (ACs) and mesenchymal stem cells (MSCs) would exhibit enhanced sensitivity to chondrogenic stimuli, such as TGF-β3, and would require a reduced concentration of TGF-β3 to achieve an equivalent level of chondrogenesis compared to monocultures of each cell type. Furthermore, it was hypothesized that compared to monocultures, the chondrogenic phenotype of AC/MSC co-cultures would be more stable upon the removal of TGF-β3 from the culture medium. These hypotheses were investigated by culturing ACs and MSCs alone and in a 1:3 ratio on electrospun poly(ɛ-caprolactone) scaffolds. All cell populations were cultured for two weeks with 0, 1, 3, or 10 ng/ml of TGF-β3. After two weeks growth factor supplementation was removed, and the constructs were cultured for two additional weeks. Cell proliferation, extracellular matrix production, and chondrogenic gene expression were evaluated after two and four weeks. The results demonstrated that co-cultures of ACs and MSCs require a reduced concentration and duration of TGF-β3 exposure to achieve an equivalent level of chondrogenesis compared to AC or MSC monocultures. Thus, the present work implicates that the promise of co-cultures for cartilage engineering is enhanced by their robust phenotype and heightened sensitivity to TGF-β3.