Effect of growth factors on chondrogenic differentiation of rabbit mesenchymal cells embedded in injectable hydrogels

In this study, a hydrogel scaffold of poly(NiPAAm-co-AAc) was utilized as an injectable delivery carrier containing cell and growth factors for engineering of cartilage tissue. Rabbit mesenchymal cells (MCs) were embedded in composite hydrogels co-encapsulated with transforming growth factor beta-3 (TGF β-3), or basic fibroblast growth factor (bFGF). These hydrogel constructs were evaluated to determine the effects of growth factors on chondrogenic differentiation. To determine the optimal conditions for neocartilage formation, hydrogel scaffolds were assessed for glycosaminoglycan (GAG) content, DNA content, total collagen content, and reverse transcription-polymerase chain reaction (RT-PCR), and histological and immunohistochemical analyses were performed. Total collagen and GAG content were detected at their highest levels in the hydrogel scaffold with TGF β-3. RT-PCR analysis of the resultant cartilage tissue revealed that a hydrogel scaffold with a TGF β-3 was optimal for cartilage tissue formation, as determined via the production of collagen Type II, aggrecan, and SOX9, as well as cartilage oligomeric matrix protein (COMP) gene expression. Additionally, the proliferation rate and cartilage-specific ECM production were both significantly higher in the presence of TGF β-3 than in controls or bFGF. This shows that the dramatic increase in the number of cells for the samples with TGF β-3 was accompanied by the maintenance of the cell phenotypes. Collectively, these results reveal that growth factors in a hydrogel embedded with rMCs are potential candidate materials for the engineering of cartilage tissue.