Chondrogenesis of rabbit mesenchymal stem cells in fibrin/hyaluronan composite scaffold in vitro

Scaffold material is expected to play a crucial role in induction of chondrogenic differentiation of mesenchymal stem cells (MSCs) for cartilage tissue engineering. Here we demonstrated the feasibility of a fibrin/hyaluronan (HA) composite hydrogel as a potent scaffold for support of chondrogenesis of rabbit MSCs (rMSCs). rMSCs were prepared in three-dimensional cultures of pellet, alginate layer, and fibrin/HA gel. Specimens in each group were cultured in chondrogenic defined media for 4 weeks in the absence or presence of transforming growth factor β1 (TGF-β1) treatment. Viability of rMSCs was somewhat reduced until 4 weeks, which was less significant in fibrin/HA gels than in the alginate layer (*p < 0.05). The fibrin/HA group showed transient size reduction by about 35% at 1 week, but showed significantly higher mechanical strength than the alginate group. In safranin-O and alcian blue stains, accumulation of sulfated glycosaminoglycans (GAGs) was observed clearly from 1 week, and homogenously in the entire area at 4 weeks in the fibrin/HA group. Of note, TGF-β1 treatment showed no additional effect on GAGs accumulation in the fibrin/HA group. The alginate and pellet groups, however, showed much lower levels of GAGs accumulation only in the presence of TGF-β1. Biochemical assays for GAGs and collagen, and expression of chondrogenic markers also showed much better results in the fibrin/HA group, even without TGF-β treatment than the other groups. These results demonstrated that fibrin/HA composite gel efficiently promoted chondrogenic differentiation of rMSCs, even without TGF-β treatment, and that it could be a useful tool for use in cartilage tissue engineering.