This study was to evaluate the effect of hybrid microspheres (MS) composed of gelatin transforming growth factor-beta (TGF-β1)-loaded MS and chitosan MS on the enhancement of differentiation of adipose-derived stem cells (ASCs) into chondrocytes in pellet culture in vitro and the reparative capacity of pellet from ASCs and the hybrid MS-TGF used to repair cartilage defects in vivo.

The morphology of the controlled-released MS was observed with scanning electron microscopy (SEM) and mechanical property was also tested in this study. In vitro TGF-β1 release was evaluated by an enzyme-linked immunosorbent assay. The protein expression of Collagen II was tested by Western blot. In addition, a preliminary study on cartilage regeneration was also performed in vivo.

When chondrogenic differentiation of ASCs in both MS was evaluated, the protein expression of Collagen II became significantly increased for the hybrid MS-TGF, as compared with the gelatin MS-TGF. Mechanical result showed that the hybrid MS was superior to the gelatin MS. Observation of histology in vivo demonstrated that the pellet from ASCs and the hybrid MS-TGF promoted cartilage regeneration in the defects of articular cartilage much better than other groups.

Our study demonstrated that the pellet from ASCs and the hybrid MS-TGF can provide an easy and effective way to construct the tissue engineered cartilage in vitro and in vivo.