The objective of this study was to evaluate the proliferation and chondrogenic differentiation of rat bone marrow-derived mesenchymal stem cells (MSCs) cultured with gelatin hydrogel microspheres of cell scaffold which can release transforming growth factor-beta 1 (TGF-beta 1). Gelatin was dehydrothermally cross-linked in different conditions in a water-in-oil emulsion state to obtain gelatin hydrogel microspheres with different water content. The microspheres functioned not only as the scaffold of MSC, but also the carrier matrix of TGF-beta 1 release. The MSC proliferation depended on the water content of microspheres. Higher MSC proliferation was observed for the gelatin microspheres with lower water content. When cultured with the gelatin hydrogel microspheres, MSC formed their aggregates, in contrast to culturing with hydrogel sheets. The cell viability was significantly high compared with that of the hydrogel sheet. The production of sulfated glycosaminaglycan (sGAG) from MSC was examined as a measure of chondrogenic differentiation, after their culturing in a normal and chondrogenic differentiation media. For both the cultures, the amount of sGAG produced was significantly higher for MSC cultured with the gelatin microspheres than that of the gelatin sheet. Stronger differentiation of MSC was achieved in culture with the microspheres incorporating TGF-beta 1 than that of MSC cultured in the medium containing the same amount of TGF-beta 1. It is concluded that the gelatin hydrogel microspheres function well as both the scaffold of MSC and the matrix of TGF-beta 1 release, resulting in enhanced MSC aggregation and the consequent promotion of cell proliferation and differentiation. (C) Koninklijke Brill NV, Leiden, 2010