Chondrogenic differentiation of human mesenchymal stem cells: a comparison between micromass and pellet culture systems.

High-density cell culture is pivotal for the chondrogenic differentiation of human mesenchymal stem cells (hMSCs). Two high-density cell culture systems, micromass and pellet culture, have been used to induce chondrogenic differentiation of hMSCs. In micromass culture, the induced-cartilage tissues were larger, more homogenous and enriched in cartilage-specific collagen II but the fibrocartilage-like feature, collagen I, and hypertrophic chondrocyte feature, collagen X, were markedly decreased compared to those in pellet culture. Furthermore, real time RT-PCR analysis demonstrated that collagen II and aggrecan mRNA were up-regulated while collagen X and collagen I mRNA were down-regulated in micromass culture. Thus, the micromass culture system is a promising tool for in vitro chondrogenic studies.