beta 1 integrins play a controversial role during chondrogenesis. Since the maturation of chondrocytes relies on a signaling switch from cell-cell to cell-matrix interactions, we hypothesized that beta 1 integrins play a different role at the earlier (mainly cell-cell interaction) from the later stage (mainly cell-matrix interaction) of chondrogenesis. Our data showed: in plain medium, sox9, collagen X, and collagen II gene expressions of ASCs were induced by beta 1-integrin blockage at day 14. In chondrogenic medium, however, sox 9, sox6, and collagen II gene expression were induced at day 4 but inhibited at day 14. In addition, both beta 1-integrin blockage and TGF-beta 1 down-regulated Rock-1 and -2 gene expression and produced the round cells. We concluded that 131 integrins play a more important role at the later stages than earlier stages of chondrogenesis, and that the onset of chondrogenesis promoted by beta 1-integrin blockage might be through inhibiting Rock signaling. (C) 2008 Elsevier Inc. All rights reserved.