Figure 5

Regulation of chondrocyte hypertrophic differentiation by Runx1 and Bapx1. (a) Levels of Col10a1 mRNA levels in primary chondrocytes adenovirally transfected with GFP, Runx1 or Bapx1 after 5 days of culture. Data are expressed as means (bars) ± s.d. (error bars) of three samples per group *P < 0.01. (b) Levels of Bapx1 and Col10a1 mRNA in primary chondrocytes lentivirally transfected with shRNAs against Bapx1(L-siBapx1) or control (L-siControl). Data are expressed as means (bars) ± s.d. (error bars) of three samples per group *P < 0.01. (c) Levels of Col10a1 mRNA in primary articular chondrocytes adenovirally transfected with GFP or Runx1, and lentivirally transfected with L-siBapx1 or L-siControl. Data are expressed as means (bars) ± SD (error bars) of three samples per group *P < 0.01. (d) Schematic of proposed mechanism for inhibitory effects of Runx1 against OA development. Runx1 induces Col2a1 expression via direct binding to its 5′-flanking region and in cooperation with Sox5, Sox6, and Sox9. Runx1 suppresses hypertrophic differentiation through induction of Bapx1.