STAT3 regulates leptin-induced BMP-2 mRNA in human primary chondrocytes.

(A) Cells were kept as controls or treated with leptin for 1, 4, 8, and 24 h, and the phosphorylations of STAT3 and STAT5 were determined by Western blot. (B-C) Cells were transfected with (B) ERK1- or ERK2-specific siRNA or (C) STAT3- or STAT5-specific siRNA and then kept as controls or treated with leptin for 4 h. (B) The phosphorylations of STAT3 and STAT5 were determined by Western blot and (C) the BMP-2 mRNA expression was determined by real-time PCR. (D) Cells were kept as controls or treated with leptin for 1, 4, and 8 h, and the STAT3-BMP-2 promoter binding activity was analyzed by chromatin immunoprecipitation and real-time PCR. Results in (A) and (B) are representative of three independent experiments with similar results. Data in (C) and (D) are mean ± SEM from three to four independent experiments. *, P < 0.05 vs. siCL/control or untreated cells. #, P < 0.05 vs. siCL/leptin-treated cells.