Figure 1. Celastrol promoted the osteogenic differentiation of BM-MSCs in vitro. (A) BM-MSCs were seeded into 96-well plates at a density of 8×103 cells/well and treated with different concentrations of Celastrol for 48 h. Cell viability was determined using CCK-8 assay. (B, C) Representative images of Alizarin Red S staining (B) and quantitative analysis (C) of matrix mineralization of BM-MSCs cultured in the osteogenesis induction medium for 21 days. Scale bar: 100 μm. (D, E) Analysis of ALP activity (D) and osteocalcin secretion (E) of BM-MSCs cultured in the osteogenesis induction medium for 48 hours (n = 3 per group). (F) qRT-PCR analysis of the relative levels of Osterix and Runx2 mRNA expression in BM-MSCs cultured in the osteogenesis induction medium for 48 hours (n = 3 per group). Results are shown as mean ± SD. Statistical significance was determined using analysis of variance (one-way ANOVA). *P < 0.0001 compared with control.