XBP1s overexpression in BMSCs induces RANKL secretion and OCL formation. (A) Real-time PCR demonstrating the effects of overexpression of Flag-hXBP1s on gene expression of RANKL and OPG in KM101 cells with or without TNFα treatment (n = 3; mean ± SD; *P < .05). (B) Effects of overexpression of Flag-hXBP1s on the baseline and TNFα-induced sRANKL protein expression in both the conditioned medium and total cell lysates of KM101 cells as determined by anti-RANKL Western blot analysis. (C) Effects of overexpression of Flag-hXBP1s on the capacity of healthy donor BMSCs to support OCL formation. The healthy donor BMSCs with or without Flag-hXBP1s overexpression were cocultured with hBMMs for 21 days. The number of TRAP-positive multinucleated cells was calculated (n = 3; mean ± SD; *P < .05). (D) Effects of overexpression of Flag-hXBP1s on the capacity of mBMSCs to support OCL formation. The mBMSCs with or without Flag-hXBP1s overexpression were cocultured with mBMMs for 12 days (n = 3; mean ± SD; *P < .05).