BMI1 and bone disorder: As a systemic skeletal disease, SOP occurs mainly due to a reduction in bone formation caused by two factors: 1) decrease in the number of BMSCs and 2) less differentiation of BMSCs into osteoblasts and more into adipocytes.[31] The present study found that mice with Prx1‐driven Bmi‐1 conditional knockout showed the SOP phenotype, including reduced bone mass and increased bone marrow adiposity in vivo, and decreased proliferation and osteogenic differentiation and increased adipogenic differentiation of BMSCs in vitro.