MBD2 and osteoporosis: Previously, our lab investigated a novel epigenetic regulatory role of histone lysine demethylase 4B (KDM4B), a histone 3 lysine 9 trimethylation (H3K9me3) demethylase, in skeletal aging and osteoporosis.3 Ablation of KDM4B in MSCs promotes cellular senescence and adipogenesis, while inhibiting osteogenesis, suggesting suppression of H3K9me3 may be essential to prevent skeletal aging, MSC exhaustion, and osteoporosis.3 However, our previous studies were mainly focused on long bones supporting the vertebrate limb and MSCs isolated from the bone marrow of these bones.