STAT3 regulates osteogenesis, making it critical for skeletal development and bone homeostasis

Skeletal deformities are typical clinical manifestations of autosomal dominant hyper-immunoglobulin E syndrome (AD-HIES), but the treatment is still limited. AD-HIES is mainly caused by dominant-negative mutations in signal transducer and activator of transcription 3 (STAT3). Clarifying the mechanisms by which STAT3 inactivation destructs bone metabolism is, therefore, important. Although, a few lines of data indicate osteoporosis induced by STAT3 inactivation may be related to increased osteoclast activity, here, we firstly report that deletion of Stat3 in osteoblasts, but not in osteoclasts, induced AD-HIES-like bone defects, including craniofacial malformation, osteoporosis, and spontaneous bone fracture in mice, and these defects were resulted from impaired osteogenesis induced by STAT3 inactivation in osteoblasts, but not increased osteoclast activity. Mechanistic analysis revealed a novel regulatory model in which STAT3 drove osteoblast differentiation via promoting distal-less homeobox 5 transcription in cooperation with MSX1. Furthermore, inducible deletion of Stat3 in osteoblasts also inhibited osteogenesis and induced bone loss in adult mice. Meaningfully, pharmacological inhibition of STAT3 induced bone loss, while activation of STAT3 partially prevent bone loss due to tail sus-pension. Taken together, STAT3 is critical for both modulating skeletal development and maintaining bone homeostasis, and inactivation of STAT3 in osteoblasts, but not in osteoclasts, induced AD-HIES-related skeletal deformities by impairing osteogenesis, providing new insights for their treatment. To analyze the effects of deleting Stat3 in osteoblasts on global gene expression patterns, we performed RNA-seq with total RNA extracted from the calvarias of newborn OsxCre;Stat3fl/fl and OsxCre littermates.