Autoregulation of Osteocyte Sema3A Orchestrates Estrogen Action and Counteracts Bone Aging

Cell Metab. 2019 Mar 5;29(3):627-637.e5. doi: 10.1016/j.cmet.2018.12.021. Epub 2019 Jan 17.

Abstract

Osteocyte survival is key to bone homeostasis and is perturbed in menopause and aging. However, it remains unknown how osteocyte-mediated maintenance of the skeleton is regulated by the osteoprotective factor semaphorin 3A (Sema3A), a secreted protein that is known to reduce bone resorption and enhance bone formation. Here, we show that estrogen induces osteocyte expression of Sema3A, which acts on its receptor on osteocytes to promote their survival and maintain bone homeostasis. Postnatal global and conditional deletion of Sema3a in osteoblastic cells resulted in a severe osteoporotic phenotype marked by fewer osteocytes. This phenotype was recapitulated by osteocyte-specific deficiency of either Sema3A or its receptor component neuropilin-1 (Nrp1). A stimulator of soluble guanylate cyclase-cGMP signaling mimicked Sema3A action and ameliorated bone loss after ovariectomy. We further show that serum levels of SEMA3A decreased with age or after menopause in humans. Thus, we provide a mechanistic insight into the estrogen action and a promising therapeutic approach to protect against bone-related aging.

Keywords: Sema3A; bone aging; osteocyte.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / metabolism*
  • Animals
  • Bone Resorption / metabolism
  • Estrogens / metabolism*
  • Female
  • HEK293 Cells
  • Humans
  • Menopause / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Middle Aged
  • Neuropilin-1 / metabolism
  • Osteocytes / cytology
  • Osteocytes / metabolism*
  • Osteogenesis / physiology
  • Semaphorin-3A / physiology*

Substances

  • CD304 antigen, human
  • Estrogens
  • SEMA3A protein, human
  • Sema3a protein, mouse
  • Semaphorin-3A
  • Neuropilin-1