From the article:
Our laboratory recently discovered that bone matrix is maintained by a protein called Sema3A, which is secreted by osteocytes. This led us to suspect that there might be a mechanistic relationship between estrogen and Sema3A."
Sema3A does indeed appear to be linked to estrogen: the researchers found that blood serum levels of the protein decrease in premenopausal women as they get older – and drop even further once women reach menopause. But how, at the biological level, are estrogen and Sema3A related? And what is Sema3A doing in bone tissue?
“When we genetically removed Sema3A from the osteoblast lineage cells (including osteocytes) of mice, we found that intravenous estrogen no longer prevented bones from deteriorating after an ovariectomy,” lead author Mikihito Hayashi describes. “In addition, we found that Sema3A sets off a chain of signaling events that promote the survival of osteocytes in these mice. This suggests that Sema3A serves as a key mechanistic link between estrogen and bone maintenance.