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Gut microbiota influences bone mass



DOI:10.1038/bonekey.2012.127

Sjögren and colleagues used peripheral quantitative computed tomography to show that mice raised in a germ-free environment developed increased trabecular volumetric bone mineral density (277±14 mg/cm3) at seven and nine weeks, compared with conventionally raised mice (208±10 mg/cm3; P0.01). Trabecular number was increased while trabecular separation was decreased. Further investigations showed that the germ-free mice had lower levels of CD4+ T-cells, fewer CD11b+/GR 1-osteoclast precursor cells and reduced expression of tumor necrosis factor alpha in their bone and bone marrow. All cells and markers returned to normal levels after recolonization of the gut.

The authors conclude that the increase in bone mass was affected by the lower levels of CD4+ T-cells in the circulation and in bone marrow, showing for the first time that the gut microbiota directly includes the immune system and osteoclastogenesis.

Editor's comment: The intriguing relationship between the gut microbiota, the immune system and the bone marrow is investigated in this study in which a complete absence of gut microbiota is shown to result in significantly increased bone mass in mice. It reveals that post-natal bone remodeling is partly mediated by the latent inflammatory state induced by our gut microbiota. These results could have interesting implications for osteoporosis therapy.


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