The presence of commensal microbiota—benign microorganisms that reside in the body—enhances the activity of osteoclasts, which are cells that break down bone tissue, and osteoblasts, which are cells that synthesize bone, according to Okayama University.
Researchers there worked with mice that were free of any microorganisms (germ-free, or GF) and mice that were free of certain pathogens but still host to commensal microbiota (specific pathogen-free, or SPF).
At eight weeks old, the SPF mice were larger than the GF mice but had lower mineral density in their alveolar bones, which the researchers attributed to the presence of commensal microbiota.
By analyzing the blood serum of the mice for substances associated with osteoclast activity, the researchers also concluded that commensal microbiota cause greater osteoclast development and activity.
Further, the researchers found that the expression of osteocalcin messenger RNA, which facilitates bone mineralization, is significantly higher in SPF mice, providing another link between commensal microbiota and bone-remodeling processes.
The precise mechanism of commensal microbiota affecting the expression of osteoblast-specific genes such as osteocalcin needs further investigation, the researchers said.
The researchers also noted that their results suggest the commensal microbiota prevents excessive mineralization possibly by stimulating osteocalcin expression in osteoblasts and enhances both osteoblast and osteoclast activity by regulating specific transcription factors.
The study, “Commensal Microbiota Enhance Both Osteoclast and Osteoblast Activities,” was published by Molecules.
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