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The capillary within bone that couples osteogenesis and angiogenesis

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DOI:10.1038/bonekey.2014.84

Kusumbe et al. investigated the coupling mechanism that links osteogenesis with the growth of blood vessels within bone.

Using immunohistochemistry, they showed that the vascular network focuses blood containing high levels of oxygen and nutrients preferentially into capillaries near the growth plate of bone. Immunostaining also revealed that the progenitor cells responsible for producing new osteocytes and osteoblasts aligned themselves along a capillary subtype named type H. These are small and express both CD31 and endomucin (Emcn). Interestingly, studies in ageing mice revealed that type H endothelium decreases significantly as a result of ageing.

The authors propose that type H endothelial cells support perivascular osteoprogenitor cells and promote the local growth of new blood vessels.

Editor’s comment: The authors identify a new capillary subtype, CD31-high Emcn-high type H cells, in the murine skeletal system, which couple angiogenesis to osteogenesis. HIF-1a plays a key role in inducing type H cells, and aging enhances degradation of HIF-1a and reduces type H cells. Because prolyl-4-hydroxylase inhibitors protect HIF-1a from degradation and increase type H cells, this approach may offer novel therapeutic strategies for aging-induced bone loss.

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