The changes of bone vessels and their role in bone loss in tail-suspended rats

Bone loss is one of the highest risk factors during long spaceflight for astronauts which can lead to health problems and increase fracture risk, but the mechanisms are still unclear. Bone is highly vascularized tissue, the vascular system in bone plays an important role in the development, regeneration and remodeling of bone. However, little is known about how the blood vessels in bones change and its effect on microgravity-induced osteoporosis, we investigated the above issues with tail-suspended rat model in this study. The result showed that the blood vessel volume and vessel number in long bones increased and H-type blood vessels (CD31^hiEmcn^hi vessels) reduced; moreover, exercise could alleviate the decrease of H-type blood vessels and osteogenesis in tail-suspended rats. These results revealed that changes of bone blood vessels may be a main reason for microgravity-induced bone mass rapid loss.