| The bone mass of astronauts may significantly decrease in space environment, due to the reduction of mechanical stimulation caused by loss of gravity. Researches on the mechanism of bone loss in models of microgravity report that the occurrence of osteoporosis in astronauts in space is closely related to intra-osteal vascular remodeling. In microgravity environment, the blood flow of the lower limbs significantly reduces, and blood pressure is lowered, resulting in the remodeling of intra-osteal vessels, reduction of vessel number and the constriction of vessel diameter, and the reduction of bone perfusion. The above mechanism affects the flow of interstitial fluid and the transfer of substances in bone lacuna-tubule. In this way, the microenvironment of osteocytes changes. Osteocytes, which serve as mechanoreceptor in bone tissue, regulate the activation of osteoblasts and osteoclasts under the regulation of interstitial shear stress. The balance of bone formation and resorption is destroyed and disused osteoporosis occurs. This paper reviews the recent studies on vascular remodeling and bone mass loss under microgravity. The relationship between them is clarified. This may provide help for the preventing and treating osteoporosis in the space environment. |