[Effects of microgravity on the gene expression and cellular functions of osteoblasts].

Skeleton system may adapt to multiform mechanical stimulus including gravity so as to modulate the balance between bone formation and absorption. Osteopenia under microgravity is mainly due to decrease of bone formation which relates closely to the low level of osteoblast activity. The proliferation and adhesive ability of osteoblast are reduced. The cells also express less messenger and protein of the differentiation and maturation-related substances, such as alkaline phosphatase, osteocalcin and type I collagen. The secretion of many growth factors is decreased and osteoblast responses less to them. It still remains unknown why the osteoblast is disfunctioned under microgravity. A hypothesis suggests the cellular shape changes may be the answer.