| Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. Osteoporosis is a major public health issue because of its association with fragility fractures. The benefits of physical exercise and fitness have long been understood. In addition to medical treatment, another strong factor in the prevention of osteoporosis is exercise. Several studies have shown that exercise and increased activity lowers the risk of osteoporosis and helps maintain bone mineral density in women who are postmenopausal. Mechanical loading can inhibit bone resorption and increase bone formation in vivo. Bone cells can transduce mechanical signals into anabolic biochemical responses. However, the mechanisms of mechanotransduction are unknown. The purpose of this paper is to investigate that the effect of cyclic biaxial mechanical strain on proliferation and synthetic function of bone matrix and that the effect of cyclic biaxial mechanical strain on the expression of integrin α2,β1,β3 on the membrane of osteoblasts in the osteoblasts isolated from 3 month-old and 6 month-old normal female Sprague-Dawley (SD) rats and osteoporotic rats. We established animal model of osteoporosis in 3 old- months and 6old-months female Sprague-Dawley rats(SD) with ovariectomy. Animals were divided into 4 groups: 3control group,3ovx group,6control group and 6ovx group. Osteoblasts were isolated from rats in every group, respectively . The osteoblasts were cultured in F-12 medium contained The Effect of Mechanical Stimulation on Osteoblaste from Osteoporotic Rats——— Li Liangwith10% fetal bovine serum(FBC) and grown to subconfluency in Flexercell apparatus in a humidified incubator with 5% CO2 and 95% air at 37℃. Flexercell apparatus can provides an essentially uniform strain field for cells attached on silastic membrane. Mechanical strain was applied to the cells for periods of 30min, 2,4 and 8 hours every day,lasting 2 days. The amplitude of mechanical strain applied to the cells were 400,1 000 and 4 000 μ strain, respectively , at a frequency of one hertz(1 H). Unstrained cells were used as control. The expression of integrin α2,β1,β3 on the membrane of osteoblasts and proliferation activity of the osteoblasts were studied with Flow Cytometry(FCM). The content of osteocalcin,carboxyterminal propeptide of type-I procollage(PICP),total protein secreted by osteoblasts were detected with the isotope labelling method. The change of cytoskeletal architecture of osteoblasts with Phalloidin strain actin filaments was visualized by confocal microscopy The results showed: 1) the secretion of estrogen were depressed and bone mass were decressed and biomechanic properties of bone were impaired in osteoporotic rats at 3 months after ovariectomy .The characters of osteoporosis in these rats are higher bone turnover rate resembling with women post-menopause osteoporosis.2) that there are some expression of integrin α2,β1,β3 on the membrane of osteoblasts in every group without mechanical strain and the expression of integrin β1 is highest in every group. The expression of integrin α2,β1 of osteoblasts in 6ovx group are lower than that of osteoblasts in other groups. There are not obvious difference in the expression of integrinα2,β1,β3 among other groups. 3)The proliferation activities of osteoblasts are higher in 3ovx group and 6ovx group than that in normal rats without mechanical strain. 4) the osteoblasts in 3control group are most sensitive to mechanical stimulation in our experiment. The mechanical strain induces the up-regulation of expression of integrin α2,β1,β3 on the membrane of osteoblasts from 3control group and promoted prolifration and differentiation of osteoblasts from 3control group at 400μstrain. The expression of integrin α2,β1,β3 and Doctorship Thesis of Sichuan University------Abstractsynthesize function of bone matrix in osteobla...
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