The purpose of this paper is to investigate that the effect of cyclic biaxial mechanical strain on proliferation and synthetic function in the osteoblasts isolated from 3 month-old normal female Sprague-Dawley (SD) rats and osteoporotic rats. The osteoblasts were cultured in F-12 medium contained with 10% fetal bovine serum (FBC) and grown to subconfluency in Flexercell apparatus in a humidified incubator with 5% CO2 and 95% air at 37 degrees C. Mechanical strain was applied to the cells for periods of 30 min, 2, 4 and 8 hours every day,lasting 2 days. The amplitude of mechanical strain applied to the cells were 400, 1000 and 4000 microm strain respectively, at a frequency of one hertz (1 H). Unstrained cells were used as control. The results showed that proliferation activity of osteoblast in osteoporotic rats are higher than that in normal rats without mechanical strain the mechanical strain can elevate the proliferation activity and the synthetic function of osteoblast from normal rats at 400, 1000 microm strain. However, the mechanical strain increased significantly the proliferation in the osteoblasts and suppressed obviously the synthetic function in the osteoblasts at 4000 microm strain. The mechanical strain don't affect the proliferation activity and the synthetic function of osteoblast from osteoporotic rats at 400 microm strain. The mechanical strain decrease the proliferation activity of osteoblast from osteoporotic rats at 1000 microm strain. The mechanical strain can elevate the proliferation activity and the synthetic function of osteoblast from osteoporotic rats at 4000 microm strain. In our study, the reaction of the osteoblasts from normal rats and osteoporotic rats to the mechanical stimulation suggested that there are more highly sensitive to the mechanical stimulation in the osteoblasts from normal rats than that from osteoporotic rats.
Animals ; Apoptosis ; Cell Division ; Cell Separation ; Cells, Cultured ; Female ; Osteoblasts ; metabolism ; pathology ; Osteocalcin ; biosynthesis ; Osteoporosis ; pathology ; Rats ; Rats, Sprague-Dawley ; Stress, Mechanical