The Effects Of Simulated Microgravity On Spindle Structure In Osteoblastic Cells

The development of space industry promoted the growing up and improvement of aerospace medicine and space cellular biology. Recently the study of biological effects of microgravity, including the effects on cell morphology, cell cycle and cell apoptosis are focused.In the earlier study, our group found that the effects of microgravity could induce the change of microtubule and spindle structure, the arrest of cell cycle and the change of protein expression of spindle checkpoint in human osteosarcoma cells. In order to study the effect of microgravity in osteoblastic cells, we detected the effects of microgravity simulated by rotating wall vessel on microtubule, spindle structure, cell cycle and cell apoptosis in hFOB1.19 cells and rat primary osteoblastic cells.We cultured the osteoblastic cells from 24 hours to 96 hours, and then observed the abnormality of spindle structure which labeled byα-tubulin and photographed by laser scanning microscope. The results displayed that after 48-hour effect of microgravity the three-polar or four-polar spindle could be detected and after 72/96-hours effect of microgravity the five-polar or six-polar spindle can be detected in hFOB1.19 cells, and the incidence rate of multipolar spindle were 3.87%, 10.08%, 11.94%, 12.16% respectively; however after 96-hour effect of microgravity the three-polar spindle began to appear and the incidence rate of multipolar spindle kept in a low level in rat primary osteoblastic cells. Making use of flow cytometry to detect the change of cell cycle, the results showed that the cell number of S phase is obviously increased in hFOB1.19 cells, however after 72-hour effect of microgravity the cell number of G2/M phase was increased in rat primary osteoblastic cells. Simulated microgravity made the proportion of early apoptotic and late death cells increased in osteoblastic cells.The results showed that the effect of simulated microgravity induced disorganization of microtubule and growing in number of multipolar spindle. The effect of simulated microgravity also resulted in abnormity of cell division and cell cycle arrest. In addition, the extent of this damage was gradually increased along with prolongation of effect time of simulated microgravity in osteoblastic cells which demonstrated that cells was failed to repair themselves. Consequently, the number of apoptotic cells was increased.