Hughes-Fulford M, Lewis M L
Laboratory of Cell Growth and Differentiation, Department of Veterans Affairs, San Francisco, California, 94121, USA.
Exp Cell Res. 1996 Apr 10;224(1):103-9. doi: 10.1006/excr.1996.0116.
Space flight is an environmental condition where astronauts can lose up to 19% of weight-bearing bone during long duration missions. We used the MC3T3-E1 osteoblast to investigate bone cell growth in microgravity (10(-6) to 10(-9)g). Osteoblasts were launched on the STS-56 shuttle flight in a quiescent state with 0.5% fetal calf serum (FCS) medium and growth activation was initiated by adding fresh medium with 10% FCS during microgravity exposure. Four days after serum activation, the cells were fixed before return to normal Earth gravity. Ground controls were treated in parallel with the flight samples in identical equipment. On landing, cell number, cell cytoskeleton, glucose utilization, and prostaglandin synthesis in flight (n = 4) and ground controls (n = 4) were examined. The flown osteoblasts grew slowly in microgravity with total cell number significantly reduced (55 +/- 6 vs 141 +/- 8 cells per microscopic field). The cytoskeleton of the flight osteoblasts had a reduced number of stress fibers and a unique abnormal morphology. Nuclei in the ground controls were large and round with punctate Hoechst staining of the DNA nucleosomes. The flight nuclei were 30% smaller than the controls (P < 0.0001) and oblong in shape, with fewer punctate areas. Due to their reduced numbers, the cells activated in microgravity used significantly less glucose than ground controls (80.2 +/- 0.7 vs 50.3 +/- 3.7 mg of glucose/dl remaining in the medium) and had reduced prostaglandin E2 (PGE2) synthesis when compared to controls (57.3 +/- 17 vs 138.3 +/- 41 pmol/ml). Cell viability was normal since, on a per-cell basis, glucose use and prostaglandin synthesis were comparable for flight and ground samples. Taken together, these data suggest that growth activation in microgravity results in reduced growth, causing reduced glucose utilization and reduced prostaglandin synthesis, with significantly altered actin cytoskeleton in osteoblasts.
太空飞行是一种环境条件，在长期任务中，宇航员可能会损失高达19%的负重骨骼。我们使用MC3T3-E1成骨细胞来研究微重力环境（10^(-6)至10^(-9)g）下的骨细胞生长情况。成骨细胞在STS-56航天飞机飞行中以0.5%胎牛血清（FCS）培养基处于静止状态发射，在微重力暴露期间通过添加含10%FCS的新鲜培养基启动生长激活。血清激活4天后，细胞在返回正常地球重力之前进行固定。地面对照组在相同设备中与飞行样本平行处理。着陆后，检查飞行组（n = 4）和地面对照组（n = 4）的细胞数量、细胞细胞骨架、葡萄糖利用和前列腺素合成情况。在微重力环境下，飞行的成骨细胞生长缓慢，总细胞数量显著减少（每个显微镜视野55±6个细胞对141±8个细胞）。飞行成骨细胞的细胞骨架应力纤维数量减少，形态独特且异常。地面对照组的细胞核大且呈圆形，DNA核小体有散在的Hoechst染色。飞行组的细胞核比对照组小30%（P < 0.0001），呈椭圆形，散在区域较少。由于数量减少，在微重力环境下激活的细胞消耗的葡萄糖明显少于地面对照组（培养基中剩余葡萄糖80.2±0.7mg/dl对50.3±3.7mg/dl），与对照组相比前列腺素E2（PGE2）合成减少（57.3±17pmol/ml对138.3±41pmol/ml）。细胞活力正常，因为基于单个细胞，飞行组和地面组样本的葡萄糖利用和前列腺素合成相当。综上所述，这些数据表明微重力环境下的生长激活导致生长减少，引起葡萄糖利用减少和前列腺素合成减少，成骨细胞中的肌动蛋白细胞骨架也发生了显著改变。
