Carmeliet G, Nys G, Stockmans I, Bouillon R
Laboratorium voor Experimentele Geneeskunde en Endocrinologie, Katholieke Universiteit Leuven, Gasthuisberg, Belgium.
Bone. 1998 May;22(5 Suppl):139S-143S. doi: 10.1016/s8756-3282(98)00007-6.
Bone loss is observed after exposure to weightlessness in both astronauts and inflight animals. Histological and biochemical studies on rats have shown a decrease in bone formation, probably as a result of altered osteoblast function. To investigate whether microgravity alters osteoblast differentiation in vitro, the human osteosarcoma cell line MG-63 was used as a model. MG-63 cells can be induced to differentiate by treating the cells with 1,25(OH)2D3 (10(-7) mol/L) and transforming growth factor-beta 2 (TGFbeta2) (10 ng/mL). The message level of differentiation-related genes was quantitated via competitive reverse transcription-polymerase chain reaction (RT-PCR), both in untreated and hormone-treated cells cultured under microgravity for 9 days aboard the unmanned Foton 10 spaceflight, and compared to ground and inflight unit-gravity cultures. At microgravity, gene expression for collagen Ialpha1 following treatment was reduced to 51% of unit-gravity levels (p < 0.05). The amount of alkaline phosphatase messenger ribonucleic acid (mRNA) following treatment at microgravity increased by only a factor of 5 compared to the tenfold increase at unit gravity (p < 0.02). The osteocalcin message level in treated cells cultured at microgravity was only 19% of the level found in cells grown at unit gravity (p < 0.02). In conclusion, microgravity reduces the differentiation of osteoblastic MG-63 cells in response to systemic hormones and growth factors.
在宇航员和太空飞行的动物中，暴露于失重环境后均观察到骨质流失。对大鼠进行的组织学和生化研究表明，骨形成减少，这可能是成骨细胞功能改变所致。为了研究微重力是否会在体外改变成骨细胞的分化，使用人骨肉瘤细胞系MG-63作为模型。MG-63细胞可以通过用1,25(OH)2D3（10(-7) mol/L）和转化生长因子-β2（TGFβ2）（10 ng/mL）处理细胞来诱导分化。通过竞争性逆转录-聚合酶链反应（RT-PCR）对未处理和经激素处理的细胞中分化相关基因的信息水平进行定量，这些细胞在无人的Foton 10太空飞行中于微重力条件下培养9天，并与地面和飞行中的单位重力培养物进行比较。在微重力条件下，处理后I型胶原α1的基因表达降至单位重力水平的51%（p < 0.05）。与单位重力下增加10倍相比，微重力下处理后碱性磷酸酶信使核糖核酸（mRNA）的量仅增加了5倍（p < 0.02）。在微重力条件下培养的处理细胞中骨钙素的信息水平仅为在单位重力下生长的细胞中发现水平的19%（p < 0.02）。总之，微重力会降低成骨细胞MG-63细胞对全身激素和生长因子的反应性分化。
