title: Simulated microgravity inhibits the proliferation and osteogenesis of rat bone marrow mesenchymal stem cells.
abstract: OBJECTIVE
  Microgravity is known to affect the differentiation of bone marrow mesenchymal stem cells (BMSCs). However, a few controversial findings have recently been reported with respect to the effects of microgravity on BMSC proliferation. Thus, we investigated the effects of simulated microgravity on rat BMSC (rBMSC) proliferation and their osteogeneic potential.
  
  
  METHODS
  rBMSCs isolated from marrow using our established effective method, based on erythrocyte lysis, were identified by their surface markers and their proliferation characteristics under normal conditions. Then, they were cultured in a clinostat to simulate microgravity, with or without growth factors, and in osteogenic medium. Subsequently, proliferation and cell cycle parameters were assessed using methylene blue staining and flow cytometry, respectively; gene expression was determined using Western blotting and microarray analysis.
  
  
  RESULTS
  Simulated microgravity inhibited population growth of the rBMSCs, cells being arrested in the G(0)/G(1) phase of cell cycle. Growth factors, such as insulin-like growth factor-I, epidermal growth factor and basic fibroblastic growth factor, markedly stimulated rBMSC proliferation in normal gravity, but had only a slight effect in simulated microgravity. Akt and extracellular signal-related kinase 1/2 phosphorylation levels and the expression of core-binding factor alpha1 decreased after 3 days of clinorotation culture. Microarray and gene ontology analyses further confirmed that rBMSC proliferation and osteogenesis decreased under simulated microgravity.
  
  
  CONCLUSIONS
  The above data suggest that simulated microgravity inhibits population growth of rBMSCs and their differentiation towards osteoblasts. These changes may be responsible for some of the physiological changes noted during spaceflight.
authors: China Astronaut Research and Training Center, Laboratory of Space Cell and Molecular Biology, Beijing, China.
authors: Z Q
authors: ZQ
authors: Dai
authors: R
authors: R
authors: Wang
authors: S K
authors: SK
authors: Ling
authors: Y M
authors: YM
authors: Wan
authors: Y H
authors: YH
authors: Li
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D002453:Cell Cycle; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D006133:Growth Substances / Q000494:pharmacology; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010012:Osteogenesis; D051381:Rats; D018474:Weightlessness Simulation / Q000009:adverse effects*
chemical_list: D006133:Growth Substances