title: Conditioned media from microvascular endothelial cells cultured in simulated microgravity inhibit osteoblast activity.
abstract: OBJECTIVE
  Gravity contributes to the maintenance of bone integrity. Accordingly, weightlessness conditions during space flight accelerate bone loss and experimental models in real and simulated microgravity show decreased osteoblastic and increased osteoclastic activities. It is well known that the endothelium and bone cells cross-talk and this intercellular communication is vital to regulate bone homeostasis. Because microgravity promotes microvascular endothelial dysfunction, we anticipated that the molecular cross-talk between endothelial cells exposed to simulated microgravity and osteoblasts might be altered.
  
  
  RESULTS
  We cultured human microvascular endothelial cells in simulated microgravity using the rotating wall vessel device developed by NASA. Endothelial cells in microgravity show growth inhibition and release higher amounts of matrix metalloproteases type 2 and interleukin-6 than controls. Conditioned media collected from microvascular endothelial cells in simulated microgravity were used to culture human osteoblasts and were shown to retard osteoblast proliferation and inhibit their activity.
  
  
  CONCLUSIONS
  Microvascular endothelial cells in microgravity are growth retarded and release high amounts of matrix metalloproteases type 2 and interleukin-6, which might play a role in retarding the growth of osteoblasts and impairing their osteogenic activity.
  
  
  CONCLUSIONS
  We demonstrate that since simulated microgravity modulates microvascular endothelial cell function, it indirectly impairs osteoblastic function.
authors.affiliation: Dipartimento di Scienze Biomediche e Cliniche Luigi Sacco, Università di Milano, Via GB Grassi 74, Milano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cazzaniga
authors.affiliation: Dipartimento di Scienze Biomediche e Cliniche Luigi Sacco, Università di Milano, Via GB Grassi 74, Milano, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Castiglioni
authors.affiliation: Dipartimento di Scienze Biomediche e Cliniche Luigi Sacco, Università di Milano, Via GB Grassi 74, Milano, Italy.
authors.forename: Jeanette A M
authors.initials: JA
authors.lastname: Maier
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D018929:Cell Culture Techniques; D049109:Cell Proliferation / Q000187:drug effects*; D017077:Culture Media, Conditioned / Q000378:metabolism / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D010006:Osteoblasts / Q000187:drug effects*; D010012:Osteogenesis / Q000187:drug effects; D014893:Weightlessness
chemical_list: D017077:Culture Media, Conditioned