[64]

Proteomic Evaluation of Human Mesenchymal Stem Cells (MSCs) Exposed to Microgravity.     S. Mazhari1, A.M. Frias2, J. Chamberlain1, C.Porada1, J.M.S. Cabral2, E.D. Zanjani1, G.Almeida‑Porada1. 1Dept Animal Biotech, UNR, USA and 2 CEBQ, IST, Portugal

   We have previously reported that microgravity (mG) can alter/impair the differentiative potential of MSCs upon transplantation. Since MSCs may be responsible, in part, for maintaining normal replacement of cells within different organs, alterations in the physiology of this stem cell population could have a significant impact upon the health of humans subjected to conditions of microgravity during space travel.  In order to start dissecting mechanisms by which mG alters MSCs differentiation, proteomic analysis of MSCs grown under mG and normal G conditions was performed and these results compared with the MSC differentiation potential in vivo or in vitro.  To this end, we grew MSCs under either mG or normal G conditions for 5 days, extracted cellular proteins and separated the proteins by 2-D polyacrylamide gel electrophoresis. The bands in the gels were analyzed and 94 unique mG in-gel digested proteins were analyzed by mass spectrometry. We found that in MSC grown under mG conditions there was down-regulation of: 1) bone related proteins such as osteocalcin and Hsp47/colligin; 2) motility/shape-related proteins such as Syntenin and Calreticulin; 3) Liver-related proteins like serum albumin precursor, serum albumin, glyceraldehyde 3-phosphate dehydrogenase, Hsp70-like protein, and Iodothyronine-5’-monodeiodinase; and 4) Fetuin, a serum glycoprotein that inhibits unwanted mineralization in soft tissues such as kidney. Furthermore, up-regulation of proteins involved in muscle atrophy/degradation such as Caldesmon and Ubiquitin, and control of myogenesis such as Nuclear ribonucleoprotein-H was also found. These results corroborate not only with the in vivo and in vitro assays that showed that osteocytic and hepatocytic differentiation of MSC was impaired under mG conditions but also with physiologic alterations  experienced during space travel. (Supported by NASA NAG9-1340)