Cytoskeleton structure and adhesion properties of human stromal precursors under conditions of simulated microgravity

During spaceflight and in simulated microgravity (SMG), cytoskeleton rearrangements were observed in lymphocytes, glial cells and osteoblasts. One potential mechanism for the cytoskeletal gravisensitivity of cells is the disruption of the extracellular matrix and integrin interactions. We investigated the effect of SMG on the structure of the actin cytoskeleton, distribution of cellular vinculin, the expression of some integrin subtypes and cellular adhesion molecules in cultured mesenchymal stem cells (hMSCs) derived from human bone marrow in vitro. Simulated microgravity was produced by desktop RPM equipment (Dutch Space, Netherlands). Cells were exposed to simulated microgravity for 30 min to 120 h. The results showed that the actin cytoskeleton was reorganized very quickly (30 min). Later (6, 24, and 48 h), the number of cells with disrupted actin cytoskeletons was increased; however, after 120 h of exposure, cells partly regained their F-actin structures. RPM exposure augmented the number of cells that express integrin-α2. We also observed a decrease in the number of VCAM-1-positive cells and changes in the expression of ICAM-1. Our findings indicate that SMG induces reversible microfilament reorganization in hMSCs and alters their adhesion properties. © 2009 Pleiades Publishing, Ltd.