[Mesenchymal stem cells release membrane microparticles in the process of apoptosis].

Though mesenchymal stem cells (MSC) have been clinically used to repair a variety of damaged tissues, the underlying mechanisms remain elusively as the majority of the ex vivo expanded MSC die shortly after transplantation. To explore the mechanism in which the death cells play tissue repair effect, apoptosis of rat bone marrow MSC was induced by culturing cells in the conditions of hypoxia or/and serum-free medium, and the subcellular structures in the supernatants were analyzed. The results showed that apoptosis occurred in the presence of either hypoxia or serum-free condition as well, and the apoptotic proportion reached up to (17.44 ± 2.15) after the cells were treated by hypoxia plus serum free culture for 72 hours. The flow cytometric analysis of the sub-cellular substances harvested by ultracentrifugation of the supernatants found that the MSC released substantial amount of membrane microparticles into the supernatants, which expressed CD29, CD44A and Annexin-V-binding phosphatidylserine. It is concluded that the MSC can release membrane microparticles after induction, the amount of these membrane microparticles was around 15-fold of the parent cell numbers. The membrane microparticles is the mediators in the cross-talk between the transplanted cells and their surrounding tissues. This study provides some novel information for the mechanisms of MSC therapy.