BACKGROUND: Mesenchymal stem cells (MSCs) have been proved to posses the immunosuppressive effect on proliferation of lymphocytes. However, MSCs have a feature of nonuniformity. In addition, the immunosuppressive effect of Stro-1+ MSCs is obviously stronger than that of Stro-1- MSCs.
OBJECTIVE: To investigate whether the significant difference in suppressive effect between Stro-1+ and Stro-1- MSCs still exists following the physical separation of MSCs from lymphocytes.
METHODS: 1×104 and 3×104 Stro-1+ or Stro-1- MSCs were seeded in the lower chamber of transwell plate for 1-2 hours in order to achieve cell attachment, and then 1×104 reactive peripheral blood lymphocytes (PBLs) were incubated with stimulating PBLs of the same amount in the upper chamber of the transwell plate. After 5 days of culture, proliferation of the PBLs was measured by 3H-TDR incorporation.
RESULTS AND CONCLUSION: The immunosuppressive effect of Stro-1+ MSCs was significantly stronger than that of Stro-1- MSCs when there was a direct connection between MSCs and PLBs. However, the immunosuppressive effects of the two subsets followed using transwell culture system were decreased than before. It is indicated that the direct connection between MSCs and PBLs may play a key role in the immunosuppressive effect of MSCs, and few soluble factors contribute a little during this. Furthermore, such “cross-talk” between cells is the prerequisite for MSCs to play the advantaged immune regulation.