OBJECTIVETo explore the influence of bone marrow (BM) mesenchymal stem cells (MSCs) on macrophage activation after lipopolysaccharide (LPS) stimulation.

METHODSMouse BM MSCs were isolated and purified by adherence screening, and mouse peritoneal macrophages (MPM) were collected by sodium thioglycollate peritoneal injection, and the co-culture system was established by planting macrophages on the MSCs monolayer. The grouping of experiments: group A: MPM; group B: MPM + LPS; group C: MPM + LPS + MSC; group D: MPM + LPS + MSC supernatant. Cell culture supernatants were collected to detect the changes of TNF-alpha/TGF-beta and nitrogen monoxide (NO) after stimulating macrophages with LPS for 18 hours. At the same time Escherichia coli standard strain (ATCC25922) was added into the culture system and incubated for another 24 hours, macrophages were stained and phagocytosis were examined.

RESULTSThe concentrations of TNF-alpha and NO in culture supernatants were increased significantly to (147.4 +/- 37.1) pg/ml and (59.9 +/- 8.7) micromol/L respectively after macrophage activation, however, at the present of MSC, the concentration of TNF-alpha was dramatically decreased [(97.6 +/- 30.3) pg/ml, P = 0.032], and the concentration of NO was decreased to (50.9 +/- 29.5) micromol/L (P > 0.05). The concentrations of TNF-alpha and NO were further decreased after addition of MSC supernatants [(58.3 +/- 31.5) pg/ml and (-3.4 +/- 2.3) micromol/L respectively, P < 0.01]. There was no change in the phagocytic rate and phagoindex of macrophages after activation.

CONCLUSIONSMSCs can inhibit the activation of mouse peritoneal macrophages after stimulating with LPS but has no influence on the phagocytosis.