Here, we found that UC-MSCs secrete a large amount of PGE2; however, with the decline of the PGE2 level in UC-MSCs and UC-MSCs conditional medium, both showed a lower ability to promote the production of IL-10 in LPS-stimulated RAW264.7 cells and in LPS-induced ALI mice. The gene discussed is IL10; the disease is acute respiratory distress syndrome.