Immunomodulatory effect of CD200-positive human placenta-derived stem cells in the early phase of stroke

Human placenta amniotic membrane-derived mesenchymal stem cells (AMSCs) regulate immune responses, and this property can be exploited to treat stroke patients via cell therapy. We investigated the expression profile of AMSCs cultured under hypoxic conditions and observed interesting expression changes in various genes involved in immune regulation. CD200, an anti-inflammatory factor and positive regulator of TGF-β, was more highly expressed under hypoxic conditions than normoxic conditions. Furthermore, AMSCs exhibited inhibition of pro-inflammatory cytokine expression in co-cultures with LPS-primed BV2 microglia, and this effect was decreased in CD200-silenced AMSCs. The AMSCs transplanted into the ischemic rat model of stroke dramatically inhibited the expression of pro-inflammatory cytokines and up-regulated CD200, as compared with the levels in the sham-treated group. Moreover, decreased microglia activation in the boundary region and improvements in behavior were confirmed in AMSC-treated ischemic rats. The results suggested that the highly expressed CD200 from the AMSCs in a hypoxic environment modulates levels of inflammatory cytokines and microglial activation, thus increasing the therapeutic recovery potential after hypoxic-ischemic brain injury, and further demonstrated the immunomodulatory function of AMSCs in a stroke model.