Clinical And Preclinical Studies On The Role Of CD200R In Acute Cerebral Ischemia

Objective:To investigate the role of CD200R in ischemic stroke by clinical data analysis and MCAO rat model.Methods:In the first clinical study,the clinical baseline data,imaging data and neurological function scores of 57 patients with acute cerebral infarction and 26 healthy controls were collected.The peripheral blood mononuclear cells and plasma were collected on the day of admission,and the proportion of CD200R~+monocytes was measured by flow cytometry and the levels of inflammatory cytokines in plasma were determined by Luminex assay.In the second preclinical study,human mesenchymal stem cells(hMSCs)were transplanted to middle cerebral artery occlusion(MCAO)rats by striatal stereotactic injection one day since stroke onset.The neurological deficits of MCAO rats were assessed by modified neurological severity score(m NSS),the volume of cerebral infarction was evaluated by triphenyltetrazolium chloride(TTC)staining,and M1 and M2 microglia polarization as well as the proportion of CD200R~+microglia were quantitatively analyzed by flow cytometry.The m RNA expression levels of inflammatory cytokines,CD200 and CD200R in the ischemic brain tissues were evaluated by RT-PCR.Results:The percentage of CD200R-positive monocytes in the peripheral blood was significantly higher in patients with acute cerebral infarction than that in the control group(P=0.001),and logistic regression analysis showed that the upregulation of CD200R~+monocytes was closely related to the incidence and development of ischemic stroke(OR=1.440,P=0.004).Spearman correlation analysis showed that the proportion of CD200R~+monocytes was positively correlated with C-reactive protein(r=0.1212,P=0.0322),neurotrophil-to-lymphocyte ratio(r=0.070,P=0.0465)and CD14~+monocytes percentage(r=0.4144,P<0.0001).In MCAO rats,transplantation of hMSCs significantly improved neurological deficits(P=0.001)and reduced infarct volume(P=0.002).Furthermore,grafted hMSCs inhibited the activation of microglia and polarization towards to M1 phenotype,but promoted the M2polarization.RT-PCR analysis showed that m RNA levels of M1-related inflammatory cytokines were downregulated whearas m RNA expressions of M2-related cytokines were upregulated after hMSCs transplantation.In addition,hMSCs transplantation downregulated the expression of CD200R m RNA in the infarcted region and its surrounding areas,and upregulated the expression of CD200 m RNA in brain tissue and the proportion of CD200R~+microglia.Conclusion:1)The proportion of CD200R~+monocytes in peripheral blood of patients with acute cerebral infarction was significantly increased,and was closely related to the infarct position;2)The expression of CD200R in peripheral blood mononuclear cells in patients with acute cerebral infarction was positively correlated with post-stroke inflammation.3)Mesenchymal stem cells improved neurological deficits in MCAO rats and reduced the infarct volume,by inhibiting M1 microglia in brain tissues and promoting their polarization to M2.3)Mesenchymal stem cells re-established the balance of CD200-CD200R between neural cells and microglia in ischemic brain tissue,thereby promoting the restoration of homeostasis in brain tissue.4)CD200R might be a potential humoral indicator for monitoring the immune and inflammatory response and disease progression after stroke,and might be a novel target for the treatment of acute ischemic stroke.