AIM:To explore the effect of microRNA-296-5p(miR-296-5p)on neurological damage after cere-bral infarction(CI)and its regulatory relationship with angiotensin-converting enzyme 2(ACE2)signaling pathway medi-ated proliferation of endothelial progenitor cell(EPC).METHODS:Serum samples from 70 patients diagnosed with CI and accompanied by neurological damage in our hospital(CI group)and 70 healthy volunteers(healthy group)were se-lected.The mRNA expression of miR-296-5p,ACE2,and Mas in the serum of both groups were detected by RT-qPCR.The rat model of CI was constructed and SD rats were randomly divided into healthy control group,model control group,sh-miR-296-5p group,and ACE2 overexpression group(OE-ACE2 group).Neurological severity scores(NSS)score was evaluated.The CI status of rats in each group was observed by TTC staining.The mRNA expression of miR-296-5p,ACE2,and Mas in serum of rat was detected by RT-qPCR.EPC were isolated and cultured routinely,and were randomly divided into control group,sh-miR-296-5p group,OE-ACE2 group,OE-miR-296-5p+OE-ACE2 group,and sh-miR-296-5p+sh-ACE2 group.The viability of EPC was detected by CCK-8.Apoptosis of EPC was detected by flow cytometry.The mRNA expression of miR-296-5p,ACE2,and Mas in EPC was detected by RT-qPCR.The relationship between miR-296-5p and ACE2 was verified by dual luciferase reporter gene assay.RESULTS:(1)Clinical trial:compared with the healthy group,the level of miR-296-5p in serum of CI patients was obviously increased(P<0.05),while the mRNA ex-pression levels of ACE2 and Mas were obviously reduced(P<0.05).(2)Animal experiments:compared with the healthy control group,the NSS score,CI area,the level of miR-296-5p in serum,and the mRNA expression level of Mas in the model control group were obviously increased(P<0.05),while the mRNA expression level of ACE2 was obviously de-creased(P<0.05).Compared with the model control group,the NSS score,CI area,the level of miR-296-5p in serum,and the mRNA expression level of Mas in the sh-miR-296-5p group and OE-ACE2 group were obviously reduced(P<0.05),while the mRNA expression level of the ACE2 was obviously increased(P<0.05).(3)Cell experiment:Com-pared with the control group,the A450 and the level of miR-296-5p of EPC cells in the sh-miR-296-5p group and OE-ACE2 group were obviously reduced(P<0.05),the apoptosis rate,the mRNA expression level of ACE2,and Mas were obvious-ly increased(P<0.05).Compared with the sh-miR-296-5p group,the A450 and the level of miR-296-5p in the sh-miR-296-5p+sh-ACE2 group were obviously increased(P<0.05),the apoptosis rate,the mRNA expression level of ACE2,and Mas were obviously reduced(P<0.05).Compared with the OE-ACE2 group,the level of A450 and miR-296-5p in OE-miR-296-5p+OE-ACE2 group were obviously increased(P<0.05),the apoptosis rate,the mRNA expression level of ACE2,and Mas were obviously reduced(P<0.05).CONCLUSION:Knockdown of miR-296-5p may inhibit EPC proliferation by mediating the ACE2 signaling pathway,and alleviate neurological damage after CI.