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Objective To investigate the neuroprotective effects of exosomes derived from human umbilical cord mesenchymal stem cells(HUCMSCs) in cerebral palsy (CP) mice. Methods The exosomes from HUCMSCs were verified by transmission electron microscopy (TEM), nanoparticle tracking analyzer(NTA) and Western blot. The animals were randomly divided as sham operation group (sham group, n=8), model group[CP group, n=8, hypoxic induction after unilateral common carotid artery ligation combined with lipopolysaccharide(LPS) infection] and model exosome group (CP-Exo group, n=8, 125 μg exosomes was injected intravenously). Neuromotor function, the ability of grasping and balance were evaluated by Longa score, grid test and pole climbing test. The pathological lesion in brain tissue was observed with hematoxylin-eosin (HE) staining, the synaptic structure of neurons was observed by TEM, the survival of neurons was detected by toluidine blue staining, and the expression levels of PSD-95 and synaptophysin (SYP) were detected by Western blot. Results The exosomes isolated were spherical and double-membrane vesicles with an average particle size of 123nm, which expressed TSG101 protein. In animal behavior tests, Longa score in CP group was significantly higher than sham group(P＜0.01) and CP-Exo group (P＜ 0.05). There was no plaque necrosis found in exosome group and the incidence of nerve fiber demyelination in the white matter area was significantly reduced than in the CP group (P＜0.01). The synaptic structure of the sham group was relatively normal, while the other two groups showed varying degrees of pathological changes. The general trend of pathological changes was CP group＞CP-Exo group＞ sham group. The number of Nissl bodies in hippocampal pyramidal cells in CP group was significantly less than that in sham group(P＜0.01), however, which was also less than that in CP-Exo group (P＜ 0.01). The expression of PSD-95 and SYP in CP group was significantly lower than that in sham group (P＜0.01), and the levels PSD-95 and SYP in CP-Exo group was significantly higher than those in CP group(P＜0.01). Conclusions HUCMSCs exosomes can promote the recovery of neural function of cerebral palsy mice, reduce synaptic damage and protect neuron cells by increasing the expression of PSD-95 and SYP.