Abstract: Objective: To investigate the therapeutic effect of exosomes extracted from human adipose-derived mesenchymal stem cells on traumatic brain injury (TBI) and its possible mechanism. Methods: Mesenchymal stem cells(MSCs) were isolated from healthy human adipose tissue and the exosomeswere extracted by ultrafiltration. Rats were divided into four groups: sham group, PBS control group, MSCs treatment group and exosomes treatment group. 24 h After TBI, the treatment group was injected locally along the lesion area, 30μL of PBS, 2 ⅹ105MSC, 25μg protein of exosomes respectively, the total volume was30μL. We performed the Modified Neurological Severity Score(mNSS) and the forelimb Foot-Fault Test in all rats beforeinjury and at 1, 3, 7, 10, 13, 16, 21, and 30 days after TBI. The rats were sacrificed at 3 and 7 days after TBI respectively，total RNA was extracted from rat brain tissue. The expression of TNF-α and IL-1β were detected by quantitative PCR. The rats were also killed at 30 days after TBI for testing the neuronal apoptosis in lesion area by tunel-neun double immunofluorescence. Results:exosomes treatment significantly promoted the recovery of neurological deficits caused by TBI，and the therapeutic effect was similar to MSCs， its possible mechanism may be the inhibition of the acute inflammation and the reducing of the neurons apoptosis after TBI.

Key words: mesenchymal stem cells (MSCs), Exosome, traumatic brain injury (TBI), cell therapy, animal models