ObjectiveTo determine the changes in tumor necrosis factor-α (TNF-α) and interleukin-lβ (IL-1β)expression after bone marrow mesenchymal stem cells (BMSCs) transplantation in a rat pup model of hypoxic-ischemic brain damage (HIBD) and discuss the anti-inflammatory mechanism of BMSCs transplantation in the repair of HIBD.MethodsThree-day-old Sprague-Dawley rat pups were randomly divided into three groups: the transplantation group, in which a model of HIBD was established by ligation of left common carotid artery and hypoxia for two hours followed by the injection of 2μl BMSCs (2×105 cells) into the lateral ventricle; the HIBD model group, in which HIBD model was established and 2μl phosphate saline buffer was injected into the lateral ventricle; and the sham-operation group, in which no intervention was given. Histological changes in the brain were detected by HE staining and the number of cells positive for ectodermal dysplasia-1 (ED-1) staining, which is a specific marker for activated microglia, was detected by immunohistochemistry. The protein and mRNA levels of TNF-α and IL-1β were determined by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction. One-way analysis of variance and LSD test were applied for statistical analysis.ResultsHE staining showed that cellular edema and necrocytosis was not observed in cerebral white matter on the 7th post-transplantation day in the transplantation group, but observed in the HIBD model group. In the sham-operation group, cerebral white matter was normal. The number of ED-1 positive cells in the transplantation group (26.3±2.5) was significantly lower than that in the HIBD model group (33.0±4.0), but higher than that in the sham-operation group (2.3±0.6) (LSD test, allP<0.05). The contents of TNF-α and IL-1β both in the transplantation group and the HIBD model group increased and peaked 24 h after transplantation, then gradually decreased, but did not reach normal levels (sham-operation group) on the 7th day. The contents of TNF-α and IL-1β in brain tissue in the HIBD model group [TNF-α: (3.03±0.10), (5.57±0.19), (7.78±0.19), (4.39±0.20), (2.70±019)μg/L; IL-1β:(293.1±7.9), (369.8±17.5), (303.6±23.9), (226.7±21.6), (183.9±33.4) ng/L] were significantly higher than those in the transplantation group [TNF-α: (2.84±0.20), (3.80±0.14), (4.63±0.17), (3.56±0.03), (1.99± 0.17)μg/L; IL-1β: (267.6±14.5), (323.5±26.9), (211.2±24.9), (140.8±7.4), (100.2±8.3) ng/L] at 6, 12, 24, 48 h and 7 days after BMSCs transplantation, respectively. The contents of TNF-α and IL-1β in the sham-operation group [TNF-α:(1.03±0.02), (1.13±0.03), (1.05±0.02), (1.09±0.02), (1.07±0.02)μg/L; IL-1β:(63.6±13.0), (64.0±11.3), (60.8±10.0), (67.9±13.5), (66.2±11.7) ng/L] were significantly lower than those in the transplantation group and HIBD model group (LSD test, allP<0.05). TNF-α and IL-1β mRNA at 24 h after transplantation in the HIBD model group (TNF-α: 2.69±0.43; IL-1β: 3.07±0.38) were significantly higher than those in the transplantation group (TNF-α: 1.61±0.29; IL-1β: 1.08±0.11) and those in the sham-operation group (TNF-α: 0.94±0.16; IL-1β: 1.08±0.11) (LSD test, allP<0.05).ConclusionsBMSCs may play an important role in the recovery of preterm HIBD and the mechanism may involve the inhibition of microglia activation and down-regulation of the expression of inflammatory factors.