Effects of bone marrow mesenchymal stem cells transplantation on tumor necrosis factor-α and interleukin-1β in preterm rats with hypoxic-ischemic brain damage

Abstract

Objective To 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. Methods Three-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 2 μl BMSCs (2×105 cells) into the lateral ventricle; the HIBD model group, in which HIBD model was established and 2 μl 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. Results HE 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, all P<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, all P<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, all P<0.05). Conclusions BMSCs 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. Key words: Hypoxia-ischemia, brain; Mesenchymal stem cell transplantation; Tumor necrosis factor-alpha; Interleukin-1beta