骨髓间充质干细胞移植对脑缺血大鼠突触可塑性影响的实验研究

目的：探讨骨髓间充质干细胞（MSCs）移植对脑缺血大鼠神经功能恢复及突触可塑性的影响。方法：采用大鼠大脑中动脉缺血模型，分为假手术组、模型组、PBS组和MSCs组，研究脑缺血24h后移植MSCs的大鼠神经功能缺损评分（NSS）；分别测定梗死灶周围脑组织突触素（SYN）和脑源性神经营养因子（BDNF）mRNA的表达；电镜及免疫电镜下观察突触结构的变化。结果：与模型组及PBS组大鼠相比，MSCs组的NSS评分较低，SYN及BDNF mRNA的表达则明显较高；电镜检查示MSCs组大鼠突触界面曲率较大，突触后致密物质的厚度增加，突触间隙宽度变窄，突触活性带长度增加；免疫电镜示BrdU阳性细胞和宿主脑神经元形成非成熟的突触样结构。结论：MSCs移植可能通过神经营养效应调节脑缺血周围神经细胞的可塑性改善脑缺血大鼠的神经功能。

Effect of Mesenchymal Stem Cells Transplantation on Brain Synaptic Plasticity of Rats with Cerebral Ischemia

Aim : To explore mesenchymal stem cells (MSCs) transplantation on neurological functional recovery and brain synaptic plasticity of rats with cerebral ischemia. Method: Density gradient centrifugalization combined with adherence method was used to segregate and cultivate rat MSCs. Rats were divided into sham group, model group, PBS group, MSCs group randomly. The rat model of focal cerebral ischemia was established with unilateral middle cerebral artery suture occlusion method and reperfused 2 h later with suture extracted. Rats in MSCs group were transplanted MSCs labeled with 5-bromodeoxy-uridine (BrdU) through tail vein intravenous injection. Rats in PBS group were intravenously injected with PBS as control. Neurological functions of rats were evaluated with modified Neurological Severity Scores(NSS). The expressions of synaptophysin (SYN) and BDNF mRNA in cortex around cerebral infarction were tested through immunohistochemistry and RT-PCR respectively. The synaptic structure was observed through electron microscope and immunoelectron microscope. Results:To compare with model group and PBS group, the NSS was lower, the expressions of SYN and BDNF mRNA were higher significantly in MSCs group. In MSCs group, the curvature of synaptic interface was bigger, the thickness of postsynaptic density was higher, the width of synaptic cleft was narrower, the length of synaptic active zone was longer than that of PBS group and model group. Immunoelectron microscope showed that the BrdU positive cells formed unripe with synaptic appearance structure of neurons of host brain. Conclusion: Intravenous transplantation of MSCs can ameliorate neurological deficit of rats with cerebral ischemia. The mechanism may be that the transplanted MSCs can modify cerebral plasticity through neurotrophy effect and probably forming new synapses with host brain.