Abstract: Objective To investigate whether neuroprotective effect can be achieved by liposome mediatedtransforming growth factor-β1(TGF-β1) gene transfer to rat brain after transient focal cerebralischemia.Methods Transient focal cerebral ischemia in a rat model was produced by middle cerebral arteryocclusion (MCAO) for 1 hour. Reliable behavioral parameters were employed to detect successfulocclusion of the middle cerebral artery. The complex of plasmid contained LacZ marker geneand cationic liposomes were injected directly into the cerebrospinal fluid (CSF) of one group ofcontrol animals (n=18) immediately after MCAO. The other group of animals (n=18) was injectedwith liposome-TGF-β1 complexes. Five days after transfection, behavioral tests were employedto evaluate the neurologic deficits. Expression of β-galactosidase and TGF-β1 gene productswere detected by immunohistochemistry, reverse transcription polymerase chain reaction (RTPCR)and western blot analysis. Infarct volume and TUNEL-positive cells were counted. SemiquantitativeRT-PCR was used to examine the difference of caspase-3 mRNA between the twogroups.Results Liposome-mediated gene transfer of LacZ and TGF-β1 into the ischemic brain providedeffective expression of transgene. Compared with the control group, the neurologic functionof the rats injected with liposome-TGF-β1 complexes was significantly improved(P <0.01);infarct volume was smaller significantly(P <0.01); TUNEL-positive cells decreased significantly (P<0.01)and the expression of caspase-3 mRNA also decreased significantly.Conclusion Liposome-mediated gene transfer into the ischemic brain provided effectiveexpression of transgene after transient focal cerebral ischemia. Neuroprotective effect can beachieved by liposome mediated TGF-β1 gene tranfer which led to the inhibition of the activity ofcaspase-3. Gene transfer mediated by liposome may be a promising approach for the treament ofcerebral ischemia.

Key words: Liposomes; Transforming growth factor beta; Genes; Apoptosis; Brain ischemia

摘要： 目的 在缺血性脑损伤发生后，用脂质体介导外源性基因转化生长因子-β1（transforming growthfactor-β1，TGF-β1）对其进行治疗，并对其作用机制进行初步研究。方法 将大鼠一侧大脑中动脉栓塞1h以制作局灶性脑缺血模型，随机分为治疗组和对照组各18只。将含报告基因LacZ的质粒和脂质体的复合体注入对照组大鼠的脑脊液中，治疗组注射含TGF-β1的质粒和脂质体的复合体。5d后做行为试验，取动物脑组织，通过免疫组织化学、逆转录聚合酶链反应（reverse transcription polymerase chain reaction，RT—PCR）和Western blot等方法来鉴定外源基因是否表达；检测脑梗死体积和凋亡细胞数；用半定量RT-PCR比较治疗组和对照组缺血脑组织中caspase-3表达的差异。结果 由脂质体介导的LacZ基因和TGF-β1基因均在缺血脑组织中表达；和对照组相比，治疗组动物的神经功能有明显改善（P <0.01）；治疗组的脑梗死体积和凋亡阳性细胞数均显著小于对照组（P <0.01）；治疗组缺血脑组织中caspase-3 mRNA的表达显著低于对照组。结论 缺血性脑损伤发生后，脂质体介导的外源基因可在缺血脑组织中有效表达。脂质体介导TGF-β1对缺血性脑损伤具有明显的治疗作用，其作用机制可能是通过抑制caspase-3的活性而减少神经细胞的凋亡，从而改善由缺血性损伤而致的神经功能障碍。

关键词: 脂质体; 转化生长因子β; 基因; 细胞凋亡; 脑损伤