重组腺病毒载体Ad5-hBDNF-EGFP的构建与鉴定*☆

背景：基因治疗是目前脊髓损伤治疗的方向，目的基因和载体是基因治疗的关键。 目的：构建携带增强型绿色荧光蛋白基因(Enhanced green fluorescence protein, EGFP)标志人脑源性神经营养因子(human brain-derived neurotrophic factor，hBDNF)基因重组腺病毒载体。 设计、时间及地点：单一样本观察，实验于2007-09/2008-06在福建医科大学附属第一医院完成。 材料：感受态大肠杆菌DH-5α购自美国Stratagene公司；pDC316-hBDNF、载体质粒pDC316-mCMV-EGFP、腺病毒骨架质粒pBHGlox_E1,3Cre、腺病毒包装系统AdMax和包装细胞株293购自加拿大Mixcrobix-Biosystems公司。 方法：以pDC316-hBDNF为模板，聚合酶链反应扩增酶切获得hBDNF基因片段，连接到带有EGFP标记基因的载体质粒pDC316-mCMV-EGFP上，构建穿梭质粒pDC316-hBDNF-mCMV-EGFP。利用AdMax包装系统，穿梭质粒与骨架质粒pBHGlox_E1，3Cre共转染293包装细胞, 同源重组产生复制缺陷型重组腺病毒载体Ad5-hBDNF-EGFP，反复感染293细胞扩增病毒后，离子交换法纯化病毒，并测定病毒颗粒数及滴度。 主要观察指标：①hBDNF基因原始质粒聚合酶链反应鉴定。②穿梭质粒pDC316-hBDNF-mCMV-EGFP的构建及鉴定。③重组腺病毒Ad5-hBDNF-EGFP的包装、扩增及纯化。④毒种目的基因的聚合酶链反应鉴定。⑤纯化病毒的滴度测定结果。 结果：经聚合酶链反应鉴定、限制性酶切分析及序列测定，证明已正确构建重组穿梭质粒pDC316-hBDNF-mCMV-EGFP和重组腺病毒载体Ad5-hBDNF-EGFP；扩增纯化后，测得重组腺病毒颗粒数为2.4×1011VP / mL，A260/A280值约为2.0，滴度为0.8×1010 CCID50/ mL。 结论：已成功构建重组腺病毒载体Ad5-hBDNF-EGFP，为hBDNF基因功能及基因治疗的进一步研究奠定实验基础。     

构建睫状神经营养因子和绿色荧光蛋白基因转导的重组腺病毒载体

目的 以重组腺病毒(rAd)为载体构建腺病毒-睫状神经营养因子-内部核糖体进入位点-绿色荧光蛋白(Ad-CNTF-IRES-GFP).方法 先构建Psp-CNTF-IRES-GFP质粒,再制备PDC316-CNTF-IRES-GFP质粒,然后在脂质体的作用下,用构建好的PDC316-CNTF-IRES-GFP质粒与骨架质粒PBHG在293-LP细胞中构建Ad-CNTF-IRES-GFP腺病毒,并扩增、纯化,鉴定病毒活性.最后,将Ad-CNTF-IRES-GFP转染人源性骨髓间充质细胞(MSCs),观察MSCs的CNTF表达情况.结果 成功扩增CNTF基因,扩增后的CNTF基因与基因文库序列完全相符;成功制备PDC316-CNTF-IRES-GFP质粒及Ad-CNTF-IRES.GFP腺病毒,测得Ad-CNTF-IRES-GFP腺病毒的病毒活性单位(pfu)为2.3x1011;构建好的Ad-CNTF-IRES-GFP成功转染MSCs,而凡转染后的MSCs表达CNTF的量为未转染MSCs表达量的20倍.结论 本方法能够成功构建Ad-CNTF-IRES-GFP腺病毒载体,而且转染后的MSCs高度表达CNTF.     

BDNF基因重组逆转录病毒表达载体pLEGFP-BDNF的构建与鉴定

目的构建脑源性神经营养因子(BDNF)基因重组逆转录病毒表达载体。方法根据 BDNF基因已知序列,设计合成一对引物并导入HindⅢ和BamH Ⅰ酶切位点;从大鼠海马组织提取总 RNA,逆转录聚合酶链反应(RT-PCR)获得编码BDNF的基因片段,与克隆载体pMD 18-T Simple连接构建pMDT-BDNF质粒;经HindⅢ、BamHⅠ双酶切,获得BDNF基因片断再克隆至逆转录病毒载体 pLEGFP-N1中构建重组质粒pLEGFP-BDNF。结果限制性内切酶酶切分析和PCR法鉴定表明为正确重组子,测序结果证实与已知序列吻合。结论构建的重组逆转录病毒表达载体 pLEGFP-BDNF含有序列正确的大鼠BDNF基因,可以作为今后治疗老年性痴呆动物模型转基因实验的基因来源。     

腺病毒载体Ad-BDNF-EGFP构建及其在神经干细胞中的表达

摘要 目的 研究腺病毒载体Ad-BDNF -EGFP的构建及在神经干细胞（NSCs）中的表达。方法 通过RT-PCR从在大鼠的海马中获得BDNF基因,通过基因克隆以及HEK293包装,获得了含增强绿色荧光蛋白(EGFP)基因的重组腺病毒表达载体pAd-BDNF-EGFP,将其感染原代培养的神经干细胞,观察EGFP及BDNF两种基因的表达,镜下测定转染率,并检测RT-PCR产物,证实BDNF的存在。转染后的神经干细胞经G418筛选,抗性细胞传代扩增后获得成功转染BDNF基因的NSCs克隆。结果 荧光显微镜下可见感染后的NSCs表达EGFP而发出绿色荧光;通过RT-PCR证明感染后的NSCs具有表达BDNF的能力;用ELISA鉴定细胞上清中分泌的BDNF, 72h的含量达到最高值,为12.78ng/ml;证明通过构建病毒的感染可以使神经干细胞获得分泌BDNF的能力,且EGFP基因可作为神经干细胞移植研究中良好的示踪剂。结论 腺病毒病毒介导EGFP基因及BDNF基因在大鼠胚胎神经干细胞中成功表达,为应用以神经干细胞直接作为基因靶细胞,介导基因治疗中枢神经系统疾病莫定了基础。     

hBDNF-GFP基因转染神经干细胞后hBDNF的表达及生物学特性研究

目的 探讨慢病毒载体介导入脑源性神经营养因子(hBDNF)和绿色荧光蛋白(GFP)基因转染大鼠神经干细胞(NSCs)后hBDNF的表达及其生物学特性的变化.方法 构建hBDNF和GFP基因共表达的慢病毒载体并转染NSCs(hBDNF-GFP-NSCs组),同时设GFP转染NSCs组(GFP-NSCs组)和未转染的NSCs组(NSCs组).应用RT-PCR和Western blot法分别检测3组细胞中hBDNFmRNA和蛋白的表达:ELISA检测hBDNF-GFP-NSCs组细胞转染前后培养液中hBDNF含量的变化:使用上述3组细胞的上清液培养背根神经节(DRG)与NSCs,观察DRG的生长情况并应用流式细胞法检测NSCs分化为神经元的比例.结果 RT-PCR、Western blot结果显示转染后7 d hBDNF-GFP-NSCs组hBDNF mRNA和蛋白的表达均明显强于GFp-NSCs组和NSCs组;EUSA检测显示hBDNF-GFP转染NSCs后上清中hBDNF含量增加,第5天分泌达最高峰,与转染前比较差异均有统计学意义(P<0.05);使用hBDNF-GFP-NSCs组上清液培养DRG和NSCs,4 d后DRG很快伸出突起,流式细胞法检测显示NSCs分化为神经元的比例高于其他两组.结论 NSCs可作为基因转染载体,被hBDNF-GFP基因重组慢病毒转染后仍可保持原有生物学特性,并稳定表达和分泌有生物学活性的hBDNF和GFP.     

脑源性神经营养因子基因转染可促进弥漫性轴突损伤神经元修复和轴突再生

应用脂质体将外源脑源性神经营养因子基因导入弥漫性轴突损伤模型大鼠脑内,力图通过脑源性神经营养因子促进神经元再生及修复的作用,促进损伤大鼠的形态功能恢复。结果显示基因转染后弥漫性轴突损伤额叶皮质神经元的形态得到改善,额叶皮质组织神经丝蛋白表达增加,证实脑源性神经营养因子可促进弥漫性轴突损伤后神经元的修复及轴突的再生。     

腺病毒介导的GDNF基因转移体外表达及生物学活性研究

为利用重组腺病毒介导的胶质细胞源性神经营养因子（GDNF）基因转移治疗帕金森病（PD）提供依据。方法：采用免疫组化、RT－PCR及ELISA定量分析观察人GDNF腺病毒（Ad-GDNF)在大鼠星形胶质 PC12细胞的表达,通过观察病毒直接感染及病毒感染的PC12细胞上清对中脑原代培养细胞中的TH阳性细胞（DA能神经元）生存能力和形态分化的影响来验证其生物学活性。结果Ad-GDNF在星形胶质细胞、PC12细胞及大鼠中脑原代培养细胞均可有效表达,其表达产物对中脑DNA能神经元的生存和形态分化均有显著的促进作用。结论：腺病毒介导的GDNF基因转移可在体外有效表达,且表达产物具有生物学活性,提示该手段在PD治疗方面具有良好的应用前景。     

重组大鼠质粒pEGFP-GDNF的构建及真核细胞转染

目的　构建携带大鼠胶质细胞源性神经营养因子(GDNF)基因的真核细胞表达载体,为应用GDNF进行如帕金森综合征之类的神经元退化性疾病的基因治疗打基础。方法　采用RT- PCR方法从大鼠胎脑组织总RNA中扩增出该基因的c DNA序列,并克隆到增强型绿色荧光蛋白(EGFP)报告基因的真核表达载体p EGFP- C1中,对重组质粒p EGFP- GDNF进一步鉴定。采用电转及阳离子脂质体将重组质粒p EGFP- GDNF转染至SH- SY5 Y细胞。结果　大鼠GDNF c DNA已正确地克隆到真核表达载体p EGFP- C1中,而构建成重组大鼠质粒p EGFP-GDNF。GDNF基因可稳定表达在细胞中。结论　真核细胞表达载体p EGFP- GDNF以及表达GDNF工程细胞SH-SY5 Y的成功构建,为进一步开展GDNF基因治疗PD等中枢神经系统疾病奠定了基础。     

胶质细胞源性营养因子及内皮素B受体基因共转染小鼠神经干细胞*☆

背景：胶质细胞源性神经营养因子与内皮素B受体基因的缺失将导致肠神经系统发育异常。神经干细胞移植不仅可以从解剖和功能上修复神经系统,还可以作为基因转染的载体。 目的：拟将携带胶质细胞源性神经营养因子和内皮素B受体基因的重组腺病毒转染至小鼠神经干细胞,并观察目的基因的表达。 设计：细胞-基因学观察。 材料：新生昆明小鼠由华中科技大学同济医学院动物实验中心提供。jetPEI转染试剂为PolyPlus 公司产品;携带绿色荧光蛋白的胶质细胞源性神经营养因子、内皮素B受体基因共表达腺病毒由本室孙念峰博士和张景辉博士构建并惠赠。 方法：无菌条件下取新生小鼠脑组织,制备单细胞悬液。取携带绿色荧光蛋白的胶质细胞源性神经营养因子和内皮素B受体基因共表达腺病毒,溶解于NaCl中制备JetPEI/DNA复合体。用DMEM/F12完全培养基调整次代神经干细胞密度为5×108 L-1,向24孔板中每孔加入400 μL细胞悬液、100 μL JetPEI/DNA复合体,置37 ℃、体积分数为5%的CO2培养箱中,分别于转染24,48,72 h后收集神经干细胞。 主要观察指标：采用荧光显微镜、流式细胞仪检测转染效率,RT-PCR检测目的基因在神经干细胞内的表达。 结果：转染24 h后即可在荧光显微镜下观察到绿色荧光蛋白的表达,转染24,48,72 h后绿色荧光蛋白阳性率分别为15.36%,24.67%,25.73%。各转染时间点神经干细胞均表达胶质细胞源性神经营养因子及内皮素B受体基因,转染24 h条带亮度较低,72 h时外源基因表达水平最高。 结论：运用jetPEI试剂成功将目的基因转染至小鼠神经干细胞内,且胶质细胞源性神经营养因子和内皮素B受体基因在靶细胞中得到有效转录和表达。     

预防性应用尼莫地平对面神经损伤大鼠BDNF及GDNF表达的影响

目的探讨预防性应用尼莫地平对面神经损伤大鼠脑源性神经营养因子(brain derived neurotrophic factor,BDNF)和胶质细胞源性神经营养因子(glial cell line-derived neurotrophic factor,GDNF)表达的影响。方法 96只SD大鼠随机分为假手术组、单纯损伤组、尼莫地平预处理组、尼莫地平后处理组,每组24只。假手术组不损伤面神经,单纯损伤组建立大鼠面神经损伤模型。尼莫地平预处理组在模型建立前给予尼莫地平,持续给药到术后2周。尼莫地平后处理组在模型建立后给予尼莫地平,持续给药2周。应用Western blot方法观察大鼠面神经损伤后1、3、6个月BDNF和GDNF的表达。结果与单纯损伤组相比,尼莫地平后处理组造模后1个月大鼠BDNF、GDNF的表达均升高(均P<0.05)。尼莫地平预处理组和后处理组BNDF和GDNF的表达在各时间点差异均有统计学意义(均P<0.05)。结论预防性应用尼莫地平可以调节面神经损伤大鼠GDNF和BDNF的表达,充分发挥其神经保护作用。     

维拉帕米与神经生长因子促进大鼠坐骨神经再生的协同作用

背景：实验证明周围神经损伤时,轴突的变性与神经元凋亡都与Ca2+的超载有着极其密切的关系。 目的：利用大鼠坐骨神经损伤模型观察L型钙离子通道阻滞剂维拉帕米联合神经生长因子促进周围神经再生的协同作用。 设计、时间及地点：随机对照动物实验,于2007-04/2008-11在辽宁医学院手外科实验室完成。 材料：同系健康雄性SD大鼠32只,体质量220~260 g;维拉帕米为辽宁卫星制药厂产品,国药准字H21022847;神经生长因子为sigma公司产品。 方法：同系SD大鼠32只随机分为4组,每组8只,分别在右侧梨状肌下缘5 mm切断坐骨神经后立即原位缝合造成坐骨神经损伤模型。①维拉帕米+神经生长因子组：腹腔注射维拉帕米4 mg/(kg•d),术侧腓肠肌肉注射神经生长因子0.6 μg/d。②维拉帕米组：腹腔注射维拉帕米4 mg/(kg•d),术侧腓肠肌注射等量生理盐水。③神经生长因子组：术侧腓肠肌注神经生长因子0.6 μg/d,并腹腔注射等量生理盐水。④空白对照组：分别腹腔,肌注等量生理盐水。以左侧坐骨神经为正常对照。 主要观察指标：术后12周对各组再生神经进行大体观察,神经电生理测定,组织学观察及有髓神经纤维计数。 结果：术后12周,维拉帕米+神经生长因子组足部溃疡的出现与愈合以及展抓反射出现的时间均早于其他各组。神经传导速度恢复率和有髓神经纤维计数恢复率分析表明：维拉帕米+神经生长因子组>维拉帕米组>神经生长因子组>空白对照组。光镜和电镜下可见：维拉帕米+神经生长因子组再生的神经纤维最多,轴突较为粗大。有髓神经纤维多,髓鞘完整,优于其他3组。神经纤维直径恢复率分析表明：维拉帕米+神经生长因子组>神经生长因子组>维拉帕米组>空白对照组。 结论：维拉帕米与神经生长因子对促进周围神经形态结构和功能的恢复均具有明显的协同作用。     

Guinea pigs as an animal model for sciatic nerve injury

The overwhelming use of rat models in nerve regeneration studies is likely to induce skewness in treatment outcomes.To address the problem,this study was conducted in 8 adult guinea pigs of either sex to investigate the suitability of guinea pig as an alternative model for nerve regeneration studies.A crush injury was inflicted to the sciatic nerve of the left limb,which led to significant decrease in the pain perception and neurorecovery up to the 4th weak.Lengthening of foot print and shortening of toe spread were observed in the paw after nerve injury.A 3.49 ± 0.35 fold increase in expression of neuropilin 1(NRP1) gene and 2.09 ± 0.51 fold increase in neuropilin 2(NRP2) gene were recorded 1 week after nerve injury as compared to the normal nerve.Ratios of gastrocnemius muscle weight and volume of the experimental limb to control limb showed more than 50% decrease on the 30 th day.Histopathologically,vacuolated appearance of the nerve was observed with presence of degenerated myelin debris in digestion chambers.Gastrocnemius muscle also showed degenerative changes.Scanning electron microscopy revealed loose and rough arrangement of connective tissue fibrils and presence of large spherical globules in crushed sciatic nerve.The findings suggest that guinea pigs could be used as an alternative animal model for nerve regeneration studies and might be preferred over rats due to their cooperative nature while recording different parameters.     

Human umbilical cord blood stem cells and brain-derived neurotrophic factor for optic nerve injury:a biomechanical evaluation

Treatment for optic nerve injury by brain-derived neurotrophic factor or the transplantation of human umbilical cord blood stem cells has gained progress, but analysis by biomechanical indicators is rare. Rabbit models of optic nerve injury were established by a clamp. At 7 days after injury, the vitreous body received a one-time injection of 50 μg brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood stem cells. After 30 days, the maximum load, maximum stress, maximum strain, elastic limit load, elastic limit stress, and elastic limit strain had clearly improved in rabbit models of optical nerve injury after treatment with brain-derived neurotrophic factor or human umbilical cord blood stem cells. The damage to the ultrastructure of the optic nerve had also been reduced. These findings suggest that human umbilical cord blood stem cells and brain-derived neurotrophic factor effectively repair the injured optical nerve, improve biomechanical properties, and contribute to the recovery after injury.     

Dexamethasone prevents vascular damage in early-stage non-freezing cold injury of the sciatic nerve

Non-freezing cold injury is a prevalent cause of peripheral nerve damage, but its pathogenic mechanism is poorly understood, and treatment remains inadequate. Glucocorticoids have anti-inflammatory and lipid peroxidation-inhibiting properties. We therefore examined whether dexamethasone, a synthetic glucocorticoid compound, would alleviate early-stage non-freezing cold injury of the sciatic nerve. We established Wistar rat models of non-freezing cold injury by exposing the left sciatic nerve to cold(3–5°C) for 2 hours, then administered dexamethasone(3 mg/kg intraperitoneally) to half of the models. One day after injury, the concentration of Evans blue tracer in the injured sciatic nerve of rats that received dexamethasone was notably lower than that in the injured sciatic nerve of rats that did not receive dexamethasone; neither Evans blue dye nor capillary stenosis was observed in the endoneurium, but myelinated nerve fibers were markedly degenerated in the injured sciatic nerve of animals that received dexamethasone. After dexamethasone administration, however, endoneurial vasculopathy was markedly improved, although damage to the myelinated nerve fiber was not alleviated. These findings suggest that dexamethasone protects the blood-nerve barrier, but its benefit in non-freezing cold injury is limited to the vascular system.     

Chemically extracted aceUular allogeneic nerve graft combined with ciliary neurotrophic factor promotes sciatic nerve repair

A chemically extracted acellular allogeneic nerve graft can reduce postoperative immune rejection, similar to an autologous nerve graft, and can guide neural regeneration. However, it remains poorly understood whether a chemically extracted acellular allogeneic nerve graft combined with neurotrophic factors provides a good local environment for neural regeneration. This study investigated the repair of injured rat sciatic nerve using a chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor. An autologous nerve anastomosis group and a chemical acellular allogeneic nerve bridging group were prepared as controls. At 8 weeks after repair, sciatic functional index, evoked potential amplitude of the soleus muscle, triceps wet weight recovery rate, total number of myelinated nerve fibers and myelin sheath thickness were measured. For these indices, values in the three groups showed the autologous nerve anastomosis group 〉 chemically extracted acellular nerve graft ＋ ciliary neurotrophic factor group 〉 chemical acellular allogeneic nerve bridging group. These results suggest that chemically extracted acellular nerve grafts combined with ciliary neurotrophic factor can repair sciatic nerve defects, and that this repair is inferior to autologous nerve anastomosis, but superior to chemically extracted acellular allogeneic nerve bridging alone.     

Combination therapy using evening primrose oil and electrical stimulation to improve nerve function following a crush injury of sciatic nerve in male rats

Peripheral nerve injuries with a poor prognosis are common. Evening primrose oil (EPO) has beneficial biological effects and immunomodulatory properties. Since electrical activity plays a major role in neural regeneration, the present study investigated the effects of electrical stimulation (ES), combined with evening primrose oil (EPO), on sciatic nerve function after a crush injury in rats. In anesthetized rats, the sciatic nerve was crushed using small haemostatic forceps followed by ES and/or EPO treatment for 4 weeks. Functional recovery of the sciatic nerve was assessed using the sciatic functional index. Histopathological changes of gas-trocnemius muscle atrophy were investigated by light microscopy. Electrophysiological changes were assessed by the nerve conduction velocity of sciatic nerves. Immunohistochemistry was used to determine the remy-elination of the sciatic nerve following the interventions. EPO + ES, EPO, and ES obviously improved sciatic nerve function assessed by the sciatic functional index and nerve conduction velocity of the sciatic nerve at 28 days after operation. Expression of the peripheral nerve remyelination marker, protein zero (P0), was in-creased in the treatment groups at 28 days after operation. Muscle atrophy severity was decreased significantly while the nerve conduction velocity was increased significantly in rats with sciatic nerve injury in the injury+ EPO + ES group than in the EPO or ES group. Totally speaking, the combined use of EPO and ES may pro-duce an improving effect on the function of sciatic nerves injured by a crush. The increased expression of P0 may have contributed to improving the functional effects of combination therapy with EPO and ES as well as the electrophysiological and histopathological features of the injured peripheral nerve.     

Boric acid reduces axonal and myelin damage in experimental sciatic nerve injury

hTe aim of this study was to investigate the effects of boric acid in experimental acute sciatic nerve injury. Twenty-eight adult male rats were randomly divided into four equal groups (n = 7): control (C), boric acid (BA), sciatic nerve injury (I) , and sciatic nerve injury + boric acid treatment (BAI). Sciatic nerve injury was generated using a Yasargil aneurysm clip in the groups I and BAI. Boric acid was given four times at 100 mg/kg to rats in the groups BA and BAI atfer injury (by gavage at 0, 24, 48 and 72 hours) but no injury was made in the group BA.In vivo electrophysiological tests were performed at the end of the day 4 and sciatic nerve tissue samples were taken for histopathological examination. The amplitude of compound action potential, the nerve conduction velocity and the number of axons were signiifcantly lower and the myelin structure was found to be broken in group I compared with those in groups C and BA. However, the amplitude of the compound action potential, the nerve conduction velocity and the number of axons were signiifcantly greater in group BAI than in group I. Moreover, myelin injury was signiifcantly milder and the intensity of nuclear factor kappa B immunostaining was signiifcantly weaker in group BAI than in group I. hTe results of this study show that administration of boric acid at 100 mg/kg atfer sciatic nerve injury in rats markedly reduces myelin and axonal injury and improves the electrophysiological function of injured sciatic nerve possibly through alleviating oxidative stress reactions.