大鼠Bdnf基因慢病毒载体的构建及其在骨髓间质干细胞中的表达

Construction of Rat Bdnf Gene Lentiviral Vector and Its Expression in Mesenchymal Stem Cells

摘要:

骨髓间质干细胞（MSCs）是目前基因工程正在探讨应用的靶细胞，为构建带有脑源性神经营养因子（Bdnf）基因慢病毒载体并使其在大鼠骨髓间质干细胞中表达，采用RT-PCR技术获得大鼠Bdnf基因编码区（CDS）片段，限制性内切酶酶切和基因重组构建慢病毒载体质粒PNL-BDNF-IRES₂-EGFP，在脂质体介导下与包装质粒HELPER，包膜质粒VSVG共转染293T细胞包装生产慢病毒。所获慢病毒感染大鼠MSCs（rMSCs）后，PCR和免疫细胞化学法检测在rMSCs中Bdnf基因的插入和表达。结果显示所获的Bdnf基因经测序后与GenBank报道序列完全一致。重组慢病毒载体质粒PNL-BDNF-IRES2-EGFP经鉴定正确。三质粒共转染293T细胞成功，收集、浓缩病毒后测定其滴度为6.7×10⁷TU/mL， PCR证实Bdnf基因插入病毒基因组。感染rMSCs后RT-PCR、免疫细胞化学染色及Western检测各组细胞均有BDNF蛋白表达，其中试验组BDNF-rMSCs更大量表达BDNF，与其余2组(Mock-rMSCs、rMSCs)比较差异具有统计学意义。构建带有Bdnf基因慢病毒载体并在大鼠骨髓间质干细胞中成功表达，为今后基因修饰干细胞的移植后长期观察研究奠定了基础。

Abstract:

Recently, mesenchymal stem cells (MSCs) have been one of the target cells of gene engineering. To construct the lentiviral (LV) vectors carrying the brain-derived neurotrophic factor (Bdnf) gene, the rat mesenchymal stem cells (rMSCs) were infected and finally the Bdnf gene-modified rMSCs was obtained. The CDS region of the rat Bdnf gene was obtained with reverse transcriptase-polymerase chain reaction (RT-PCR), and the transfer plasmid (PNL-BDNF-IRES₂-EGFP) of the LV vector was constructed. The three plasmids of LV vector: PNL-BDNF-IRES₂-EGFP, HELPER, and VSVG were cotransfected to 293T cells to produce the LV vectors, which enabled the coexpression of the Bdnf gene and the enhanced green fluorescent protein (Egfp) gene. rMSCs were separated from the bone marrow of 2-month-old F344 rats, cultured in vitro, and identified. rMSCs were infected by the LV vectors that were produced already and were identified with fluorescent microscope, RT-PCR, immunocytochemical staining, and western blot. The result of sequencing showed that the sequence of the cloned Bdnf gene was consistent with that reported in the GenBank. The PNL-BDNF-IRES2-EGFP plasmid that was identified showed the correct sequence. After the 3 plasmids of LV vectors were cotransfected to the 293T cells, considerable green fluorescence in 293T cells was observed under the fluorescent microscope; the supernatant was collected and concentrated using ultracentrifugation, and the titer of the replication_defective LV vector particles measured was found to be 6.7×10⁷ TU/mL. After the constructed LV vectors infected the rMSCs, the results obtained using RT-PCR, immunocytochemical staining, and western blot showed that the expression of BDNF in the Bdnf-rMSCs group (experimental group, EG) was significantly higher than that in the PNL-IRES2-EGFP-rMSCs group (mock group, MG) and the rMSCs group (control group, CG) at both mRNA and protein levels. LV vectors carrying the Bdnf> gene were constructed successfully. The Bdnf gene-modified rMSCs could express BDNF to a higher degree. This greatly facilitates the next step in the study, such as the long period of therapeutic observation of cerebral ischemia with Bdnf gene-modified rMSCs.