慢病毒介导EGFP基因修饰的人羊膜上皮细胞重建角膜表层的实验研究

背景研究发现人羊膜上皮细胞（AECs）具有干细胞的某些特性，已有学者用其进行眼表重建，其可能是角膜表层重建的一种新型种子细胞。目的探讨经慢病毒载体（pLenti6／V5一DEST）介导增强型绿色荧光蛋白（EGFP）基因修饰的人AECs作为组织工程化角膜表层一种新的细胞来源的应用价值。方法利用慢病毒载体携带标记基因EGFP转染人AECs，荧光显微镜下观察转染基因的瞬时表达，倒置显微镜下观察转染细胞的生长形态，用流式细胞仪检测转染细胞中EGFP的阳性表达率，然后应用EGFP基因修饰的人AECs构建复层上皮细胞一角膜基质移植材料。手术切除兔眼的全部角膜缘组织制备角膜缘干细胞缺损动物模型，随机分为2组，实验组兔眼移植EGFP基因修饰的人AECs构建的复层上皮细胞一角膜基质移植材料，对照组兔眼移植无上皮细胞的角膜基质移植材料，每天裂隙灯下观察2组兔眼角膜的混浊、结膜上皮化和新生血管化情况。1个月后处死动物摘除眼球，荧光显微镜下观察角膜植片中EGFP的表达，用免疫组织化学法检测其细胞角蛋白8（CK8）、CKl8和CKl2的表达，以鉴定移植细胞分化为角膜样的上皮细胞。结果大多数转染细胞筛选出的抗性克隆以及培养的克隆细胞与正常体外培养的人AECs形态相似，流式细胞仪检测显示瞬时转染48h的人AECs中EGFP阳性表达率最高，为61．50％，与12、24、96h转染组15．24％、38．27％、39．10％比较差异均有统计学意义（P〈0．05），与72h转染组的58．36％比较差异无统计学意义（P〉0．05）。实验组10只兔眼中有6只眼角膜恢复透明，组织片在荧光显微镜下观察能发出绿色荧光，免疫组织化学结果显示CK8、CKl8、CKl2表达均为细胞质棕色染色，细胞核蓝染。对照组兔眼角膜均混浊、水肿，荧光显微镜下未见荧光，且部分角膜组织有CK8、CKl8表达，无CKl2表达。结论EGFP基因修饰的人AECs构建的复层上皮细胞一角膜基质移植材料能较好地重建角膜缘干细胞缺乏的兔眼角膜表层，可能是组织工程角膜表层一种新的细胞来源。慢病毒载体是一种安全有效的基因转移工具。

Reconstruction of corneal surface layer using human amniotic epithelial cells modified by lentiviral vector-mediated EGFP gene

Background Studies demonstrated that human amniotic epithelial cells (AECs) have some characteristics of embryonic stem cells and they were used to re-establish the surface of eyes. Human AECs may serve as new seed cells in tissue engineering for corneal epithelium reconstitution in the future. Objective The present study was to investigate the application value of human amniotic epithelium cells transfected by lentiviral vectormediated enhanced green fluorescent protein (EGFP) gene as new seed cell source for engineering the corneal surfacelayer. Methods Lentiviral vector carrying the objective gene EGFP was transfected into human amniotic epithelial cells (pLenti6/V5-DEST),and the transient expression of the transgene in the human amniotic epithelial cells was observed under the fluorescence microscope. Flow cytometry was used to detect the positive expression rates of EGFP in transfected cells. The transfected human amniotic epithelial cells were seeded onto the fresh corneal stromal surface of New Zealand white rabbit and cultured in vitro. The stem cell deficiency ( SCD ) models were established by cutting off the limbus of cornea in 20 eyes of New Zealand white rabbits, and the model rabbits were then divided into 2 groups randomly. The transplanted grafts carrying the pLenti6/V5-DEST-EGFP gene-transferred human amniotic epithelium cells were regarded as the pLenti6/V5-DEST-EGFP group, and the corneal stroma graft without any epithelial cell served as the control group. The opacity of stroma and corneal conjunctivalization and vascularization were observed daily. The rabbits' eyes were extracted one month after operation. The expression of EGFP in the cornea was detected under the fluorescence microscope, and the expression of CK8, CK18 and CK12 in cornea was detected by immunohistochemical staining. Results The shape of the transferred human amniotic epithelial cells resembled normal human amniotic epithelial cells. 48 hours after the transient transfection of EGFP presented with the highest expression level throughout the observation duration, with a positive expression rate of EGFP of 61.5% ,showing significant differences in comparison with that of 12 ( 5.24% ) , 24 ( 38.27% ) or 96 ( 39. 10% ) hours ( P ＜0. 05) post-transfection; but no obvious difference was found in the positive rate of transiently transfected EGFP between 48 hours and 72 hours ( 58.36% ) ( P＞0. 05 ). Six cornea grafts were clear in 1 month and two corneas were rejected during the observation period in the pLenti6/V5-DEST-EGFP group. A few new blood vessels were seen around the graft. Ten corneas of the control group became opaque and cloudy with new blood vessels growth around the grafts. Imunohistochemistry revealed the positive expressions of CK8, CK1 8 and CK12 in the corneal epithelial layer in the pLenti6/V5-DEST-EGFP group. However,the expression of CK12 was absent in the control group. Conclusion Human amniotic epithelium cells transfected with the pLenti6/V5-DEST-EGFP gene is a new and ideal feed cell type to reconstruct the corneal surface layer. Lentivirus is a relatively safe gene transfection vector.