目的：探讨移植色素上皮衍生因子(pigment epithelial-derived factor，PEDF)蛋白修饰人脐带来源间充质干细胞(human umbilical cord-derived mesenchymal stem cells，hUCMSCs)在治疗大鼠视网膜色素变性的作用。

方法：分离和培养hUCMSCs，以PEDF重组慢病毒转染hUCMSCs。实验RCS大鼠(royal college of surgeon rat，RCS)随机分为3组干预，每组8只。实验组视网膜下腔注射PEDF-hUCMSCs； hUCMSCs对照组注射等量hUCMSCs，PBS对照组注射等量PBS。 注射后4、8wk观察视网膜电图(electroretinogram，ERG)，检测视网膜外核层厚度，观察绿色荧光蛋白(green fluorescent protein，GFP)了解细胞的存活情况，通过视网膜切片免疫荧光染色观察其在体吞噬功能，通过MERTK蛋白的表达检测重建吞噬能力来评价疗效。

结果：携带 PEDF基因的重组慢病毒载体，能高效感染hUCMSCs，感染后的 hUCMSCs进行传代培养，慢病毒可延长目的基因在细胞内的表达。移植后8wk视功能上ERG中b波幅值实验组明显高于对照组，移植后4、8wk形态学上视网膜外核层(outer nuclear layer，ONL)厚度实验组均高于对照组，差异均有统计学意义(P<0.05)。移植后4、8wk时GFP染色发现转染PEDF慢病毒的hUCMSCs细胞均能在视网膜下腔存活，视网膜切片行免疫荧光染色显示移植的PEDF-hUCMSCs对感光细胞脱落的外节碎片有吞噬作用。移植后4、8wk时MERTK蛋白的表达检测实验组蛋白条带灰度值明显高于对照组，提示实验组中MERTK蛋白表达也明显增加，RPE重建吞噬能力提高。

结论：移植PEDF蛋白修饰hUCMSCs对RCS大鼠视网膜有保护作用。

METHODS: The hUCMSCs were isolated and cultured, hUCMSCs were transfected with PEDF recombinant lentivirus. Experimental royal college of surgeon(RCS)rats were randomly divided into 3 groups, 8 rats in each group. The experimental group was injected with PEDF-hUCMSCs subcutaneously. The hUCMSCs control group was injected with the same amount of hUCMSCs. The PBS control group was injected with the same amount of PBS. At 4 and 8wk after injection, electroretinography(ERG), the thickness of retinal outer nuclear layer(ONL)and green fluorescent protein(GFP)staining were observed. Immunofluorescence staining of retinal sections and the phagocytosis of MERTK protein were evaluated to determine phagocytosis.

RESULTS: PEDF gene carrying recombinant lentiviral vector could efficiently infect hUCMSCs. After infection, hUCMSCs were sub cultured and the lentivirus prolonged the expression in the cells of the target gene. At 8wk after transplantation, the amplitude of b-wave in ERG were significantly higher in the experimental group than in the control groups. At 4 and 8wk after transplantation, morphological changes of ONL thickness in the experimental group were significantly higher than those in the control groups(all P<0.05). At 4 and 8wk after transplantation, hUCMSCs infected by lentiviral vector carrying PEDF were found survival in the subretinal cavity by GFP staining, and the PEDF-hUCMSCs were found having phagocytosis for outer segment fragments of photorecepter cells by immunofluorescence staining. At 4 and 8wk after transplantation, the Protein band gray values in experimental group were significantly higher than that in control groups, which indicated that the expressions of MERTK protein in experimental group were also increased significantly, and the phagocytic capacity of RPE were improved.

CONCLUSION: Transplantation of pigment epithelium-derived protein modified human umbilical cord-derived mesenchymal stem cells has a protective effect on the retina of RCS rats.