摘要目的:研究间充质干细胞(MSCs)来源小胞外囊泡(sEVs)对小鼠视网膜光损伤的作用及其可能的机制。方法:人脐带来源MSCs采用流式细胞术鉴定表面标记蛋白，收集第3~5代MSCs培养上清，超速离心收集sEVs并采用透射电子显微镜鉴定形态。将65只清洁级8~10周龄健康雌性BALB/c小鼠按照随机数字表法随机分为正常组(17只)、磷酸盐缓冲液(PBS)组(24只)和sEVs组(24只)。PBS组和sEVs组小鼠右眼玻璃体腔分别注射2 μl PBS和2 μl sEVs后，在蓝光照度930 lx的环境下照射6 h；正常组小鼠不做处理。分组处理后3 d，采用苏木精－伊红染色观察视网膜结构，原位末端转移酶标记(TUNEL)染色进行凋亡细胞计数，视网膜电图(ERG)检测小鼠视网膜功能，mRNA转录组测序技术检测PBS组与sEVs组小鼠视网膜mRNA表达差异情况，并进行差异基因KEGG聚类分析，实时荧光定量PCR法进一步验证差异基因表达。结果:培养的MSCs中CD90、CD105表达阳性，而CD34、CD45表达阴性，提取的MSC-sEVs呈直径为80~140 nm的双层膜囊泡结构。苏木精－伊红染色结果显示，PBS组小鼠视网膜外核层细胞核排列紊乱，sEVs组视网膜结构紊乱程度轻于PBS组。sEVs组视网膜凋亡细胞计数为(14.60±4.04)个/视野，少于PBS组的(24.00±8.52)个/视野，差异有统计学意义( t＝2.37， P<0.05)。sEVs组ERG a波振幅为(64.38±16.70)μV，高于PBS组的(16.78±6.37)μV，差异有统计学意义( P<0.05)；PBS组和sEVs组b波振幅分别为(132.40±39.41)μV和(154.86±34.08)μV，明显低于正常组的(338.38±27.41)μV，差异均有统计学意义(均 P<0.05)。mRNA测序共发现差异表达基因110个，其中sEVs组下调基因109个。KEGG聚类分析结果提示，差异基因主要集中于炎症性疾病、免疫相关信号通路。PCR结果显示，sEVs组视网膜中趋化因子配体2、趋化因子受体2、白三烯B4、白细胞免疫球蛋白样受体A6和白细胞介素1β的mRNA相对表达水平低于PBS组，差异均有统计学意义(均 P<0.05)。 结论:MSC-sEVs可以减轻蓝光造成的视网膜结构和功能损害，这种保护作用可能是通过抑制炎症反应来实现的。

abstractsObjective:To investigate the effect of small extracellular vesicles (sEVs) derived from mesenchymal stem cells (MSCs) in mouse model of retinal light injury and the possible mechanism.Methods:Human umbilical cord derived MSCs were identified by flow cytometry.Supernatants of passage 3-5 MSCs were collected.sEVs were harvested by ultracentrifugation and were identified by transmission electron microscopy.Sixty-five healthy female SPF-grade BALB/c mice aged 8-10 weeks were randomly divided into normal group (17 mice), phosphate buffered saline (PBS) group (24 mice) and sEVs group (24 mice). Mice in PBS and sEVs groups were intravitreally injected with 2 μl of PBS and sEVs, respectively, and were exposed to 930 lx blue light for 6 hours.No intervention was administered to the normal group.Three days after lighting, mice retinal structure was observed by hematoxylin-eosin staining.Apoptotic retinal cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Retinal function was tested by electroretinogram.Differentially expressed mRNAs between PBS group and sEVs group were assayed by mRNA transcriptome sequencing and were analyzed through KEGG cluster analysis.The differential mRNAs were verified via real-time quantitative PCR.The study protocol was approved by the Animal Ethics Committee of Tianjin Medical University Eye Hospital (No.TJYY20201221035).Results:MSCs were positive for CD90 and CD105, negative for CD34 and CD45.The extracted MSC-sEVs showed a bilayer membrane vesicle with a diameter of 80-140 nm.Hematoxylin-eosin staining showed the arrangement of photoreceptor nuclei was disordered in outer nuclear layer in PBS group.The disorder of photoreceptor nuclei arrangement of sEVs group was slighter than that of PBS group.The apoptotic cell number of sEVs group was (14.60±4.04)/visual field, which was lower than (24.00±8.52)/visual field of PBS group, with a statistically significant difference ( t=2.37, P<0.05). The a-wave amplitude of sEVs group was (64.38±16.70)μV, which was higher than (16.78±6.37) μV of PBS group, showing a statistically significant difference ( P<0.05). The b-wave amplitudes of PBS and sEVs groups were (132.40±39.41) μV and (154.86±34.08) μV, respectively, which were lower than (338.38±27.41) μV of normal group, and the differences were statistically significant (both at P<0.05). A total of 110 differentially expressed mRNAs were detected.There were 109 downregulated mRNAs in sEVs group.Differentially expressed mRNAs were mainly inflammation- and immune-related pathways.PCR showed that the expression level of C-C motif chemokine ligand 2, C-C motif chemokine receptor 2, leukotriene B4, leukocyte Ig-like receptor A6 and interleukin-1β in sEVs group were significantly decreased in comparison with PBS group (all at P<0.05). Conclusions:MSC-sEVs can ameliorate blue light-induced retinal structural and functional damage.The protective effect may be achieved through inhibiting inflammatory response.