Epigenetics has become one of the major research directions of human genome after genome sequencing, and plays an important role in many complex pathophysiological processes such as tumor, biological development, aging and neuropathy. The metabolic memory phenomenon in diabetic retinopathy (DR) suggests that the pathogenesis of DR has a complicated relationship with epigenetic factors. Many studies show the changes and roles of histone modification, DNA methylation and non-coding RNA in the development of DR. However, the current understanding of how epigenetic modifications affect diseases is limited, and most studies on histone modifications have not been carried out in DR. There is still a lot of room for development in epigenetic research on DR. At the same time, epigenetic modification is very complicated, and how to integrate the interaction of different modifications in the development stage of DR is the focus of future research work.

Mesenchymal stem cells (MSCs) are considered as an ideal treatment for multiple diseases including ocular disease.Recent studies have demonstrated that MSCs-derived exosomes have similar functions with MSCs.Exosomes are nanovesicles surrounded by a phospholipid layer that shuttle active cargo between different cells.They are capable of passing the biological barrier and have potentials to be utilized as natural carrier for the ocular drug delivery.

Objective To observe the effects of exosomes derived from rat mesenchymal stem cells (MSC-exosomes) on the rat experimental autoimmune uveitis (EAU) model.Methods Twelve Lewis rats were randomly divided into experimental group and control group by random number table,with 6 rats in each group.Rats in the experimental group were established with EAU model,100 μl of MSC-exosomes (50 μg) were periocular injected on the 9th day after modeling while the control rats were injected with the same volume of phosphate buffer.At different time points after modeling,the retinal structure was observed by hematoxylin and eosin (HE) staining,and the clinical and pathological manifestations were evaluated.T cells from the two groups were analyzed by flow cytometry,Immunohistochemical staining was used to observe the expression of macrophage surface marker CD68.The effect of MSC-exosomes on T cells was measured by lymphocyte proliferation assays.And flow cytometry was used to detect Th 1,Th 17 and regulatory T cells Variety.Electroretinogram (ERG) was used to evaluate the retinal function.Data were compared between the two groups using the t test.Results HE staining showed that the retina structure of the experimental group was more complete than that of the control group on the 15th day after modeling.Immunohistochemical staining showed that the positive expression of CD68 in the experimental group was significantly less than that in the control group.On the 15th day after modeling,the retinal pathological score of the experimental group was lower than that of the control group.On the 9th to 13th day after modeling,compared to the control group,the average clinical scores of the retina in the experimental group were lower,and the difference was statistically significant (t=3.665,3.21,3.181,4.121,3.227;P＜0.01).The results of T cell proliferation assay showed that exosomes (1.0,10.0 μg/ml) inhibited the proliferation of T cells under different concentrations of R16 (1,10,30 μg/ml),and the difference was statistically significant (F=1 1.630,4.188,6.011;P＜0.05).The results of flow cytometry showed that the number ofThl,Th17 and Treg cell subsets in the experimental group was decreased compared with the control group,and the difference was statistically significant (t=7.374,4.525,6.910;P＜0.01).There was no difference in the proportion of cells in the T cells and lymph nodes (t=1.126,0.493,0.178;P=0.286,0.632,0.862).The results of ERG showed that,compared with the control group,the amplitudes of 0.01,3.0 cd/m2 a wave and b wave of the experiment group were all increased on the 15th day after modeling,and the differences were statistically significant (t=3.604,4.178,4.551,2.566,P＜0.05).Conclusions MSC-exosomes can reduce the clinical and pathological manifestations of EAU,protect retinal function,reduce ocular macrophage infiltration,down-regulate the proportion of inflammatory cells in the eye,and inhibit T cell proliferation.