Based on the pathogenic mechanisms of age-related macular degeneration (AMD),tremendous preclinical and clinical trials have demonstrated that cell transplantation which aim to replace impaired retinal pigment epithelium (RPE) with healthy RPE cells is a promising approach to treat AMD.So far,choices of cell sources mainly are autologous RPE,iris pigment epithelium,fetal RPE,human embryonic stem cell-derived RPE and human induced pluripotent stem cell-derived RPE,and some of them are undergoing clinical researches.Grafting manners in cell-based therapies are various including RPE sheet or RPE-choroid complex transplantation,RPE cell suspension injection,and RPE sheet transplantation with scaffolds.This review is limited to cell-based therapies for RPE that damaged first in the progress of AMD and focus on recent advances in cell sources,transplantation methods,preclinical and clinical trials,and the obstacles that must be overcome.

Background Choroidal neovascularization (CNV) is one of the primary causes leading to visual damage in many fundus diseases.Many evidences indicate that macrophage activation and monocyte chemoattractant protein-1 (MCP-1) play important roles in CNV.However, the dynamic expression of macrophage and MCP-1 in the initial stage of CNV is not clear.Objective This study was to investigate the dynamic changes of F4/80 and MCP-1 expressions in retina-choroid tissue with experimental CNV.Methods Laser-induced CNV models were monocularly established in 105 SPF 8-week-old male wild type C57BL/6 mice.The mice were sacrificed at 6,12,24, 48 and 72 hours after photocoagulation, respectively, and the retina-choroid tissue sections and choroidal flatmounts were prepared.The histopathological examination was carried out to observe the changes of morphology and structure as well as inflammatory response in CNV.The expression and distribution of F4/80 and MCP-1 protein in retinachoroid were detected by double immunofluorescence technique.The expression and distribution of F4/80 in choroid were examined by immunofluorescence.The relative expression levels of F4/80 mRNA and the content of MCP-1 protein in RPE-choroid complex were assayed using real-time quantitative PCR and ELISA,respectively.The use and care of the mice complied with the Regulation for the Administration of Affair Concerning Experimental Animals by Ethic Committee of Experimental Animals of Nanjing Medical University.Results The rupture of Bruch membrane, RPE, outer nuclear layer and choroid was exhibited under the optical microscope 6 hours after photocoagulation.Infiltration of inflammatory cells and tissue edema were seen as the lapse of photocoagulation time, and proliferation of vascular endothelial cells was found 72 hours after photocoagulation.F4/80 was expressed in photocoagulation area 6 hours later, and MCP-1 was expressed around the area.With the lapse of photocoagulation time,the expression intensity of MCP-1 weakened and that of F4/80 enhanced.The contents of MCP-1 protein in RPE-choroid complex were (31.25±4.73), (276.31 ±4.20), (331.95 ±5.86), (221.24±4.42), (179.89 ± 4.10) and (130.80 ± 5.90) pg/mg in the normal control group, photocoagulation 6-, 12-, 24-, 48-and 72-hour groups, respectively,with a significant difference among the groups (F=1 416.46 ,P＜0.01).The contents of MCP-1 protein peaked at 12 hours after photocoagulation and then gradually declined.The expression levels of MCP-1 protein in different time groups were higher than those in the normal control group (all at P＜0.01).A significant difference in F4/80 mRNA expression in RPE-choroid complex was also found among the groups (F =762.72, P＜0.01, and a gradually raising tendency was seen over time, showing evidently increase in comparison with the normal control group (all at P＜0.01).Conclusions Inflammatory response occurs in the early stage of experimental CNV.MCP-1 responds to the CNV at early stage,and the accumulation and activation of macrophage play an important role in the development of CNV.

Objective:To observe the flow density (FD) of macular and optic disc and area of foveal avascular zone (FAZ) in severe nonproliferative diabetic retinopathy (S-NPDR).Methods:A prospective cross-sectional study. From October 2019 to April 2020, 31 eyes of 25 S-NPDR patients (S-NPDR group) who were diagnosed in the ophthalmological examination of Jiangsu Province Hospital and 30 eyes of 30 age- and sex-matched healthy volunteers (control group) were included in this study. Optical coherence tomography angiography (OCTA) was used to scan the macular area of 6 mm×6 mm and optic disc of 4.5 mm×4.5 mm. The software automatically divides it into three concentric circles centered on the macular fovea, which were foveal area with a diameter of 1 mm, parafoveal area of 1 to 3 mm, and foveal peripheral area of 3 to 6 mm. The area around the optic disc was divided into 8 areas: nasal upper, nasal lower, inferior nasal, inferior temporal, temporal lower, temporal upper, superior temporal and superior nasal. The FD of the optic disc, the superficial capillary layer (SCP) and deep capillary layer (DCP) of the retina and FAZ area were measured. The FD and FAZ area were compared between the two groups by independent sample t test. The correlation between FAZ area and FD was analyzed by Pearson correlation. Results:In parafoveal and perifoveal area, compared with the control group, the FD of SCP ( t=6.470, 5.220; P<0.001) and DCP ( t=7.270, 7.370; P<0.001) decreased in S-NPDR group. In foveal area, there was statistically significant difference in the FD of DCP between the two groups ( t=2.250, P=0.030), while the difference in FD of SCP between the two groups was not statistically significant ( t=0.000, P=0.900). The FAZ area in S-NPDR group was larger than that in control group, and the difference was statistically significant ( t=2.390, P=0.030). The FD in the S-NPDR group was lower than that in the control group except the superior nasal, the difference was statistically significant ( t=7.520, 5.000, 4.870, 3.120, 2.360, 2.120, 5.410, 5.560, 2.640; P<0.05). Pearson correlation analysis showed that the FAZ area of S-NPDR was negatively correlated with FD of SCP ( r=-0.513, P=0.004), and had no correlation with FD of DCP ( r=0.034, P=0.859). Conclusion:The overall FD in macular area and optic disc of patients with S-NPDR decreased and the FAZ area enlarged.

Objective:To investigate the changes of macular region structure before and after operation in patients with macular epiretinal membrane,and its relationship with the visual function of patients.Methods:The clinical data of 60 patients with macular epiretinal membrane (60 eyes) in our hospital from February 2014 to August 2016 were retrospectively analyzed.All patients were examined with optical coherence tomography (OCT) examination,and observed the changes ofmacula central fovea and retinal each azimuth thickness,and the best corrected visual acuity (BCVA) was recorded before and after operation,and the correlations of them were analysised.Results:The visual acuity was improved in 53 patients (53 eyes) after operation,accounting for 88.33％,and the visual acuity was unchanged in 7 patients (7 eyes),accounting for 11.67％.The preoperative BCVA of patients was (0.18± 0.07),and it was (0.38± 0.12) at 3 months after operation,which was significantly higher than before operation (P＜0.05).Postoperative macular central thickness,inner side of the inner ring thickness,nasal side of the inner ring thickness,above the inner ring thickness,below the inner ring thickness,outer ringtemporal side thickness,external ring nasal side thickness,above the outer ring thickness,below the outer ring thickness in patients compared with the preoperative were significantly lower,the difference was statistically significant (P＜0.05).The Pearson correlation analysis showed that preoperative macular central thickness,preoperative inner side of the inner ring thickness,preoperative outer ring temporal side thickness,the difference of macular fovea thickness before and after operation,the difference of the medial temporal before and after operationwas,the difference of outer ring temporal side before and after operation were negatively correlated with postoperative BCVA (P＜0.05).Conclusion:Vitrectomy can significantly reduce macular retinal thickness in patients with macular epiretinal membrane,and it can improve the visual function of patients,and the shape ofmacular region before operation had some influence on postoperative visual acuity.

Retinal degenerative diseases are the common cause of blindness for all ages.Cell replacement therapy is the main strategy for treating retinal degenerative diseases.Recently, several retinal pigment epithelium(RPE) transplantation clinical trials have taken place worldwide and greatly enhanced the visual function of patients.However, irreversible loss of photoreceptors has been found in the late stage of diseases.Thus, photoreceptor transplantation is essential for the treatment of late-stage retinal degenerative diseases.How to obtain the clinical-grade amount of human cone photoreceptors remains to be one of the technical obstacles.This review introduced the present clinical trials of RPE transplantation and research achievements of photoreceptor transplantation.Furthermore, we will focus on the studies of stem cell-derived human photoreceptor differentiation.Lastly, the difficulties and future directions of stem cell-based therapy for retinal degenerative diseases will be discussed.

Objective: To observe the effect of internal limiting membrane peeling and transplantation on vision-related quality of life in refractory macular hole. Methods: A retrospective clinical study. Thirty patients (30 eyes) with refractory macular hole diagnosed in Ophthalmology Department of The First Affiliated Hospital of Nanjing Medical University from January to December 2016 were included in this study. There were 13 males (13 eyes) and 17 females (17 eyes), with the mean age of 57.3±6.9 years. There were 15 patients(15 eyes) with large macular diameter, 12 patients (12 eyes) with high myopia macular hole, and 3 patients (3 eyes) with secondary traumatic macular hole. The BCVA examination was performed using the Snellen visual acuity chart, which was converted into logMAR visual acuity. OCT was performed to measure the macular retinal thickness (CRT), base diameter and minimum diameter of macular hole. Then, the macular hole index(MHI) was calculated. The logMAR BCVA was 1.52±0.30, MHI was 0.51±0.19. The Chinese version of visual-related quality of life scale-25 (CVRQoL-25) was used to evaluate the vision-related quality of life of patients. The CVRQoL-25 score was 57.60±7.13. All patients underwent 23G vitrectomy combined with inner limited membrane peeling and autologous ILM transplantation. The follow-up was at least 3 months after surgery. The changes of BCVA, MHI, CRT and CVRQoL-25 score before and after surgery were comparatively analyzed. Paired t test was performed to compare the measurement data before and after surgery, and Spearman rank correlation analysis was used for the correlation analysis among the parameters. Results: At 3 months after surgery, the hole closure was detected in 28 eyes (93.3%), not detected in 2 eyes (6.7%). The logMAR BCVA was 1.16±0.33, CRT was 161.00±15.26, and CVRQoL-25 scores was 70.83±9.77. Compared with before surgery, the BCVA (t=4.386, P=0.000) and CVRQoL-25 score (t=-5.991, P=0.000) after surgery were improved. Spearman rank correlation analysis showed that CVRQoL-25 score was negatively correlated with preoperative and postoperative logMAR BCVA (r=−0.536, −0.796; P=0.002, 0.000); positively correlated with preoperative MHI (r=0.421, P=0.020) and postoperative CRT (r=0.589, P=0.001). Conclusion Internal limiting membrane peeling and transplantation for refractory macular hole can significantly improve the vision-related quality of life and visual acuity, while achieved a high hole closure rate (93.3%).

Objective: To study the damage effects of blue-light exposure on retinal morphology and function in mouse. Methods: Twenty 8-week-old clean C57BL/6J mice were randomly divided into blue-light exposure group and normal control group by coin tossing method.The mice in the blue-light exposure group was exposed to 10 000 lx blue light for 5 days after dark adaptation for 24 hours, and the mice in the normal control group was kept under the normal light intensity for 5 days at 12-hour light/12-hour darkness cycles.The retinal thickness was detected by optical coherence tomography (OCT), and retinal function was evaluated by electroretinogram (ERG). The mice was sacrificed and the frozen section and flat mount of eyeball wall was created at 24 hours after irradiation.The expressions of rhodopsin (Rho), zonula occludens-1 (ZO-1) and β-catenin in the retinas were detected by immunofluorescent staining.The use and care of the experimental animals adhered to ARVO Statement by American Society of Visual and Ophthalmological Sciences (No.IACUC-1803029). Results: The thickness of the retinal outer nuclear layer at 200, 400, 600, 800 and 1 000 μm from the superior and inferior to optic nerves were thinned in the mice of the blue-light exposure group compared with those of the normal control group, showing significant differences between the two groups (all at P<0.05). The b-wave amplitude of the scotopic and photopic ERG was (305.50±41.52)μV and (119.50±6.67)μV in the blue-light exposure group, respectively, which was significantly reduced in comparison with (415.50±28.77)μV and (139.75±8.26)μV of the normal control group (both at P<0.05). Immunofluorescent staining showed that the retinal pigment epithelial (RPE) cells of the mice exhibited hexagonal shape with regular arrangement, retinal morphology was regular, and the expressions of Rho, ZO-1 and β-catenin proteins showed stronger fluorescence in the retinas of normal control group.However, structural disorder, diminishing fluorescence intensity of Rho, ZO-1 and β-catenin were found in the blue-light exposure group.The morphology of the retina was disordered while the cell structure was destroyed. Conclusions Blue-light irradiation results in morphological and functional damages of retina.

Circular RNA (circRNA) is a new group of endogenous non-coding RNAs produced by back-splicing, which has multiple molecular functions such as acting as microRNA sponges, regulators of transcription and splicing, adaptors for protein-protein interaction. Recent studies have shown that circRNA play an essential role in development and progression of retinal microvascular dysfunction, diabetic retinopathy, age-related macular degeneration, proliferative vitreoretinopathy, eye diseases caused by hyperhomocysteine and ocular malignancy. In pathological conditions, the differential expression of circRNA alters the transcription and translation of corresponding genes, thus changing the activity and function of cells. CircRNA may become a new marker and prognostic indicator of fundus diseases, and its targeted intervention may also become a potential treatment for fundus diseases.

Replacement of diseased retinal pigment epithelium (RPE) cells with healthy RPE cells by transplantation is one option to treat several retinal degenerative diseases including age-related macular degeneration,which are caused by RPE loss and dysfunction.A cellular scaffold as a carrier for transplanted cells,may hold immense promise for facilitating cell migration and promoting the integration of RPE ceils into the host environment.Scaffolds can be prepared from a variety of natural and synthetic materials.Strategies,such as surface modification and structure adjustment,can improve the biomimetic properties of the scaffolds,optimize cell attachment and cellular function following transplantation and lay a foundation of clinical application in the future.

Optical coherence tomography (OCT), as a high-resolution, non-invasive, in-vivo image method has been widely used in retinal field, especially in the examination of fundus diseases. Nowadays, the modality has been gradually popularized in most of the national basic-level hospitals. However, OCT is only employed as a diagnostic tool in most cases, ophthalmologists lack of awareness of further exploring the information behind the raw data. In the era of fast-developing artificial intelligence, on the basis of standardized information management, a more comprehensive OCT database should be established. Further original image processing, lesion analysis, and artificial intelligence development of OCT images will help improve the understanding level of vitreoretinal diseases among clinicians and assist ophthalmologists to make more appropriate clinical decisions.