OBJECTIVE:To investigate the effect of human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-Exs) on diabetic retinal neurodegeneration (DRN).METHODS:Exosomes were isolated from human umbilical cord mesenchymal stem cells (hucMSC) and identified using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and Western blotting (WB). Rats were intraperitoneally injected with Streptozotocin (STZ) to establish a diabetes mellitus model, and blood glucose levels and body weight were assessed. The rats were intravitreally injected with phosphate buffered saline (PBS; diabetic group) or hucMSC-Exs (hucMSC-Exs group). A control group of rats were not treated with STZ and were intravitreally injected with PBS (normal control group). Hematoxylin-eosin (HE) staining was used to observe changes in retinal structure and to count the number of retinal ganglion cells (RGCs) four weeks after intravitreal injection. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay (TUNEL) was used to detect retinal cell apoptosis. The retinal expression of p38 mitogen-activated protein kinase (p38MAPK), phosphorylated p38MAPK (p-p38MAPK), Bcl-2 and Bax was measured using WB to investigate the mechanism by which hucMSC-Exs affects DRN.RESULTS:Using TEM, NTA and WB, hucMSC-Exs were successfully isolated. No significant change was observed after injection in the normal control group. All rats injected with STZ developed hyperglycemia. HE staining revealed that hucMSC-Exs effectively alleviated retinal structure disruption and reduced the apoptosis of RGCs (P < 0.05). Cells positive for TUNEL (TUNEL+) occurred at a higher rate in the diabetic group than in other groups (P < 0.05). Compared with the normal control group, the expression of p-p38MAPK was significantly increased in the diabetic group and decreased in the hucMSC-Exs group (P < 0.01). The expression of Bax was significantly decreased while Bcl-2 expression was significantly increased in hucMSC-Exs group (P < 0.01).CONCLUSION:These findings suggest that intravitreal injection of hucMSC-Exs can reduce DRN and protect retinal structure, and that these effects are mediated through inhibition of the p38MAPK pathway.

AIM: To assess the protective effect of human umbilical cord mesenchymal stem cell exosomes (hucMSC-Exs) in a diabetic rat model by using a variety of retinal bioassays. METHODS: hucMSCs were subjected to differential ultracentrifugation for the collection of exosomes, and transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) using a NanoSight analysis system and Western blotting (WB) were used to analyze the expression of surface marker proteins such as CD63, CD9 and Calnexin. Streptozotocin (STZ) was injected into the intraperitoneal cavity to establish a diabetic model. Rats were divided into a normal group, diabetic group and hucMSC-Ex group. Fundus fluorescein angiography (FFA), optical coherence tomography (OCT) and other live imaging methods were used to observe the fundus of the rats. Finally, the eyeballs of rats from each group were collected for hematoxylin-eosin (HE) staining to further analyze the retinal structure. RESULTS: Through TEM, NTA and WB, we successfully isolated hucMSC-Exs. Subsequent FFA and OCT confirmed that hucMSC-Exs effectively prevented early retinal vascular damage and thickening of the retina. Finally, HE staining of rat retinal sections revealed that exosomes effectively alleviated retinal structure disruption caused by diabetes. CONCLUSION: hucMSC-Exs have a protective effect on the retina in diabetic rat through FFA, OCT and HE staining.

AIM To provide a detailed description of the natural history of persistent subretinal fluid (SRF) after successful repair of rhegmatogenous retinal detachment (RRD) and its association with visual outcome. METHODS This was a prospective long-term follow-up for eyes undergoing scleral buckling (SB) surgery for macula-off RRD. Examinations were carried out preoperatively and postoperatively at 1, 3, 6, 9 and 12mo, until persistent SRF had completely resolved. One month postoperatively, optical coherence tomography (OCT) was used to classify SRF into three patterns: bleb-like loculated (BL), shallow-diffused (SD), and multiple blebs (MB). Serial OCT imaging was used to evaluate morphological changes in SRF until its complete disappearance. Patients were divided into two groups depending on the presence or absence of persistent SRF. RESULTS A total of 59 patients (59 eyes) were included. There were no statistical differences between two groups at baseline, except for the proportion of patients with high myopia and a younger age. One month after surgery, OCT detected persistent SRF in 49 eyes (83.1%). The 3 morphological patterns of SRF were observed in 27 eyes (55.1%) with BL, 13 eyes (26.5%) with SD, and 9 eyes (18.4%) with MB. The mean time for complete absorption differed significantly across the three SRF patterns (F=8.097, P=0.001), which was 8.8±6.1, 20.1±12.1, and 16.7±10.2mo in BL, SD, and MB, respectively. In 9 of the 13 eyes with SD, the pattern transformed into MB type. In cases involving MB, the size and number of blebs decreased gradually until they had been completely absorbed. Eyes with persistent SRF were more likely to demonstrate disruption of the ellipsoid zone (49.0% vs 10%, P=0.034). The final best-corrected visual acuity of two groups was 0.37±0.11 (with SRF) vs 0.34±0.12 (without SRF) logMAR (P=0.499), respectively. CONCLUSION High preoperative myopia and younger age are associated with persistent SRF. BL is the most commonly observed pattern with the shortest duration and gradually disappeared. Most cases involving SD SRF transform into MB type during resolution. The size and number of the MBs decrease gradually until they were completely absorbed. The absence of persistent SRF may contribute to slow visual recovery in the short-term but does not influence the final visual outcome.

Dear Editor,We describe in detail a case of dominant cystoid macular dystrophy（DCMD） patient carrying a novel heterozygous RP1 L1 mutation. DCMD is a unique form of macular dystrophy; the appearance of cystic spaces in the macula indicates its onset, while the rest of the retina is

AIM: To explore the protective effects of aminoguanidine (AG) on retinal apoptosis in mice with oxygen-induced retinopathy (OIR).METHODS:A total of 80 C57BL/6J mice, aged 7 days, were randomly divided into four groups:normal, high oxygen, high oxygen saline and high oxygen treated with AG. In the normal group, mice were housed in normoxic conditions from postnatal day P7 to P17. Mice in the other 3 groups were placed under hyperoxic conditions (75±2%O2) in an oxygen-regulated chamber for 5 days and subsequently placed in normoxic conditions for 5 days. Mice in the AG group were treated once daily, from P12 to P17, with AG hemisulfate (100mg/kg body weight, intraperitoneally) dissolved in physiological saline. An equivalent amount of 0.9% physiological saline was administered, as above, to mice in the high oxygen saline group. Ten mice were randomly selected from each group on P14 and on P17, euthanized and the retinas examined. Apoptotic cells in the retina were detected using the terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) method. The expression of nitric oxide synthase (iNOS) in the retina was detected by immunohistochemistry and changes in rod cells were observed using electron microscopy.RESULTS:TUNEL-positive cells and iNOS immunoreactive neurons were present in the inner nuclear and ganglion cell retinal layers of mice in the high oxygen group. The number of TUNEL-positive cells was significantly greater in the high oxygen group compared with the normal group (t=-20.81, P14d <0.05; t=-15.05, P17d<0.05). However, the number of TUNEL-positive cells in the AG treatment group was significantly lower (t=-13.21, P14d<0.05; t=-6.61,P17d <0.05) compared with the high oxygen group. The expression of iNOS was significantly higher in the high oxygen group compared with the normal group (t=-21.95, P14d<0.05; t=-17.30, P17d<0.05). However, the expression of iNOS in the AG treatment group was significantly lower (t=-12.17,P14d<0.05; t=-10.30,P17d<0.05) compared with the high oxygen group. The outer segments of the rods were disorganized and short in the high oxygen group. Rod morphology appeared to be slightly improved in the AG group.CONCLUSION:AG may protect retinal neurons in OIR by inhibiting apoptosis. The mechanism may be related to iNOS.