ABSTRACT
Background Acute retinal ischemia anoxic injury is common in eye disorders,such as acute glaucoma,central retinal artery occlusion and ischemic optic neuropathy,etc.This will cause retinal ischemia anoxic injury and induce retinal ganglion cells (RGCs) death in addition.Endogenous cannabinoid (CB) and its receptors are involved in the central nervous system injury,ischemia,inflammation,and poisoning and other physiological and pathological process.Objective This study was to investigate the effect of CB on RGCs damage induced by oxygen-glucose deprivation (OGD).Methods The eyeballs were obtained from 6-week-old normal C57BL/6J mice to prepare retinal frozen sectionsand the expression and distribution of cannabinoid receptors (CB1R and CB2R) in RGCs was detected by immunofluorescence staining.The eyeballs of ten newborn C57BL/6J mice (postnatal 0-3 days) were obtained after immersed by 75％ alcohol and the retinas were isolated in preeooling DMEM for the primary culture of RGCs.The cells were identified by detecting the expression of Brn3a,a marker of RGCs,with immunofluorescence staining.Then the cells cultured for 14 days were divided into normal control group (in complete culture medium+95％ air+5％ CO2) and OGD group (in glucose-free medium+95％ N2 +4％ CO2 + 1％ O2) for 20 hours.The mitochondrial damage and RGCs morphology changed were evaluated by JC-1 staining to observe the mitochondrial membrane potential change.SR141716A (CB1R antagonist,1 μmol/L),SR144528 (CB2R antagonist,1 μmol/L) and 5 or 10 μmol/L WIN 55212-2 (CB1R and CB2R agonist) were added,and the survival rate of RGCs was assayed MTT.Results CBR was positively expressed in various layers of normal mouse retinas.The cells in the normal control group showed uniform size and polygon in shape with the long and thin axons,and the expression of Brn-3a was seen in the cells.However,in the OGD group,cell shrinkage and fragments were found and most of the axons disappeared.The expression of Brn-3a was evidently weakened.The fluorescence intensity of JC-1 was evidently weakened in the OGD group compared with the normal control group,showing the reduce of mitochondrial membrane potential.MTT assay showed that the survival rate of RGCs was (100.00± 13.87)％,which was significantly higher than (89.52-± 18.16)％ in the normal control group (q =8.065,P =0.008).The mean survival rates of RGCs were (116.63±22.21)％ and (112.61 ±19.02)％ in the cells treated by SR141716A and SR144528,and that in the normal cells was (89.52 ± 18.16)％ in the OGD group,with significant differences between SR141716A-or SR144528-treated cells and normal cells (q =29.780,17.391;both at P＜ 0.01).Conclusions Hypoxia and glucose-free up-regulate the expression of CB and activate CB pathway.Inhibition of activation CBR process has a neuroprotection effect under the Hypoxia and glucose-free condition.
ABSTRACT
Background Retinal neovascularization is associated with various disorders.Studying the pathogenesis of retinal neovascularization is of important significance.Oxygen-induced retinopathy(OIR) mouse model is a common animal model for the study of retinal neovascular diseases.However, conventional modeling methods usually cause high animal mortality and low rate of success.Objective This study aimed to establish a modified method of mouse OIR model.Methods Eighty 1-week-old SPF C57BL/6J mice were randomly divided into normal control group and OIR group with 40 mice for each.The newborn mice of the normal control group were kept in a normal air environment with their breast-feeding mothers, but the mice of postnatal 2 days (P2) in the OIR group were raised with two litters per cage until P7.The P7 mice exposed to oxygen tank containing 80％ oxygen together with one or another mother mouse alternately daily for 5 days and then returned to the normal air environment.The success rate of modeling,mortality rate of maternal mice and survival rate of immature mice were evaluated.The mixed solution of fluorescein isothiocyanate (FITC) and PBS with 4％ paraformaldehyde was infused into the hearts of P12, P14,P17 and P21 mice and the eyeballs were obtained after the mice were sacrificed for histopathological examination of retinas and preparation of retinal flatmounts.The number of vascular endothelial cells extending inner limiting membrane was counted and the distribution of retinal vessels was evaluated.The use and care of the animals complied with the Statement of ARVO.Results The survival rate of the neonatal mice was 100％ both in the normal control group and the OIR group,and the survival rate of maternal mice was 85.7％ in the OIR group.Retinal new vessels were found in the mice of the OIR group,with the success rate of modeling 100％.The retinal vessels distributed from optical disc toward periphery in P14 mice in the normal group.However,in the OIR group,non-perfusion area at the posterior pole was seen in P12 mice,new blood vessels at the periphery were found in P14 mice, neovascularization at the junction area between vascular area and non-perfusion area as well as leakages were exhibited in P17 mice,and less non-perfusion area and new vessels were seen in P21 mice.Retinal inner limiting membrane was smooth in the mice of the normal group, and the vascular endothelial cell nucleus extending inner limiting membrane were seen in P12 mice and peaked in P17 mice.The vascular endothelial cell nucleus were (11.44±2.01), (31.24±1.50) and (9.23-±1.12)/slide in P14, P17 and P21 mice in the OIR group,which were significantly more than (0.27±0.14) , (0.30±0.11) and (0.32±0.16)/slide in P14, P17 and P21 mice in the normal group (t=47.90,61.30,40.70,all at P＜0.05).Conclusions The method of OIR modeling is modified by alternating maternal mice,exposing to 80％ oxygen-nitrogen mixture gas and cohabitating immature mice.Modified modeling method is simple with the low death rate of maternal mice and stable OIR phenotype.