Differential expression of claudin-23 in retina of oxygen-induced retinopathy mice

Abstract

Background Researches showed that some claudin subtypes are closely related to the integrity of blood retina barrier and participate in pathological angiogenesis.Ciaudin-23 is a novel discovered claudin subtype.Understanding its expression in the retina and its relationship with retinal vascular lesion is very important for the targeting treatment of retinal vascular diseases.Objective The aim of this study was to investigate the differential expression of claudin-23 in the retina of mice with oxygen-induced retinopathy(OIR).Methods OIR mice models were established by putting postnatal day 7 (P7)SPF C57BL/6J mice in the enclosed container with oxygen concentration of 75％ ±3％ together with mother mice for 5 days.The age-matched normal mice were used as controls.Fluorescein isothiocyanate dextran (FITC-dextran) was retro-orbitally injected to mice to confirm the models by whole-mount retina.Expressions of claudin-23 mRNA and protein in P12,P17 and P25 mice retinas were examined using real-time PCR and Western blot.lmmunofluorescent staining of frozen section was used to identify the expression and location of claudin-23 in the normal and OIR mice.Results Tortuous and engorged retinal vessels were found in P17 mice retina of the OIR group.Nonperfusion zones,abnormal capillary network and lots of pathological neovascular tufts were observed on the whole-mount retinas.The level of claudin-23 mRNA was slowly increased with the aging,reaching 2.3 fold in P25 normal mice more than P7 mice.However,that in OIR mice demonstrated 12.5-fold elevation from P7 to P25.There were no significant change in the mRNA and protein levels of claudin-23 in P7 mice retina between the normal group and OIR group(P＞0.05).But the mRNA level of claudin-23 in P12,P17 and P25 mice retinas was significantly higher in the OIR group than that in normal group(P＜0.05).The protein level of claudin-23 in P25 mice retina was significantly higher in the OIR group than that in normal group(P＜0.05).Claudin23 expressed mainly in inner nuclear cell layer and retinal ganglion cell layer of the normal mice,but claudin-23 expression was obviously increased in OIR mice.No colocalization of claudin-23 and Isolectin B4 was found in the retina in both normal and OIR mice by double immunofluorescent staining.Conclusions Claudin-23 expression upregulates in the retina of OIR mice.Claudin-23 locates in retinal neurons but not vascular endothelial cells. Key words: Claudin-23; Retina; Oxygen-induced retinopathy