Abstract
Purpose :
Endothelial glycocalyx is vital to maintain normal vascular function， while it is destroyed in retinal vessel of diabetic. Endomucin (EMCN) is a typical membrane glycoprotein that is mainly expressed in endothelial cells. We want to detinvestigate the protein expression change of EMCN under hyperglycemia. Moreover, we research the role of EMCN in endothelial glycocalyx in the retinas of streptozotocin-induced diabetic rats.
Methods :
Immunofluorescence was used to detect the localization of EMCN in retinal tissue of normal rats. The role of EMCN in diabetic retinopathy (DR) was assessed using the streptozotocin-induced diabetic rats. Western blot was used to detect the expression of EMCN in retina. Adeno-associated virus (AAV)-EMCN or its control carrying mCherry was injected intravitreally 2 weeks before diabetes induced. 8 weeks after diabetes induced, vascular glycocalyx was detected by electron microscopy and immunofluorescence. Then, FITC-labeled concanavalin A (ConA) was used to reflect the magnitude of leukocytes adhesion to retinal endothelium cells and FITC-labeled dextran was used to observe retinal vascular leakage.
Results :
EMCN was specifically expressed in retinal vascular endothelial cells of normal rat. The expression of EMCN in retinal tissue of diabetic rats down-regulated significantly compared with the control group (p<0.001). The structure of glycocalyx with electron microscopy and immunofluorescence staining located in retinal vascular endothelium was observed in both control and AAV-EMCN group, rather than in the DM and AAV-mCherry group. The adherent leukocyte was significantly elevated in diabetic rats versus normal rodent retinas (P < 0.001). AAV-EMCN was able to reduce the number of accumulated leukocyte to below the diabetic group (P < 0.01). Besides, diffuse leakage of FITC- dextran around the retinal vessels was observed in both DM group and AAV-mCherry group. The structure of retinal vascular in the control group could be clearly observed and there was no vascular leakage. In AAV-EMCN group, only a small amount of fluorescence leakage was observed.
Conclusions :
These results indicated that EMCN protected diabetics from retinal vascular degeneration by restoring endothelial glycocalyx. EMCN may represent a novel therapeutic strategy for DR, since it targets the endothelial glycocalyx degradation of the disease.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.