Establishment Of Chronic Ocular Hypertension Glaucoma Model In Rats By Episcleral Veins Cauterization

ObjectiveTo observe retinal structure in rat chronic ocular hypertension glaucoma model established by episcleral veins cauterization(EVC),which provided research basis for optic nerve injury and protection mechanism of glaucoma.To observe the effect of mitochondria targeted antioxidant peptide SS31 on the retina of chronic ocular hypertension glaucoma model in rats,which provide experimental evidence for a new method of glaucomatous optic nerve protection.Methods1)Forty Sprague–Dawley(SD)rats were randomly selected.The baseline intraocular pressure(IOP)was measured three days before operation.The right eye was cauterized three episcleral veins as the experimental eye to,while the left eyes were considered as comparison.IOP was measured immediately,1-7 days,14 days,21 days and 28 days after operation.The thickness of ganglion cell complex(GCC)and whole retina were measured by optical coherence tomography(OCT)before and 28 days after operation.The rats were executed at 28 days after operation,carrying out the paraffin-embedding,hematoxylin eosin(HE)staining to count retinal ganglion cells(RGCs)and measure retinal thickness.2)A total of 60 SD rats were allocated randomly into four groups.In the normal control(NC)group: no treatment.In the EVC group: EVC was done in right eyes.In the EVC combine SS31 injection group: EVC was done in both eyes.After 21 days,intravitreal injections with SS31 was done in the right eyes,while the left eyes were injected with normal saline(NS).In the SS31 injection group: without EVC,only intravitreal injection was performed at 21 days.Baseline IOP was measured 3 days before surgery,and IOP was measured at 6h,1-7 days,14 days,21 days and 28 days after surgery.The thickness of GCC and whole retina were measured by OCT before and 28 days after surgery.The rats were executed at 28 days after surgery,carrying out the paraffin-embedding,hematoxylin eosin(HE)staining to count retinal ganglion cells(RGCs)and measure retinal thickness.Result1)There was no significant difference in IOP between left and right before operation(P>0.05).The IOP in the experimental eyes was higher than that in the control eyes at immediately,1-7 days,14 days,and 21 days after EVC(P < 0.001).There was no significant difference in IOP between the experimental eyes and the control eyes at 28 days after surgery(P > 0.05).The results of OCT showed that the thickness of GCC in the experimental eyes after operation was thinner than that before operation(P < 0.001),and the thickness of GCC in the experimental eyes was thinner than that in the control eyes after operation(P < 0.001).The results of HE staining showed that the thickness of the inner,middle,outer retina and GCC in the experimental eyes was thinner than that of the control eyes(P <0.05),and the change of the inner retina was the most obvious,and the reduction rate was 32.16%.The number of RGCs in the experimental eyes was significantly lower than that in the control eyes(P < 0.001).2)There was no significant difference in IOP between the groups before operation(P>0.05).The IOP increased at 6 hours,1-7 days,14 days,and 21 days after EVC(P < 0.001),and the IOP decreased to normal at 28 days after surgery(P > 0.05).The results of OCT showed that the thickness of GCC after surgery was thinner than that before surgery in the EVC group(P < 0.001).The thickness of GCC in the EVC group was thinner than that in the NC group after surgery(P < 0.001).The thickness of GCC in the EVC+SS31 group was thicker than that in the EVC group(P < 0.001).The results of HE staining showed that the thickness of the inner,middle,outer retina and GCC was thinner than that of the NC group(P < 0.05).The thickness of GCC and the inner retina of the EVC+SS31 group were thicker than those of the EVC group(P < 0.05).The number of RGCs in the EVC group was significantly lower than that in the NC group,and the number of RGCs in the EVC+SS31 group was higher than that in the EVC group(P<0.05).Conclusion1)EVC could cause elevated IOP for 21 days after operation and reduce RGCs and thin retina,especially the inner retina.EVC is an effective method to establish chronic ocular hypertension glaucoma model in rats.2)It was preliminarily concluded that mitochondrial targeting antioxidant peptide SS31 had protective effects on retina and RGCs of chronic ocular hypertension glaucoma model in rats.