Remote Ischemic Preconditioning Protects Retinal Ganglion Cells In Streptozotocin Induced Diabetic Rats

Objective To investigate whether remote ischemic preconditioning(RIPC) can protect retinal ganglion cell in STZ induced Type 1 diabetic rat model.Methods 35 healthy male Sprague-Dawley(SD)rats were randomly divided into control rats(n=20), diabetes rats(n=25). Control rats were divided into control group(n=10) and control+ RIPC group(n=10). Type 1 diabetic rat model was induced by a single intraperitoneal injection of streptozotocin(STZ, 60 mg/kg in 0.1mol/L) dissolving in sodium citrate solution. Control rats received an equal volume of sodium citrate solution. 72 hours after injection, blood sample was examined and blood glucose levels> 16.7 mol/L were considered diabetic. Diabetic rats were randomly divided into diabetic group(n=10) and diabetic+ RIPC group(n=10). RIPC was conducted by tightening a tourniquet around the upper thigh and releasing for three cycles everyday. Body weight and blood glucose were assessed every week. After 12 weeks of RIPC, eyes were enucleated. Expression of Brn3 a positive RGC, GFAP and Nrf2 in different groups was examined by immunohistochemical study.Results At 12 weeks, the numbers of rats in control group, control+ RIPC group, diabetic group and diabetic+ RIPC group are 10,8,9 and 8, respectively. Over the course of experiment, blood glucose level of control rats remained 6-8 mmol/L. Control rats showed a gradual gain in weight. Body weight were lower in diabetic rats than in the corresponding control groups. Blood glucose levels were increased in diabetic rats compared with non-diabetic controls. immunostaining showed that Brn3 a positive cells were localized in the nuclear of cells in retinal ganglion cell layer. The numbers of Brn3 a positive cells in control group, control+ RIPC group, diabeticgroup and diabetic+ RIPC group are 18.45±3.97,17.18±3.37,15.41±3.07 and 20.18±1.64 respectively. There was a significant decrease of Brn3 a positive cells between diabetic group and control group(p=0.0406).The number of RGC was significantly increased in diabetic+ RIPC group than that in diabetic group(p=0.004). In control group and control+ RIPC group, glial fibrillary acidic protein(GFAP) was confined to retinal nerve fiber layer and retinal ganglion cell layer. In diabetic rats, GFAP expression was distributed throughout all layers of the retina in diabetic rats and was upregulated compare to that in control rats(p=0.001). The average of density of expressions of GFAP was significant decreased in diabetic+ RIPC group in comparison to diabetic group(p=0.035). Nrf2 was expressed in plasma in retinal ganglion cell layer, inner nuclear layer and outer nuclear layer.Conclusion RIPC may protect RGC and reduce glial reactivity in STZ induced diabetic rats.