Diabetes retinopathy (DR) is a blinding ocular complication of diabetes, and its pathological mechanism is complex. The damage to the retinal neurovascular unit (NVU) and the imbalance of its coupling mechanism are important pathological foundations. Autophagy plays an important role in the progression of DR. Oxidative stress, endoplasmic reticulum stress, hypoxia, and competitive endogenous RNA regulatory networks can affect the occurrence of autophagy, and autophagy induced cell death is crucial in NVU dysfunction. Retinal neurocyte are non- renewable cells, and adaptive autophagy targeting neuronal cells may provide a new direction for early vision rescue in patients with DR. It is necessary that exploring the possible autophagy interrelationships between ganglion cells, glial cells, and vascular constituent cells, searching for targeted specific cell autophagy inhibitors or activators, and exploring the impact of autophagy on the NVU complex more comprehensively at the overall level. Adopting different autophagy intervention methods at different stages of DR may be one promising research directions for future DR.
ObjectiveTo establish a rat model of diabetic microangiopathopathy and simulate the biochemical and pathological changes of diabetic retinal and renal microangiopathopathy. MethodsForty healthy male Sprague-Dawley rats were randomly divided into blank group and model group (10 and 30 rats, respectively). After the rats in blank group and model group were fed ordinary diet and high-fat and high-sugar diet for 5 weeks, respectively, the rats in model group were injected with 1% streptozotocin (STZ) through the abdominal cavity at the dose of 35 mg/kg to establish a type 2 diabetes model. After modeling, the rats were continuously fed until the 10th week (4 weeks after modeling), the general conditions of the rats were observed, and samples were collected for follow-up experiments. Serum creatinine (CREA), triglyceride (TG), total cholesterol (TC), high density lipoprotein (HDL-C), low density lipoprotein (LDL-C), microalbuminuria, urinary creatinine (UCr) and urine sugar were detected. Calculate the kidney index and microalbumin/urinary creatinine ratio (UACR). Optical coherence tomography angiography (OCTA) was used to observe the vascular changes and non-perfusion area of retinal superficial capillary plexus. The morphological and structural changes of kidney and retina were observed by hematoxylin-eosin and periodate Scheff staining. The expression of nerve fibers and nucleus of Müller cells in rat retina was observed by immunofluorescence staining. Ultrastructural results of retina were observed by transmission electron microscope. Independent sample t test was used for comparison between groups. ResultsFour weeks after modeling, compared with blank group, the body weight of rats in model group was significantly decreased, and random glucose was significantly increased, with statistical significance (t=5.755, －51.291; P＜0.05). Renal index, urinary glucose and UACR were significantly increased, while UCr was significantly decreased, with statistical significance (t=10.878, 137.273, 3.482, －6.110; P＜0.05). CREA decreased, TG, TC, HDL-C, LDL-C increased, and the differences were statistically significant (t=－28.012, 33.018, 118.018, 13.585, 16.480; P＜0.05). OCTA examination showed that there was no perfusion area of shallow retinal capillaries. The optical microscope showed that the inner boundary membrane of retina in model group was swollen and thickened, the surface was uneven, the inner and outer nuclear layer cells were disordered and the density decreased. Glomerular congestion was accompanied by cortical tubular epithelial swelling, widening of the mesangial area, and thickening of the basement membrane. The results of immunostaining showed that the inner and outer plexiform layers of the retina showed lamellar strong green fluorescence expression, and the inner and outer nuclear layers showed scattered dot green fluorescence expression. Transmission electron microscopy showed that the basal membrane of retinal microvessels in model group was slightly thickened, vascular endothelial cells edema, endothelial nucleus and perinucleus contraction, nuclear membrane contraction, mild mitochondrial swelling, vacuolation. ConclusionHigh-glucose and high-fat feeding plus a single intraperitoneal injection of STZ 35 mg/kg can successfully establish a microangiopathic model of type 2 diabetes.