动物造模,糖尿病视网膜病变 z-bio 2021-12-30 392

　　Introduction: Diabetic retinopathy occurs in approximately one-third of diabetic patients. This is the main cause of blindness among adults between the ages of 24 and 70. The overall prevalence of type 1 diabetes patients seems to be higher than that of type 2 diabetes patients. Approximately 25% of patients with type 1 diabetes begin to develop symptoms of DR within 5 years after the onset of diabetes and increase to 80% within 15 years. Interestingly, although gender is not known to affect susceptibility to type 1 or type 2 races, socioeconomic status does affect susceptibility to DR. The onset and progression of diabetes is caused by many factors, including the long-term course of diabetes, poor blood sugar control and increased blood pressure. High blood sugar can lead to microvascular disease, which can lead to microvascular disease, bleeding and thickening of the basement membrane. The result is increased blood-retinal barrier permeability (BRB), leakage and diabetic macular edema (DME). Increased vascular permeability causes capillary occlusion, causes retinal ischemia, and leads to increased levels of vascular endothelial growth factor (VEGF). Retinal ischemia and elevated vegf levels promote angiogenesis. Based on the typical morphology of angiogenesis, DR can be classified as non-proliferative DR (NPDR) or proliferative (PDR). Microvascular injury and loss of NPDR pericytes can develop into microvascular tumors, spots and spot hemorrhages, cotton wool spots, and non-perfused capillary proliferative DR. Changes in microglia and DME may also occur in NPDR. In PDR, new blood vessels cause bleeding in the retina and vitreous, leading to retinal detachment. DME can also occur in PDR. Disease models help us understand the mechanisms that lead to DR diseases. Several animal models have been developed to study the etiology and etiology of DR, and to develop and test therapeutic methods for the treatment of the disease. Since DR is a complex disease with genetic and environmental impact, animal models can also be developed through induction or genetic mutations. Induction models are created through surgery, drugs, diet, laser or chemical damage. Use breeding and gene editing to create genetic models. Many species have been used, including mice, rats, cats, dogs, pigs, and non-human primates, but due to their small size and short life span, mice and rats have been studied the most. The playback speed is fast, and the most effective research can be completed. Rodents are also the focus of most genetic research, discovering certain hereditary hyperglycemia or obesity. However, the DR phenotype of the dog model seems to be most similar to human DR. Surprisingly, non-human primates have shown relative resistance to induced DR. Cats usually do not suffer from cataracts. On the contrary, the eye structure of pigs and zebrafish is similar to that of humans, the structure of blood vessels is easy to visualize, the life span is short, and the fecundity is high (zebrafish). Although there is no single animal model that can represent the complete vascular and neurological complications of human DR in the early and late stages. The model described in this article helps determine the mechanism of DR and develop new therapies. Induction model: The induction model has been established through five methods: pancreatectomy, alloxan administration, streptozotocin (STZ), high galactose diet, laser or chemical damage. All induction methods are still under study, but the most common is the use of streptozotocin. This is because the occurrence of the disease is the fastest. It is believed that alloxan is less effective in inducing diabetes, and it takes the longest time for diet to develop. Technically speaking, models caused by surgery or injuries are the most difficult. The most commonly used models for inducing DR are mice and rats, but whole cats, pigs, rabbits, monkeys, and zebrafish are also used. In large animals, the pathology of inducible DR is usually slow, so rodents and zebrafish are preferred. Pancreatectomy: One of the oldest methods of inducing diabetes in animal models is pancreatectomy or removal of beta cells from the pancreas. Complete removal of the pancreas in adult dogs can induce diabetes. This technique is usually applied to large animals such as cats and monkeys. In adult cats, hyperglycemia develops within 3 weeks after surgery. When combined with alloxan, it can be shortened within one week after surgery. Three months after the onset of hyperglycemia, the basal capillary membrane thickened. Other symptoms of DR, such as microaneurysms, non-perfused areas of capillaries, and angiogenesis, usually take 5 to 9 years to develop. Therefore, maintaining the model is very time-consuming. BRB leakage in the monkey model occurred within 1 year of hyperglycemia. However, ten years later, the monkeys have not yet developed proliferative retinopathy. Despite the removal of the pancreas and long-term diabetes, monkeys seem to be able to resist the induction of DR very well. Only 30% of diabetic patients will develop DR. This suggests that primates may have other biological mechanisms to re-regulate the homeostasis of chronic seizures. Understanding the regulatory factors that contribute to the physiological differences of species is very important for the development of appropriate disease models.

　　Alloxan: Alloxan is a derivative of uric acid that directly acts on the β cells of the pancreas. Intravenous injection of alloxan causes hypoglycemia due to pancreatic islet necrosis. Beta cell death causes the release of insulin stored in these cells, which can cause hypoglycemia and diabetes within 24 hours. Dunn and McLetchie also created a rat model of diabetes induced by intraperitoneal injection of alloxan in rats. Diabetic rabbits exhibit fatigue and weight loss. Rats fed alloxan exhibited hyperlipidemia, polyuria, diabetes, and hyperglycemia. Alloxan-induced cell death is mediated by inhibition of glucokinase, an enzyme in the glucose-insulin regulatory pathway expressed in the liver and pancreas. The drug may be toxic to liver and kidney cells, but proper dosage can avoid toxicity. Alloxan has a specific effect on pancreatic β cells, and has no toxic effect on α, δ or pancreatic exocrine cells. The compound is unstable at room temperature and room temperature. Alloxan has been used to induce a variety of animals, including mice, rats, dogs and pigs, and rabbits. All models damage pancreatic beta cells. A single dose of alloxan can be given to mice of 8-10 weeks of age to induce hyperglycemia and cause diabetes. It was previously believed that alloxan-induced diabetic mice did not develop cell or vascular diseases. Recent studies have shown that alloxan can cause the loss of retinal ganglion cells (RGC) within 7 days. Alloxan also causes changes in microglia. Three-month-old animals have thicker cell bodies and shorter dendrites. Rats developed hyperglycemia and diabetes within one week after using alloxan. Angiogenesis occurred 2-9 months after induction, and cataract occurred within one year. After 15 months, thickening of the capillary basement membrane was observed. Alloxan in puppies induces diabetes once a week for 5 consecutive weeks. This makes retinopathy very similar to human DR, but it may take 53-69 months for dogs to develop DR after the onset of alloxan diabetes. After starting the administration of alloxan, bleeding, loss of acellular capillary pericytes and microaneurysms were observed. This is a feasible PDR model. The phenotype lasted for 11 months. Compared with the dog model, the pig DR model induced by alloxan showed hyperglycemia within 48 hours. 60 days after the administration of alloxan, pigs induced by alloxan also developed cataracts and capillary collapse. Streptozotocin (Streptozotocin, STZ): Streptozotocin is an antibiotic used in cancer chemotherapy. Intraperitoneal injection of streptozotocin and intravenous injection of streptozotocin in rats resulted in various forms of persistent hyperglycemia, as well as features of diabetes and polydipsia. The mechanism of STZ-induced diabetes is due to the destruction of pancreatic islet cells and the loss of β cells. Beta cells express low-affinity glucose transporter 2 (GLUT2), and streptozotocin absorbs STZ because its structure is similar to glucose and N-acetylglucosamine. Other cells, including hepatocytes and renal tubular cells, also express GLUT2 and suffer similar damage to STZ. The mechanism of action of streptozotocin is cell death caused by DNA fragmentation. Streptozotocin-induced DR has been observed in a variety of animal models, including mice, rabbits, pigs, rats, dogs, zebrafish and monkeys. STZ is generally more effective than alloxan. Several STZ-induced diabetes procedures have been developed in mice, providing a total of 150-400 mg/kg of streptozotocin in 5 doses. Hyperglycemia usually occurs within 2 weeks and can be maintained for up to 22 months regardless of the dose. After 4-5 weeks of hyperglycemia, the DR phenotype of STZ-induced mice showed increased astrocytes. GC loss occurs within 6 weeks, the inner nuclear layer (INL) and outer nuclear layer (ONL) of the retina become thinner within 10 weeks, new blood vessels are formed within 16 weeks, and acellular capillaries appear within 6 months. Compared with mice, rats need low doses of streptozotocin to develop diabetes. Rodents are commonly used for streptozotocin-induced diabetes, but several other models with different outcomes and morbidities have been studied. Zebrafish adult 4-6 months, multiple intraperitoneal injections of STZ or direct injection into the caudal fin for 1 or several weeks, hyperglycemia occurs within 3 weeks, and the plexus layer (IPL) becomes thin within the 4th week. Photosensitive segmental layer (PSL) thinning, pyramidal receptor dysfunction and neuronal damage. After the induction of diabetes, the model was maintained for about 80 days. A single dose of streptozotocin is used to induce larger animal models such as rabbits, dogs and non-human primates. A single dose of STZ induced hyperglycemia in rabbits weighing 1.5 kg. 135 days later, retina and preretinal hemorrhage, vascular disease, venous thrombosis and proliferative retinopathy were found. Dogs aged 4.5 to 17 months and weighing 11 kg and 24 kg using a single dose of alloxan/STZ will develop hyperglycemia within 2 days. In alloxan/STZ-induced diabetic dogs, the monkey’s basement membrane thickens within 1 year, and after 4 to 5 years, shadow cells and smooth muscle cells are lost. A 12-year-old monkey taking a single dose of streptozotocin will develop diabetes and develop ischemic retinopathy with cotton spots and strong fluorescent spots 10 years later. High-sugar diet: Several high-sugar diet models have been developed, including mice, rats, rabbits, dogs, and zebrafish. Retinopathy induced by continuous exposure to galactose is similar to human diabetes. Maintaining galactose can keep the disease going. However, animals fed galactose lacked diabetes and metabolic disorders. Six weeks after the high galactose diet, the mice developed hyperglycemia. Fifteen months after surgery, blood sugar levels increased, endothelial cells decreased, and acellular capillaries increased. After 21 months, the lesions included hemangioma and thickening of the retina. Although these mice have a longer onset of retinopathy, they live longer than other models, and can be observed for up to 26 months. Similarly, rats maintained a high-galactose diet for more than 2 years. A continuous high-sugar diet rodent phenotype with thickening of acellular capillaries and capillary basement membrane was observed. In contrast, large animals usually take longer to develop DR, whether it is drug-induced or dietary. Rabbits on a high sucrose diet developed intense fluorescent spots at the 24th week, and microaneurysms appeared at the 12th week. Within a year, dogs with a 30% increase in galactose can cause symptoms of more complex diseases, such as DR and cataracts. Hyperglycemic zebrafish has evolved into a model. The zebrafish were placed in fresh water and water with a glucose concentration of 0% and 2%, respectively. After 28 days, hyperglycemia and IPL improved. Since the model has only been maintained for 28 days so far, the characteristics of retinal structure, vessel structure visualization and fluorescence expression are similar. Because of their short lifespan and large reproduction scale, shortening the experiment time, zebrafish are a powerful model for studying DR. Hypoxia causes retinopathy: In recent years, retinal neovascularization models and vascular leakage models lacking hyperglycemia have been used in research. It was later discovered that retinal damage was caused by the release of angiogenic factors. Several different models of retinal neovascularization are used in mice, rats, primates and zebrafish. Mouse models exposed to hyperoxia usually return to normal air 7-12 days after birth, and when retinal blood vessels grow under hyperoxic conditions, the retina becomes hypoxic. In these models, oxygen-induced retinopathy (OIR) manifests as angiogenic and non-perfused areas, accompanied by the appearance of microvessels. This usually occurs 5 days after exposure. Cytokine induction: The alkaline burn model leads to increased cytokine activity and DR-like angiogenesis. This model is not commonly used, and a painful method is needed to induce the formation of new blood vessels in the mouse retina. This technique has been applied to inbred mouse strains, such as BALB/c mice. Including placing a 2 mm filter disc 1NaOH on the ocular surface of adult mice. Angiogenesis is usually observed within 2 weeks, and the level of angiogenic retinal inflammatory cytokines in mice is also elevated. Cytokines can be a secondary factor in the phenotype of angiogenic diseases, but they can play an important role in maintaining the disease state.

　　Genetic model: There are many ways to inherit DR in mice, rats and zebrafish. These models include spontaneous, strain-specific and genetic variation. For example, some inbred mice, including non-obese diabetes (NOD) and db/db, show hyperglycemia (the main feature of diabetes) and are still research models of diabetes. Rodents are often used as genetic models for DR because they are easy to maintain, have a good genetic background, are easy to manipulate, and can generate gene knockout or transgenic models. Conclusion: Animal models play an important role in understanding the etiology and pathophysiology of DR and developing feasible therapies to prevent and alleviate the disease. DR is a challenging disease model because it is a complex disease involving multiple genetic and environmental factors. Combining genetic and/or induced models can provide a more accurate DR model. Most existing models can only better simulate the early stages of the disease, which limits the practicality of the model, and the treatment is usually limited to the early progression of the disease. In addition, animal models of retinal neovascularization without hyperglycemia have been developed. These models can be used to understand the causes of advanced DR disease and formulate appropriate treatment plans. A correct understanding of the pathophysiology and limitations of each available model is important to determine the best model for your research.