The BB-rat--an authentic model of human diabetic retinopathy

Progressive ultrastructural damage and thickening of the basement membrane of the retinal pigment epithelium in spontaneously diabetic BB rats

Ultrastructural examination of the neural retina and retinal pigment epithelium was performed in spontaneously diabetic BB rats and non-diabetic littermate controls at various time points during the course of diabetes. Four types of progressive changes occur in diabetic rats: (1) There is a progressive thickening of the basal laminae of the retinal pigment epithelium and the retinal capillaries. (2) In addition to this thickening, there is a progressive, often focal, thickening of the rest of Bruch's membrane, and by 11 1/2 months it contains numerous randomly oriented collagen fibrils. (3) There are progressive ultrastructural changes in retinal pigment epithelial cells consisting of marked dilation of the basal infoldings, the formation of large vacuoles and cell swelling. (4) Rare degenerative changes were noted in retinal capillary pericytes. Since non-diabetic littermates do not show comparable changes, it is likely that they are diabetes-related, suggesting that progressive damage to the retinal pigment epithelium may occur during the course of diabetes.

Pancreatic islet allograft prevents basement membrane thickening in the diabetic rat retina

Progressive basement membrane thickening is a characteristic structural abnormality in diabetic tissues including the retina. We examined the effect of pancreatic islet allotransplantation on basement membrane thickening and irregularities in retinal capillaries of the streptozotocin-diabetic rat. Diabetic animals received intraportal or intracerebral pancreatic islet allografts. Animals with functioning allografts demonstrated euglycaemia and a normal body weight gain during the 400-day post-transplantation period. The characteristic thickening of capillary basement membranes was completely prevented in animals with successful transplantation. The present findings suggest that islet allotransplantation may be a rational therapeutic approach in the treatment of diabetes mellitus and the prevention of ensuing secondary complications.

Prevention of diabetic retinal capillary pericyte degeneration and loss by pancreatic islet allograft

Degeneration and loss of retinal capillary pericytes are characteristic features of diabetic retinopathy. The effect of pancreatic islet cell allotransplantation across a major histocompatibility barrier on diabetic pericyte changes was examined in streptozotocin induced diabetic rats 14 months post-transplantation. Morphological studies of the retinal microvasculature were carried out using qualitative and quantitative morphological techniques. We describe significant prevention of pericyte degeneration and loss after successful allotransplantation suggesting that pancreatic islet allograft is a promising therapeutical approach in the prevention of diabetic retinopathy.

Aldose reductase in the BB rat: isolation, immunological identification and localization in the retina and peripheral nerve

Aldose reductase was purified from testis of non-diabetic BB rats using DEAE cellulose, hydroxylapatite and sephadex G-100 column chromatography. The molecular weight of the isolated enzyme was found to be 36,500 +/- 1000. Antibody against the isolated enzyme was raised in rabbits. It was purified by affinity chromatography, characterised by double immunodiffusion and Western blot analysis and used to localize the enzyme in retina and in peripheral nerve of the BB rat. In the retina, aldose reductase immunoreactivity was seen in the ganglion cells, Müller cell processes, retinal pigment epithelium and in the pericytes and endothelial cells of retinal capillaries. In peripheral nerve, aldose reductase immunoreactivity was found in the paranodal cytoplasm of Schwann cells and in pericytes and endothelial cells of endoneurial capillaries.