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J.-M. Shin, S.-J. Park, H.-S. Park, M.-H. Chun, S.-J. Oh; Diabetes-Induced Changes of Morphology and Alpha Smooth Muscle Actin and Occludin Expression in the Rat Retinal Vasculature. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3450.
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Diabetes causes functional changes in the retinal vasculature. These include alterations in the rate of blood flow and in the permeability. The key factors of these events are considered as contractile proteins and tight junction proteins. In this study, we investigated the morphological and immunochemical changes of the microvessels and their representative proteins in the rat retina following long-standing diabetes insults, for better understanding on the pathophysiology of neovascularization.
Diabetic condition was induced by a single intravenous injection of streptozotocin in Sprague-Dawely rats aged of 8 weeks. The animals showing high blood glucose levels (above 300 mg/dl) were cared for 1, 4, and 12 weeks, respectively. The retinas were processed for alpha smooth muscle actin ( α-SMA ) and occludin immunohistochemistry and electron microscopy.
In the whole-mounted retina of normal, arterioles were differentiated with α-SMA immune-labeling and spirally wrapped smooth muscle cells, whereas venules with scanty of smooth muscle cells in their wall. The arterioles numbered 5 to 7 were extended radially from the optic disc to the periphery as branching, and gave rise to capillaries demarcated with α-SMA labeled pericytes penetrating into the inner retina throughout their courses. The venules were located in between the arterioles. Occludin was labeled the boundary of the endothelial cells. During diabetes, the capillary networks immuno-labeled by α-SMA in the inner retina were more remarkable due to reduce of thickness of the inner retina. The protein levels of α-SMA were gradually reduced, and those of occludin no large different. In the diabetic retina, the endothelial cells, pericytes and endothelial cells were showed degenerating morphology such as pyknotic nuclei, increase of endocytotic vesicles, myelin-like structures, and electron-dense cytoplasm with electron microscopy.
There results suggest that diabetes causes not only functional changes such as reduce of contractile activity in the smooth muscle cells and the pericytes, but also morphological changes including increase of adluminal endocytotic vesicles in the endothelial cells of the retinal microvessels.
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