Downregulation of Fibronectin Overexpression Reduces Basement Membrane Thickening and Vascular Lesions in Retinas of Galactose-Fed Rats

Abstract

Overexpression of extracellular matrix (ECM) components is closely associated with the development of vascular basement membrane (BM) thickening, a histological hallmark of diabetic microangiopathy. To determine whether BM thickening of retinal capillaries could be prevented by down regulating synthesis of fibronectin, an ECM component, we used antisense oligos targeted against translation initiation site of the fibronectin transcript in galactose-fed rat, an animal model of diabetic retinopathy. After 2 months of galactose-feeding, intravitreal administration of 3 mol/l antisense fibronectin oligos was initiated at monthly intervals for 3 months. The antisense strategy significantly reduced fibronectin mRNA and protein level in the retinas of treated eyes compared with untreated eyes of galactose-fed rats (130 ؎ 16 vs. 179 ؎ 18% of control, P < 0.01, and 144 ؎ 28 vs. 204 ؎ 22% of control, respectively, r ‫؍‬ 0.9) and resulted in partial reduction of retinal capillary BM width (123 ؎ 16 vs. 201 ؎ 12 nm, P < 0.03). In eyes treated with antisense fibronectin oligos, ϳ35% reduction in both pericyte loss and acellular retinal capillaries was observed (P < 0.04 and P < 0.03, respectively). Glycohemoglobin level was consistently elevated in the treated (6.9 ؎ 0.6%) and untreated (6.5 ؎ 0.7%) galactose-fed rats compared with control rats (4.5 ؎ 0.8%). Overall, these results indicate that downregulation of fibronectin synthesis reduces BM thickening in retinal capillaries with beneficial effect to retinal lesions. The antisense fibronectin oligos may provide a useful approach for reducing vascular lesions in diabetic retinopathy. The thickened vascular BM may be a potential therapeutic target for preventing retinal lesions in diabetic retinopathy. Diabetes 52: 1229 -1234, 2003

Connective Tissue Growth Factor Is Necessary for Retinal Capillary Basal Lamina Thickening in Diabetic Mice

“…Our findings indicated that CTGF is necessary for BL thickening and identified CTGF as a possible therapeutic target to prevent this early change in the retina caused by diabetes. That this may be a clinically relevant approach is indicated by recent studies that have shown that prevention of BL thickening can ameliorate the subsequent development of acellular capillaries in rodent models of diabetes (Roy et al 2003;Oshitari et al 2006). We detected a significant increase in particularly the endothelial cell BL in diabetic CTGF 1/1 mice compared with control CTGF 1/1 mice.…”

“…BL thickening results from increased synthesis and/or decreased breakdown of its macromolecular components such as collagen type IV, fibronectin, and laminin (Roy et al 1994;Spirin et al 1999;Nishikawa et al 2000). Experimental prevention of BL thickening ameliorated early retinal vascular changes caused by diabetes (Roy et al 2003;Oshitari et al 2006). In galactose-fed rats, a model for type 2 diabetes, downregulation of fibronectin synthesis partly prevented retinal BL thickening but also reduced pericyte and endothelial cell loss (Roy et al 2003).…”

“…Experimental prevention of BL thickening ameliorated early retinal vascular changes caused by diabetes (Roy et al 2003;Oshitari et al 2006). In galactose-fed rats, a model for type 2 diabetes, downregulation of fibronectin synthesis partly prevented retinal BL thickening but also reduced pericyte and endothelial cell loss (Roy et al 2003). Combined downregulation of the mRNA levels of the extracellular matrix components fibronectin, collagen type IV, and laminin not only prevented the increase in their protein levels but also reduced vascular leakage in the retinas of rats with streptozotocin (STZ)-induced diabetes (Oshitari et al 2006).…”

The role of Raf-1 kinase in diabetic retinopathy

“…Oligonucleotides targeted against the translation initiation site of the fibronectin transcript have reduced fibronectin mRNA and protein level, and capillary basement membrane thickening in galactose-fed rats, another animal model of diabetic retinopathy [73]. Transfection of microvascular endothelial cells with AS-connexin 43 oligonucleotides is shown to inhibit glucose-induced alterations in intercellular communication and maintain vascular homeostasis [55].…”

Effect of Combined Antisense Oligonucleotides Against High-Glucose–and Diabetes-Induced Overexpression of Extracellular Matrix Components and Increased Vascular Permeability

“…In vivo and in vitro studies have shown that diabetes selectively increases basement membrane gene expression in retinal vascular cells and that the excess synthesis of basement membrane components contributes, at least in part, to the development of thickened vascular basement membranes (6 -9). We have recently shown that the fibronectin antisense oligonucleotides (AS-oligos) reduce overexpression of basement membrane components and partially prevent the development of thickened vascular basement membrane in retinal capillaries of galactose-fed rats, an animal model of diabetic retinopathy, with beneficial consequences to histological lesions such as pericyte loss and acellularity (9). However, in order to completely prevent and reverse vascular basement membrane thickening, and regulate functional abnormalities, a more effective antisense strategy is necessary.…”