GLIAL-CELL INVOLVEMENT IN VASCULAR OCCLUSION OF DIABETIC-RETINOPATHY

Twenty areas of retinal vascular occlusion from ten eyes of 6 diabetic patients were studied by immunohistochemistry to type IV collagen (ba sement membranes), von Willebrand factor (endothelial cells), and to g lial fibrillary acid protein (glial cells) on serial sections,In all s tudied lesions immunoreactivity to type IV collagen and von Willebrand factor was confined to the retinal vascular walls whereas the materia l accumulated to occlude the vascular lumens centrally displayed immun oreactivity to glial fibrillary acid protein. All arterioles observed in the lesions were occluded, These arterioles had retained their circ ular shape, and the intravascular glial protein immunoreactivity commu nicated with the extravascular glial tissue through localised breaks i n the vascular wall, The intravascular immunoreactivity was found to c ontinue inside the arteriole along its successive diminishing to reach the capillary level. The venules were only occluded in less than half of the studied lesions, These venules were collapsed to assume a bean -like shape, and sequences with total obliteration of the vascular lum en alternated with sequences where a residual space corresponding to t he former lumen displayed immunoreactivity to glial protein, The paper suggests that glial cell invasion, but not endothelial cells or basem ent membrane thickening, occludes the vascular lumen in areas of retin al non-perfusion secondary to diabetic retinopathy.