VEGF localisation in diabetic retinopathy

Abstract

Aim: To determine the staining pattern of vascular endothelial growth factor (VEGF) at different stages of diabetic retinopathy (including post-laser photocoagulation) and to compare staining in excised fibrovascular and fibrocellular (non-diabetic) preretinal membranes.

Methods: Immunohistochemical localisation of VEGF, using antibodies raised against VEGF165 and VEGF121,165,189, was carried out on specimens of normal human retina (n = 15), diabetic retinas ((a) with no overt retinopathy (n = 19), (b) with intraretinal vascular abnormalities but no proliferative retinopathy (n = 6), (c) with active proliferative retinopathy (n = 6), (d) with no residual proliferative retinopathy after photocoagulation therapy (n = 15)), excised diabetic fibrovascular membranes (n = 19), and non-diabetic fibrocellular membranes (n = 7). The degree and pattern of immunostaining was recorded.

Results: In general, VEGF was absent from the majority of normal retinas. VEGF staining was apparent in most diabetic tissues but the staining pattern was dependent on both the specificity of the antibody used and the category of tissue. Staining with the VEGF165 antibody was generally confined to endothelial cells adn perivascular regions while the VEGF121,165,189 antibody was also associated with extravascular components of the inner retina. Intensity of immunostaining of diabetic eyes was dependent on the severity of retinopathy being least in diabetics with no overt retinopathy and greatest in retinas with proliferative retinopathy. Interestingly, the intensity of immunostaining in diabetic retinas which had undergone laser surgery for proliferative retinopathy was reduced to basal levels. Moderate to intense immunostaining was observed in all fibrovascular and fibrocellular membranes examined.

Conclusions: This study supports a circumstantial role for VEGF in the pathogenesis of both the preclinical and proliferative stages of diabetic retinopathy.

Figures

Figure 1

Photomicrographs demonstrating VEGF immunostaining of normal retina (A), diabetic retina with no obvious retinopathy (B), diabetic retina with obvious intraretinal vascular changes but no evidence of PDR (C, D), diabetic retina with PDR (E, F), and diabetic retina after laser treatment for PDR (G, H). Sections were immunostained with either an antibody raised against VEGF165 (A, C, E, G) or VEGF121,165,189 (B, D, F, H). Immunostaining was greatest in diabetic retinas with PDR for both antibodies tested, minimal in normal retinas, and intermediate in diabetic retinas without PDR. It was interesting to note that immunostaining in lasered diabetic retinas with no current evidence of PDR was greatly reduced compared with the staining intensity in retinas with PDR. Magnification, A-E, G ×90; F, H ×70.

Figure 2

Photomicrographs demonstrating VEGF immunostaining of PDR retina and excised membranes. Intense immunostaining for VEGF165 is localised to the vasculature (A) while VEGF121,165,189 immunostaining is observed in both vascular and extravascular tissue (B). Moderate to intense staining can be observed in all specimens of excised fibrovascular (C) and fibrocellular (D) epiretinal membranes. Immunoreactivity for VEGF was abolished in control sections of PDR retina and membranes processed with omission of the primary antibody (E) or prior incubation of the antibody with VEGF. Magnification, A, B ×200; C-F ×70.