Abstract
AIMS: This study investigated the presence of the cytokine tumour necrosis factor alpha (TNF alpha) and the vascular adhesion glycoproteins ICAM-1, VCAM-1, E-selectin, P-selectin, and PECAM within fibrovascular membranes of eyes with proliferative diabetic retinopathy (PDR). METHODS: The presence of these molecules was determined by immunohistochemical staining using monoclonal antibodies and the APAAP technique. RESULTS: Staining for TNF alpha was observed on the retinal vascular endothelium of five of 12 specimens, on infiltrating cells within all membranes, and on the extracellular matrix of nine specimens. This staining wa abolished by absorption of the monoclonal antibody with human recombinant TNF alpha. Likewise, ICAM-1 staining was given by infiltrating cells and extracellular matrix of nine membranes and by the endothelium of three of the specimens. VCAM-1, E-selectin, and P-selectin staining was observed on the vascular endothelium of 5/12, 4/12, and 3/12 epiretinal membranes respectively. PECAM was expressed by the endothelium of 4/12 specimens, by infiltrating cells of 8/12 membranes, and also by the extracellular matrix of two of the specimens. CONCLUSION: The widespread distribution of TNF alpha and the nature of the adhesion molecules expressed by vascular endothelial cells in PDR membranes suggest that local activation of TNF alpha and enhanced expression of vascular cell adhesion molecules may play an important role in the development of the proliferative phase of diabetic retinopathy.