Localisation of opticin in human proliferative retinal disease

This study sought to determine the distribution of opticin, an extracellular matrix small leucine-rich repeat protein secreted by the non-pigmented ciliary body epithelium (CBE), in pathological eye tissues including posterior hyaloid membranes (PHM) and epiretinal membranes (ERM) from subjects with proliferative diabetic retinopathy (PDR), central retinal vein occlusion (CRVO) and proliferative vitreoretinopathy (PVR). Eight enucleated eyes and eleven surgically excised PHMs/ERMs from patients with PDR, CRVO or PVR were analysed by immunohistochemistry for the presence and distribution of opticin, vitreous (delineated by a type II collagen antibody) and blood vessels (using CD31 and CD34 antibodies as endothelial markers). Opticin was present at the basal surface of the non-pigmented CBE and, in a patchy distribution, within CBE cells in all 8 enucleated globes. It also co-localised with the type II collagen of vitreous, where present, in these eyes. Opticin was present in 16 of the 19 PHMs/ERMs, where it was arranged in layers (10 membranes), diffusely (4 membranes) or in foci (2 membranes). Where in a layered pattern, opticin co-localised with vitreous type II collagen incorporated into the membrane, whereas the other two patterns did not co-localise with type II collagen labelling. We concluded that even in advanced proliferative retinal disease, the CBE continues to express and secrete opticin. Opticin was co-distributed with vitreous type II collagen and was also present in the pre-retinal membranes of proliferative retinopathies, where it could play a role in their development.