Abstract
Purpose: :
To identify and quantify the proliferating cell types in 4 different types of human epiretinal membranes (ERMs).
Methods: :
Idiopathic (iERM) and post retinal detachment epiretinal membranes (ERMpRD) and membranes from eyes with proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR) were collected from human subjects during vitrectomy surgery (n=28) and immediately fixed in 4% paraformaldehyde. The membranes were immunolabeled with the MIB 1 or SP6 antibodies that stain the nuclear specific antigen Ki-67 to detect proliferating cells. Anti-GFAP, -vimentin, -ezrin, ricin and Hoechst stains were used to further characterise the proliferating cell types. The numbers of proliferating cells were quantified from digital images captured using a laser scanning confocal microscope (Olympus Fluoview 500) and correlated with cell type, disease condition and duration. On average the membranes were present in the eye for 1 month (PVR), 3 months (ERMpRD), 6.5 months (PDR), and 11 months (iERMs).
Results: :
All types of membranes contained dividing glia, RPE and immune cells but in different proportions. PVR membranes contained on average the highest nuclear density (5082 cells/mm2) and the highest ratio of dividing cells to total nuclei (2.32%); ERMpRD, PDR and iERM membranes contained fewer, but significant numbers of dividing cells (0.30%, 1.0%, and 0.73% of total nuclei, respectively).
Conclusions: :
ERMs of all types are highly cellular and contain proliferating glia, RPE and immune cells even out to 11 months duration (iERMs). The fact that PVR membranes contained the most dividing cells correlates with their aggressive behaviour, and hence suggests a rationale for early removal from the eye. However, proliferation is a common event in all types of ERMs and continues over many months and this need not cause clinical problems. These findings suggest that treatment strategies may need to consider the early proliferative and late contractile and/or possibly the inflammatory characteristics of the membranes to prevent the ensuing effects on the retina.
Keywords: proliferation • proliferative vitreoretinopathy • retinal glia