Purpose
Proliferative diabetic retinopathy (PDR) is a late stage manifestation of diabetic retinopathy characterized by neovascularization, fibrosis, and the formation of an epiretinal membrane (ERM). The exact molecular mechanisms of PDR membrane formation remain unclear. We used immunohistochemical methods to study the cellular composition and unique molecular markers in PDR ERMs versus idiopathic ERMs.
Methods
ERMs were obtained from patients undergoing pars plana vitrectomy. ERMs were designated as either PDR-related or idiopathic based on the patient’s history prior to vitrectomy. All collected ERMs were cryo-protected, fixed in paraformaldehyde, and cryo-sectioned. The sectioned membranes were stained with glial fibrillary protein (GFAP), alpha-smooth muscle actin (SMA), and isolectin-IB4 (IB4), markers for retinal glial cells, myofibroblasts, and vascular endothelial cells, respectively. Control slides without primary antibodies were made for each immunostain. Immunoreactivity of each marker was visualized using fluorescent light microscopy.
Results
SMA and GFAP immunoreactivity is seen primarily in the cytoplasm of cells in PDR ERMs while IB4 immunoreactivity is localized in the stromal region of PDR ERMs. Qualitative imaging suggests that SMA and IB4 immunoreactivities are increased in ERMs from PDR patients compared to idiopathic ERM. In contrast, GFAP immunoreactivity appears to be prominent in both PDR and idiopathic ERMs, suggesting similar involvement of glial cells in both ERM types
Conclusions
Myofibroblasts and vascular endothelial cells are major components of ERMs in PDR and appear to be involved in the formation of ERMs in diabetes, while glial cells are expressed in both idiopathic and diabetic ERMs. This research may further elucidate the role of various molecular markers in PDR membranes and provide new targets for therapeutic interventions.