Vitreoretinal interface features in epiretinal membrane associated with pseudoexfoliation syndrome

To describe the morphology and histopathology of the vitreoretinal interface (VRI) in eyes with pseudoexfoliation syndrome (PEX) and epiretinal membrane (ERM) (pERM) in comparison to eyes without PEX and idiopathic ERM (iERM).

Specimens of ERM and internal limiting membrane (ILM) were obtained during pars plana vitrectomy with membrane peeling from 10 symptomatic eyes with pERM and 16 eyes with iERM. Specimens were processed as flat-mounts for immunocytochemistry and prepared by ultrathin series sectioning for transmission electron microscopy (TEM). Cellular and extracellular composition were compared and correlated with clinical data.

The extracellular distribution of the VRI showed significant differences between pERM and iERM in the following aspects. Immunostaining revealed that all pERM specimens were positive for fibrillin-1, collagen IV and TGFβ1, which are key regulatory factors or structural components of the extracellular matrix, while these markers were rarely detected positive in the iERM group. Glial cell markers, GFAP and vimentin, were consistently positive in both groups. TEM revealed abundant vitreous collagen and evidence of vitreous remodeling in pERM eyes, including the presence of fibrous long-spacing collagen (FLSC). In contrast, iERM specimens showed sparse collagen strands with no evidence of FLSC.

Eyes with pERM showed excessive production and subsequent accumulation of extracellular matrix material and elastic proteins such as fibrilin compared to eyes with iERM. Our data suggest that PEX may affect the VRI in a manner similar to the anterior segment, based on the detection and alteration of common structures such as collagen in the pERM.