Abnormal lymphatic-like differentiation and endothelial progenitor cell activation in hemi retinal vein occlusion

PurposePathological vascular differentiation in retinal vein occlusion-related neovessel formation remains poorly characterized. The role of the intraocular lymphatic-like differentiation or endothelial progenitor cell activity has not been studied in this disease.MethodsAn eye with hemi retinal vein occlusion (RVO) underwent vitrectomy, neovessel membrane located at the optic nerve head was removed and subjected to immunohistochemistry. Characterization of the neovascular tissue was performed using hematoxylin and eosin, α-smooth muscle actin and pan-endothelial cell adhesion molecule (CD31). Expression of lymphatic endothelial cell (LEC) markers was studied by lymphatic vessel hyaluronan endothelial receptor-(LYVE)-1, podoplanin (PDPN), and prospero homeobox protein (Prox)-1. Potential vascular stem/progenitor cells were identified by active cellular proliferation (Ki67) and expression of the stem cell marker CD117.ResultsSpecimen contained blood vessels lined by ECs and surrounded by pericytes. Immunoreactivity for LYVE-1 and Prox-1 was detected, with Prox-1 being more widely expressed in the vessels. PDPN expression was found in the extravascular structures representing potentially monocyte- or bone-marrow derived cells. Expression of stem cell marker CD117 in actively proliferating Ki67-expressing ECs suggested for vascular endothelial stem cell activity.ConclusionsIntraocular lymphatic-like differentiation coupled with endothelial stem/progenitor cell activation may be involved in the pathology of neovessel formation in ischemia-induced human hemi-RVO.