Evidence Of Lymphatic Vessels In The Developing And Young Adult Human Retina and Choroid

Purpose: : To undertake a complete characterisation of the lymphatics in the retina and choroid and human during development and early adulthood. Methods: : Multiple marker immunohistochemistry with lymphatic endothelial specific markers including PROX1, LYVE-1A, Podoplanin, D-240, VEGF-C and VEGF-R3 of retinal and choroidal wholemounts; transverse sections and TEM. Vascular endothelial specific markers (CD34, CD39) were also applied to the same tissue. Results: : Lymph vessel growth was found to have a topography of growth that centered around the optic nerve head. Vasculogenesis and angiogenesis appear to precede lymphangiogenesis. Significant structural evidence of lymphatic vessels were found in both the human retina and choroid, but the extent of lymph vasculature was greater in the choroid than the retina. Structural evidence of lymphatic vessels included double-layered vessel walls, lymphatic valves, branch patterns typical of lymphatics, high endothelial cells labelled with lymphatic endothelial specific markers. Conclusions: : The identification of a significant lymphatic vasculature within the human retina and choroid, and localisation of lymphatic growth factors and receptors necessitates greater understanding of the interaction of the lymphatic vasculature; blood vessels and immune response in the pathogenesis of retinal and choroidal neovascularization.