Indications of lymphatic endothelial differentiation and endothelial progenitor cell activation in the pathology of proliferative diabetic retinopathy

Abstract

ABSTRACT.Purpose: Proliferative diabetic retinopathy (PDR) is characterized by ischaemiaand inflammation-induced neovascularization, but the pathological vascular differentiation in PDR remains poorly characterized. Here, endothelial progenitor and growth properties, as well as potential lymphatic differentiation, were investigated in the neovascular membrane specimens from vitrectomized patients with PDR. Methods: The expression of pan-endothelial CD31 (PECAM-1), ETS-related gene (ERG), a-smooth muscle actin (a-SMA), and stem/progenitor cell marker CD117 (c-kit) and cell proliferation marker Ki67 was investigated along with the markers of lymphatic endothelial differentiation (vascular endothelial growth factor receptor (VEGFR)-3; prospero-related homeobox gene-1 (Prox-1), lymphatic vessel endothelial receptor [LYVE)-1 and podoplanin (PDPN)] by immunohistochemistry. Lymphocyte antigen CD45 and pan-macrophage marker CD68 were likewise investigated. Results: All specimens displayed CD31, ERG and a-SMA immunoreactivity in irregular blood vessels. Unexpectedly, VEGFR3 and Prox-1 lymphatic marker positive vessels were also detected in several tissues. Prox-1 was co-expressed with CD117 in lumen-lining endothelial cells and adjacent cells, representing putative endothelial stem/progenitor cells and pro-angiogenic perivascular cells. Immunoreactivity of CD45 and CD68 was detectable in all investigated diabetic neovessel specimens. PDPN immunoreactivity was also detected in irregular lumen-forming structures, but these cells lacked CD31 and ERG that mark blood and lymphatic endothelium. Conclusions: Although the inner part of human eye is physiologically devoid of lymphatic vessels, lymphatic differentiation associated with endothelial stem/ progenitor cell activation may be involved in the pathogenesis of human PDR. Further studies are warranted to elucidate whether targeting lymphatic factors could be beneficial in the treatment of patients with the sight-threatening forms of DR.

The microenvironment of proliferative diabetic retinopathy supports lymphatic neovascularization

“…PDR specimens were fixed and processed as reported previously (see also supplementary material, Supplementary materials and methods).…”

“…The pathogenesis of the end‐stage disease, proliferative DR (PDR), is characterized by ischaemia‐induced abnormal angiogenesis and vascular leakage due to compromised vascular integrity after pericyte/smooth muscle cell (SMC) loss and capillary regression, coupled with inflammatory and fibrotic responses within the metabolically imbalanced retina . Ultimately, these processes lead to neovascular and/or fibrotic tissue growth towards the vitreous with the involvement of neuroglia and inflammatory cells, activation of progenitor/stem cells, and the recently discovered abnormal lymphatic‐like endothelial differentiation . If untreated, increased vascular permeability, neovascularization and fibrosis will lead to vision loss due to vitreous haemorrhage, tractional retinal detachment, and neovascular glaucoma.…”

“…The development of new treatment strategies requires systematic mechanistic and functional studies on vascular cells in the context of three‐dimensional (3D) microenvironments, including relevant cell–cell and cell–extracellular matrix (ECM) interactions . Although numerous useful animal models of diabetes and oxygen depletion‐induced or pericyte depletion‐induced retinopathy have been developed, they provide limited information regarding the proliferative neovascular tissue formation and properties in human PDR .…”

Deregulation of ocular nucleotide homeostasis in patients with diabetic retinopathy

“…occlusion; retinal fibrosis; and in the proliferative form, invasion of abnormal blood vessels from the retinal circulation, growth of newly formed vessels (neovascularization), and lymphangiogenesis [1][2][3][4]. Numerous factors, such as vascular endothelial growth factor (VEGF) and angiopoietins (Ang), neurotrophic mediators somatostatin and neurotrophins, erythropoietin (EPO), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGFβ1), and other cytokines and chemokines, have been shown to be implicated in the pathogenesis of DR [3][4][5][6][7].…”

A Combination of Antigen Retrieval Methods Significantly Enhances the Unmasking of Tedious Antigens of Lymphangiogenesis and Angiogenesis in Canine Mammary Tumour

“…Most of our samples didn't yielded any significant AR for lymphangiogenesis and angiogenesis markers with sodium citrate buffer alone [17] [ Figure 1 acidic and basic pH treatment as suggested by Hayat [8], and van Everbroeck et al [41] that sometimes multiple AR methods in combinations are needed to optimize the immuno-detection of antigens [ Table 3, Figures 1(a)-8(c)]. …”