Intracellular cytoskeleton and junction proteins of endothelial cells in the porcine iris microvasculature

Abstract

Recently we reported studies of the iris microvasculature and its endothelial cells using intra-luminal micro-perfusion, fixation, and silver staining, suggesting that the iris vascular endothelium may be crucial for maintaining homeostasis in the ocular anterior segment. Here we present information regarding the intracellular structure and cell junctions of the iris endothelium. Thirty-seven porcine eyes were used for this study. The temporal long posterior ciliary artery was cannulated to assess the iris microvascular network and its endothelium using intra-luminal micro-perfusion, fixation, and staining with phalloidin for intracellular cytoskeleton f-actin, and with antibodies against claudin-5 and VE-cadherin for junction proteins. Nuclei were counterstained with Hoechst. The iris was flat-mounted for confocal imaging. The iris microvasculature was studied for its distribution, branch orders and endothelial morphometrics with endothelial cell length measured for each vessel order. Our results showed that morphometrics of the iris microvasculature was comparable with our previous silver staining. Abundant stress fibres and peripheral border staining were seen within the endothelial cells in larger arteries. An obvious decrease in cytoplasmic stress fibres was evident further downstream in the smaller arterioles, and they tended to be absent from capillaries and veins. Endothelial intercellular junctions throughout the iris vasculature were VE-cadherin and claudin-5 immuno-positive, indicating the presence of both adherent junctions and tight junctions between vascular endothelial cells throughout the iris microvasculature. Unevenness of claudin-5 staining was noted along the endothelial cell borders in almost every order of vessels, especially in veins and small arterioles. Our results suggest that significant heterogeneity of intracellular structure and junction proteins is present in different orders of the iris vasculature in addition to vascular diameter and shape of the endothelia. Detailed information of the topography and intracellular structure and junction proteins of the endothelium of the iris microvasculature combined with unique structural features of the iris may help us to further understand the physiological and pathogenic roles of the iris vasculature in relevant ocular diseases.

A novel in vivo model of puncture-induced iris neovascularization

“…Iris arteries and veins originate from the outer limbus limits of the uvea and progress up on the inner iris bordered by the pupil. Plenty of anastomosis is found between arteries and veins [1], allowing nutrition and oxygen supply not only to the iris tissue but also to the anterior chamber of the eye, and therefore maintain intraocular homeostasis [2]. In mammals, the development of the eye is not final at birth.…”

Tongxinluo Reverses the Hypoxia-suppressed Claudin-9 in Cardiac Microvascular Endothelial Cells

“…[ 7 8 9 ] We analyzed and found that claudin-5, claudin-9, and claudin-11 are highly expressed in the heart, and they have all been reported to be expressed in endothelial cells. [ 10 11 12 13 ] Although hypoxia has been found to disrupt tight junctions, especially claudin-5 in cerebral endothelial cells,[ 14 15 ] the effects of hypoxia on claudin-5, claudin-9, and claudin-11 in cardiac microcirculation have not been explored.…”

“…[ 9 ] Claudin-5 is generally believed to be the main claudin subtype in endothelial cells, and it plays a crucial role in the endothelial barrier. [ 10 11 ] Claudin-9 and claudin-11 have also been reported to be expressed in endothelial cells, and function as important tight junction proteins. [ 12 13 ] Hypoxia has been found to disrupt tight junction complexes, especially claudin-5, causing cerebral endothelial barrier dysfunction.…”

Endothelial Tight Junctions Are Opened in Cholinergic-Evoked Salivation In Vivo

“…Endothelial cells are the innermost component of blood vessels, and tight junctions (TJs) located at the most apical portion of their lateral membranes serve as gatekeepers for the endothelial paracellular pathway (Tsukita et al 2001;González-Mariscal et al 2008). Previous studies have shown that the vascular endothelium is crucial for maintaining homeostasis in the ocular anterior segment (Yang et al 2015). Treatment with fenofibric acid prevents the aberrant distribution of TJ proteins in rat retinal endothelial cells, which is a possible mechanism for reducing excessive permeability in diabetic patients (Roy et al 2015).…”