Myoendothelial Junctions of Mature Coronary Vessels Express Notch Signaling Proteins.

Patricia E Mccallinhart,Olivia E Clark,Aaron J Trask,Lauren A Biwer,Brenda Lilly,Brant E Isakson

doi:10.3389/fphys.2020.00029

Abstract

RationaleMyoendothelial junctions (MEJs) within the fenestrae of the internal elastic lamina (IEL) are critical sites that allow for endothelial cell (EC) - vascular smooth muscle cell (VSMC) contact and communication. Vascular Notch signaling is a critical determinant of normal vasculogenesis and remodeling, and it regulates cell phenotype via contact between ECs and VSMCs. To date, no studies have linked Notch signaling to the MEJ despite it requiring cell-cell contact. Furthermore, very little is known about Notch in the adult coronary circulation or the localization of Notch signaling and activity within the mature intact blood vessel.ObjectiveWe tested the hypothesis that vascular Notch signaling between ECs and VSMCs occurs at MEJs.Methods and ResultsNotch receptor and ligand immunofluorescence was performed in human coronary EC and VSMC co-cultures across transwell inserts (in vitro MEJs) and in the intact mouse coronary circulation. Human coronary VSMC Notch activity induced by human coronary ECs at the in vitro MEJ was assessed using a CBF-luciferase construct. We observed Jagged1, Notch1, Notch2, and Notch3 expression within the in vitro and in vivo MEJs. We also demonstrated a 3-fold induction (p < 0.001) of human coronary VSMC Notch signaling by ECs at the in vitro MEJ, which was completely blocked by the Notch inhibitor, DAPT (p < 0.01).ConclusionWe demonstrate for the first time in mature blood vessels that Notch receptors and ligands are expressed within and are active at coronary MEJs, demonstrating a previously unrecognized mode of Notch signaling regulation between the endothelium and smooth muscle.

Highlights

Heterocellular communication between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) is a demonstrated component to normal vascular development and physiology, dictating vascular function and vessel remodeling (Rostama et al, 2014)
We examined the localization of Notch receptors and ligands within the fenestrae of intact Coronary resistance microvessels (CRMs) internal elastic lamina (IEL)
myoendothelial junctions (MEJs) are recognized as fenestrae, or pores, that are located along the IEL

Summary

Introduction

Heterocellular communication between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) is a demonstrated component to normal vascular development and physiology, dictating vascular function and vessel remodeling (Rostama et al, 2014). It is important to note that in large conduit arteries such as the aorta, there are little to no fenestrae within the IEL, limiting the direct contact and communication between the ECs and VSMCs; as the diameter of the vessel decreases, the number of fenestrae increases, making the microvessels the major sites of fenestrae and potential myoendothelial junctions (MEJs). Fenestrae of the IEL can harbor MEJs – sites of direct physical contact and communication between ECs and VSMCs (Heberlein et al, 2010). There is much reported on calcium signaling pathways at the MEJ, there is surprisingly little known about other potential heterocellular communication pathways (Biwer et al, 2016)

Methods

Results

Conclusion