Abstract P173: Collagen-iii, An Index Of Vascular Maintenance

Abstract

Brain capillary integrity is compromised during stroke (Hu 2017). Re-establishing the blood-brain barrier (BBB) post-stroke requires integration of cues from endothelial cells (EC), pericytes (PC), and the extracellular matrix (ECM) to promote vessel remodeling. Two ECM components, Types III and IV Collagen (Col-III and Col-IV, respectively), support vascular growth and maintenance. Here, we utilized a murine embryonic stem cell (ESC) model to investigate how ECM mis-regulation impacts PC and EC collagen synthesis. ECM stability was targeted by administering α,α-dipyridyl (iron chelator) (Ikeda 1992) or Type IV Collagenase to ESC-derived vessels. Our aim was to establish potential mechanistic roles of both Col-III and Col-IV in promoting vascular maintenance. We observed by qRT-PCR that α,α-dipyridyl administration decreased Col3a1 expression, but not Col4a1, in a dose-dependent manner. Analysis by immunostaining and confocal microscopy revealed increases in vascular-associated and interstitial Col-IV with the lower doses of α,α-dipyridyl, but decreases in both Col-IV regions at higher doses. Preliminary imaging data for Col-III, however, suggested decreases in both vascular-associated and interstitial Col-III with lower doses, but increases in these Col-III regions with the highest α,α-dipyridyl dose. In separate experiments, Type IV Collagenase exposure reduced both vascular and interstitial Col-IV despite apparent increases in Col3a1 and Col4a1 gene expression. Taken together, these data suggest that perturbations to the ECM microenvironment surrounding developing blood vessels can elicit various compensatory responses depending on the severity and specificity of the ECM component targeted. These observations, support the idea that dynamic remodeling of the microvessel wall, and specifically the surrounding ECM, may contribute to microvascular instability, as seen in the BBB following acute ischemic stroke.