Regulation of neovasculogenesis in co-cultures of aortic adventitial fibroblasts and microvascular endothelial cells by cell-cell interactions and TGF-β/ALK5 signaling.

Kristi L Kiick,Xinqiao Jia,Eric W Fowler,Robert E Akins,Rebecca A Scott,Mária A Deli

doi:10.1371/journal.pone.0244243

Abstract

Adventitial fibroblasts (AFs) are critical mediators of vascular remodeling. However, the contributions of AFs towards development of vasculature and the specific mechanisms by which these cells regulate physiological expansion of the vasa vasorum, the specialized microvasculature that supplies nutrients to the vascular wall, are not well understood. To determine the regulatory role of AFs in microvascular endothelial cell (MVEC) neovasculogenesis and to investigate the regulatory pathways utilized for communication between the two cell types, AFs and MVECs were cultured together in poly(ethylene glycol)-based hydrogels. Following preliminary evaluation of a set of cell adhesion peptides (AG10, AG73, A2G78, YIGSR, RGD), 7.5wt% hydrogels containing 3 mM RGD were selected as these substrates did not initiate primitive tubule structures in 3D MVEC monocultures, thus providing a passive platform to study AF-MVEC interaction. The addition of AFs to hydrogels promoted MVEC viability; however, increasing AF density within hydrogels stimulated MVEC proliferation, increased microvessel density and size, and enhanced deposition of basement membrane proteins, collagen IV and laminin. Importantly, AF-MVEC communication through the transforming growth factor beta (TGF-β)/activin receptor-like kinase 5 (ALK5) signaling pathway was observed to mediate microvessel formation, as inhibition of ALK5 significantly decreased MVEC proliferation, microvessel formation, mural cell recruitment, and basement membrane production. These data indicate that AFs regulate MVEC neovasculogenesis and suggest that therapeutics targeting the TGF-β/ALK5 pathway may be useful for regulation of vasculogenic and anti-vasculogenic responses.

Highlights

The vasa vasorum is a specialized microvasculature that supplies the outer layers of large blood vessels with oxygen and nutrients [1]
In vitro cell culture systems comprising synthetic biomaterials provide valuable platforms for studying cell interactions and signaling cascades. Such platforms could be of great use for Neovasculogenesis regulated by fibroblasts and endothelial cells via cell interactions and activin receptor-like kinase 5 (ALK5) signaling understanding signaling mechanisms involved in Adventitial fibroblasts (AFs) regulation of microvessel formation, in providing insight into signaling mechanisms regulating neovasculogenesis, and in identifying potential therapeutic approaches for regulating maladaptive vascular remodeling
Multiple biologically active laminin peptides, including AG73, AG10, A2G78, and YIGSR, which target multiple extracellular matrix (ECM) receptors, such as α6β1, α3β1, α-dystroglycan, 67-kDa laminin receptor, and syndecan [39,40,41], and the fibronectin-derived peptide, RGD, which target α5β1 and αvβ3 [42], interact with microvascular cells. These peptide motifs were evaluated in a subset of preliminary experiments that investigated the potential of Neovasculogenesis regulated by fibroblasts and endothelial cells via cell interactions and ALK5 signaling these ligands to support microvascular endothelial cell (MVEC)-matrix interactions

Summary

Introduction

The vasa vasorum is a specialized microvasculature that supplies the outer layers of large blood vessels with oxygen and nutrients [1]. Neovasculogenesis regulated by fibroblasts and endothelial cells via cell interactions and ALK5 signaling material support were provided by a. In the conduct of this study, the following authors received salary support: a. Kiick received no specific funding for this work

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