Artery or vein: to be or not to be?

Colon stroma mediates an inflammation-driven fibroblastic response controlling matrix remodeling and healing

Chronic inflammation is often associated with the development of tissue fibrosis, but how mesenchymal cell responses dictate pathological fibrosis versus resolution and healing remains unclear. Defining stromal heterogeneity and identifying molecular circuits driving extracellular matrix deposition and remodeling stands to illuminate the relationship between inflammation, fibrosis, and healing. We performed single-cell RNA-sequencing of colon-derived stromal cells and identified distinct classes of fibroblasts with gene signatures that are differentially regulated by chronic inflammation, including IL-11-producing inflammatory fibroblasts. We further identify a transcriptional program associated with trans-differentiation of mucosa-associated fibroblasts and define a functional gene signature associated with matrix deposition and remodeling in the inflamed colon. Our analysis supports a critical role for the metalloprotease Adamdec1 at the interface between tissue remodeling and healing during colitis, demonstrating its requirement for colon epithelial integrity. These findings provide mechanistic insight into how inflammation perturbs stromal cell behaviors to drive fibroblastic responses controlling mucosal matrix remodeling and healing.

Developmental Perspectives on Arterial Fate Specification

Blood vessel acquisition of arterial or venous fate is an adaptive phenomenon in response to increasing blood circulation during vascular morphogenesis. The past two decades of effort in this field led to development of a widely accepted paradigm of molecular regulators centering on VEGF and Notch signaling. More recent findings focused on shear stress-induced cell cycle arrest as a prerequisite for arterial specification substantially modify this traditional understanding. This review aims to summarize key molecular mechanisms that work in concert to drive the acquisition of arterial fate in two distinct developmental settings of vascular morphogenesis: de novo vasculogenesis of the dorsal aorta and postnatal retinal angiogenesis. We will also discuss the questions and conceptual controversies that potentially point to novel directions of investigation and possible clinical relevance.

Pericytes in Vascular Development

Purpose of review

Pericytes are essential components of capillaries in many tissues and organs, contributing to vessel stability and integrity, with additional contributions to microvascular function still being discovered. We review current and foundational studies identifying pericyte differentiation mechanics and their roles in the earliest stages of vessel formation.

Recent findings

Recent advances in pericyte-focused tools and models have illuminated critical aspects of pericyte biology including their roles in vascular development.Pericytes likely collaborate with endothelial cells undergoing vasculogenesis, initiating direct interactions during sprouting and intussusceptive angiogenesis. Pericytes also provide important regulation of vascular growth including mechanisms underlying vessel pruning, rarefaction, and subsequent regrowth.