pericytes

Pericytes are contractile mural cells embedded in the basement membrane of microvessels, primarily capillaries and post-capillary venules, closely associated with endothelial cells. They envelop the abluminal surface of capillaries with thin processes that wrap around the endothelium. In the central nervous system, they are abundant and contribute to the integrity of the blood-brain barrier and regulation of cerebral blood flow; in other tissues they support vascular stability and remodeling.

Pericytes share a common basement membrane with endothelial cells and express markers such as PDGFR-β, NG2 (CSPG4), CD146, and RGS5; marker expression overlaps with other cell types, so identification relies on location and a combination of markers.

They regulate endothelial proliferation and maturation of tight junctions, produce extracellular matrix, and secrete signaling molecules such as TGF-β and angiopoietins that promote vessel stabilization. Some pericytes express alpha-smooth muscle actin and can constrict capillaries, contributing to fine-tuning capillary diameter and cerebral blood flow. They participate in angiogenesis by migrating along sprouts and supporting maturation of new vessels, and they help maintain vessel integrity by reinforcing the basement membrane.

Developmentally, pericytes originate from mesenchymal progenitors; in the central nervous system they may derive from neural crest in some contexts. Recruitment to nascent vessels is mediated by endothelial PDGF-BB signaling through PDGFR-β.

Clinically, pericyte loss or dysfunction is linked to breakdown of the blood-brain barrier in diabetes and neurodegenerative diseases; tumor vasculature often shows altered pericyte coverage, affecting stability and drug delivery.

Research relies on lineage tracing and imaging of PDGFR-β and NG2 to assess pericyte coverage and behavior.