Pericyte

Pericytes are contractile cells that accompany endothelial cells along the walls of capillaries and small venules, forming part of the microvascular wall. They are embedded in the basement membrane and encase the abluminal side of endothelial tubes, where they help regulate blood flow and vessel stability.

Pericytes display a spindle-shaped morphology with long processes that wrap around capillaries. They express a set of markers including PDGFR-β, NG2 (chondroitin sulfate proteoglycan 4), desmin, and, in some tissues, alpha-smooth muscle actin. Marker expression can vary by tissue and developmental stage, reflecting diverse functions.

Functions of pericytes include regulation of capillary diameter and blood flow, stabilization of the endothelial layer, and control of angiogenesis and vascular remodeling. They participate in the maintenance of the blood–brain barrier and cerebrovascular integrity, influence endothelial proliferation, and modulate permeability through paracrine signaling (involving PDGF, TGF-β, and angiopoietins) and direct cell–cell communication via gap junctions. Pericytes also contribute to clearance of metabolic waste and extracellular matrix remodeling in the microvasculature.

Development and origins are diverse; pericytes arise from mesenchymal progenitors in many tissues, while in some central nervous system regions they share developmental roles with neural crest-derived cells. Their exact lineage can vary by organ.

Clinical relevance is notable: pericyte loss or dysfunction is linked to microvascular rarefaction and blood–retinal barrier breakdown in diabetic retinopathy, BBB disruption in neurodegenerative diseases, and altered tumor vasculature that affects drug delivery. Research continues to define their diagnostic and therapeutic potential in vascular pathologies.