stromavasculature

Stromavasculature refers to the vascular component embedded within the connective tissue stroma of an organ. It encompasses the microvasculature, including capillaries and postcapillary venules, as well as small arteries and veins that reside in the stroma, and the lymphatic network. Perivascular cells such as pericytes and smooth muscle cells, together with the basement membrane and surrounding extracellular matrix, form a coordinated vascular-stromal unit that supports tissue perfusion, waste exchange, and signaling between blood vessels and resident stromal and parenchymal cells.

Anatomy and variation: The stromal vasculature varies across tissues in vessel density, permeability, and the balance between blood and lymphatic vessels. Continuous, fenestrated, and sinusoidal capillaries reflect lineage and organ-specific needs. Perivascular cells regulate vessel stability and tone, while the extracellular matrix provides structural support and influences vessel growth and remodeling.

Physiology and function: Stromavasculature supplies oxygen and nutrients, removes CO2 and metabolites, and enables immune cell trafficking. It participates in tissue repair by coordinating angiogenesis and remodeling in response to injury. The vascular niche interacts with resident stem and progenitor cells, supporting homeostasis and regeneration. In addition, it plays a role in hormonal and paracrine signaling that affects organ function.

Development and regulation: Vascular networks form via vasculogenesis and angiogenesis, guided by growth factors such as VEGF and angiopoietins, and modulated by fibroblasts, immune cells, and matrix remodelers. Dysregulation of stromal angiogenesis or fibrosis can alter tissue architecture and function.

Clinical relevance: Abnormal stromavasculature is seen in aging, fibrosis, and tumors, where desmoplastic stroma and leaky, irregular vessels influence progression and treatment response. Markers such as CD31 and VE-cadherin identify endothelial components, while PDGFR-β and α-smooth muscle actin mark pericytes and smooth muscle cells.