Endothelial Heterogeneity along the Vascular Tree

Endothelial cells (ECs) vary widely along the vascular system, reflecting differences in structure, gene expression, and function. Large vessels have three layers intima, media, and adventitia while small arterioles and venules have thinner walls, and capillaries consist mainly of a single EC layer and basement membrane, sometimes supported by pericytes or specialized cells.

ECs exhibit distinct molecular profiles depending on vessel type and size. Arterial ECs express markers such as Neuropilin 1 and Notch1/4/5, whereas venous ECs express Neuropilin 2 and Endomucin. Microvascular ECs show enhanced expression of basement membrane proteins, while large vessel ECs are enriched in genes for extracellular matrix remodeling.

Vascular heterogeneity is shaped both by genetic programming with arterial or venous identity established early in development and by biomechanical stimuli, such as shear stress, which regulate gene expression, angiogenesis, and vascular tone. This diversity enables the vascular system to adapt to different functional demands across organs and tissues.