Spatio-Temporal Proliferative Heterogeneity of Intra-Organ Endothelial Cells.

BACKGROUND Blood vessels play a crucial role in supplying tissues with oxygen and nutrients. The maintenance of normal blood vessel number and integrity requires a continuous supply of new endothelial cells (ECs) through self-replication. While it is established that ECs across different tissues exhibit heterogeneity in molecular signatures and regenerative capacities, the extent of proliferation heterogeneity among ECs within the same organ or tissue remains largely unexplored. METHODS An EC-specific proliferation tracing system was developed to investigate the proliferative heterogeneity of ECs in the heart, liver, and lung. A combination of RNA sequencing, spatial transcriptomics, and single-cell RNA sequencing was used to uncover the underlying mechanisms of this heterogeneity. An MAPK signaling inhibitor was administered in vivo to functionally assess pathway involvement. Injury models, including transverse aortic constriction, myocardial infarction, partial hepatectomy, and pneumonectomy, were utilized to assess stress-induced EC proliferation. RESULTS EC proliferation exhibits marked intraorgan heterogeneity. In the heart, ECs in the upper part of the ventricular septum, the superior-inner left ventricle wall, and the apex showed elevated proliferation. In the liver, E-CAD (e-cadherin)±1 liver sinusoidal EC displayed a distinct proliferative advantage. In the lung, PLVAP (plasma membrane vesicle-associated protein)+ ECs renew more actively than CAR4 (carbonic anhydrase 4)+ ECs. Multiomics analysis revealed regional transcription diversity. In vivo MAPK inhibition confirmed its role in regulating EC proliferative heterogeneity. CONCLUSIONS This study uncovers regional and subtype-specific proliferation in the heart, liver, and lung, driven by distinct gene expression programs. These findings highlight the spatial and functional diversity of microvascular ECs and offer a framework for developing organ-specific vascular regenerative strategies.