The endothelium first forms in the blood islands in the extra-embryonic yolk sac and then throughout the embryo to establish circulatory networks that further acquire organ-specific properties during development to support diverse organ functions. Here, we investigated the properties of endothelial cells (ECs), isolated from four human major organsthe heart, lung, liver, and kidneys in individual fetal tissues at three months' gestation, at gene expression, and at cellular function levels. We showed that organ-specific ECs have distinct expression patterns of gene clusters, which support their specific organ development and functions. These ECs displayed distinct barrier properties, angiogenic potential, and metabolic rate and support specific organ functions. Our findings showed the link between human EC heterogeneity and organ development and can be exploited therapeutically to contribute in organ regeneration, disease modeling, as well as guiding differentiation of tissue-specific ECs from human pluripotent stem cells.
Overall design: We examined the human fetal organ sets from three donors, constituting three biological replicates at 3 months' gestation (100-125 days). At this stage, all four major organs of interest - the heart, kidney, lung, and liver - have an established microvascular supply and exhibit organ-specific function. The heart beats at 120-160 bpm and is approximately 2 cm, the lungs have developed the entire air-conducting bronchial tree up to 20 generations with respiratory ducts and start to form barriers between alveoli and blood vessels, the liver is the major site of blood cell production and has also started to produce bile, and the kidneys have established nephrons and start to produce urine.
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