Pericytes: not only an anatomical “internet” coordinating coronary vessels, but also key functional players?

Aims determination of the distribution of pericytes (P) in the human coronary system and their functional characterization. We found that interconnected P not only engird the endothelial cell tube (E) of all coronary microvessels, but also form a continuous intimal tissue net in the subendothelium of all coronary arteries and veins. Regardless of vascular origin P are typically connected to the E via abundant gap junctions. Smooth muscle cells extend down the arterial tree but stop abruptly at the junction between muscular arterioles (diam. >20 μm) and endarterioles (diam. 10–20 μm). The latter, the most important vessel segments for blood flow regulation, thus consist only of an inner E and outer tube of P. Pure cultures of P can be established in presence of human placental serum and passaged whilst retaining their typical histological and functional features. P reveal a high procoagulatory potency (activation of X, formation of the prothrombin complex). In co‐culture with endothelial cells of human coronary venular origin spontaneous formation of microvessels can be observed that resembles closely natural angiogenesis. The tip cells in capillary sprouts, though to direct this process, appear to be P and not endothelial cells. Thus, the interconnected P in the heart probably play a central role in the control of myocardial blood flow, hemostasis and angiogenesis. Supported by the Friedrich‐Baur‐Stiftung Munich.