Myoendothelial junctions in human brain arterioles

Background: The purpose of this work was to determine whether myoendothelial junctions were present in human brains. Summary of Report: We examined vessels of approximately 30-70 μm i.d. from the brains of five autopsied adult patients. Myoendothelial junctions were found in vessels throughout this range, in both surface arterioles and penetrating arterioles, and were classified into three types. The number of myoendothelial junctions, expressed per unit length of vessels, was five times greater in the smallest than in the largest vessels. Thus, we found 1.62 junctions per millimeter length in arterioles <60 μm diameter and 0.31 junctions per millimeter length in arterioles >220 μm diameter. Conclusions: These findings provide an anatomic basis for communication between endothelial cells and smooth muscle of brain microvessels in humans. The function of this intercellular communication is not yet known; however, findings in animals suggest that endothelium may be required for propagated constriction in brain vessels. The existence of myoendothelial junctions in human brain provides a basis for the hypothesis that propagated constriction depends on transmission of some message or messenger between endothelial cells and muscle.