Jiang, Q., Lagos-Quintana, M., Liu, D., Shi, Y., Helker, C., Herzog, W., and le Noble, F. (2013) miR-30a Regulates Endothelial Tip Cell Formation and Arteriolar Branching. Hypertension (Dallas, Tex. : 1979). 62(3):592-8.
Microvascular rarefaction increases vascular resistance and pressure in systemic arteries and is a hallmark of fixed essential
hypertension. Preventing rarefaction by activation of angiogenic processes could lower blood pressure. Endothelial tip cells
in angiogenic sprouts direct branching of microvascular networks; the process is regulated by microRNAs, particularly the
miR-30 family. We investigated the contribution of miR-30 family members in arteriolar branching morphogenesis via delta-like
4 (Dll4)-Notch signaling in a zebrafish model. The miR-30 family consists of 5 members (miR-30a-e). Loss-of-function experiments
showed that only miR-30a reduced growth of intersegmental arterioles involving impaired tip cell function. Overexpression
of miR-30a stimulated tip cell behavior resulting in augmented branching of intersegmental arterioles. In vitro and in vivo
reporter assays showed that miR-30a directly targets the Notch ligand Dll4, a key inhibitor of tip cell formation. Coadministration
of a Dll4 targeting morpholino in miR-30a morphants rescued the branching defects. Conversely, conditional overexpression
of Notch intracellular domain restored arteriolar branching in miR-30a gain-of-function embryos. In human endothelial cells,
loss of miR-30a increased DLL4 protein levels, activated Notch signaling as indicated in Notch reporter assays, and augmented
Notch downstream effector, HEY2 and EFNB2 (ephrin-B2), expression. In spheroid assays, miR-30a loss- and gain-of-function
affected tip cell behavior, consistent with miR-30a targeting Dll4. Our data suggest that miR-30a stimulates arteriolar branching
by downregulating endothelial Dll4 expression, thereby controlling endothelial tip cell behavior. These findings could have
relevance to the rarefaction process and, therefore, to hypertension.