Dicer-dependent endothelial microRNAs are necessary for postnatal angiogenesis

Abstract

Posttranscriptional gene regulation by microRNAs (miRNAs) is important for many aspects of development, homeostasis, and disease. Here, we show that reduction of endothelial miRNAs by cell-specific inactivation of Dicer, the terminal endonuclease responsible for the generation of miRNAs, reduces postnatal angiogenic response to a variety of stimuli, including exogenous VEGF, tumors, limb ischemia, and wound healing. Furthermore, VEGF regulated the expression of several miRNAs, including the upregulation of components of the c-Myc oncogenic cluster miR-17-92. Transfection of endothelial cells with components of the miR-17-92 cluster, induced by VEGF treatment, rescued the induced expression of thrombospondin-1 and the defect in endothelial cell proliferation and morphogenesis initiated by the loss of Dicer. Thus, endothelial miRNAs regulate postnatal angiogenesis and VEGF induces the expression of miRNAs implicated in the regulation of an integrated angiogenic response.endothelium ͉ VEGF M icroRNAs (miRNAs) are short (Ϸ22 nt) noncoding RNAs derived from long primary transcripts through sequential processing by the enzymes Drosha and Dicer. Dicer-generated miRNAs are incorporated into the RNA-induced silencing complex that mediates miRNA-dependent translational suppression or in some instances cleavage of respective mRNA targets or translational activation (1, 2). The significance of miRNAs in mammalian biology has been dissected by Dicer gene disruption in mice. Mutant and disrupted Dicer alleles caused embryonic lethality associated with a loss of pluripotent stem cells (3) and defective blood vessel formation (4). Tissue-specific inactivation of Dicer has led to the conclusion that Dicer is essential for several processes, for example, limb, lung, and skin morphogenesis, the maintenance of hair follicles, T cell development/ differentiation, and neuronal survival (5-11).The growth of blood vessels is essential for organ growth and tissue repair. During adulthood, most blood vessels remain quiescent to fulfill their main function of conducting nutritive blood flow to organs; however, during pathological events such as tissue ischemia, inflammation, and tumor progression, endothelial cells (ECs) become activated and angiogenesis ensues to provide conduits for blood flow (12). An imbalance in the growth of blood vessels contributes to the pathogenesis of numerous disorders (13), and the growth of vessels is a complex process, requiring a finely tuned balance between numerous stimulatory and inhibitory signals (14). VEGF has been identified as a central mediator of angiogenesis (15). We (16) and others (17) have recently shown that reduction of miRNA levels via Dicer silencing strongly impacts EC functions in vitro, suggesting a critical role for miRNAs in angiogenesis. The role of Dicer-regulated miRNAs in ovarian angiogenesis is suggested by data obtained in mice expressing a global hypomorphic Dicer1 allele, where female mice are infertile because of corpus luteum insufficiency and defective ovarian angiogenesis...

miR‐342‐5p Is a Notch Downstream Molecule and Regulates Multiple Angiogenic Pathways Including Notch, Vascular Endothelial Growth Factor and Transforming Growth Factor β Signaling

“…Evidence has indicated that miRNAs are essential for vessel development and homeostasis 25, 26. Knockout of Dicer, an enzyme essential for miRNA biogenesis, specifically in ECs results in reduced angiogenic response to limb ischemia and VEGF stimulation 27. It has been speculated that miRNAs are potential targets of therapies for cardiovascular diseases 28.…”

MicroRNA-10a regulation of proinflammatory phenotype in athero-susceptible endothelium in vivo and in vitro

“…Disruption of the tightly regulated spatial and temporal expression of miRNAs is implicated in human diseases such as cancer, infectious diseases, and cardiovascular diseases. In the vascular system, endothelial miRNA-mediated angiogenesis has been demonstrated by mutation or disruption of Dicer (22,23), the rate-limiting enzyme involved in miRNA maturation, and individual miRNAs associated with proangiogenic or antiangiogenic endothelial phenotypes have been identified (24,25). Furthermore, endothelial miR-126 has been shown to suppress vascular cell adhesion molecule 1 (VCAM-1) expression in vitro, implicating miRNAs in the control of endothelial responses to vascular perturbation (26).…”

Endothelial miR-17∼92 cluster negatively regulates arteriogenesis via miRNA-19 repression of WNT signaling

“…The miRNA17∼92 cluster, a polycistronic miRNA that produces six individual miRNAs (miR-17, miR-18a, miR-19a, miR19b, miR-20a, and miR-92a), has been demonstrated to exhibit various biological functions regulating multiple cellular processes involved in proliferation, oncogenesis, differentiation, angiogenesis, and survival (2)(3)(4)(5). The region encoding for this cluster, C13orf25, is amplified in multiple types of lymphomas, including diffuse large B-cell lymphoma, follicular lymphoma, and some solid tumors (6).…”