MiR-221 Is Required for Endothelial Tip Cell Behaviors during Vascular Development

Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Developmental Cell (Impact Factor: 9.71). 02/2012; 22(2):418-29. DOI: 10.1016/j.devcel.2012.01.008
Source: PubMed


Angiogenesis requires coordination of distinct cell behaviors between tip and stalk cells. Although this process is governed by regulatory interactions between the vascular endothelial growth factor (Vegf) and Notch signaling pathways, little is known about the potential role of microRNAs. Through deep sequencing and functional screening in zebrafish, we find that miR-221 is essential for angiogenesis. miR-221 knockdown phenocopied defects associated with loss of the tip cell-expressed Flt4 receptor. Furthermore, miR-221 was required for tip cell proliferation and migration, as well as tip cell potential in mosaic blood vessels. miR-221 knockdown also prevented "hyper-angiogenesis" defects associated with Notch deficiency and miR-221 expression was inhibited by Notch signaling. Finally, miR-221 promoted tip cell behavior through repression of two targets: cyclin dependent kinase inhibitor 1b (cdkn1b) and phosphoinositide-3-kinase regulatory subunit 1 (pik3r1). These results identify miR-221 as an important regulatory node through which tip cell migration and proliferation are controlled during angiogenesis.

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    • "miR221 is likely to alter an appropriate balance in regulatory and catalytic subunits of PI3K that may indeed affect the receptor tyrosine kinasemediated activation of PI3K and local PI3K activity in separate subcellular compartments such as growing filopodia of tip embryonic ECs. miR-221 directs proliferation of embryonic ECs through vascular endothelial growth factor C (VEGF-C)/Fms-related tyrosine kinase 4 (Flt4) signaling [64] that is modulated by PI3K3R1 that stimulates interaction of PI3K with VEGF-Cactivated Flt4 (VEGFR3), a receptor for VEGF-C and VEGF- D [69]. Activation of notch signaling in stalk ECs was shown to inhibit both Flt4 and miR-221 that leads to increase in CDKN1B levels and reducing proliferation [64]. "
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    ABSTRACT: A cluster of miR-221/222 is a key player in vascular biology through exhibiting its effects on vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). These miRNAs contribute to vascular remodeling, an adaptive process involving phenotypic and behavioral changes in vascular cells in response to vascular injury. In proliferative vascular diseases such as atherosclerosis, pathological vascular remodeling plays a prominent role. The miR-221/222 cluster controls development and differentiation of ECs but inhibits their proangiogenic activation, proliferation, and migration. miR-221/222 are primarily implicated in maintaining endothelial integrity and supporting quiescent EC phenotype. Vascular expression of miR-221/222 is upregulated in initial atherogenic stages causing inhibition of angiogenic recruitment of ECs and increasing endothelial dysfunction and EC apoptosis. In contrast, these miRNAs stimulate VSMCs and switching from the VSMC "contractile" phenotype to the "synthetic" phenotype associated with induction of proliferation and motility. In atherosclerotic vessels, miR-221/222 drive neointima formation. Both miRNAs contribute to atherogenic calcification of VSMCs. In advanced plaques, chronic inflammation downregulates miR-221/222 expression in ECs that in turn could activate intralesion neoangiogenesis. In addition, both miRNAs could contribute to cardiovascular pathology through their effects on fat and glucose metabolism in nonvascular tissues such as adipose tissue, liver, and skeletal muscles.
    Full-text · Article · Jul 2015
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    • "Overexpressing miR-221/222 reduced the in vitro cellular motility and microvasculature formation ability of late EPCs (Figure 4D), which partly explained why these 2 miRs were more abundant in disease EPCs and in mature ECs. Since EPCs are capable of forming new blood vessels even in the absence of a pre-existing vessel network [6] and knockdown experiments showed that miR-221 is required for endothelial tip cell behaviors during vascular development [39], we examined the role of miR-221/222 in the formation of the blood vessels in vivo. Over-expression of either miR-221 or miR-222 in zebrafish embryos resulted in the deregulation of blood vessel pattern during development (Figure 4E, abnormal blood vessels indicated by arrows). "
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    ABSTRACT: Background Endothelial progenitor cells (EPCs) play a fundamental role in not only blood vessel development but also post-natal vascular repair. Currently EPCs are defined as early and late EPCs based on their biological properties and their time of appearance during in vitro culture. Both EPC types assist angiogenesis and have been linked to ischemia-related disorders, including coronary artery disease (CAD). Results We found late EPCs are more mobile than early EPCs and matured endothelial cells (ECs). To pinpoint the mechanism, microRNA profiles of early EPCs late EPCs, and ECs were deciphered by small RNA sequencing. Obtained signatures made up of both novel and known microRNAs, in which anti-angiogenic microRNAs such as miR-221 and miR-222 are more abundant in matured ECs than in late EPCs. Overexpression of miR-221 and miR-222 resulted in the reduction of genes involved in hypoxia response, metabolism, TGF-beta signalling, and cell motion. Not only hamper late EPC activities in vitro, both microRNAs (especially miR-222) also hindered in vivo vasculogenesis in a zebrafish model. Reporter assays showed that miR-222, but not miR-221, targets the angiogenic factor ETS1. In contrast, PIK3R1 is the target of miR-221, but not miR-222 in late EPCs. Clinically, both miR-221-PIK3R1 and miR-222-ETS1 pairs are deregulated in late EPCs of CAD patients. Conclusions Our results illustrate EPCs and ECs exploit unique miRNA modalities to regulate angiogenic features, and explain why late EPC levels and activities are reduced in CAD patients. These data will further help to develop new plasma biomarkers and therapeutic approaches for ischemia-related diseases or tumor angiogenesis. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-802) contains supplementary material, which is available to authorized users.
    Full-text · Article · Sep 2014 · BMC Genomics
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    • "These miRNAs can also specifically promote cancer cell proliferation by regulating the p27 (Kip1) tumour suppressor gene [74], indicating that the regulation of proliferation by miR-221/222 is cell-type specific. More recent studies have shown that these miRNAs control different target genes: miR-222 is involved in inflammation mediated by vascular growth factors [77], whereas miR-221 is required for vascular remodelling [78]. Similarly, a study performed in a murine model of liver tumorigenesis showed that miR-221 but not miR-222 accelerated tumour growth [79]. "
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    ABSTRACT: MicroRNAs are one class of small, endogenous, non-coding RNAs that are approximately 22 nucleotides in length; they are very numerous, have been phylogenetically conserved, and involved in biological processes such as development, differentiation, cell proliferation, and apoptosis. MicroRNAs contribute to modulating the expression levels of specific proteins based on sequence complementarity with their target mRNA molecules and so they play a key role in both health and disease. Angiogenesis is the process of new blood vessel formation from preexisting ones, which is particularly relevant to cancer and its progression. Over the last few years, microRNAs have emerged as critical regulators of signalling pathways in multiple cell types including endothelial and perivascular cells. This review summarises the role of miRNAs in tumour angiogenesis and their potential implications as therapeutic targets in cancer.
    Full-text · Article · Aug 2014 · BioMed Research International
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