Key Event Overview
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AOPs Including This Key Event
|AOP Name||Event Type||Essentiality|
|Disruption of VEGFR Signaling Leading to Developmental Defects||KE||Strong|
Level of Biological Organization
How this Key Event works
The cardiovascular system is the first functional organ system to develop in the vertebrate embryo, reflecting its critical role during normal development and pregnancy. Blood vessels are key regulators of organogenesis by providing oxygen, nutrients and molecular signals [Maltepe et al. 1997; Chung and Ferrara, 2011; Eshkar-Oren et al. 2015].
Vascular development commences in the early embryo with in situ formation of nascent vessels from angioblasts, leading to a primary capillary plexus (vasculogenesis). After the onset of blood circulation, the primary vascular pattern is further expanded as new vessels sprout from pre-existing vessels (angiogenesis). Both processes, vasculogenesis and angiogenesis, are regulated by genetic signals and environmental factors dependent on anatomical region, physiological state, and developmental stage of the embryo. The developing vascular network is further shaped into a hierarchical system of arteries and veins, through progressive effects on blood vessel arborization, branching, and pruning (angioadaptation). These latter influences include hemodynamic forces, regional changes in blood flow, local metabolic demands and growth factor signals.
Disruptions in embryonic vascular patterning-adaptation may result in adverse pregnancy outcomes, including birth defects, angiodysplasias and cardiovascular disease, intrauterine growth restriction or prenatal death. Some chemicals may act as potential vascular disrupting compounds (pVDCs) altering the expression, activity or function of molecular signals regulating blood vessel development and remodeling. Critical pathways involve receptor tyrosine kinases (e.g., growth factor-signaling), G-protein coupled receptors (e.g., chemokine signaling), and GPI-anchored receptors (e.g. uPAR system). Embryonic vascular disruption has been implicated in the etiology of human birth defects associated with medications taken by women of child-bearing potential (WOCBP) [van Gelder et al. 2009] and thalidomide teratogenesis in animal studies [Therapontos et al. 2009; Vargesson et al. 2015].
How it is Measured or Detected
Methods that have been previously reviewed and approved by a recognized authority should be included in the Overview section above. All other methods, including those well established in the published literature, should be described here. Consider the following criteria when describing each method: 1. Is the assay fit for purpose? 2. Is the assay directly or indirectly (i.e. a surrogate) related to a key event relevant to the final adverse effect in question? 3. Is the assay repeatable? 4. Is the assay reproducible?
A number of experimental and computational models are fit for purpose of monitoring vascular development and assessing vascular insufficiency [Knudsen and Kleinstreuer 2011]. These include: transgenic zebrafish that express enhanced green fluorescent protein in blood vessels [Jin et al. 2005]; chick embryos [Therapontos et al. 2009; Vargesson, 2015]; and rodent embryo culture [Ellis-Hutchings et al. 2016]. Phenotypic readouts of angiogenic vessel formation of the intersegmental vessels (ISVs) in transgenic zebrafish embryos has been used to screen and validate anti-angiogenic compounds [Tran et al. 2007; Yano et al. 2012; Yozzo et al. 2013; Tal et al. 2014; McCollum et al. 2016]. In transgenic zebrafish embryos, live-cell imaging has been used to quantitatively detect the trajectory dynamics of vascular patterning [Clendenon et al. 2013; Shirinfard et al. 2013] and confocal cell imaging has been used to develop a quantitative assay capable of detecting relatively subtle changes (~8%) in ISV length relative to controls during chemical exposure [Tal et al. 2016]. Computational approaches have also been used to predict vascular insufficiency. For example, an in vitro signature for potential vascular disrupting chemicals (pVDCs) was mined for developmental toxicity based on ToxCast [Kleinstreuer et al. 2011; Knudsen and Kleinstreuer, 2011]. This has since been applied to the ToxCast inventory to rank order 1060 chemicals for validation testing [McCollum et al. 2016; Tal et al. 2016; Knudsen et al. 2016]. As such, a chemical’s potential to disrupt vascular patterning, remodeling, or utero-placental circulation could be a class predictor of developmental toxicity solely based on HTS in vitro data in combination with our understanding the embryology behind vascular development.
Evidence Supporting Taxonomic Applicability
Complex functional assays such as the rat aortic explant assay (AEA), rat whole embryo culture (WEC), and the zebrafish embryotoxicity (ZET) along with transcriptomic signatures provide a tiered approach to evaluate HTS signatures and their taxonomic implications for conserved pathways to prioritize further in vivo testing studies [Ellis-Hutchings et al. 2016; Franzosa et al. 2016].
Chung AS, Ferrara N. Developmental and pathological angiogenesis. Annual review of cell and developmental biology. 2011;27:563-84. PubMed PMID: 21756109.
Clendenon SG, Sankaran DG, Shirinifard A, McColluma CW, Bondesson MB, Gustafssona JA and Glazier JA. Arsenic exposure inhibits angiogenesis in zebrafish via downregulation of both VEGFA and VEGFR2. Microscopy and Microanalysis. 2013 19(S2): 778-779.
Ellis-Hutchings RG, Settivari RS, McCoy AT, Kleinstreuer N, Franzosa J, Knudsen TB and Carney EW. Embryonic vascular disruption: linking high throughput signaling signatures with functional consequences. 2016 (in preparation).
Eshkar-Oren I, Krief S, Ferrara N, Elliott AM, Zelzer E. Vascular patterning regulates interdigital cell death by a ROS-mediated mechanism. Development (Cambridge, England). 2015 Feb 15;142(4):672-80. PubMed PMID: 25617432.
Franzosa JA, Settivari RS, Ellis-Hutchings RG, Kleinstreuer NC, Houck KA, Carney EW and Knudsen TB. RNA-Seq analysis of the functional-link between vascular disruption and adverse developmental consequences. 2016 (in preparation).
Jin SW, Beis D, Mitchell T, Chen JN,Stainier DY. Cellular and molecular analyses of vascular tube and lumen formation in zebrafish. Development. 2005 132: 5199-209.
Kleinstreuer NC, Judson RS, Reif DM, Sipes NS, Singh AV, Chandler KJ, et al. Environmental impact on vascular development predicted by high-throughput screening. Environmental health perspectives. 2011 Nov;119(11):1596-603. PubMed PMID: 21788198. Pubmed Central PMCID: PMC3226499.
Knudsen TB, Kleinstreuer NC. Disruption of embryonic vascular development in predictive toxicology. Birth defects research Part C, Embryo today : reviews. 2011 Dec;93(4):312-23. PubMed PMID: 22271680.
Maltepe E, Schmidt JV, Baunoch D, Bradfield CA, Simon MC. Abnormal angiogenesis and responses to glucose and oxygen deprivation in mice lacking the protein ARNT. Nature. 1997 Mar 27;386(6623):403-7. PubMed PMID: 9121557.
McCollum CW, Vancells JC, Hans C, Vazquez-Chantada M, Kleinstreuer N, Tal T, Knudsen T, Shah SS, Merchant FA, Finnell RH, Gustafsson J-A, Cabrera R and Bondesson M (2016) Identification of vascular disruptor compounds by a tiered analysis in zebrafish embryos and mouse embryonic endothelial cells. (submitted).
Shirinifard A, McCollum CW, Bondesson MB, Gustafsson JA, Glazier JA and Clendenon SG. 3D Quantitative analyses of angiogenic sprout growth dynamics Devel Dynam. 2013 242(5): 518-526.
Tal T, Kilty C, Smith A, LaLone C, Kennedy B, Tennant A, McCollum C, Bondesson M, Knudsen T, Padilla S and Kleinstreuer N (2016) Screening for chemical vascular disruptors in zebrafish to evaluate a predictive model for developmental vascular toxicity. (submitted).
Tal TL, McCollum CW, Harris PS, Olin J, Kleinstreuer N, Wood CE, Hans C, Shah S, Merchant FA, Bondesson M, Knudsen TB, Padilla S and Hemmer MJ. Immediate and long-term consequences of vascular toxicity during zebrafish development. Reproductive Toxicology. 2014;48:51-61.
Therapontos C, Erskine L, Gardner ER, Figg WD, Vargesson N. Thalidomide induces limb defects by preventing angiogenic outgrowth during early limb formation. Proceedings of the National Academy of Sciences of the United States of America. 2009 May 26;106(21):8573-8. PubMed PMID: 19433787. Pubmed Central PMCID: 2688998.
Tran TC, Sneed B, Haider J, Blavo D, White A, Aiyejorun T, et al. Automated, quantitative screening assay for antiangiogenic compounds using transgenic zebrafish. Cancer research. 2007;67: 11386-92.
van Gelder MM, van Rooij IA, Miller RK, Zielhuis GA, de Jong-van den Berg LT, Roeleveld N. Teratogenic mechanisms of medical drugs. Human reproduction update. 2010 Jul-Aug;16(4):378-94. PubMed PMID: 20061329.
Vargesson N. Thalidomide-induced teratogenesis: history and mechanisms. Birth defects Research Part C, Embryo today: reviews. 2015 Jun;105(2):140-56. PubMed PMID: 26043938.
Yozzo KL, Isales GM, Raftery TD,Volz DC. High-content screening assay for identification of chemicals impacting cardiovascular function in zebrafish embryos. Environmental science & technology. 2013;47: 11302-10.