Disorders of retinal vessel growth and function are responsible for vision loss in retinopathy of prematurity (ROP), a leading cause of vision impairment and blindness in childhood. ROP develops as a result of excessive growth of abnormal pre-retinal blood vessels, a compensatory mechanism that overcomes an earlier phase of hyperoxia-induced vaso-obliteration. Elucidation of the molecular bases of angiogenic cell function and behavior in physiological and pathological processes will have important therapeutic implications for the treatment of human retinal vascular diseases. The long term goal of our laboratory is to uncover the in vivo functions of the matricellular protein CCN1, also known as cysteine-rich protein 61, and the functional consequences of its expression, or lack thereof, in development and ischemic retinopathy. The CCN1 protein is an inducible immediate-early gene-encoded extracellular matrix (ECM) protein required for proper vascular development. In our preliminary studies, we have found that over-expression of CCN1 in the retina via either gene- or cell-based therapy, enhanced normal retinal vascularization and reduced pathological angiogenesis in the model of oxygen-induced retinopathy (OIR). In vitro data showed that CCN1 functions primarily through direct binding to specific integrins and ECM proteins, and/or indirectly through modulation of growth factor and Wnt protein expression and/or activity, thereby triggering signaling events that culminate in the regulation of cell adhesion, migration, proliferation, gene expression, differentiation, and survival. Our hypothesis is that CCN1 normalizes the biological mechanisms of retinal vessel formation during development and following OIR and overrides those leading to abnormal vessel formation.
In Specific Aim 1, we will use mutant mice with inducible conditional inactivation of the CCN1 gene to determine how loss of CCN1 in endothelial cells (ECs) causes defective retinal vessel growth. We will identify interactions with Wnt- and Notch-derived signals known to influence functional specialization of ECs (tip and stalk cell phenotypes) and sprouting angiogenesis. We will further determine whether and how forced expression of CCN1 in ECs only, allows normal retinal vessel formation in OIR.
In Specific Aim 2, we will define the molecular interactions of CCN1 with astrocytes, the primary proangiogenic cells responsible for retinal vessel formation and patterning during development, and we will determine the functional significance of CCN1 loss in astrocytes (and/or in ECs) in mutant mice on astrocyte activation state and behavior (e.g., migration, density and ensheathment) during development and in OIR.
In Specific Aim 3, we will define the dynamics of the CCN1 promoter activity and identify the functional elements responsible for CCN1 gene modulation both in cultured retinal ECs subjected to hyperoxic stress and in retinas of OIR mice. This proposal will provide new insights into the molecular mechanisms of CCN1 activities in vivo and may foster future safer, less destructive, and more effective therapies to harness ischemia-induced neovascularization in ROP.
Pathological angiogenesis is the hallmark of ischemic retinopathy, a leading cause of visual impairment in all age groups and a major financial burden for health care systems. Our project investigates the in vivo regulation and function of a specific component of the extracellular environment referred to as CCN1/Cyr61 in retinal vessel development and determines how this protein normalizes the mechanism of retinal vessel formation and prevents abnormal vessel growth in response to oxygen-induced retinopathy. Knowledge gained from these studies is also a promising opportunity to develop therapeutic applications using this protein or small molecules that control its expression to enhance the formation of normally functioning retinal blood vessels and improve the pharmacotherapy of retinal ischemic diseases.
|Chaqour, Julienne; Lee, Sangmi; Ravichandra, Aashreya et al. (2018) Abscisic acid - an anti-angiogenic phytohormone that modulates the phenotypical plasticity of endothelial cells and macrophages. J Cell Sci 131:|
|Lee, Sangmi; Elaskandrany, Menna; Lau, Lester F et al. (2017) Interplay between CCN1 and Wnt5a in endothelial cells and pericytes determines the angiogenic outcome in a model of ischemic retinopathy. Sci Rep 7:1405|
|Chaqour, Brahim (2016) Regulating the regulators of angiogenesis by CCN1 and taking it up a Notch. J Cell Commun Signal 10:259-261|
|Jadhav, Vaishnavi; Luo, Qianyi; M Dominguez 2nd, James et al. (2016) Per2-Mediated Vascular Dysfunction Is Caused by the Upregulation of the Connective Tissue Growth Factor (CTGF). PLoS One 11:e0163367|
|Yan, Lulu; Lee, Sangmi; Lazzaro, Douglas R et al. (2015) Single and Compound Knock-outs of MicroRNA (miRNA)-155 and Its Angiogenic Gene Target CCN1 in Mice Alter Vascular and Neovascular Growth in the Retina via Resident Microglia. J Biol Chem 290:23264-81|
|Krupska, Izabela; Bruford, Elspeth A; Chaqour, Brahim (2015) Eyeing the Cyr61/CTGF/NOV (CCN) group of genes in development and diseases: highlights of their structural likenesses and functional dissimilarities. Hum Genomics 9:24|
|Bhatwadekar, Ashay D; Yan, Yuanqing; Stepps, Valerie et al. (2015) miR-92a Corrects CD34+ Cell Dysfunction in Diabetes by Modulating Core Circadian Genes Involved in Progenitor Differentiation. Diabetes 64:4226-37|
|Chintala, Hemabindu; Krupska, Izabela; Yan, Lulu et al. (2015) The matricellular protein CCN1 controls retinal angiogenesis by targeting VEGF, Src homology 2 domain phosphatase-1 and Notch signaling. Development 142:2364-74|
|Agrawal, Saloni; Chaqour, Brahim (2014) MicroRNA signature and function in retinal neovascularization. World J Biol Chem 5:1-11|
|Chaqour, Brahim (2013) Molecular control of vascular development by the matricellular proteins CCN1 (Cyr61) and CCN2 (CTGF). Trends Dev Biol 7:59-72|
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