Notch3 Is Critical for Proper Angiogenesis and Mural Cell Investment

Abstract

Rationale:The heterotypic interactions of endothelial cells and mural cells (smooth muscle cells or pericytes) are crucial for assembly, maturation, and subsequent function of blood vessels. Yet, the molecular mechanisms underlying their association have not been fully defined.Objective: Our previous in vitro studies indicated that Notch3, which is expressed in mural cells, mediates these cell-cell interactions. To assess the significance of Notch3 on blood vessel formation in vivo, we investigated its role in retinal angiogenesis. Methods and Results:We show that Notch3-deficient mice exhibit reduced retinal vascularization, with diminished sprouting and vascular branching. Moreover, Notch3 deletion impairs mural cell investment, resulting in progressive loss of vessel coverage. In an oxygen-induced retinopathy model, we demonstrate that Notch3 is induced in hypoxia and interestingly, pathological neovascularization is decreased in retinas of Notch3-null mice. Analysis of oxygen-induced retinopathy mediators revealed that angiopoietin-2 expression is significantly reduced in the absence of Notch3. Furthermore, in vitro experiments showed that Notch3 is sufficient for angiopoietin-2 induction, and this expression is additionally enhanced in the presence of hypoxia-inducible factor 1␣. Conclusions: These results provide compelling evidence that Notch3 is important for the investment of mural cells and is a critical regulator of developmental and pathological blood vessel formation. (Circ Res. 2010;107:860-870.)Key Words: Notch3 Ⅲ retina Ⅲ angiogenesis Ⅲ smooth muscle cell Ⅲ pericytes Ⅲ blood vessel B lood vessel formation is a dynamic and complex process that serves a vital role in both health and disease. At the onset of blood vessel formation, endothelial cells coalesce into tube-like structures, which become stabilized by the recruitment of mural cells such as pericytes and vascular smooth muscle cells (VSMCs) that encase the nascent vessel. 1,2 A host of reports have implied that endothelial cells and mural cells are closely associated, and the interactions between them are required for the regulation of vessel formation, stabilization, remodeling and function in vivo and in vitro. [2][3][4] However, the way in which endothelial and mural cells communicate with each other remains poorly understood. Several different ligand-receptor systems have been implicated in heterotypic cell interactions to regulate the development and maintenance of the vasculature. Endothelial cell-secreted platelet-derived growth factor-B is known to be necessary for the recruitment of pericytes to newly formed vessels through platelet-derived growth factor receptor-␤. [5][6][7] Angiopoietin (Ang)-1 and Tie2 signaling has been shown to be critical for vessel maturation and stabilization, 3,8 whereas the differentiation of VSMCs surrounding blood vessels depends on endothelial-derived transforming growth factor-␤. 3,9 In addition to these signaling mediators, it is believed that additional receptor-ligand pairs regulate vascular cellce...

A Novel Population of Local Pericyte Precursor Cells in Tumor Stroma that Require Notch Signaling for Differentiation

“…Notch 3 receptor and its target activation gene Heyl were found robustly increased in pericytes relative to EC and other sorted cell populations, an observation that concurs with previous reports studying the differentiation of other vascular mural cells such as VSMC [12]. Furthermore, we showed that coculture of endothelial cells engineered to overexpressed Jagged1 stimulate CD146 − /CD45 − / CD31 − cells to express the pericyte marker NG2 + , reminiscent of earlier studies sustaining the importance of the Jagged-1-Notch3-Heyl axis for perivascular mural cell differentiation and maintenance [12][13][14]. Conversely, drug-mediated inhibition of Notch signaling with a γ-secretase inhibitor decreased their differentiation into NG2 + cells.…”

Mesenchymal Stem Cells: Roles and Relationships in Vascularization

“…65,66 By regulating PDGFRb expression, Notch signaling has been suggested to possess a role in mural cell recruitment. 67,68 Notch signaling is also crucial for angiogenic sprouting and plays a role in endothelial-pericyte interactions. 67,69,70 Demonstrating the possibility of other pathways associated with pericyte recruitment, stromal-derived factor 1-a (SDF-1a) has been recently implicated in pericyte recruitment, along with its role in endothelial tube formation and maturation.…”

“…67,68 Notch signaling is also crucial for angiogenic sprouting and plays a role in endothelial-pericyte interactions. 67,69,70 Demonstrating the possibility of other pathways associated with pericyte recruitment, stromal-derived factor 1-a (SDF-1a) has been recently implicated in pericyte recruitment, along with its role in endothelial tube formation and maturation. 60,71 Still, pericyte recruitment associated with SDF-1a may be due to crosstalk between SDF-1a and PDGF-BB pathways.…”

Hypomorphic Notch 3 alleles link Notch signaling to ischemic cerebral small-vessel disease

“…In adult tissues, Notch 3 expression is restricted to arterial vSMC, which are also the focus of CADASIL pathology (13). Studies in knockout mouse models implicated Notch 3 activity in vSMC differentiation (14,15) and in the susceptibility of the brain to ischemic challenges (16). However, the role of Notch signaling in CADASIL pathobiology, the nature of the CADASIL mutations, and the mechanisms associating Notch 3 activity to vessel degeneration, remain enigmatic (8,13).…”