Notch3 is critical for proper angiogenesis and mural cell investment.
BACKGROUND
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.


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 1α.


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.
Liu
Hua
H
National Children's Research Institute, The Ohio State University, Columbus, OH 43205, USA.
Zhang
Wenbo
W
Kennard
Simone
S
Caldwell
Ruth B
RB
Lilly
Brenda
B
D042702:Angiopoietin-2 / Q000235:genetics; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000502:physiology; D002450:Cell Communication / Q000502:physiology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010100:Oxygen / Q000633:toxicity; D020286:Pericytes / Q000166:cytology / Q000502:physiology*; D000071656:Receptor, Notch3; D051880:Receptors, Notch / Q000235:genetics* / Q000378:metabolism; D012171:Retinal Vessels / Q000166:cytology / Q000502:physiology
D042702:Angiopoietin-2; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C499374:NOTCH3 protein, human; C499373:Notch3 protein, mouse; D000071656:Receptor, Notch3; D051880:Receptors, Notch; D010100:Oxygen