Abstract
Angiogenesis is largely driven by motile endothelial tip-cells capable of invading avascular tissue domains and enabling new vessel formation. Highly responsive to Vascular Endothelial Growth-Factor-A (VEGFA), endothelial tip-cells also suppress angiogenic sprouting in adjacent stalk cells, and thus have been a primary therapeutic focus in addressing neovascular pathologies. Surprisingly, however, there remains a paucity of specific endothelial tip-cell markers. Here, we employ transcriptional profiling and a lacZ reporter allele to identify Kcne3 as an early and selective endothelial tip-cell marker in multiple angiogenic contexts. In development, Kcne3 expression initiates during early phases of angiogenesis (E9) and remains specific to endothelial tip-cells, often adjacent to regions expressing VEGFA. Consistently, Kcne3 activation is highly responsive to exogenous VEGFA but maintains tip-cell specificity throughout normal retinal angiogenesis. We also demonstrate endothelial tip-cell selectivity of Kcne3 in several injury and tumor models. Together, our data show that Kcne3 is a unique marker of sprouting angiogenic tip-cells and offers new opportunities for investigating and targeting this cell type.
Highlights
New blood vessel formation, or neovascularization, is a necessary physiological process that is highly coordinated with tissue growth and homeostasis, but is frequently dysregulated in disease states ranging from cancer to ischemia [1,2,3]
To further examine Vascular Endothelial Growth-Factor-A (VEGFA)-induced effects on endothelial tip cells (ETCs), we evaluated the expression of defined ETC and endothelial stalk cells (ESCs) signature markers
◂Fig. 2 Kcne3 is activated in ETCs during normal and pathogenic retinal angiogenesis. a–c β-galactosidase staining of P7 retina from heterozygous Kcne3–lacZ reporter mice at low and high-power showing specific expression in ETCs and weaker expression in ESCs along the angiogenic front. c Comparative fluorescent isolectin (IB4) showing the overall vascular pattern compared to that in b; staining shows that Kcne3–lacZ is absent from hyaloid vessels, but labels endothelial cells at the vascular front. d Schematic illustration of regimen for short-term Oxygen‐induced retinopathy (OIR) experiments
Summary
New blood vessel formation, or neovascularization, is a necessary physiological process that is highly coordinated with tissue growth and homeostasis, but is frequently dysregulated in disease states ranging from cancer to ischemia [1,2,3]. Angiogenesis, the primary mode of neovascularization, ensues through selection and sprouting of migratory endothelial cells (ECs) that break away from their stable positions within pre-existing blood vessels to form lumenized tubules that further remodel into an elaborate network of arteries, veins and capillaries [4, 5]. ETCs express abundant levels of vascular endothelial growth-factor-A receptor 2 (VegfR2), and are highly responsive to the pro-migratory effects of VEGFA produced by tissues under oxygen and nutrient depravation [6]. Trailing behind ETCs are phenotypically distinct endothelial stalk cells (ESCs). ESCs are highly proliferative but exhibit reduced
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