Preferential activity of Tie2 promoter in arteriolar endothelium.
The tyrosine kinase Tie2/Tek (the receptor for angiopoietins) is considered one of the most reliable markers of the endothelial phenotype, across organisms, organs, and developmental stages. However, endothelium is intrinsically heterogeneous in origin, composition and function, presenting an arteriolar/venular asymmetry. In this regard, the expression of Tie2 along the vascular tree, although thought to be homogenous, has not been systematically investigated. Therefore we questioned whether the activity of Tie2 promoter is uniform in the microvascular endothelium. To this end, we analyzed in situ the expression of the markers beta-galactosidase [LacZ(Tie2)] and green fluorescent protein (GFP) [GFP(Tie2)], placed under the Tie2 promoter in transgenic mice, in whole mount tissue samples, which allow the simultaneous evaluation of its relative distribution in various microvascular compartments. In the mesenteries of LacZ(Tie2) and GFP(Tie2) mice, we found that the activity of Tie2 promoter is asymmetrically distributed, being much stronger in arteries and arterioles than on the venular side of the vascular tree. This observation was replicated in the diaphragm of LacZ(Tie2) mice. The capillaries presented a mosaic pattern of Tie2 promoter activity. Stimulation of angiogenesis either by wounding, or by intraperitoneal injection of Vascular Endothelial Growth Factor (VEGF), revealed that the arteriolar/venular asymmetry is established at endothelial cellular level early during new capillary formation, even before the starting of the microvascular blood flow. In conclusion, a strong Tie2 promoter activity qualifies as a novel marker of the arteriolar phenotype in microvascular endothelium.
Anghelina
Mirela
M
Davis Heart and Lung Research Institute, Division of Cardiology, Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210, USA.
Moldovan
Leni
L
Moldovan
Nicanor I
NI
D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism*; D003964:Diaphragm / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D005819:Genetic Markers; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D007763:Lac Operon; D037102:Lectins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D018919:Neovascularization, Physiologic; D011401:Promoter Regions, Genetic; D042787:Receptor, TIE-2 / Q000378:metabolism* / Q000502:physiology; D013152:Splanchnic Circulation / Q000187:drug effects / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D014945:Wound Healing; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
D005819:Genetic Markers; D037102:Lectins; D042461:Vascular Endothelial Growth Factor A; D049452:Green Fluorescent Proteins; D042787:Receptor, TIE-2; D001616:beta-Galactosidase