Localization of Ang-1, -2, Tie-2, and VEGF expression at endothelial-pericyte interdigitation in rat angiogenesis.
Endothelial cells and pericytes play critical role in angiogenesis, which is controlled, in part, by the angiopoietin (Ang)/Tie-2 system and vascular endothelial growth factor (VEGF). Here, we investigated Ang, Tie-2, and VEGF expression within endothelial cells and pericyte interdigitations (EPI), which consist of cytoplasmic projections of pericytes and corresponding endothelial indentations. After subcutaneous implantation of a thermoreversible gelation polymer disc in rats, the capillary density was low on day 5, increased to a peak on day 7, and then decreased on days 10-20. A small number of EPI were observed on day 5, then increased sharply to a peak on day 10, but had decreased on day 20. Light and electron microscopy immunohistochemical and RNA in situ hybridization analyses revealed that Tie-2 localized at endothelial cells, and Ang-2 localized at endothelial cells and pericytes, while Ang-1 and VEGF localized at pericytes, and Ang-1 was most intensely observed at EPI of pericytes. Conventional quantitative RT-PCR and Western blot analyses revealed that the level of Ang-1 was low on days 5-7, then increased on days 10-20, while the level of VEGF was high on days 5-10, but had decreased on day 20. The level of Ang-2 remained high and Tie-2 remained at the level of the control on days 5-20. The present study showed that the angiogenic phase might be initiated by increases in Ang-2 and VEGF, while the microvessel maturation phase might be initiated by a relative increase in Ang-1 and a decrease in VEGF. Moreover, EPI might serve as a pathway for the Ang-1/Tie-2 system, with VEGF promoting pericyte recruitment for microvascular integrity.
Wakui
Shin
S
Department of Toxicologic Pathology, Azabu University School of Veterinary Medicine, Kanagawa, Japan. wakui@azabu-u.ac.jp
Yokoo
Kiyofumi
K
Muto
Tomoko
T
Suzuki
Yoshihiko
Y
Takahashi
Hiroyuki
H
Furusato
Masakuni
M
Hano
Hiroshi
H
Endou
Hitoshi
H
Kanai
Yoshikatsu
Y
D042683:Angiopoietin-1 / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D042702:Angiopoietin-2 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002196:Capillaries / Q000378:metabolism / Q000648:ultrastructure; D004195:Disease Models, Animal; D019085:Fluorescent Antibody Technique, Direct; D005786:Gene Expression Regulation; D008297:Male; D016253:Microscopy, Immunoelectron; D009389:Neovascularization, Pathologic / Q000378:metabolism* / Q000473:pathology; D020286:Pericytes / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D042787:Receptor, TIE-2 / Q000235:genetics / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
D042683:Angiopoietin-1; D042702:Angiopoietin-2; C467629:Angpt1 protein, rat; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D042787:Receptor, TIE-2