VEGF and angiopoietin-1 stimulate different angiogenic phenotypes that combine to enhance functional neovascularization in adult tissue.
OBJECTIVE
Therapeutic angiogenesis requires an understanding of how growth factors such as vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) result in physiological neovascularization. This study determined the physiological mechanism by which adenoviral delivery of growth factor combinations alter vascular phenotype and functionality.


METHODS
Adenovirus-mediated gene transfer into the adjacent fat pad of the rat mesentery was used to characterize induction of angiogenesis by VEGF and Ang-1, in a model that permitted a detailed examination of the neovessel phenotype.


RESULTS
Ang-1 combined with VEGF resulted in a distinct vascular phenotype from either factor alone. Microvascular perfusion was significantly enhanced in all groups, but VEGF produced short, narrow, highly branched and sprouting vessels, with normal pericyte coverage. Ang-1 induced broader, longer neovessels, with no increase in branching or sprouting, yet a significantly higher pericyte ensheathment. Combination of Ang-1 and VEGF generated a significantly higher degree of functionally perfused, larger, less branched, and more mature microvessels, resulting from increased efficiency of sprout to vessel formation. Ang-1 and VEGF also caused differential effects on larger compared with smaller blood vessels, a finding reproduced in vitro.


CONCLUSIONS
Ang-1 and VEGF use different physiological mechanisms to enhance neovascularization of relatively avascular tissue. Administration of both growth factors combines these physiological mechanisms to give greater enhancement of neovascularization than either growth factor alone. These results suggest that effective revascularization therapy may require combination growth factor treatment.
Benest
Andrew V
AV
Microvascular Research Laboratories, Department of Physiology, University of Bristol, Bristol, UK.
Salmon
Andrew H
AH
Wang
Wenying
W
Glover
Colin P
CP
Uney
James
J
Harper
Steven J
SJ
Bates
David O
DO
D000256:Adenoviridae; D042683:Angiopoietin-1 / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D006801:Humans; D008297:Male; D008643:Mesentery / Q000098:blood supply* / Q000166:cytology; D018919:Neovascularization, Physiologic / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014161:Transduction, Genetic; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics
D042683:Angiopoietin-1; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A