Fibulin-5 functions as an endogenous angiogenesis inhibitor.
Ablation of the fibulin-5 gene (fbln5) in mice results in loose skin, emphysematous lungs and tortuous vessels. Additionally, fbln5(-/-) animals display an apparent increase in vascular sprouting from systemic and cutaneous vessels. From these observations, we hypothesized that a de-regulation of vascular sprouting occurs in the absence of endogenous fibulin-5. To test this hypothesis, vascular sprouts from the long thoracic artery were quantified and polyvinyl alcohol sponges were implanted subcutaneously in wild-type and fbln5(-/-) mice to assess fibrovascular invasion. Results showed a significant increase in in situ sprouting from vessels in fbln5(-/-) mice and a significant increase in vascular invasion, with no increase in fibroblast migration, into sponges removed from fbln5(-/-) mice compared with wild-type mice. Localization of fibulin-5 in wild-type mice showed the protein to be present subjacent to endothelial cells (ECs) in established vessels at the periphery of the sponge, and as a component of the newly formed, loose connective tissue within the sponge. These results suggest that fibulin-5 could function as an inhibitor molecule in initial sprouting and/or migration of ECs. To elucidate the molecular mechanism that drives the increased angiogenesis in the absence of fibulin-5, expression of vascular endothelial growth factor (VEGF) and the angiopoietins (Angs) was determined in sponges implanted for 12 days in wild-type and fbln5(-/-) mice. Quantitative RT-PCR showed message levels for VEGF and all three Angs to be elevated by several fold in the area of invasion of sponges from fbln5(-/-) mice compared with wild-type mice. Expression of Ang-1 was also shown to be elevated (30-fold) in vitro in aortic smooth muscle cells isolated from fbln5(-/-) mice when compared with wild-type cells, with no change in the expression of the Ang-1 mediating transcription factor, ESE-1. Taken together, these results suggest that the normal angiogenic process is enhanced in the absence of fibulin-5.
Sullivan
Kaitlyn M
KM
Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada.
Bissonnette
Rachel
R
Yanagisawa
Hiromi
H
Hussain
Sabah N
SN
Davis
Elaine C
EC
D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D020533:Angiogenesis Inhibitors / Q000502:physiology*; D042682:Angiopoietins / Q000096:biosynthesis; D000818:Animals; D002465:Cell Movement; D042783:Endothelial Cells / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D018919:Neovascularization, Physiologic; D011142:Polyvinyl Alcohol; D011994:Recombinant Proteins / Q000235:genetics; D012867:Skin / Q000098:blood supply; D015503:Surgical Sponges; D013895:Thoracic Arteries / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis
D033942:Adaptor Proteins, Vesicular Transport; D020533:Angiogenesis Inhibitors; D042682:Angiopoietins; D016326:Extracellular Matrix Proteins; C120769:Fbln5 protein, mouse; C118534:Itsn protein, mouse; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D011142:Polyvinyl Alcohol