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A Two-Way Communication between Microglial Cells and Angiogenic Sprouts Regulates Angiogenesis in Aortic Ring Cultures

Rymo, Simin F.; Gerhardt, Holger; Wolfhagen Sand, Fredrik LU ; Lang, Richard; Uv, Anne and Betsholtz, Christer (2011) In PLoS ONE 6(1).
Abstract
Background: Myeloid cells have been associated with physiological and pathological angiogenesis, but their exact functions in these processes remain poorly defined. Monocyte-derived tissue macrophages of the CNS, or microglial cells, invade the mammalian retina before it becomes vascularized. Recent studies correlate the presence of microglia in the developing CNS with vascular network formation, but it is not clear whether the effect is directly caused by microglia and their contact with the endothelium. Methodology/Principal Findings: We combined in vivo studies of the developing mouse retina with in vitro studies using the aortic ring model to address the role of microglia in developmental angiogenesis. Our in vivo analyses are... (More)
Background: Myeloid cells have been associated with physiological and pathological angiogenesis, but their exact functions in these processes remain poorly defined. Monocyte-derived tissue macrophages of the CNS, or microglial cells, invade the mammalian retina before it becomes vascularized. Recent studies correlate the presence of microglia in the developing CNS with vascular network formation, but it is not clear whether the effect is directly caused by microglia and their contact with the endothelium. Methodology/Principal Findings: We combined in vivo studies of the developing mouse retina with in vitro studies using the aortic ring model to address the role of microglia in developmental angiogenesis. Our in vivo analyses are consistent with previous findings that microglia are present at sites of endothelial tip-cell anastomosis, and genetic ablation of microglia caused a sparser vascular network associated with reduced number of filopodia-bearing sprouts. Addition of microglia in the aortic ring model was sufficient to stimulate vessel sprouting. The effect was independent of physical contact between microglia and endothelial cells, and could be partly mimicked using microglial cell-conditioned medium. Addition of VEGF-A promoted angiogenic sprouts of different morphology in comparison with the microglial cells, and inhibition of VEGF-A did not affect the microglia-induced angiogenic response, arguing that the proangiogenic factor(s) released by microglia is distinct from VEGF-A. Finally, microglia exhibited oriented migration towards the vessels in the aortic ring cultures. Conclusions/Significance: Microglia stimulate vessel sprouting in the aortic ring cultures via a soluble microglial-derived product(s), rather than direct contact with endothelial cells. The observed migration of microglia towards the growing sprouts suggests that their position near endothelial tip-cells could result from attractive cues secreted by the vessels. Our data reveals a two-way communication between microglia and vessels that depends on soluble factors and should extend the understanding of how microglia promote vascular network formation. (Less)
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organization
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published
subject
in
PLoS ONE
volume
6
issue
1
publisher
Public Library of Science
external identifiers
  • wos:000286513100013
  • scopus:79251551934
ISSN
1932-6203
DOI
10.1371/journal.pone.0015846
language
English
LU publication?
yes
id
0e78bc7f-e764-4a02-b3e5-083659e80bd1 (old id 1878263)
date added to LUP
2011-04-01 08:36:16
date last changed
2017-11-12 03:45:24
@article{0e78bc7f-e764-4a02-b3e5-083659e80bd1,
  abstract     = {Background: Myeloid cells have been associated with physiological and pathological angiogenesis, but their exact functions in these processes remain poorly defined. Monocyte-derived tissue macrophages of the CNS, or microglial cells, invade the mammalian retina before it becomes vascularized. Recent studies correlate the presence of microglia in the developing CNS with vascular network formation, but it is not clear whether the effect is directly caused by microglia and their contact with the endothelium. Methodology/Principal Findings: We combined in vivo studies of the developing mouse retina with in vitro studies using the aortic ring model to address the role of microglia in developmental angiogenesis. Our in vivo analyses are consistent with previous findings that microglia are present at sites of endothelial tip-cell anastomosis, and genetic ablation of microglia caused a sparser vascular network associated with reduced number of filopodia-bearing sprouts. Addition of microglia in the aortic ring model was sufficient to stimulate vessel sprouting. The effect was independent of physical contact between microglia and endothelial cells, and could be partly mimicked using microglial cell-conditioned medium. Addition of VEGF-A promoted angiogenic sprouts of different morphology in comparison with the microglial cells, and inhibition of VEGF-A did not affect the microglia-induced angiogenic response, arguing that the proangiogenic factor(s) released by microglia is distinct from VEGF-A. Finally, microglia exhibited oriented migration towards the vessels in the aortic ring cultures. Conclusions/Significance: Microglia stimulate vessel sprouting in the aortic ring cultures via a soluble microglial-derived product(s), rather than direct contact with endothelial cells. The observed migration of microglia towards the growing sprouts suggests that their position near endothelial tip-cells could result from attractive cues secreted by the vessels. Our data reveals a two-way communication between microglia and vessels that depends on soluble factors and should extend the understanding of how microglia promote vascular network formation.},
  author       = {Rymo, Simin F. and Gerhardt, Holger and Wolfhagen Sand, Fredrik and Lang, Richard and Uv, Anne and Betsholtz, Christer},
  issn         = {1932-6203},
  language     = {eng},
  number       = {1},
  publisher    = {Public Library of Science},
  series       = {PLoS ONE},
  title        = {A Two-Way Communication between Microglial Cells and Angiogenic Sprouts Regulates Angiogenesis in Aortic Ring Cultures},
  url          = {http://dx.doi.org/10.1371/journal.pone.0015846},
  volume       = {6},
  year         = {2011},
}