title: Apoptosis regulates endothelial cell number and capillary vessel diameter but not vessel regression during retinal angiogenesis.
abstract: The growth of hierarchical blood vessel networks occurs by angiogenesis. During this process, new vessel growth is accompanied by the removal of redundant vessel segments by selective vessel regression ('pruning') and a reduction in endothelial cell (EC) density in order to establish an efficient, hierarchical network. EC apoptosis has long been recognised for its association with angiogenesis, but its contribution to this process has remained unclear. We generated mice in which EC apoptosis was blocked by tissue-specific deletion of the apoptosis effector proteins BAK and BAX. Using the retina as a model, we found that apoptosis made a minor contribution to the efficiency of capillary regression around arteries where apoptosis was most concentrated, but was otherwise dispensable for vessel pruning. Instead, apoptosis was necessary for the removal of non-perfused vessel segments and the reduction in EC density that occurs during vessel maturation. In the absence of apoptosis, increased EC density resulted in an increase in the diameter of capillaries, but not arteries or veins. Our findings show that apoptosis does not influence the number of vessels generated during angiogenesis. Rather it removes non-perfused vessel segments and regulates EC number during vessel maturation, which has vessel-specific consequences for vessel diameter.
authors.affiliation: Development and Cancer Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia University of Melbourne, Department of Medical Biology, 1G Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Emma C
authors.initials: EC
authors.lastname: Watson
authors.affiliation: Development and Cancer Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Monica N
authors.initials: MN
authors.lastname: Koenig
authors.affiliation: Development and Cancer Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia University of Melbourne, Department of Medical Biology, 1G Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Zoe L
authors.initials: ZL
authors.lastname: Grant
authors.affiliation: University of Melbourne, Department of Medical Biology, 1G Royal Parade, Parkville, Victoria 3052, Australia Systems Biology and Personalised Medicine Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Lachlan
authors.initials: L
authors.lastname: Whitehead
authors.affiliation: Development and Cancer Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Trounson
authors.affiliation: University of Melbourne, Department of Medical Biology, 1G Royal Parade, Parkville, Victoria 3052, Australia Cell Signalling and Cell Death Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Grant
authors.initials: G
authors.lastname: Dewson
authors.affiliation: Development and Cancer Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia University of Melbourne, Department of Medical Biology, 1G Royal Parade, Parkville, Victoria 3052, Australia lcoultas@wehi.edu.au.
authors.forename: Leigh
authors.identifier: 0000-0001-6466-0890
authors.initials: L
authors.lastname: Coultas
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology*; D008297:Male; D051379:Mice; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000503:physiopathology; D012160:Retina / Q000166:cytology / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D051028:bcl-2-Associated X Protein
keywords: Angiogenesis; Apoptosis; Endothelial cell; Hyaloid vessels; Tissue remodelling