title: Hypoxia-induced responses by endothelial colony-forming cells are modulated by placental growth factor.
abstract: Endothelial colony-forming cells (ECFCs), also termed late outgrowth endothelial cells, are a well-defined circulating endothelial progenitor cell type with an established role in vascular repair. ECFCs have clear potential for cell therapy to treat ischaemic disease, although the precise mechanism(s) underlying their response to hypoxia remains ill-defined.
  
  
  
  In this study, we isolated ECFCs from umbilical cord blood and cultured them on collagen. We defined the response of ECFCs to 1% O2exposure at acute and chronic time points.
  
  
  
  In response to low oxygen, changes in ECFC cell shape, proliferation, size and cytoskeleton phenotype were detected. An increase in the number of senescent ECFCs also occurred as a result of long-term culture in 1% O2. Low oxygen exposure altered ECFC migration and tube formation in Matrigel®. Increases in angiogenic factors secreted from ECFCs exposed to hypoxia were also detected, in particular, after treatment with placental growth factor (PlGF). Exposure of cells to agents that stabilise hypoxia-inducible factors such as dimethyloxalylglycine (DMOG) also increased PlGF levels. Conditioned medium from both hypoxia-treated and DMOG-treated cells inhibited ECFC tube formation. This effect was reversed by the addition of PlGF neutralising antibody to the conditioned medium, confirming the direct role of PlGF in this effect.
  
  
  
  This study deepens our understanding of the response of ECFCs to hypoxia and also identifies a novel and important role for PlGF in regulating the vasculogenic potential of ECFCs.
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Michelle B
authors.initials: MB
authors.lastname: Hookham
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Imran H A
authors.initials: IH
authors.lastname: Ali
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Christina L
authors.initials: CL
authors.lastname: O'Neill
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Emer
authors.initials: E
authors.lastname: Hackett
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Melanie H
authors.initials: MH
authors.lastname: Lambe
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Tina
authors.initials: T
authors.lastname: Schmidt
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Reinhold J
authors.initials: RJ
authors.lastname: Medina
authors.affiliation: Eye & Ear Clinic, Royal Victoria Hospital, Grosvenor Road, Belfast, BT12 6BA, UK.
authors.forename: Sara
authors.initials: S
authors.lastname: Chamney
authors.affiliation: Regional Neonatal Unit, Royal Maternity Hospital, Grosvenor Road, Belfast, BT12 6BA, UK.
authors.forename: Bharathi
authors.initials: B
authors.lastname: Rao
authors.affiliation: Eye & Ear Clinic, Royal Victoria Hospital, Grosvenor Road, Belfast, BT12 6BA, UK.
authors.forename: Eibhlin
authors.initials: E
authors.lastname: McLoone
authors.affiliation: Regional Neonatal Unit, Royal Maternity Hospital, Grosvenor Road, Belfast, BT12 6BA, UK.
authors.forename: David
authors.initials: D
authors.lastname: Sweet
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: Alan W
authors.initials: AW
authors.lastname: Stitt
authors.affiliation: Centre for Experimental Medicine, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK. d.brazil@qub.ac.uk.
authors.forename: Derek P
authors.initials: DP
authors.lastname: Brazil
mesh_terms: D000600:Amino Acids, Dicarboxylic / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000378:metabolism; D004338:Drug Combinations; D042783:Endothelial Cells / Q000378:metabolism* / Q000502:physiology*; D066026:Endothelial Progenitor Cells / Q000378:metabolism; D005312:Fetal Blood / Q000378:metabolism / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000473:pathology*; D007797:Laminin / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000502:physiology; D000072483:Placenta Growth Factor / Q000378:metabolism*; D010926:Placental Hormones / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism
chemical_list: D000600:Amino Acids, Dicarboxylic; D017077:Culture Media, Conditioned; D004338:Drug Combinations; D007797:Laminin; C000608036:PGF protein, human; D010926:Placental Hormones; D011509:Proteoglycans; C059485:matrigel; D000072483:Placenta Growth Factor; D003094:Collagen; C040947:oxalylglycine
keywords: Endothelial colony-forming cells; Endothelial progenitor cells; Hypoxia; Migration; Placental growth factor; Senescence