title: EGFL6 promotes endothelial cell migration and angiogenesis through the activation of extracellular signal-regulated kinase.
abstract: Angiogenesis is required for bone development, growth, and repair. It is influenced by the local bone environment that involves cross-talks between endothelial cells and adjacent bone cells. However, data regarding factors that directly contribute to angiogenesis by bone cells remain poorly understood. Here, we report that EGFL6, a member of the epidermal growth factor (EGF) repeat superfamily proteins, induces angiogenesis by a paracrine mechanism in which EGFL6 is expressed in osteoblastic-like cells but promotes migration and angiogenesis of endothelial cells. Co-immunoprecipitation assays revealed that EGFL6 is secreted in culture medium as a homodimer protein. Using scratch wound healing and transwell assays, we found that conditioned medium containing EGFL6 potentiates SVEC (a simian virus 40-transformed mouse microvascular endothelial cell line) endothelial cell migration. In addition, EGFL6 promotes the endothelial cell tube-like structure formation in Matrigel assays and angiogenesis in a chick embryo chorioallantoic membrane. Furthermore, we show that EGFL6 recombinant protein induces phosphorylation of ERK in SVEC endothelial cells. Inhibition of ERK impaired EGFL6-induced ERK activation and endothelial cell migration. Together, these results demonstrate, for the first time, that osteoblastic-like cells express EGFL6 that is capable of promoting endothelial cell migration and angiogenesis via ERK activation. Thus, the EGLF6 mediates a paracrine mechanism of cross-talk between vascular endothelial cells and osteoblasts and might offer an important new target for the potential treatment of bone diseases, including osteonecrosis, osteoporosis, and fracture healing.
authors.affiliation: School of Pathology and Laboratory Medicine, The Universityof Western Australia, Western Australia 6009, Australia
authors.forename: Shek Man
authors.initials: SM
authors.lastname: Chim
authors.forename: An
authors.initials: A
authors.lastname: Qin
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tickner
authors.forename: Nathan
authors.initials: N
authors.lastname: Pavlos
authors.forename: Tamara
authors.initials: T
authors.lastname: Davey
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Yajun
authors.initials: Y
authors.lastname: Guo
authors.forename: Ming Hao
authors.initials: MH
authors.lastname: Zheng
authors.forename: Jiake
authors.initials: J
authors.lastname: Xu
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000098:blood supply; D019556:COS Cells; D002135:Calcium-Binding Proteins; D015815:Cell Adhesion Molecules; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D002642:Chick Embryo; D002522:Chlorocebus aethiops; D049033:Chorioallantoic Membrane / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018919:Neovascularization, Physiologic / Q000187:drug effects; D009842:Oligopeptides / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology; D010010:Osteoclasts / Q000166:cytology; D019899:Paracrine Communication / Q000187:drug effects; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization / Q000187:drug effects; D020836:Protein Structure, Quaternary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D015815:Cell Adhesion Molecules; C485745:Egfl6 protein, mouse; D006023:Glycoproteins; D009363:Neoplasm Proteins; D009842:Oligopeptides; D010455:Peptides; D012333:RNA, Messenger; C047981:arginyl-glycyl-aspartic acid; D048049:Extracellular Signal-Regulated MAP Kinases