title: Endothelial cell-derived semaphorin 3A inhibits filopodia formation by blood vascular tip cells.
abstract: Vascular endothelial growth factor (VEGF)-A is a well-known major chemoattractant driver of angiogenesis--the formation of new blood vessels from pre-existing ones. However, the repellent factors that fine-tune this angiogenic process remain poorly characterized. We investigated the expression and functional role of endothelial cell-derived semaphorin 3A (Sema3A) in retinal angiogenesis, using genetic mouse models. We found Sema3a mRNA expression in the ganglion cell layer and the presence of Sema3A protein on larger blood vessels and at the growing front of blood vessels in neonatal retinas. The Sema3A receptors neuropilin-1 and plexin-A1 were expressed by retinal blood vessels. To study the endothelial cell-specific role of Sema3A, we generated endothelial cell-specific Sema3A knockout mouse strains by constitutive or inducible vascular endothelial cadherin-Cre-mediated gene disruption. We found that in neonatal retinas of these mice, both the number and the length of tip cell filopodia were significantly increased and the leading edge growth pattern was irregular. Retinal explant experiments showed that recombinant Sema3A significantly decreased VEGF-A-induced filopodia formation. Endothelial cell-specific knockout of Sema3A had no impact on blood vessel density or skin vascular leakage in adult mice. These findings indicate that endothelial cell-derived Sema3A exerts repelling functions on VEGF-A-induced tip cell filopodia and that a lack of this signaling cannot be rescued by paracrine sources of Sema3A.
authors.affiliation: Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, ETH Zurich, Zurich 8093, Switzerland.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Ochsenbein
authors.affiliation: Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, ETH Zurich, Zurich 8093, Switzerland.
authors.forename: Sinem
authors.initials: S
authors.lastname: Karaman
authors.affiliation: Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, ETH Zurich, Zurich 8093, Switzerland.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Proulx
authors.affiliation: Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, ETH Zurich, Zurich 8093, Switzerland.
authors.forename: Michaela
authors.initials: M
authors.lastname: Berchtold
authors.affiliation: Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, ETH Zurich, Zurich 8093, Switzerland.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Jurisic
authors.affiliation: Institute of Molecular Life Sciences, University of Zurich, Zurich 8057, Switzerland.
authors.forename: Esther T
authors.initials: ET
authors.lastname: Stoeckli
authors.affiliation: Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, ETH Zurich, Zurich 8093, Switzerland michael.detmar@pharma.ethz.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Detmar
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000166:cytology*; D042783:Endothelial Cells / Q000378:metabolism*; D055786:Gene Knockout Techniques; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000378:metabolism; D039942:Neuropilin-1 / Q000378:metabolism; D011485:Protein Binding; D011554:Pseudopodia; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D012165:Retinal Ganglion Cells / Q000378:metabolism; D012171:Retinal Vessels / Q000378:metabolism; D040121:Semaphorin-3A / Q000235:genetics / Q000378:metabolism*; D012867:Skin / Q000098:blood supply / Q000187:drug effects / Q000473:pathology
chemical_list: D009419:Nerve Tissue Proteins; C492114:Plxna1 protein, mouse; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D040121:Semaphorin-3A; D039942:Neuropilin-1
keywords: Angiogenesis; Blood vessels; Development; Semaphorin 3A; Tip cells