title: Platelet activation receptor CLEC-2 regulates blood/lymphatic vessel separation by inhibiting proliferation, migration, and tube formation of lymphatic endothelial cells.
abstract: The platelet activation receptor CLEC-2 plays crucial roles in thrombosis/hemostasis, tumor metastasis, and lymphangiogenesis, although its role in thrombosis/hemostasis remains controversial. An endogenous ligand for CLEC-2, podoplanin, is expressed in lymphatic endothelial cells (LECs). We and others have reported that CLEC-2-deficiency is lethal at mouse embryonic/neonatal stages associated with blood-filled lymphatics, indicating that CLEC-2 is essential for blood/lymphatic vessel separation. However, its mechanism, and whether CLEC-2 in platelets is necessary for this separation, remains unknown. We found that specific deletion of CLEC-2 from platelets leads to the misconnection of blood/lymphatic vessels. CLEC-2(+/+) platelets, but not by CLEC-2(-/-) platelets, inhibited LEC migration, proliferation, and tube formation but had no effect on human umbilical vein endothelial cells. Additionally, supernatants from activated platelets significantly inhibited these three functions in LECs, suggesting that released granule contents regulate blood/lymphatic vessel separation. Bone morphologic protein-9 (BMP-9), which we found to be present in platelets and released upon activation, appears to play a key role in regulating LEC functions. Only BMP-9 inhibited tube formation, although other releasates including transforming growth factor-β and platelet factor 4 inhibited proliferation and/or migration. We propose that platelets regulate blood/lymphatic vessel separation by inhibiting the proliferation, migration, and tube formation of LECs, mainly because of the release of BMP-9 upon activation by CLEC-2/podoplanin interaction.
authors.affiliation: Department of Clinical and Laboratory Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Osada
authors.forename: Osamu
authors.initials: O
authors.lastname: Inoue
authors.forename: Guo
authors.initials: G
authors.lastname: Ding
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Shirai
authors.forename: Hirotake
authors.initials: H
authors.lastname: Ichise
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Hirayama
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Takano
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yatomi
authors.forename: Masanori
authors.initials: M
authors.lastname: Hirashima
authors.forename: Hideki
authors.initials: H
authors.lastname: Fujii
authors.forename: Katsue
authors.initials: K
authors.lastname: Suzuki-Inoue
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ozaki
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002465:Cell Movement; D049109:Cell Proliferation; D003433:Crosses, Genetic; D042783:Endothelial Cells / Q000166:cytology; D005091:Exons; D005434:Flow Cytometry; D055427:Growth Differentiation Factor 2 / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D037181:Lectins, C-Type / Q000378:metabolism / Q000502:physiology*; D042601:Lymphatic Vessels / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D015539:Platelet Activation; D000098853:Podoplanin
chemical_list: D055427:Growth Differentiation Factor 2; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins; C529518:CLEC-2 protein, mouse; C104778:CLEC2B protein, human; C490441:Pdpn protein, mouse; D000098853:Podoplanin; C117468:PDPN protein, human