title: Tissue-type plasminogen activator deficiency delays bone repair: roles of osteoblastic proliferation and vascular endothelial growth factor.
abstract: Further development in research of bone regeneration is necessary to meet the clinical demand for bone reconstruction. Recently, we reported that plasminogen is crucial for bone repair through enhancement of vessel formation. However, the details of the role of tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) in the bone repair process still remain unknown. Herein, we examined the effects of plasminogen activators on bone repair after a femoral bone defect using tPA-deficient (tPA(-/-)) and uPA-deficient (uPA(-/-)) mice. Bone repair of the femur was delayed in tPA(-/-) mice, unlike that in wild-type (tPA(+/+)) mice. Conversely, the bone repair was comparable between wild-type (uPA(+/+)) and uPA(-/-) mice. The number of proliferative osteoblasts was decreased at the site of bone damage in tPA(-/-) mice. Moreover, the proliferation of primary calvarial osteoblasts was reduced in tPA(-/-) mice. Recombinant tPA facilitated the proliferation of mouse osteoblastic MC3T3-E1 cells. The proliferation enhanced by tPA was antagonized by the inhibition of endogenous annexin 2 by siRNA and by the inhibition of extracellular signal-regulated kinase (ERK)1/2 phosphorylation in MC3T3-E1 cells. Vessel formation as well as the levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) were decreased at the damaged site in tPA(-/-) mice. Our results provide novel evidence that tPA is crucial for bone repair through the facilitation of osteoblast proliferation related to annexin 2 and ERK1/2 as well as enhancement of vessel formation related to VEGF and HIF-1α at the site of bone damage.
authors.affiliation: Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Kawao
authors.affiliation: Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Tamura
authors.affiliation: Life Science Research Institute, Kinki University, Osakasayama, Osaka, Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Okumoto
authors.affiliation: Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and.
authors.forename: Masato
authors.initials: M
authors.lastname: Yano
authors.affiliation: Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Okada
authors.affiliation: Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and.
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsuo
authors.affiliation: Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and hkaji@med.kindai.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kaji
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017306:Annexin A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D001861:Bone Regeneration; D001842:Bone and Bones / Q000098:blood supply / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D003433:Crosses, Genetic; D005260:Female; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: D017306:Annexin A2; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator
keywords: bone repair; cell proliferation; osteoblast; plasminogen activator; vessel formation