title: Impaired angiogenesis during fracture healing in GPCR kinase 2 interacting protein-1 (GIT1) knock out mice.
abstract: G protein coupled receptor kinase 2 (GRK2) interacting protein-1 (GIT1), is a scaffold protein that plays an important role in angiogenesis and osteoclast activity. We have previously demonstrated that GIT1 knockout (GIT1 KO) mice have impaired angiogenesis and dysregulated osteoclast podosome formation leading to a reduction in the bone resorbing ability of these cells. Since both angiogenesis and osteoclast-mediated bone remodeling are involved in the fracture healing process, we hypothesized that GIT1 participates in the normal progression of repair following bone injury. In the present study, comparison of fracture healing in wild type (WT) and GIT1 KO mice revealed altered healing in mice with loss of GIT1 function. Alcian blue staining of fracture callus indicated a persistence of cartilagenous matrix in day 21 callus samples from GIT1 KO mice which was temporally correlated with increased type 2 collagen immunostaining. GIT1 KO mice also showed a decrease in chondrocyte proliferation and apoptosis at days 7 and 14, as determined by PCNA and TUNEL staining. Vascular microcomputed tomography analysis of callus samples at days 7, 14 and 21 revealed decreased blood vessel volume, number, and connection density in GIT1 KO mice compared to WT controls. Correlating with this, VEGF-A, phospho-VEGFR2 and PECAM1 (CD31) were decreased in GIT1 KO mice, indicating reduced angiogenesis with loss of GIT1. Finally, calluses from GIT1 KO mice displayed a reduced number of tartrate resistant acid phosphatase-positive osteoclasts at days 14 and 21. Collectively, these results indicate that GIT1 is an important signaling participant in fracture healing, with gene ablation leading to reduced callus vascularity and reduced osteoclast number in the healing callus.
authors.affiliation: Aab Cardiovascular Research Institute and the Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America ; Orthopaedic Department, The First Affiliated Hospital of Nanjing Medical University, Jiangsu, China.
authors.forename: Guoyong
authors.initials: G
authors.lastname: Yin
authors.affiliation: Center for Musculoskeletal Research and the Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Tzong-Jen
authors.initials: TJ
authors.lastname: Sheu
authors.affiliation: Aab Cardiovascular Research Institute and the Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Prashanthi
authors.initials: P
authors.lastname: Menon
authors.affiliation: Aab Cardiovascular Research Institute and the Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Jinjiang
authors.initials: J
authors.lastname: Pang
authors.affiliation: Center for Musculoskeletal Research and the Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Hsin-Chiu
authors.initials: HC
authors.lastname: Ho
authors.affiliation: Center for Musculoskeletal Research and the Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Shi
authors.affiliation: Center for Musculoskeletal Research and the Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Chao
authors.initials: C
authors.lastname: Xie
authors.affiliation: Aab Cardiovascular Research Institute and the Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Elaine
authors.initials: E
authors.lastname: Smolock
authors.affiliation: Aab Cardiovascular Research Institute and the Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Chen
authors.initials: C
authors.lastname: Yan
authors.affiliation: Center for Musculoskeletal Research and the Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zuscik
authors.affiliation: Aab Cardiovascular Research Institute and the Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America.
authors.forename: Bradford C
authors.initials: BC
authors.lastname: Berk
mesh_terms: D000818:Animals; D016723:Bone Remodeling / Q000235:genetics; D001842:Bone and Bones / Q000098:blood supply / Q000000981:diagnostic imaging / Q000378:metabolism; D002146:Bony Callus / Q000098:blood supply / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics*; D019902:Chondrocytes / Q000502:physiology; D017102:Fracture Healing / Q000235:genetics*; D020690:GTPase-Activating Proteins; D015870:Gene Expression; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000235:genetics*; D010010:Osteoclasts / Q000166:cytology / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics*; D055114:X-Ray Microtomography
chemical_list: D018797:Cell Cycle Proteins; D020690:GTPase-Activating Proteins; C120767:Git2 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; D010750:Phosphoproteins