title: Mesenchymal Stem Cell-Derived Exosomes Promote Fracture Healing in a Mouse Model.
abstract: : Paracrine signaling by bone-marrow-derived mesenchymal stem cells (MSCs) plays a major role in tissue repair. Although the production of regulatory cytokines by MSC transplantation is a critical modulator of tissue regeneration, we focused on exosomes, which are extracellular vesicles that contain proteins and nucleic acids, as a novel additional modulator of cell-to-cell communication and tissue regeneration. To address this, we used radiologic imaging, histological examination, and immunohistochemical analysis to evaluate the role of exosomes isolated from MSC-conditioned medium (CM) in the healing process in a femur fracture model of CD9-/-mice, a strain that is known to produce reduced levels of exosomes. We found that the bone union rate in CD9-/-mice was significantly lower than wild-type mice because of the retardation of callus formation. The retardation of fracture healing in CD9-/-mice was rescued by the injection of exosomes, but this was not the case after the injection of exosomes-free conditioned medium (CM-Exo). The levels of the bone repair-related cytokines, monocyte chemotactic protein-1 (MCP-1), MCP-3, and stromal cell-derived factor-1 in exosomes were low compared with levels in CM and CM-Exo, suggesting that bone repair may be in part mediated by other exosome components, such as microRNAs. These results suggest that exosomes in CM facilitate the acceleration of fracture healing, and we conclude that exosomes are a novel factor of MSC paracrine signaling with an important role in the tissue repair process.
  
  
  
  This work focuses on exosomes, which are extracellular vesicles, as a novel additional modulator of cell-to-cell communication. This study evaluated the role of exosomes isolated from mesenchymal stem cell (MSC)-conditioned medium (MSC-CM) in the fracture-healing process of CD9-/-mice, a strain that is known to produce reduced levels of exosomes. Retardation of fracture healing in CD9-/-mice was rescued by the injection of MSC exosomes, but this was not the case after the injection of exosome-free CM. This study finds that MSC exosomes are a novel factor of MSC paracrine signaling, with an important role in the tissue repair process.
authors.affiliation: Department of Orthopaedics Surgery, Integrated Health Sciences, Institute of Biomedical and Health Science, Hiroshima University, Hiroshima, Japan fu09100913@yahoo.co.jp.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Furuta
authors.affiliation: Department of Orthopaedics Surgery, Integrated Health Sciences, Institute of Biomedical and Health Science, Hiroshima University, Hiroshima, Japan.|Department of Regenerative Medicine, Medical Center for Translational and Clinical Research, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Miyaki
authors.affiliation: Department of Regenerative Medicine, Medical Center for Translational and Clinical Research, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishitobi
authors.affiliation: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ogura
authors.affiliation: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Department of Orthopaedics Surgery, Integrated Health Sciences, Institute of Biomedical and Health Science, Hiroshima University, Hiroshima, Japan.|Department of Regenerative Medicine, Medical Center for Translational and Clinical Research, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Naosuke
authors.initials: N
authors.lastname: Kamei
authors.affiliation: Department of Reproductive Biology, National Center for Child Health and Development, Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Miyado
authors.affiliation: Department of Regenerative Medicine, Medical Center for Translational and Clinical Research, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Yukihito
authors.initials: Y
authors.lastname: Higashi
authors.affiliation: Department of Orthopaedics Surgery, Integrated Health Sciences, Institute of Biomedical and Health Science, Hiroshima University, Hiroshima, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ochi
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D015519:Bone Density / Q000187:drug effects; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D055354:Exosomes / Q000187:drug effects / Q000378:metabolism*; D017102:Fracture Healing / Q000187:drug effects; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000378:metabolism; D060245:Tetraspanin 29 / Q000172:deficiency / Q000378:metabolism; D013977:Tibia / Q000187:drug effects / Q000254:growth & development
chemical_list: D017077:Culture Media, Conditioned; D016207:Cytokines; D035683:MicroRNAs; D060245:Tetraspanin 29
keywords: Cytokine; Endochondral ossification; Exosomes; Fracture healing; Mesenchymal stem cells; microRNA