title: The fate and role of bone graft-derived cells after autologous tendon and bone transplantation into the bone tunnel.
abstract: BACKGROUND
  Grafting bone between the tendon graft and the bone tunnel in anterior cruciate ligament reconstruction increases the mechanical strength of the tendon graft. However, the biological role of the bone graft is unclear. The purpose of this research was to elucidate the role of bone graft cells after autologous tendon graft into the bone tunnel with an autologous bone graft in green fluorescent protein (GFP) transgenic rats.
  
  
  METHODS
  The Achilles tendons of Sprague-Dawley (SD) wild-type rats and bone of GFP rats were harvested and transplanted into bone tunnels drilled in the femurs at the knees of SD rats. The femurs were harvested at 1, 2, and 4 weeks after transplantation and histologically investigated using hematoxylin and eosin staining and immunostaining of heat shock protein 47 (HSP47), macrophages, and type I and type III collagens. Biomechanical tests were performed on the tendon graft 2 and 4 weeks after transplantation to evaluate the ultimate force to failure.
  
  
  RESULTS
  A small number of GFP-positive cells was seen in the tendon graft 2 weeks after transplantation. The cell count in the tendon graft was increased at 4 weeks after transplantation. HSP47-positive cells and macrophage-stained cells present in the tendon graft corresponded with the GFP-positive cells. By 2 weeks after transplantation, the relative areas of immunostained type I and III collagens in the tendon graft had declined significantly in the bone graft group compared to the control. The ultimate failure load in the bone graft group was higher than that in the control group at both 2 and 4 weeks after transplantation.
  
  
  CONCLUSIONS
  This research showed that, within 4 weeks of transplantation, bone graft cells migrate to the tendon graft, where they differentiate into cells involved in collagen production and macrophages. Bone graft cells may contribute to the early stage remodeling of tendon grafts.
authors.affiliation: Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Komiyama
authors.forename: Yuji
authors.initials: Y
authors.lastname: Arai
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kajikawa
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Yoshida
authors.forename: Toru
authors.initials: T
authors.lastname: Morihara
authors.forename: Ryu
authors.initials: R
authors.lastname: Terauchi
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kida
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Fujiwara
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kawata
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kubo
mesh_terms: D000125:Achilles Tendon / Q000637:transplantation*; D000818:Animals; D030801:Animals, Genetically Modified; D001696:Biomechanical Phenomena; D016025:Bone Transplantation / Q000379:methods*; D002465:Cell Movement / Q000502:physiology; D002470:Cell Survival; D004195:Disease Models, Animal; D005260:Female; D005269:Femur / Q000473:pathology / Q000601:surgery*; D006084:Graft Rejection; D006085:Graft Survival; D007150:Immunohistochemistry; D007719:Knee Joint / Q000473:pathology / Q000601:surgery; D018613:Microscopy, Confocal / Q000379:methods; D010011:Osteocytes / Q000637:transplantation*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012307:Risk Factors; D013718:Tensile Strength; D016378:Tissue Transplantation / Q000379:methods; D020858:Tissue and Organ Harvesting; D014182:Transplantation, Autologous; D014945:Wound Healing / Q000502:physiology