title: Coordinate and synergistic effects of extensive treadmill exercise and ovariectomy on articular cartilage degeneration.
abstract: Although osteoarthritis (OA) is a multifactorial disease, little has been reported regarding the cooperative interaction among these factors on cartilage metabolism. Here we examined the synergistic effect of ovariectomy (OVX) and excessive mechanical stress (forced running) on articular cartilage homeostasis in a mouse model resembling a human postmenopausal condition.
  
  
  
  Mice were randomly divided into four groups, I: Sham, II: OVX, III: Sham and forced running (60 km in 6 weeks), and IV: OVX and forced running. Histological and immunohistochemical analyses were performed to evaluate the degeneration of articular cartilage and synovitis in the knee joint. Morphological changes of subchondral bone were analyzed by micro-CT.
  
  
  
  Micro-CT analyses showed significant loss of metaphyseal trabecular bone volume/tissue volume (BV/TV) after OVX as described previously. Forced running increased the trabecular BV/TV in all mice. In the epiphyseal region, no visible alteration in bone morphology or osteophyte formation was observed in any of the four groups. Histological analysis revealed that OVX or forced running respectively had subtle effects on cartilage degeneration. However, the combination of OVX and forced running synergistically enhanced synovitis and articular cartilage degeneration. Although morphological changes in chondrocytes were observed during OA initiation, no signs of bone marrow edema were observed in any of the four experimental groups.
  
  
  
  We report the coordinate and synergistic effects of extensive treadmill exercise and ovariectomy on articular cartilage degeneration. Since no surgical procedure was performed on the knee joint directly in this model, this model is useful in addressing the molecular pathogenesis of naturally occurring OA.
authors.affiliation: Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Miyatake
authors.affiliation: Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muneta
authors.affiliation: Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Miyoko
authors.initials: M
authors.lastname: Ojima
authors.affiliation: Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Yamada
authors.affiliation: Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Matsukura
authors.affiliation: Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Kahaer
authors.initials: K
authors.lastname: Abula
authors.affiliation: Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sekiya
authors.affiliation: Department of Cartilage Regeneration, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan. tsuji.orj@tmd.ac.jp.
authors.forename: Kunikazu
authors.initials: K
authors.lastname: Tsuji
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000209:etiology* / Q000473:pathology; D001842:Bone and Bones / Q000473:pathology; D005260:Female; D007719:Knee Joint / Q000473:pathology; D051379:Mice; D020370:Osteoarthritis, Knee / Q000209:etiology* / Q000473:pathology; D010052:Ovariectomy; D010805:Physical Conditioning, Animal; D011897:Random Allocation; D012420:Running
keywords: Forced running; Joint inflammation; Mechanical stress; Naturally occurring osteoarthritis model; Ovariectomy