title: Growth and repair factors, osteoactivin, matrix metalloproteinase and heat shock protein 72, increase with resolution of inflammation in musculotendinous tissues in a rat model of repetitive grasping.
abstract: BACKGROUND
  Expression of the growth factor osteoactivin (OA) increases during tissue degeneration and regeneration, fracture repair and after denervation-induced disuse atrophy, concomitant with increased matrix metalloproteinases (MMPs). However, OA's expression with repetitive overuse injuries is unknown. The aim of this study was to evaluate: 1) OA expression in an operant rat model of repetitive overuse; 2) expression of MMPs; 3) inflammatory cytokines indicative of injury or inflammation; and 4) the inducible form of heat shock protein 70 (HSPA1A/HSP72) as the latter is known to increase during metabolic stress and to be involved in cellular repair. Young adult female rats performed a high repetition negligible force (HRNF) food retrieval task for up to 6 weeks and were compared to control rats.
  
  
  METHODS
  Flexor digitorum muscles and tendons were collected from 22 young adult female rats performing a HRNF reaching task for 3 to 6 weeks, and 12 food restricted control (FRC) rats. OA mRNA levels were assessed by quantitative polymerase chain reaction (qPCR). OA, MMP-1, -2, -3, and -13 and HSP72 protein expression was assayed using Western blotting. Immunohistochemistry and image analysis was used to evaluate OA and HSP72 expression. ELISA was performed for HSP72 and inflammatory cytokines.
  
  
  RESULTS
  Flexor digitorum muscles and tendons from 6-week HRNF rats showed increased OA mRNA and protein expression compared to FRC rats. MMP-1, -2 and -3 progressively increased in muscles whereas MMP-1 and -3 increased in tendons with HRNF task performance. HSP72 increased in 6-week HRNF muscles and tendons, compared to controls, and co-localized with OA in the myofiber sarcolemma. IL-1alpha and beta increased transiently in tendons or muscles in HRNF week 3 before resolving in week 6.
  
  
  CONCLUSIONS
  The simultaneous increases of OA with factors involved in tissue repair (MMPs and HSP72) supports a role of OA in tissue regeneration after repetitive overuse.
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA.
authors.forename: Nagat
authors.initials: N
authors.lastname: Frara
authors.affiliation: Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Samir M
authors.initials: SM
authors.lastname: Abdelmagid
authors.affiliation: Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Tytell
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA.
authors.forename: Mamta
authors.initials: M
authors.lastname: Amin
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Popoff
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, OH, USA.
authors.forename: Fayez F
authors.initials: FF
authors.lastname: Safadi
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA. mbarbe@temple.edu.
authors.forename: Mary F
authors.initials: MF
authors.lastname: Barbe
mesh_terms: D000818:Animals; D012090:Cumulative Trauma Disorders / Q000378:metabolism* / Q000517:prevention & control; D004195:Disease Models, Animal; D005260:Female; D050884:HSP72 Heat-Shock Proteins / Q000096:biosynthesis*; D018737:Hand Strength / Q000502:physiology; D007249:Inflammation / Q000378:metabolism / Q000517:prevention & control; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis; D020782:Matrix Metalloproteinases / Q000096:biosynthesis*; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013710:Tendons / Q000378:metabolism* / Q000473:pathology
chemical_list: C503043:Gpnmb protein, rat; D050884:HSP72 Heat-Shock Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D020782:Matrix Metalloproteinases