title: Impact of cyclic mechanical stimulation on the expression of extracellular matrix proteins in human primary rotator cuff fibroblasts.
abstract: OBJECTIVE
  Mechanical stimulation plays an important role in the development and remodelling of tendons. The aim of the study was to evaluate the effects of mechanical stimulation on the expression of extracellular matrix proteins in human primary rotator cuff (RC) fibroblasts.
  
  
  METHODS
  RC fibroblasts were isolated from patients with degenerative RC tears and characterized using flow cytometry and immunohistochemistry. Cells were stimulated using the Flexcell FX5K™ Tension System. The stimulation regime was a uniaxial sinusoidal waveform with 10 % elongation and a frequency of 0.5 Hz, whereby each cycle consists of 10-s strain and 30-s relaxation. Data were normalized to mechanically unstimulated control groups for every experimental condition. RT-qPCR was performed to determine relative mRNA levels, and collagen production was measured by a colorimetric assay.
  
  
  RESULTS
  The positive expression of CD91 and CD10, and negativity for CD45 and CD4 confirmed the fibroblast phenotype of RC primary cells. RT-qPCR revealed that 10 % continuous cyclic strain for 7 and 14 days induced a significant increase in the mRNA expression both on the matrix metalloproteinases MMP1, MMP3, MMP13, and MMP14 and on the extracellular matrix proteins decorin, tenascin-C, and scleraxis. Furthermore, mechanically stimulated groups produced significantly higher amounts of total collagen.
  
  
  CONCLUSIONS
  These results may contribute to a better understanding of strain-induced tendon remodelling and will form the basis for the correct choice of applied force in rehabilitation after orthopaedic surgery. These findings underline the fact that early passive motion of the joint in order to induce remodelling of the tendon should be included within a rehabilitation protocol for rotator cuff repair.
authors.affiliation: Department of Orthopaedic Surgery, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria. birgit.lohberger@medunigraz.at.
authors.forename: Birgit
authors.initials: B
authors.lastname: Lohberger
authors.affiliation: Department of Orthopaedic Surgery, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria.
authors.forename: Heike
authors.initials: H
authors.lastname: Kaltenegger
authors.affiliation: Department of Orthopaedic Surgery, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria.
authors.forename: Nicole
authors.initials: N
authors.lastname: Stuendl
authors.affiliation: Center for Medical Research, Medical University of Graz, Stiftingtalstrasse 24, 8010, Graz, Austria.
authors.forename: Beate
authors.initials: B
authors.lastname: Rinner
authors.affiliation: Department of Orthopaedic Surgery, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Leithner
authors.affiliation: Department of Orthopaedic Surgery, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria.
authors.forename: Patrick
authors.initials: P
authors.lastname: Sadoghi
mesh_terms: D000368:Aged; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D008875:Middle Aged; D019637:Orthopedic Procedures; D010812:Physical Stimulation / Q000379:methods*; D012333:RNA, Messenger / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D017006:Rotator Cuff / Q000166:cytology*; D000070636:Rotator Cuff Injuries; D019063:Tenascin / Q000235:genetics / Q000378:metabolism; D013710:Tendons / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D003094:Collagen; D016326:Extracellular Matrix Proteins; D020781:Matrix Metalloproteinase 1; D053509:Matrix Metalloproteinase 13; D053511:Matrix Metalloproteinase 14; D019278:Matrix Metalloproteinase 3; D012333:RNA, Messenger; D019063:Tenascin; C093504:SCX protein, human; C507079:MMP13 protein, human; C511768:MMP3 protein, human; C522360:MMP1 protein, human; C507086:MMP14 protein, human
keywords: Collagen; Extracellular matrix proteins; Mechanical stimulation; Rotator cuff fibroblasts