title: Development and progression of immobilization-induced skin fibrosis through overexpression of transforming growth factor-ß1 and hypoxic conditions in a rat knee joint contracture model.
abstract: OBJECTIVE
  The purpose of this study was to investigate the pathology and mechanism of immobilization-induced skin fibrosis in a rat joint contracture model.
  
  
  METHODS
  Rats were randomly divided into control and immobilization groups. In the immobilization groups, knee joints of the rats were immobilized for 1, 2, and 4 weeks. After each immobilization, skin was dissected. To assess fibrosis in the skin, the thickness and area of adipocytes and connective tissue fibers were measured. Myofibroblasts were analyzed by immunohistochemistry by using anti-α-SMA as a marker. Gene expression levels of type I and III collagen, TGF-ß1, and HIF-1α were measured by using RT-PCR.
  
  
  RESULTS
  One week after immobilization, there was a marked increase in the area of connective tissue fibers in the immobilization group. Type I and type III collagen were significantly increased with prolonged immobilization. Higher numbers of α-SMA-positive cells were noted in the immobilized group at 2 and 4 weeks after immobilization. The expression level of TGF-β1 mRNA in the immobilization group increased after one week of immobilization. In contrast, the expression level of HIF1-α mRNA increased after 2 weeks of immobilization, and a greater increase was seen at 4 weeks after immobilization.
  
  
  CONCLUSIONS
  These results suggest that immobilization induces skin fibrosis with accumulation of types I and III collagen. These fibrotic changes may be evoked by upregulation of TGF-β1 after one week of immobilization. Additionally, upregulation of HIF-1α may relate to skin fibrosis by accelerating the differentiation of fibroblasts to myofibroblasts starting at 2 weeks after immobilization.
authors.affiliation: a Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.|b Department of Rehabilitation , Nagasaki Memorial Hospital , Nagasaki , Japan.
authors.forename: Kyo
authors.initials: K
authors.lastname: Goto
authors.affiliation: c Department of Physical Therapy Science, Unit of Physical and Occupational Therapy Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.
authors.forename: Junya
authors.initials: J
authors.lastname: Sakamoto
authors.affiliation: c Department of Physical Therapy Science, Unit of Physical and Occupational Therapy Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Nakano
authors.affiliation: a Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.|b Department of Rehabilitation , Nagasaki Memorial Hospital , Nagasaki , Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kataoka
authors.affiliation: a Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.|d Department of Rehabilitation , Nagasaki University Hospital , Nagasaki , Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Honda
authors.affiliation: a Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.|d Department of Rehabilitation , Nagasaki University Hospital , Nagasaki , Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Sasabe
authors.affiliation: a Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Origuchi
authors.affiliation: a Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences , Nagasaki University Graduate School of Biomedical Sciences , Nagasaki , Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Okita
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D024061:Collagen Type III / Q000378:metabolism; D003286:Contracture / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005355:Fibrosis / Q000473:pathology*; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology; D007719:Knee Joint / Q000378:metabolism* / Q000473:pathology; D008297:Male; D058628:Myofibroblasts / Q000378:metabolism*; D017208:Rats, Wistar; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D024061:Collagen Type III; D053773:Transforming Growth Factor beta1
keywords: Hypoxia; collagen; immobilization; myofibroblast; skin fibrosis; transforming growth factor-β1