title: Pericellular matrilins regulate activation of chondrocytes by cyclic load-induced matrix deformation.
abstract: Pericellular matrix is at the ideal location to be involved in transmitting mechanical signals from the microenvironment to a cell. We found that changes of the content of matrilins that link various pericellular molecules surrounding chondrocytes affect mechanical stimulation of chondrocyte proliferation and gene expression. Thus, pericellular matrilins may play a role in chondrocyte mechanotransduction.
  
  
  BACKGROUND
  Chondrocytes reside in a capsule of pericellular matrix (chondron), which has been hypothesized to play a critical role in transducing mechanical signals to the cell. In this study, we test the hypothesis that the levels of matrilin (MATN)-1 and -3, major components of the chondrocyte pericellular matrix network, regulate activation of chondrocyte proliferation and differentiation by cyclic load-induced matrix deformation.
  
  
  METHODS
  Functional matrilins were decreased by expressing a dominant negative mini-MATN in primary chondrocytes or by using MATN1-null chondrocytes. The abundance of matrilins was also increased by expressing a wildtype MATN1 or MATN3 in chondrocytes. Chondrocytes were cultured in a 3D sponge subjected to cyclic deformation at 1 Hz. Chondrocyte gene expression was quantified by real-time RT-PCR and by Western blot analysis. Matrilin pericellular matrix assembly was examined by immunocytochemistry.
  
  
  RESULTS
  Elimination of functional matrilins from pericellular matrix abrogated mechanical activation of Indian hedgehog signaling and abolished mechanical stimulation of chondrocyte proliferation and differentiation. Excessive or reduced matrilin content decreased mechanical response of chondrocytes.
  
  
  CONCLUSIONS
  Normal content of matrilins is essential to optimal activation of chondrocytes by mechanical signals. Our data suggest that the sensitivity of chondrocytes to the changes in the microenvironment can be adjusted by altering the content of matrilins in pericellular matrix. This finding supports a critical role of pericellular matrix in chondrocyte mechano-transduction and has important implications in cartilage tissue engineering and mechanical adaptation.
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Women's Medical University/Medical Center East, Japan.
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Kanbe
authors.forename: Xu
authors.initials: X
authors.lastname: Yang
authors.forename: Lei
authors.initials: L
authors.lastname: Wei
authors.forename: Changqi
authors.initials: C
authors.lastname: Sun
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D049109:Cell Proliferation; D002642:Chick Embryo; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D017931:DNA Primers; D005109:Extracellular Matrix; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D016326:Extracellular Matrix Proteins