Expression of matrix metalloproteinases 2 and 9 in regenerating skeletal muscle: a study in experimentally injured and mdx muscles

Dev Biol. 1999 Jan 1;205(1):158-70. doi: 10.1006/dbio.1998.9107.


Matrix metalloproteinases (MMPs) cooperatively degrade all components of the extracellular matrix (ECM). Remodeling of ECM during skeletal muscle degeneration and regeneration suggests a tight regulation of matrix-degrading activity during muscle regeneration. In this study, we investigated the expression of MMP-2 and MMP-9, in normal muscles and their regulation during regeneration process. We further investigated their secretion by C2C12 myogenic cell line. Two models of muscle degeneration-regeneration were used: (1) normal muscles in which necrosis was experimentally induced by cardiotoxin injection; (2) mdx muscles which exhibit recurrent signs of focal myofiber necrosis followed by successful regeneration. MMPs were studied by zymography; their free activity was quantified using 3H-labeled gelatin substrate and mRNA expression was followed by Northern hybridization. Muscle degeneration-regeneration was analyzed by conventional morphological methods and in situ hybridization was performed on muscle sections to identify the cells expressing these MMPs. Results show that MMP-2, but not MMP-9 expression, is constitutive in normal muscles. Upon injury, the active form of MMP-2 is transiently increased, whereas MMP-9 is induced within 24 h and remains present for several days. Quantitative assays of free gelatinolytic activity show a progressive and steady increase that culminates at 7 days postinjury and slowly returns to normal levels. In adult mdx mice, both pro and active forms of MMP-2 and MMP-9 are expressed. Northern blot results support these findings. Zymography of C2C12-conditioned medium shows that myogenic cells produce MMP-2. By in situ hybridization we localized MMP-9 mRNA in inflammatory cells and putative activated satellite cells in injured muscles. Our data allow the correlation of the differential expression of pro and/or active forms of MMP-2 and MMP-9 with different stages of the degeneration-regeneration process: MMP-9 expression is related to the inflammatory response and probably to the activation of satellite cells, whereas MMP-2 activation is concomitant with the regeneration of new myofibers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cobra Cardiotoxin Proteins
  • Collagenases / genetics*
  • Gelatinases / genetics*
  • Gene Expression Regulation, Enzymologic*
  • Matrix Metalloproteinase 2
  • Matrix Metalloproteinase 9
  • Metalloendopeptidases / genetics*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred mdx
  • Muscle, Skeletal / injuries
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / physiology*
  • Muscular Dystrophy, Animal / enzymology
  • Muscular Dystrophy, Animal / physiopathology*
  • Necrosis
  • Regeneration*


  • Cobra Cardiotoxin Proteins
  • Collagenases
  • Gelatinases
  • Metalloendopeptidases
  • Matrix Metalloproteinase 2
  • Matrix Metalloproteinase 9