Expression of Matrix Metalloproteinases 2 and 9 in Regenerating Skeletal Muscle: A Study in Experimentally Injured andmdxMuscles

Abstract

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.

Xenopus laevis gelatinase B (Xmmp-9): Development, regeneration, and wound healing

“…For instance, work suggests MMP-9 is involved in mouse muscle regeneration by activating satellite cells (Kherif et al, 1999). Miyazaki et al (1996) found that Ntmmp-9 expression is up-regulated during newt limb regeneration.…”

“…A number of MMPs found to be expressed during amphibian development, appear to be involved in the radical remodeling and cell death that occurs during amphibian metamorphosis, such as the loss of the larval tail and transformation of the intestine (Gross and Lapiere, 1962;Wang and Brown, 1993;Oofusa et al, 1994;Patterton et al, 1995;Brown et al, 1996;Ishizuya-Oka et al, 1996). MMPs are also thought to play a role in the process of regeneration in different systems (Yang and Bryant, 1994;Miyazaki et al, 1996;Kherif et al, 1999;Yang., 1999). For instance, in axolotls MMP-9 is upregulated after limb amputation and is thought to play a role in limb regeneration (Yang and Bryant, 1994;Yang et al, 1999).…”

Slow-Adhering Stem Cells Derived from Injured Skeletal Muscle Have Improved Regenerative Capacity

“…27,64,65 MMP activity increases after muscle damage, 66,67 and satellite cells have been recognized as muscle cells that express MMPs on activation. 68 Increased MMP production results in efficient migration of satellite cells into injured areas. 66,68 Up-regulated Notch1 and STAT3 signaling may contribute to improved proliferation capacity and multipotency of SASCs from injured muscle because both Notch1 and STAT3 are involved in stem cell maintenance and self-renewal.…”

“…68 Increased MMP production results in efficient migration of satellite cells into injured areas. 66,68 Up-regulated Notch1 and STAT3 signaling may contribute to improved proliferation capacity and multipotency of SASCs from injured muscle because both Notch1 and STAT3 are involved in stem cell maintenance and self-renewal. 54,55,58,69,70 Activation of Notch1 and STAT3 signaling pathways is also required for efficient muscle regeneration, 51,57 and their activation in SASCs from injured muscle may verify the highly regenerative potential and important function of this specific cell population in repairing injured muscle.…”

“…27,63,64 Specifically, MMP2 has an essential function in muscle cell proliferation and differentiation and muscle regeneration after injury. 65,66,68 The up-regulated expression of Pax3 and MMP2 observed in SASCs from injured muscle may contribute to the improved migration capacity of these cells. In addition to functioning as an important regulator of limb and muscle development, 59,71 Msx1 has also been suggested as being able to promote dedifferentiation of muscle cells and to maintain the multipotency of stem cells.…”