Emerging ideas: matrix metalloproteinase-2 in muscle atrophy.
BACKGROUND
Muscle atrophy impacts almost every patient seen for orthopaedic conditions. Unfortunately, no effective treatment is available to date. Matrix metalloproteinases (MMPs), especially MMP-2, are involved in skeletal muscle atrophy. MMP-2 null mice reportedly have substantially reduced muscle atrophy after tendon transection compared with wild-type mice, suggesting MMP-2 plays an important role in muscle atrophy. Although the exact mechanisms remain unknown, a newly-discovered intracellular form of MMP-2 suggests a possible novel mechanism of MMP-2 digesting muscle matrix during muscle atrophy. I propose a new pharmacologic treatment for muscle atrophy using selective MMP-2 inhibitors. QUESTIONS/HYPOTHESIS: I hypothesize: (1) intracellular MMP-2 plays an important role during muscle atrophy by digesting intramuscular matrix; (2) AP-1 and NFAT signal transduction pathways are responsible for expression and activation of the intracellular MMP-2 during muscle atrophy; and (3) specific MMP-2 inhibitors can serve as a novel pharmacologic strategy in treating disuse-induced muscle atrophy.


METHODS
Expression and activity of extracellular and intracellular MMP-2 will be determined in a mouse tendon transection model. The role of AP-1 and NFAT signal transduction pathways in MMP-2 transcriptional regulation in muscle atrophy will be determined using chromatin-immunoprecipitation (ChIP) and small interfering RNA (siRNA). I also will test the feasibility of treating muscle atrophy using selective MMP-2 inhibitors.


CONCLUSIONS
Understanding the signaling transduction pathway of extracellular and intracellular MMP-2 expression during muscle atrophy may lead to novel treatments for muscle atrophy that preserve the normal physiologic function of MMP-2.
San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA. liux@orthosurg.ucsf.edu
Xuhui
X
Liu
D000818:Animals; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000473:pathology; D009133:Muscular Atrophy / Q000201:enzymology* / Q000235:genetics; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics*
D012313:RNA; D020778:Matrix Metalloproteinase 2; C522362:Mmp2 protein, mouse