Matrix metalloproteinase-2 expression and promoter/enhancer activity in skeletal muscle atrophy
ABSTRACT Matrix metalloproteinase-2 (MMP-2) appears to be the dominant MMP activated during skeletal muscle atrophy. However, little is known about cell-specific regulatory mechanisms of MMP-2 transcription in vivo. In this study, we used a mouse model of muscle atrophy induced by complete Achilles tendon transection. Time-dependent muscle weight loss, nuclei density reduction, and extracellular matrix degeneration were observed consistently after Achilles tendon transection. Increased MMP-2 expression was confirmed at the mRNA and protein level. Experiments using transgenic mice with a MMP-2 promoter/enhancer reporter construct demonstrated markedly increased MMP-2 promoter/enhancer activity in atrophic skeletal muscle. Tissue-specific upregulation of MMP-2 promoter activity was observed not only in myocytes, but also in blood vessels, nerve, and fascia. The transcription factors c-Jun and FosB were expressed at high levels in atrophic muscle, suggesting a role in MMP-2 upregulation. These findings show that increased MMP-2 activity in disused atrophic muscle and supporting tissues is regulated, at least in part, by increased MMP-2 promoter/enhancer activity.
- SourceAvailable from: Elaine Del-Bel
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- "The somewhat larger MMP-2 level in the exodontias side muscle suggests its participation in the atrophic muscle process and is according to Giannelli et al. and Skittone et al. findings that observed an increased expression of MMP-2 in muscle atrophic conditions [25, 26]. "
ABSTRACT: Although disorders of the stomatognathic system are common, the mechanisms involved are unknown. Our objective was to study the changes in the masseter muscles after unilateral exodontia. Molar extraction was performed on Wistar rats (left side), and the animals were sacrificed after either 14 or 26 days. The masseter muscle was processed for histological analysis, conventional and in situ zymography, and immunohistochemistry. The morphological analysis showed unique and specific characteristics for the experimental group. By conventional zymography no significant values of 72 kDa MMP-2 (P < 0.05) were found in both of the sides of masseter muscle after 14 and 26 days of unilateral extraction. The in situ zymography showed gelatinolytic activity on all deep masseter muscles, with significant increase on the contralateral side after 14 and 26 days (P < 0.05). The immunohistochemistry demonstrated greater expression of MMP-2 than MMP-9 and MMP-14 in all masseter muscles and there were few differences in the staining of 4 TIMPs. This knowledge about morphology and molecular masticatory muscle remodeling following environmental interventions can be used to develop clinically successful treatments.BioMed Research International 06/2014; 2014:563463. DOI:10.1155/2014/563463 · 2.71 Impact Factor
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- "Metalloproteinases play an integral role during skeletal muscle atrophy in coordination with MMP negative regulators, TIMPs that prevent the formation of the active proteolytic MMPs , . While MMP-2 is considered the primary up-regulated MMP in muscle atrophy , it seems to be down-regulated in the masseter after only four days of the experiment. TIMP-2, on the other hand, reported to be down-regulated in many atrophy models, remained unchanged at the protein level throughout experimental period. "
ABSTRACT: Critical illness myopathy (CIM) is a debilitating common consequence of modern intensive care, characterized by severe muscle wasting, weakness and a decreased myosin/actin (M/A) ratio. Limb/trunk muscles are primarily affected by this myopathy while cranial nerve innervated muscles are spared or less affected, but the mechanisms underlying these muscle-specific differences remain unknown. In this time-resolved study, the cranial nerve innervated masseter muscle was studied in a unique experimental rat intensive care unit (ICU) model, where animals were exposed to sedation, neuromuscular blockade (NMB), mechanical ventilation, and immobilization for durations varying between 6 h and 14d. Gel electrophoresis, immunoblotting, RT-PCR and morphological staining techniques were used to analyze M/A ratios, myofiber size, synthesis and degradation of myofibrillar proteins, and levels of heat shock proteins (HSPs). Results obtained in the masseter muscle were compared with previous observations in experimental and clinical studies of limb muscles. Significant muscle-specific differences were observed, i.e., in the masseter, the decline in M/A ratio and muscle fiber size was small and delayed. Furthermore, transcriptional regulation of myosin and actin synthesis was maintained, and Akt phosphorylation was only briefly reduced. In studied degradation pathways, only mRNA, but not protein levels of MuRF1, atrogin-1 and the autophagy marker LC3b were activated by the ICU condition. The matrix metalloproteinase MMP-2 was inhibited and protective HSPs were up-regulated early. These results confirm that the cranial nerve innervated masticatory muscles is less affected by the ICU-stress response than limb muscles, in accordance with clinical observation in ICU patients with CIM, supporting the model' credibility as a valid CIM model.PLoS ONE 04/2014; 9(4):e92622. DOI:10.1371/journal.pone.0092622 · 3.23 Impact Factor
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- "A recent study suggests an intracellular MMP-2 form can digest intracellular matrix under certain pathologic circumstances, such as oxidative stress in the cardiac muscles . I have observed increased expression of MMP-2, MMP-9 , and MMP-13 (unpublished data) during muscle atrophy after tendon transection. However, substantially reduced muscle atrophy was observed only in MMP-2 knockout mice, but not in the MMP-9 knockout mice  and MMP-13 knockout mice (unpublished data). "
ABSTRACT: 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. 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. 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.Clinical Orthopaedics and Related Research 12/2010; 469(6):1797-9. DOI:10.1007/s11999-010-1726-5 · 2.77 Impact Factor