{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,6]],"date-time":"2026-09-06T09:06:49Z","timestamp":1788685609508,"version":"build-2803163510"},"reference-count":49,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2014,9,29]],"date-time":"2014-09-29T00:00:00Z","timestamp":1411948800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"North Norwegian Regional Health Authorities"},{"name":"The Norwegian Cancer Association"},{"name":"Erna and Olav Aakre foundation"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal Cellular Physiology"],"published-print":{"date-parts":[[2015,1]]},"abstract":"<jats:sec><jats:label\/><jats:p>Matrix metalloproteinase 2 (MMP\u20102) is a proteolytic enzyme implicated in motility, differentiation, and regeneration of skeletal muscle fibers through processing of extracellular substrates. Although MMP\u20102 has been found to be localized intracellularly in cardiomyocytes where the enzyme is thought to contribute to post\u2010ischemic loss of contractility, little is known about intracellular MMP\u20102 activity in skeletal muscle fibers. In the present study we demonstrate intracellular MMP\u20102 in normal skeletal muscle by immunohistochemical staining. Immunogold electron microscopic analyses indicated that the enzyme was concentrated in Z\u2010lines of the sarcomers, in the nuclear membrane, and in mitochondria. By use of in situ zymography, we found that gelatinolytic activity in muscle fibers was co\u2010localized with immunofluorecent staining for MMP\u20102. Staining for MMP\u20109, the other member of the gelatinase group of the MMPs, was negative. The broad\u2010spectrum metalloprotease inhibitor EDTA and the selective gelatinase inhibitor CTT2, but not the cysteine inhibitor E64, strongly reduced the gelatinolytic activity. The intracellular gelatinolytic activity was much more prominent in fast twitch type II fibers than in slow twitch type I fibers, and there was a decrease in intracellular gelatinolytic activity and MMP\u20102 expression in muscles from mice exposed to high intensity interval training. Together our results indicate that MMP\u20102 is part of the intracellular proteolytic network in normal skeletal muscle, especially in fast twitch type II fibers. Further, the results suggest that intracellular MMP\u20102 in skeletal muscle fibers is active during normal homeostasis, and affected by the level of physical activity. J. Cell. Physiol. 230: 160\u2013169, 2015. \u00a9 2014 Wiley Periodicals, Inc.<\/jats:p><\/jats:sec>","DOI":"10.1002\/jcp.24694","type":"journal-article","created":{"date-parts":[[2014,6,6]],"date-time":"2014-06-06T12:13:59Z","timestamp":1402056839000},"page":"160-169","source":"Crossref","is-referenced-by-count":33,"title":["Intracellular MMP\u20102 Activity in Skeletal Muscle Is Associated With Type II Fibers"],"prefix":"10.1002","volume":"230","author":[{"given":"Elin","family":"Hadler\u2010Olsen","sequence":"first","affiliation":[{"name":"Department of Medical Biology Faculty of Health Sciences University of Troms\u00f8 Troms\u00f8 Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ann Iren","family":"Solli","sequence":"additional","affiliation":[{"name":"Department of Medical Biology Faculty of Health Sciences University of Troms\u00f8 Troms\u00f8 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