{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:26:04Z","timestamp":1760235964233,"version":"build-2065373602"},"reference-count":45,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2021,10,13]],"date-time":"2021-10-13T00:00:00Z","timestamp":1634083200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["ES025191","P30 ES025128"],"award-info":[{"award-number":["ES025191","P30 ES025128"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Sarcoidosis is a chronic disease with unknown etiology and pathophysiology, characterized by granuloma formation. Matrix Metalloproteinase-12 (MMP12) is an elastase implicated in active granulomatous sarcoidosis. Previously, we reported that oropharyngeal instillation of multiwall carbon nanotubes (MWCNT) into C57Bl\/6 mice induced sarcoid-like granulomas and upregulation of MMP12. When Mmp12 knock-out (KO) mice were instilled with MWCNT, granuloma formation occurred 10 days post-instillation but subsequently resolved at 60 days. Thus, we concluded that MMP12 was essential to granuloma persistence. The aim of the current study was to identify potential mechanisms of granuloma resolution in Mmp12KO mice. Strikingly, an M2 macrophage phenotype was present in Mmp12KO but not in C57Bl\/6 mice. Between 10 and 60 days, macrophage populations in MWCNT-instilled Mmp12KO mice demonstrated an M2c to M2a phenotypic shift, with elevations in levels of IL-13, an M2 subtype-regulating factor. Furthermore, the M2 inducer, Apolipoprotein E (ApoE), and Matrix Metalloproteinase-14 (MMP14), a promoter of collagen degradation, were upregulated in 60-day MWCNT-instilled Mmp12KO mice. In conclusion, alveolar macrophages express two M2 phenotypes in Mmp12KO mice: M2c at 10 days when granulomas form, and M2a at 60 days when granulomas are resolving. Findings suggest that granuloma resolution in 60-day Mmp12KO mice requires an M2a macrophage phenotype.<\/jats:p>","DOI":"10.3390\/ijms222011019","type":"journal-article","created":{"date-parts":[[2021,10,13]],"date-time":"2021-10-13T21:36:15Z","timestamp":1634160975000},"page":"11019","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["The M2a Macrophage Phenotype Accompanies Pulmonary Granuloma Resolution in Mmp12 Knock-Out Mice Instilled with Multiwall Carbon Nanotubes"],"prefix":"10.3390","volume":"22","author":[{"given":"David","family":"Ogburn","sequence":"first","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sophia","family":"Bhalla","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nan","family":"Leffler","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Arjun","family":"Mohan","sequence":"additional","affiliation":[{"name":"Division of Pulmonary Disease and Critical Care Medicine, Department of Internal Medicine, Virginia Commonwealth University, Richmond, VA 23284, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anagha","family":"Malur","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Achut G.","family":"Malur","sequence":"additional","affiliation":[{"name":"Department of Microbiology & Immunology, St. George\u2019s University, St. George 999166, Grenada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Matthew","family":"McPeek","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Barbara P.","family":"Barna","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mary Jane","family":"Thomassen","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Brody School of Medicine Sciences Building, East Carolina University, Moye Boulevard, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"l5553","DOI":"10.1136\/bmj.l5553","article-title":"New advances in the management of pulmonary sarcoidosis","volume":"367","author":"Culver","year":"2019","journal-title":"BMJ"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1183\/09031936.00226911","article-title":"Global burden of chronic pulmonary aspergillosis complicating sarcoidosis","volume":"41","author":"Denning","year":"2012","journal-title":"Eur. 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