title: Scar myofibroblasts of the infarcted rat heart express natriuretic peptides.
abstract: The present study examined whether natriuretic peptide expression in the scar of post-myocardial infarcted (MI) rats was derived at least in part by residing myofibroblasts. ANP and BNP mRNA levels were significantly increased in the non-infarcted left ventricle and scar of 1-week post-MI male rats, as compared to the left ventricle of normal rats. The infarct region contained myofibroblasts and contracted cardiac myocytes residing predominantly in the epicardial border zone. In primary passage scar-derived myofibroblasts, alpha-myosin heavy chain mRNA was undetectable, whereas ANP, BNP, as well as adrenomedullin and corin mRNA expression persisted. In 1-3 day cultured primary passage myofibroblasts, prepro-ANP, mature ANP, and BNP staining was observed in the cytoplasm/perinuclear region co-incident with unorganized alpha-smooth muscle actin. Following 4-7 days in culture, myofibroblasts expressed organized alpha-smooth muscle actin filaments. However, natriuretic peptides were predominantly detected in the nucleus and cytoplasm, and thin filaments occupying the perinuclear region were positive for prepro-ANP and BNP. Isoproterenol treatment of first passage scar myofibroblasts increased protein synthesis and induced BNP mRNA expression, whereas ANP mRNA levels remained unchanged. By contrast, neither ANP nor BNP mRNAs were induced following exposure to AII despite increased protein synthesis. These data highlight the novel observation that scar myofibroblasts synthesized ANP, BNP, adrenomedullin, and expressed the pro-convertase corin. Constitutive and sympathetic-driven natriuretic peptide synthesis by myofibroblasts may in part influence reparative fibrosis.
authors.affiliation: Department of Physiology, University of Montreal, Montreal Heart Institute, Montreal, Quebec, Canada. angelo.calderone@umontreal.ca
authors.forename: Angelino
authors.initials: A
authors.lastname: Calderone
authors.forename: Samar
authors.initials: S
authors.lastname: Bel-Hadj
authors.forename: Jessica
authors.initials: J
authors.lastname: Drapeau
authors.forename: Viviane
authors.initials: V
authors.lastname: El-Helou
authors.forename: Hugues
authors.initials: H
authors.lastname: Gosselin
authors.forename: Robert
authors.initials: R
authors.lastname: Clement
authors.forename: Louis
authors.initials: L
authors.lastname: Villeneuve
mesh_terms: D053607:Adrenomedullin; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000032:analysis / Q000235:genetics*; D002478:Cells, Cultured; D002921:Cicatrix / Q000378:metabolism* / Q000473:pathology; D005576:Colforsin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D020097:Natriuretic Peptide, Brain / Q000032:analysis / Q000235:genetics; D010455:Peptides / Q000235:genetics; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000235:genetics
chemical_list: D010455:Peptides; D012333:RNA, Messenger; D000804:Angiotensin II; D020097:Natriuretic Peptide, Brain; D053607:Adrenomedullin; D005576:Colforsin; D009320:Atrial Natriuretic Factor; D012697:Serine Endopeptidases; C492879:corin protein, rat; D007545:Isoproterenol