title: Histopathological and Immunohistochemical Evaluation of Pannus Tissue in Patients with Prosthetic Valve Dysfunction.
abstract: Prosthetic valve dysfunction due to pannus formation is a rare but serious complication. Currently, limited data are available concerning the pathogenesis and immunohistochemical properties of pannus. The study aim was to investigate the morphological, histopathological and immunohistochemical characteristics of pannus formation in patients with prosthetic valve dysfunction.
  
  
  
  A total of 35 patients (10 males, 25 females; mean age 44 ± 16 years) who had undergone re-do valve surgery due to prosthetic valve obstruction was enrolled in the study. Immunohistochemical studies were aimed at evaluating the expression of alphasmooth muscle actin (α-SMA) and desmin in myofibroblasts and smooth muscle cells; epithelial membrane antigen (EMA) in epithelial cells; and CD34, Factor VIII and vascular endothelial growth factor (VEGF) in endothelial cells. Matrix metalloproteinases (MMPs) -2 and -9, and transforming growth factor-beta (TGF-β) were used to demonstrate cytokine release from macrophages, leukocytes, fibroblasts and myofibroblasts.
  
  
  
  Pannus appeared as a tough and thick tissue hyperplasia which began from outside the suture ring in the periannular region and extended to the inflow and outflow surfaces of the prosthetic valves. Histopathological analysis showed the pannus tissue to consist of chronic inflammatory cells (lymphocytes, plasma cells, macrophages and foreign body giant cells), spindle cells such as myofibroblasts, capillary blood vessels and endothelial cells laying down the lumens. Calcification was present in the pannus tissue of 19 explanted prostheses. Immunohistochemical studies revealed positive α-SMA expression in all patients, whereas 60.5% of patients were positive for desmin, 50% for EMA, 42.1% for VEGF, 39.5% for TBF-β, 42.1% for MMP-2, 86.8% for CD34, and 97.4% for Factor VIII. MMP-9 was negative in all patients.
  
  
  
  Pannus tissue appears to be formed as the result of a neointimal response in periannular regions of prosthetic valves that consist of periannular tissue migration, myofibroblast and extracellular matrix proliferation with vascular components. It is a chronic active process in which mediators such as TGF-β, VEGF and MMP-2 play roles in both matrix formation and degradation.
authors.affiliation: Department of Cardiology, Kafkas University Medical School, Kars.|Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Süleyman
authors.initials: S
authors.lastname: Karakoyun
authors.affiliation: Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Ozan Gürsoy
authors.affiliation: Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Mahmut
authors.initials: M
authors.lastname: Yesin
authors.affiliation: Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Macit
authors.initials: M
authors.lastname: Kalçık
authors.affiliation: Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Mehmet Ali
authors.initials: MA
authors.lastname: Astarcıoğlu
authors.affiliation: Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Sabahattin
authors.initials: S
authors.lastname: Gündüz
authors.affiliation: Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Ali
authors.initials: A
authors.lastname: Emrah Oğuz
authors.affiliation: Department of Pathology, Dr. Lutfi Kırdar Kartal Training and Research Hospital, Istanbul.
authors.forename: Şermin
authors.initials: Ş
authors.lastname: Çoban Kökten
authors.affiliation: Department of Pathology, Dr. Lutfi Kırdar Kartal Training and Research Hospital, Istanbul.
authors.forename: Ayşe
authors.initials: A
authors.lastname: Nimet Karadayı
authors.affiliation: Department of Cardiovascular Surgery, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul, Turkey.
authors.forename: Altuğ
authors.initials: A
authors.lastname: Tuncer
authors.affiliation: Department of Cardiovascular Surgery, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul, Turkey.
authors.forename: Cengiz
authors.initials: C
authors.lastname: Köksal
authors.affiliation: Department of Cardiology, Kafkas University Medical School, Kars.|Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Tayyar
authors.initials: T
authors.lastname: Gökdeniz
authors.affiliation: Department of Cardiology, Kafkas University Medical School, Kars.|Department of Cardiology, Kosuyolu Kartal Heart Training and Research Hospital, Istanbul.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Özkan
mesh_terms: D000199:Actins / Q000096:biosynthesis; D000328:Adult; D000368:Aged; D018952:Antigens, CD34 / Q000378:metabolism; D003893:Desmin / Q000096:biosynthesis; D005169:Factor VIII / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006349:Heart Valve Diseases / Q000601:surgery; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D008264:Macrophages / Q000378:metabolism; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008875:Middle Aged; D018396:Mucin-1 / Q000378:metabolism; D058426:Neointima / Q000378:metabolism / Q000473:pathology*; D012086:Reoperation; D016896:Treatment Outcome; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D000199:Actins; D018952:Antigens, CD34; D003893:Desmin; D018396:Mucin-1; D042461:Vascular Endothelial Growth Factor A; D005169:Factor VIII; D020782:Matrix Metalloproteinases