title: Enzymatically Modified Low-Density Lipoprotein Is Present in All Stages of Aortic Valve Sclerosis: Implications for Pathogenesis of the Disease.
abstract: BACKGROUND
  We have demonstrated previously that enzymatically degraded low-density lipoprotein (eLDL) is an essential causative component for the initiation of atherosclerosis. Here, we investigated the different stages of human aortic valve sclerosis for the presence of eLDL and effectors of the innate immune system, as well as the interaction of eLDL with isolated valvular interstitial cells/myofibroblasts to discover possible pathways leading to aortic valve sclerosis.
  
  
  RESULTS
  Human aortic valvular tissue was obtained from 68 patients undergoing valve replacement surgery. Patients were classified into 3 groups (mild, moderate, or severe aortic valve sclerosis), and clinical data for statistical analysis were gathered from all patients. Immunohistochemical staining demonstrated extensive extracellular deposits of eLDL throughout all grades of aortic valve sclerosis. Complementary analysis of lipid composition revealed higher concentrations of the decisive components of eLDL (ie, unesterified cholesterol and linoleic acid) compared with internal control tissues. Further, the complement component C3d and terminal complement complexes colocalized with eLDL compatible with the proposal that subendothelially deposited eLDL is enzymatically transformed into a complement activator at early stages of valvular cusp lesion development. Gene expression profiles of proteases and complement components corroborated by immunohistochemistry demonstrated an upregulation of the protease cathepsin D (a possible candidate for LDL degradation to eLDL) and the complement inhibitor CD55. Surprisingly, substantial C-reactive protein expression was not observed before grade 2 aortic valve sclerosis as investigated with microarray analysis, reverse transcription-polymerase chain reaction analysis, and immunohistochemistry. Finally, we demonstrated cellular uptake of eLDL by valvular interstitial cells/myofibroblasts.
  
  
  CONCLUSIONS
  The present study is a startup of a hypothesis on the pathogenesis of aortic valve sclerosis declaring extracellular lipoprotein modification, subsequent complement activation, and cellular uptake by valvular interstitial cells/myofibroblasts as integral players.
authors.affiliation: Department of Laboratory Medicine, Robert-Bosch-Hospital, Stuttgart, Germany (L.T., F.C., M.T.).
authors.forename: Laura
authors.initials: L
authors.lastname: Twardowski
authors.affiliation: Department of Laboratory Medicine, Robert-Bosch-Hospital, Stuttgart, Germany (L.T., F.C., M.T.) Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Fei
authors.initials: F
authors.lastname: Cheng
authors.affiliation: Department of Cardiovascular Surgery, Robert-Bosch-Hospital, Stuttgart, Germany (J.M., U.W.F.).
authors.forename: Jens
authors.initials: J
authors.lastname: Michaelsen
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Stefan
authors.initials: S
authors.lastname: Winter
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Ute
authors.initials: U
authors.lastname: Hofmann
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Elke
authors.initials: E
authors.lastname: Schaeffeler
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Simon
authors.initials: S
authors.lastname: Müller
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Maike
authors.initials: M
authors.lastname: Sonnenberg
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Kristin
authors.initials: K
authors.lastname: Steuer
authors.affiliation: Department of Pathology, Robert-Bosch-Hospital, Stuttgart, Germany (G.O.).
authors.forename: German
authors.initials: G
authors.lastname: Ott
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.) Department of Clinical Pharmacology, University Hospital, Tuebingen, Germany (M.S.).
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwab
authors.affiliation: Department of Cardiovascular Surgery, Robert-Bosch-Hospital, Stuttgart, Germany (J.M., U.W.F.).
authors.forename: Ulrich F W
authors.initials: UF
authors.lastname: Franke
authors.affiliation: Department of Laboratory Medicine, Robert-Bosch-Hospital, Stuttgart, Germany (L.T., F.C., M.T.) Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and University of Tuebingen, Stuttgart, Germany (F.C., S.W., U.H., E.S., S., M.S., K.S., M.S., M.T.).
authors.forename: Michael
authors.initials: M
authors.lastname: Torzewski
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000201:enzymology* / Q000276:immunology / Q000473:pathology / Q000601:surgery; D015415:Biomarkers / Q000378:metabolism; D002097:C-Reactive Protein / Q000235:genetics / Q000378:metabolism; D018958:CD55 Antigens / Q000235:genetics / Q000378:metabolism; D002114:Calcinosis / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000473:pathology / Q000601:surgery; D002402:Cathepsin D / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D003167:Complement Activation; D015933:Complement C3d / Q000032:analysis; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D020869:Gene Expression Profiling; D006349:Heart Valve Diseases / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000473:pathology / Q000601:surgery; D006801:Humans; D007150:Immunohistochemistry; D008077:Lipoproteins, LDL / Q000276:immunology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D059748:Proteolysis; D012598:Sclerosis; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; D018958:CD55 Antigens; D008077:Lipoproteins, LDL; D015933:Complement C3d; D002097:C-Reactive Protein; C533922:CTSD protein, human; D002402:Cathepsin D
keywords: C‐reactive protein; aortic valve stenosis; low‐density lipoprotein