title: Impact of γ-irradiation on extracellular matrix of porcine pulmonary valves.
abstract: BACKGROUND
  The extracellular matrix plays an important role in heart valve function. To improve the processing of porcine pulmonary valves for clinical use, we have studied the influence of cryopreservation, decellularization, and irradiation on extracellular matrix components.
  
  
  METHODS
  Decellularization was carried out followed by DNAseI/RNAseA digestion and isotonic washout. Valves were cryopreserved in 10% DMSO/10% fetal bovine serum, and then subjected to 25-40 kGy γ-radiation. Extracellular matrix constituents were evaluated by histologic staining, immunohistochemistry, transmission electron microscopy, and liquid chromatography/mass spectrometry.
  
  
  RESULTS
  Histologic, immunohistochemical, ultrastructural, and biochemical analyses demonstrated a marked reduction in the expression of extracellular matrix components particularly in the valves that had been γ-irradiated following decellularization and cryopreservation. In this group, histology and immunohistochemistry showed an obvious reduction in staining for chondroitin sulphates, versican, hyaluronan, and collagens. Transmission electron microscopy revealed the smallest fibril diameter of collagen, shortest D-period, and loss of compactness of collagen fiber packaging and fragmentation of elastic fibers. Biochemical analysis showed loss of collagen and elastin crosslinks. Decellularization followed by cryopreservation showed some reduction in staining for collagens and versican, smaller diameter, shorter D-period in collagen fibers, and ridges in elastic fibers. Cryopreservation alone showed minimal changes in ECM staining intensity, collagen, and elastin ultrastructure and biochemistry.
  
  
  CONCLUSIONS
  γ-Irradiated valves that have been decellularized and cryopreserved produces significant changes in the expression of ECM components, thus providing useful information for improving valve preparation for clinical use and also some indication as to why irradiated human heart valves were not clinically successful.
authors.affiliation: Heart Science Centre, NHLI, Imperial College London, Harefield, Middlesex, United Kingdom. p.sarathchandra@imperial.ac.uk
authors.forename: Padmini
authors.initials: P
authors.lastname: Sarathchandra
authors.forename: Ryszard T
authors.initials: RT
authors.lastname: Smolenski
authors.forename: Ada H Y
authors.initials: AH
authors.lastname: Yuen
authors.forename: Adrian H
authors.initials: AH
authors.lastname: Chester
authors.forename: Steven
authors.initials: S
authors.lastname: Goldstein
authors.forename: Albert E
authors.initials: AE
authors.lastname: Heacox
authors.forename: Magdi H
authors.initials: MH
authors.lastname: Yacoub
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Taylor
mesh_terms: D000818:Animals; D003094:Collagen / Q000378:metabolism; D054326:Coronary Sinus / Q000528:radiation effects / Q000648:ultrastructure; D003432:Cross-Linking Reagents / Q000378:metabolism; D015925:Cryopreservation / Q000379:methods*; D004549:Elastin / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D005720:Gamma Rays / Q000009:adverse effects*; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D013058:Mass Spectrometry; D046529:Microscopy, Electron, Transmission; D032389:Myocytes, Smooth Muscle / Q000528:radiation effects / Q000648:ultrastructure; D011664:Pulmonary Valve / Q000528:radiation effects* / Q000637:transplantation* / Q000648:ultrastructure; D013552:Swine; D014183:Transplantation, Heterologous; D053675:Versicans / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D006025:Glycosaminoglycans; D053675:Versicans; D003094:Collagen; D004549:Elastin