title: Ultrastructural changes of the intracellular surfactant pool in a rat model of lung transplantation-related events.
abstract: BACKGROUND
  Ischemia/reperfusion (I/R) injury, involved in primary graft dysfunction following lung transplantation, leads to inactivation of intra-alveolar surfactant which facilitates injury of the blood-air barrier. The alveolar epithelial type II cells (AE2 cells) synthesize, store and secrete surfactant; thus, an intracellular surfactant pool stored in lamellar bodies (Lb) can be distinguished from the intra-alveolar surfactant pool. The aim of this study was to investigate ultrastructural alterations of the intracellular surfactant pool in a model, mimicking transplantation-related procedures including flush perfusion, cold ischemia and reperfusion combined with mechanical ventilation.
  
  
  METHODS
  Using design-based stereology at the light and electron microscopic level, number, surface area and mean volume of AE2 cells as well as number, size and total volume of Lb were determined in a group subjected to transplantation-related procedures including both I/R injury and mechanical ventilation (I/R group) and a control group.
  
  
  RESULTS
  After I/R injury, the mean number of Lb per AE2 cell was significantly reduced compared to the control group, accompanied by a significant increase in the luminal surface area per AE2 cell in the I/R group. This increase in the luminal surface area correlated with the decrease in surface area of Lb per AE2. The number-weighted mean volume of Lb in the I/R group showed a tendency to increase.
  
  
  CONCLUSIONS
  We suggest that in this animal model the reduction of the number of Lb per AE2 cell is most likely due to stimulated exocytosis of Lb into the alveolar space. The loss of Lb is partly compensated by an increased size of Lb thus maintaining total volume of Lb per AE2 cell and lung. This mechanism counteracts at least in part the inactivation of the intra-alveolar surfactant.
authors.affiliation: Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany. knudsen.lars@mh-hannover.de
authors.forename: Lars
authors.initials: L
authors.lastname: Knudsen
authors.forename: Hazibullah
authors.initials: H
authors.lastname: Waizy
authors.forename: Heinz
authors.initials: H
authors.lastname: Fehrenbach
authors.forename: Joachim
authors.initials: J
authors.lastname: Richter
authors.forename: Thorsten
authors.initials: T
authors.lastname: Wahlers
authors.forename: Thorsten
authors.initials: T
authors.lastname: Wittwer
authors.forename: Matthias
authors.initials: M
authors.lastname: Ochs
mesh_terms: D056809:Alveolar Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure*; D000818:Animals; D048429:Cell Size; D050377:Cold Ischemia / Q000009:adverse effects; D004195:Disease Models, Animal; D005089:Exocytosis; D016040:Lung Transplantation / Q000009:adverse effects*; D008297:Male; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure*; D055031:Primary Graft Dysfunction / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D037661:Pulmonary Surfactant-Associated Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D012121:Respiration, Artificial / Q000009:adverse effects
chemical_list: D037661:Pulmonary Surfactant-Associated Proteins