title: Collagen and elastic system in the remodelling process of major types of idiopathic interstitial pneumonias (IIP).
abstract: OBJECTIVE
  Structural remodelling in acute and chronic idiopathic interstitial pneumonia (IIP) has been extensively investigated, but little attention has been directed to the elastic tissue in these situations. The aim of this study was to determine whether elastic deposition accompanies collagen deposition in the four major histological patterns of IIP: diffuse alveolar damage (DAD), organizing pneumonia (OP), non-specific interstitial pneumonia (NSIP) and usual interstitial pneumonia (UIP).
  
  
  RESULTS
  We measured, by image analysis, the content of fibres of the collagenous and elastic systems of the alveolar septum in histological slides of open lung biopsies, using the picrosirius-polarization method and Weigert's resorcin-fuchsin stain, respectively. Five groups were studied: 10 cases of DAD; nine cases of OP; nine cases of NSIP; and 10 cases of UIP. Four normal lungs were used for comparison. The content of collagen fibres was significantly higher in UIP when compared to DAD, NSIP, OP and normal lung. The content of elastic fibres was increased in comparison with normal lungs but this was not significantly different among the histological patterns.
  
  
  CONCLUSIONS
  Acute and chronic IIP cause a similar increase in the collagen and elastic contents of the lungs, representing a process of 'fibroelastosis' rather than an exclusive process of fibrosis. A profibrogenic mechanism is responsible for the unparallelled collagen augmentation observed in UIP subjects, the nature of which is yet to be determined.
authors.affiliation: Department of Pathology, Division of Pulmonary Diseases, Heart Institute (InCor), Universidade de São Paulo, São Paulo, Brazil.
authors.forename: G F
authors.initials: GF
authors.lastname: Rozin
authors.forename: M M
authors.initials: MM
authors.lastname: Gomes
authors.forename: E R
authors.initials: ER
authors.lastname: Parra
authors.forename: R A
authors.initials: RA
authors.lastname: Kairalla
authors.forename: C R R
authors.initials: CR
authors.lastname: de Carvalho
authors.forename: V L
authors.initials: VL
authors.lastname: Capelozzi
mesh_terms: D000368:Aged; D003094:Collagen / Q000378:metabolism*; D004547:Elastic Tissue / Q000378:metabolism*; D006651:Histocytochemistry; D006801:Humans; D008168:Lung / Q000737:chemistry / Q000473:pathology; D017563:Lung Diseases, Interstitial / Q000378:metabolism / Q000473:pathology*; D008875:Middle Aged
chemical_list: D003094:Collagen