Paulo. Short Running Title: Collagen/elastic system vessels in IIPs Address all correspondence to:

Background: Recently, vascular remodelling has shown to be promising as pathogenetic indicator in Idiopathic Interstitial Pneumonias (IIPs). In this study, we sought to validate the importance of the collagen/elastic system in the vascular remodelling and to study the relationships between collagen/elastic system, survival and the major histological pattern of IIPs. Material and Methods: We examined collagen/elastic system fibres in 25 acute interstitial pneumonia/diffuse alveolar damage, 22 non-specific interstitial pneumonia/non-specific interstitial pneumonia and 55 idiopathic pulmonary fibrosis/usual interstitial pneumonia cases. We used the Picrosirius-polarization method and Weigert's resorcin-fuchsin histochemistry and morphometric analysis to evaluate the amount of vascular collagen/elastic system fibres, and their association with IIPs histological pattern. In usual interstitial pneumonia (UIP) we also considered the association between vascular remodelling and parenchymal fibrosis degree. Results: The vascular measurement of collagen/elastic fibres content was significantly higher in UIP than lungs of control, diffuse alveolar damage and non-specific interstitial pneumonia. In addition, the increment of collagen/elastic fibres in UIP varied according to the parenchymal fibrosis degree an