Cellular and Connective Tissue Changes in Alveolar Septal Walls in Emphysema

Am J Respir Crit Care Med. 1999 Dec;160(6):2086-92. doi: 10.1164/ajrccm.160.6.9706031.

Abstract

Emphysema is commonly defined as enlargement of airspaces distal to terminal bronchioles accompanied by destruction of alveolar walls, but without obvious fibrosis. Morphometric techniques were used to correlate changes in components of the alveolar septa surrounding enlarged airspaces in human emphysema with the mean linear intercept (Lm) of those airspaces. Alveolar and capillary surface density decreased with increased Lm, but the ratio of these surface densities to each other remained close to normal for mild to moderate increases in Lm. This suggests that the decreased gas exchange observed in emphysema is initiated by a total loss of septa and not by selective pathological changes of the microvasculature. Increases in septal wall thickness directly correlated with increases in Lm. For the mild to moderate emphysema lesions included in this study, an increase of 100% in Lm correlated with a 130% increase in the relative volume of the alveolar septal interstitium. Significant increases occurred in both elastin (0.14 to 0.56 microm(3)/microm(2) basement membrane [BM]) and collagen (0.49 to 1. 63 microm(3)/microm(2) BM). The increase in elastin and collagen raises the possibility of a remodeling process in the connective matrix in alveolar walls. Whether or not the new connective tissue represents a disordered, nonfunctional regional response needs to be determined.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Capillaries / pathology
  • Collagen / ultrastructure
  • Connective Tissue / pathology
  • Connective Tissue / ultrastructure
  • Elastin / ultrastructure
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pulmonary Alveoli / blood supply
  • Pulmonary Alveoli / pathology*
  • Pulmonary Alveoli / ultrastructure
  • Pulmonary Emphysema / pathology*

Substances

  • Collagen
  • Elastin