Morphometric estimate of elastin fibers in human lung parenchyma

Elastin fibers are important in maintaining the structural integrity of alveolar walls and in determining the bulk elastic properties of the lung. Because disruption of the alveolar wall occurs in emphysema and because both emphysema and aging are associated with a decrease in lung elasticity, differences in the elastin network that may occur in these conditions are of interest. The authors have used light microscopy and a simple morphometric method to estimate the total length of all elastin fibers in the parenchyma of human lungs and the sizing distributions of fiber diameters. Studies have been completed on 33 lungs from males 1-85 years in age, including 9 lungs with minimal emphysema (1-10% by point count). Total elastin fiber length is constant in the adult lung and the full complement of fibers may be present by age 10 years. Average fiber diameter increases during the phase of lung growth but remains constant in the adult lung. The emphysematous lungs do not differ significantly in total elastin fiber length (p > 0.4) or in average fiber diameter (p > 0.6) compared to normal adult lungs. These morphological observations are consistent with previous biochemical studies showing that total elastin in lung parenchyma remains constant with advancing age in the adult lung. This study also indicates that minimal emphysema is not associated with a detectable decrease in the number or size of elastin fibers.