Morphometric study of elastic fibers in normal and emphysematous human lungs

The length of elastic fibers and the distribution of fiber diameters was determined by morphometry in the parenchyma of human lungs. Studies were done on 33 lungs from male subjects 1 to 85 yr of age, including 9 lungs with mild emphysema. These studies suggest that the total length of elastic fibers is present early in life, possibly by 10 yr of age, and thereafter remains constant. Average fiber diameter increases between infancy and adulthood but probably does not change further beyond the 3rd decade of life. No significant differences could be detected in either total fiber length or fiber diameter in the lungs with mild emphysema compared to normal lungs of the same age. There is considerable experimental evidence suggesting that a primary event in the pathogenesis of emphysema is the proteolytic destruction of elastic fibers. The findings in this study are not necessarily inconsistent with this hypothesis. The qualitative observations suggest that in regions adjacent to emphysematous lesions, damage has occurred to the elastic fibers. Other investigators have made similar observations. The loss of a few fibers might not be detected by a quantitative assessment of elastic fibers for the whole lung. If elastic fibers have been destroyed, the results suggest that the total number of fibers involved must be very small. It is also possible that destroyed fibers have been replaced through normal reparative processes. Whether this occurs in human lung is not known, although Johanson et al. (1973) have shown that elastic fibers in rat lung regenerate after papain injury.