Neuroendocrine cell populations in postnatal human lungs: minimal variation from childhood to old age.

Although changes in the human pulmonary neuroendocrine system have been described in association with a variety of pulmonary diseases, little is known of how the system changes with age in healthy lungs. As delineated by their immunoreactivity for neuron-specific enolase, protein gene product 9.5 and chromogranin A, the density of the system's component cells in terms of the rest of the pulmonary epithelium varied minimally between 10 groups of subjects divided according to age and ranging from children to nonagenarians, figures for the groups varying only between 2.91 and 4.19 neuroendocrine cells per 10,000 epithelial cells. In only three subjects were neuroendocrine cells found in the parenchyma; the vast majority were located in airways with about 65% in bronchi. Cells were more often arranged in the form of clusters in the younger subjects than in the elderly, in whom clusters were extremely rare, but the significance of this observation is unclear.