ONTOGENY OF NEUROENDOCRINE CELLS IN HUMAN-FETAL LUNG .1. AN ELECTRON-MICROSCOPIC STUDY

  • 1 January 1984
    • journal article
    • research article
    • Vol. 51  (4) , 449-463
Abstract
An EM study of human fetal lung was undertaken to describe the ontogeny of neuroendocrine (NE) cells and neuroepithelial bodies (NEB) and to determine their relationships to the developing nervous system. Lungs of 34 fetuses and 22 new borns were examined. Putative NE cells appeared prior to 8 wk of gestation but, by 10 wk, differentiated into NE cells and NEB. Between 13 and 24 wk the number of NE cells and NEB increased, and subpopulations of NE cells were identified: a small population of cells that reached from basement membrane to lumen and NE cells associated with an electron-dense epithelial cell. Material past 24 wk of gestation was obtained from live-born infacts who died at various postnatal ages. Much of this material represented acute pulmonary damage in which NE cells were difficult to identify. As chronic lung disease developed, NE cells, singly and in groups, were easily identified in regenerating conducting airways.Growing axons associated with both NE cells and NEB appeared as early as 10 wk of gestation. Rare cholinergic, adrenergic and nonadrenergic-noncholinergic terminals were identified in contact with NE cells and deep within NEB. Afferent axon terminals were not identified with certainty. The data presented demonstrate innervation to at least some NE cells and NEB throughout fetal life. NE cells and NEB apparently are intrapulmonary neuroreceptors with paracrine secretory function. The present study suggests more complicated mechanisms integrated with the autonomic nervous system, inducing reflex activity at the level of the CNS. A tropic role for NE cells in the developing and regenerating lung is proposed.

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