Endocrine Abstracts

Background: The study of fundamental questions related to the analysis of recent advances in the field of cellular and molecular pathways involved in lung organogenesis provides a basis for understanding the pathogenesis of acute and chronic diseases of this organ. Cells of the diffuse endocrine system - apudocytes (APUD) absorb the precursors of biogenic amines introduced from the outside and subject them to decarboxylation with further formation of biogenic amines and peptide hormones. The APUD system also includes innervated clusters of endocrinocytes - neuroepithelial bodies (NETs).

Purpose: Identification in a comparative aspect of the features of the structure of the endocrine apparatus of the APUD-system of the lungs during embryogenesis, as well as in the pathology of the organ caused by inflammatory processes. Material and methods. We studied histological preparations of the lungs in human fetuses at 9-28 weeks of fetal development and full-term newborns.

Results: By the 11th week of their embryonic development, intralobular bronchi appear, the same picture is observed in fetuses of 12 and 13 weeks. Cartilaginous plates are found only in the walls of the lobar and segmental bronchi. In the lungs of fetuses of 9-10 weeks of development, endocrine cells in the epithelium of the bronchi and in the epithelial tubules are not found. Starting from 11 weeks, argyrophilic apudocytes and NET are detected in the large bronchi. In the tubular and alveolar stages of histogenesis, the number of endocrine structures increases, and it is especially significant in the distal parts of the bronchial tree. It should be noted that the branching of the bronchial tree is ahead of the development of the endocrine apparatus in it. Open-type cells are found in the proximal sections of the bronchial tree, while closed-type cells are found in the distal ones. Apudocytes and NETs are found in all children with inflammatory lung disease. Their number is much greater than in the lungs of children who died from diseases not related to the respiratory organs. Closed-type apudocytes are often found in the bronchial epithelium.

Conclusions: We found that open-type apudocytes appear in large bronchi during the development of the lungs, i.e., earlier generations of branching of the airways. Closed-type apudocytes are more characteristic of newly formed bronchial tubes. NETs during lung development appear later than apudocytes and are also more numerous in the developing small bronchi and respiratory region.