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Alteration of Pulmonary Elasticity and Vulnerability to Protease Digestion with Aging
Author(s) -
Miura Katsutoshi
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.01965
Subject(s) - stiffness , elasticity (physics) , lung , pathology , chemistry , anatomy , medicine , materials science , composite material
An aging lung shows decreased elasticity with structural changes. Light microscopy reveals structural changes and speculates functional deterioration. Scanning acoustic microscopy (SAM) can present not only histology but also visualize elasticity of the tissue because of speed‐of‐sound (SOS) through tissues correlated with their stiffness. This study aims to detect pulmonary aging by pulmonary elasticity and vulnerability to protease digestion. Materials and Methods Formalin‐fixed paraffin‐embedded sections of young (teens), middle (the forties), and old (eighties) were measured SOS through bronchioles, peribronchial vessels, and alveolar walls. An actinase E, which has non‐specific protease activity, was applied to the section and the functional and structural changes were followed by SOS and light microscopy. Results Although blood vessels of the old‐aged group showed higher SOS values compared to the young and middle‐aged groups, no significant difference in mean SOS values was present in the bronchiolar and alveolar walls among three groups. After actinase digestion, SOS of both bronchial and alveolar walls of young and middle aged‐groups showed a significant decrease while the old aged‐group appeared no considerable decline (Fig. 1. Fig. 2). Collagen fibers constituting alveolar and bronchiolar walls kept original structures in the old‐aged group compared to the young and middle‐aged groups. Blood vessels exhibited a significant reduction according to incubation time in three groups. Conclusion Although stiffness of blood vessels tends to increase with aging, pulmonary components of bronchiolar and alveolar walls showed no significant change of stiffness with aging. Bronchiolar and alveolar walls of young and middle‐aged tissues were vulnerable to protease digestion while old‐aged ones were resistant. Modification of collagen fibers may extend in the old‐aged lung. Following SOS images after protease digestion can help evaluate not only the morphological alterations but also the mechanical properties of pulmonary tissues. Support or Funding Information This work was supported by a grant from the Japan Society for the Promotion of Science (KAKENHI), Scientific Research Grant Number (c) 15K08375 and (c) 17K1088901.Speed‐of‐sound (SOS) image after actinase E digestion The lower row of the young lung shows gradual decrease in SOS values while the upper low of the old lung exhibits no remarkable changes.Bronchial speed‐of sound (mean±SD) among young, middle, and old‐aged groups after actinase digestion.