Relaxation and creep response of the alveolar lung to diagnosis and treatments for respiratory and lung disorders

Abstract

Background The lung Extracellular Matrix (ECM) contains a considerable part of the parenchymal cells. It contains three essential components: elastin and collagen within a proteoglycan (PG) viscoelastic network. Elastin provides the lung’s elasticity property, a necessity for normal breathing, while collagen prepares structural support and strength, and PGs give stability and cushioning within tissue loading. Bacterial and viral respiratory diseases are dependent on changes in the ECM ingredients, which result in an alteration of the lung tissue strength. Purpose In the present study, this variation was investigated by changing the volume ratio of the ECM ingredients in the viscoelastic model. Purpose As a result, the relaxation curves continuously declined by reducing the volume ratios of elastin, collagen, and PGs; subsequently, the lung stiffness decreased. Also, the Standard Linear Solid (SLS) model-based results demonstrated excellent accordance with empirical data with only minor deviations. The resting relaxation modulus and the creep modulus for the ECM tissue were 51 kPa and approximately 0.02 kPa, respectively, and the maximum total modulus of elasticity reached 121 kPa. Conclusions Moreover, this model demonstrates individual alveolar mechanical behaviours and adds another pathway to the generalized Kelvin-Voigt and Maxwell models in predicting the progress of lung diseases.

Proteoglycans in mechanobiology of tissues and organs: Normal functions and mechanopathology

“…PGs in lung interstitium help maintain the proper balance between elasticity and stiffness of the lung tissue. 141 PGs also play a role in lung development: during fetal lung development, PGs influence branching and elongation of the airway tubes, a process that itself is subject to mechanical forces. 142,143 Mutations or disruptions in heparan sulfate synthesis can disrupt lung development and function.…”

“…9 PGs are present in the lung ECM, where they contribute to the mechanical and functional properties of the tissue. 141 One important role of PGs in the lung is to maintain the elasticity of the tissue such that it can stretch and increase gas exchange-surface area during inhalation and relax to resting position during exhalation. PGs in lung interstitium help maintain the proper balance between elasticity and stiffness of the lung tissue.…”

“…The lung is a highly mechanically sensitive tissue that responds to changes in both pressure and volume during breathing cycles 9 . PGs are present in the lung ECM, where they contribute to the mechanical and functional properties of the tissue 141 . One important role of PGs in the lung is to maintain the elasticity of the tissue such that it can stretch and increase gas exchange–surface area during inhalation and relax to resting position during exhalation.…”

“…One important role of PGs in the lung is to maintain the elasticity of the tissue such that it can stretch and increase gas exchange–surface area during inhalation and relax to resting position during exhalation. PGs in lung interstitium help maintain the proper balance between elasticity and stiffness of the lung tissue 141 . PGs also play a role in lung development: during fetal lung development, PGs influence branching and elongation of the airway tubes, a process that itself is subject to mechanical forces 142,143 .…”

Viscoelastic Properties of Acellular Matrices of Porcine Esophageal Mucosa and Comparison with Acellular Matrices of Porcine Small Intestine Submucosa and Bovine Pericardium

“…Proteoglycans are large molecules consisting of a core protein and long chains of carbohydrates called glycosaminoglycans. These molecules occupy spaces within the matrix and interact with water [ 12 ].…”