The role of the extracellular matrix in the reduction of lateral force transmission in muscle bundles: A finite element analysis

Silvia Spadoni; Silvia Todros; Carlo Reggiani; Lorenzo Marcucci; Piero G Pavan

doi:10.1016/j.compbiomed.2024.108488

The role of the extracellular matrix in the reduction of lateral force transmission in muscle bundles: A finite element analysis

Comput Biol Med. 2024 Apr 17:175:108488. doi: 10.1016/j.compbiomed.2024.108488. Online ahead of print.

Authors

Silvia Spadoni¹, Silvia Todros², Carlo Reggiani³, Lorenzo Marcucci³, Piero G Pavan⁴

Affiliations

¹ Department of Industrial Engineering, University of Padova, Padova, Italy.
² Department of Industrial Engineering, University of Padova, Padova, Italy. Electronic address: silvia.todros@unipd.it.
³ Department of Biomedical Sciences, University of Padova, Padova, Italy.
⁴ Department of Industrial Engineering, University of Padova, Padova, Italy; Fondazione Istituto di Ricerca Pediatrica Città Della Speranza, Padova, Italy.

PMID: 38653066
DOI: 10.1016/j.compbiomed.2024.108488

Abstract

Background and objective: Aging is associated with a reduction in muscle performance, but muscle weakness is characterized by a much greater loss of force loss compared to mass loss. The aim of this work is to assess the contribution of the extracellular matrix (ECM) to the lateral transmission of force in humans and the loss of transmitted force due to age-related modifications.

Methods: Finite element models of muscle bundles are developed for young and elderly human subjects, by considering a few fibers connected through an ECM layer. Bundles of young and elderly subjects are assumed to differ in terms of ECM thickness, as observed experimentally. A three-element-based Hill model is adopted to describe the active behavior of muscle fibers, while the ECM is modeled assuming an isotropic hyperelastic neo-Hookean constitutive formulation. Numerical analyses are carried out by mimicking, at the scale of a bundle, two experimental protocols from the literature.

Results: When comparing numerical results obtained for bundles of young and elderly subjects, a greater reduction in the total transmitted force is observed in the latter. The loss of transmitted force is 22 % for the elderly subjects, while it is limited to 7.5 % for the young subjects. The result for the elderly subjects is in line with literature studies on animal models, showing a reduction in the range of 20-34 %. This can be explained by an alteration in the mechanism of lateral force transmission due to the lower shear stiffness of the ECM in elderly subjects, related to its higher thickness.

Conclusions: Computational modeling allows to evaluate at the bundle level how the age-related increase of the ECM amount between fibers affects the lateral transmission of force. The results suggest that the observed increase in ECM thickness in aging alone can explain the reduction of the total transmitted force, due to the impaired lateral transmission of force of each fiber.

Keywords: Aging; Extracellular matrix; Finite element method; Lateral force transmission; Muscle bundle.