Title: A model for the roles of actin and myosin in adjustable preload tension and acute length adaptation

Authors: S. Omid Komari; Adam P. Klausner; Paul H. Ratz; John E. Speich

Addresses: Institute of Motion Sciences, Irvine, CA 92614, USA ' Department of Surgery, Virginia Commonwealth University, Richmond, VA, 23284, USA ' Departments of Biochemistry & Molecular Biology and Pediatrics, Virginia Commonwealth University, Richmond, VA, 23284, USA ' Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, 23284, USA

Abstract: Muscle mechanical behaviour is crucial in understanding bladder disorders. In detrusor smooth muscle (DSM), actin-myosin cross-bridges drive bladder contraction. Total tension comprises preload and active tensions. Studies suggest that actin-myosin cross-links are involved in adjustable preload stiffness (APS), which is characterised by a preload tension curve that can be shifted along the length axis as a function of strain and activation history. DSM displays length adaptation, with the active tension curve similarly shifting. Actin-myosin cross-bridges are also responsible for myogenic contractions in response to quick stretch of DSM strips and spontaneous rhythmic contractions (SRC) that may occur during bladder filling. Mechanical spring-dashpot models incorporating Kelvin/Voigt systems were developed to simulate active and preload length-tension curves, reflecting length adaptation and SRC history. Results highlight the influence of actin-myosin cross-bridge overlap and cross-links on dynamic length-tension relationships in DSM. This study offers insights into DSM mechanics, potentially advancing treatment for bladder disorders.

Keywords: biomechanics; tissue biomechanics; biomechanical models; DSM; detrusor smooth muscle; urodynamic; length-tension curve; adjustable preload tension; actin-myosin; SRC; spontaneous rhythmic contractions.

DOI: 10.1504/IJCBDD.2024.139406

International Journal of Computational Biology and Drug Design, 2024 Vol.16 No.1, pp.71 - 92

Received: 05 Mar 2022
Accepted: 05 Oct 2022
Published online: 02 Jul 2024 *

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