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COMSOL models of fluid flow in the sarcomere

Citation

Malingen, Sage et al. (2021), COMSOL models of fluid flow in the sarcomere, Dryad, Dataset, https://doi.org/10.5061/dryad.q2bvq83jb

Abstract

A highly organized and densely packed lattice of molecular machinery within the sarcomeres of muscle cells powers contraction. Although many of the proteins that drive contraction have been studied extensively, the mechanical impact of fluid shearing within the lattice of molecular machinery has received minimal attention. It was recently proposed that fluid flow augments substrate transport in the sarcomere, however, this analysis used analytical models of fluid flow in the molecular machinery that could not capture its full complexity. By building a finite element model of the sarcomere, we estimate the explicit flow field, and contrast it with analytical models. Our results demonstrate that viscous drag forces on sliding filaments are surprisingly small in contrast to the forces generated by single myosin molecular motors. This model also indicates that the energetic cost of fluid flow through viscous shearing with lattice proteins is likely minimal. The model also highlights a steep velocity gradient between sliding filaments and demonstrates that the maximal radial fluid velocity occurs near the tips of the filaments. To our knowledge, this is the first computational analysis of fluid flow within the highly structured sarcomere.

Methods

This dataset was created using COMSOL models of a 1/8th wedge of the sarcomere. The results of these models provide an estimate of the fluid flow field occurring within the sarcomere during muscle contraction and the resulting viscous drag forces that resist filament sliding. We created multiple models to capture how the flow field and the incumbent drag forces depend on sarcomere geometry (e.g. filament packing ratio, sarcomere length, filament diameters and interfilament spacing).