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bioRxiv · 10.64898/2026.10.09.757961

A conservative moving-boundary multiphysics framework reveals nonlinear coupling between osmotic flow and actin-driven cell migration

Zhou, H.·Yao, L.·Mori, Y.·Li, Y.
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Abstract

Cell migration couples membrane transport, intracellular fluid motion, and actin remodeling on a boundary that deforms with the cell. Quantitative interpretation of this coupling requires accurate one-sided membrane solute transport and conservative transfer between the G-actin and F-actin pools, because these fields determine the osmotic pressure and polymerization flux that enter the force balance. We develop an implicit immersed-boundary Stokes--Brinkman solver coupled to a sharp interface Cartesian grid advection--diffusion solver that enforces Robin conditions on the evolving membrane and advances F-actin/G-actin exchange through paired interface fluxes on the same accepted geometry. The framework resolves membrane mechanics, osmotic water permeation, solute transport, actin turnover, substrate drag, and intracellular advection in one calculation. Long-duration tests show excellent conservation of total actin and total solute under sustained interface motion and transport. The actin calculations recover biphasic dependencies on both depolymerization and substrate coupling, while pump-induced migration generates a rearward cell-relative cytosolic flow. In the fully coupled system, this flow redistributes G-actin more strongly than F-actin, reorganizes membrane polymerization and F-actin stress, and changes cell migration. Matched controls show that the coupled actin--osmotic system travels farther than the baseline-corrected sum of the isolated actin- and pump-driven responses. The calculations identify cytosolic convection as a physical route through which polarized membrane transport reorganizes the force-generating actin system and produces a nonlinear migration response.

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Zhou, H., Yao, L., Mori, Y., Li, Y.. 2026-10-16. A conservative moving-boundary multiphysics framework reveals nonlinear coupling between osmotic flow and actin-driven cell migration. https://doi.org/10.64898/2026.10.09.757961

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