Quantitative Model for Ion Transport and Cytoplasm Conductivity of Chinese Hamster Ovary Cells

Azita Fazelkhah,Elham Salimi,Michael Butler,Greg Bridges,Katrin Braasch,Samaneh Afshar,Douglas Thomson

doi:10.1038/s41598-018-36127-3

Azita Fazelkhah, Elham Salimi + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-36127-3

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Abstract

In mammalian cells cytoplasm ion concentrations and hence cytoplasm conductivity is an important indicator of their physiological state. Changes in the cytoplasm conductivity has been associated with physiological changes such as progression of cancer and apoptosis. In this work, a model that predicts the effects of physiological changes in ion transport on the cytoplasm conductivity of Chinese hamster ovary (CHO) cells is demonstrated. We determined CHO-specific model parameters, Na+/K+ ATPase pumps and ion channels densities, using a flux assay approach. The obtained sodium (PNa), potassium (PK) and chloride (PCl) permeability and Na+/K+ ATPase pump density were estimated to be 5.6 × 10−8 cm/s, 5.6 × 10−8 cm/s, 3.2 × 10−7 cm/s and 2.56 × 10−11 mol/cm2, respectively. The model was tested by comparing the model predictions with the experimentally determined temporal changes in the cytoplasm conductivity of Na+/K+ ATPase pump inhibited CHO cells. Cells’ Na+/K+ ATPase pumps were inhibited using 5 mM Ouabain and the temporal behavior of their cytoplasm conductivity was measured using dielectrophoresis cytometry. The measured results are in close agreement with the model-calculated values. This model will provide insight on the effects of processes such as apoptosis or external media ion concentration on the cytoplasm conductivity of mammalian cells.

Highlights

Ion transport is commonly modelled using a set of nonlinear equations governing the cell volume, transmembrane potential, and internal and external ion concentrations
We develop a predictive model of cytoplasm conductivity for Chinese hamster ovary (CHO) cells
Ion fluxes through the other co-transporters such as KCC (K+-Cl−) and NKCC (Na+-K+-Cl−) are assumed to be negligible according to experimental data shown in[16]

Summary

Introduction

Ion transport is commonly modelled using a set of nonlinear equations governing the cell volume, transmembrane potential, and internal and external ion concentrations. Ion fluxes through the channels and Na+/K+ ATPase pumps are required These parameters are known to vary from one cell type to another[15,16,22] and have not been previously determined for CHO cells. We develop a predictive model of cytoplasm conductivity for CHO cells. To determine ion fluxes through channels and pumps in CHO cells we employ a flux-based assay with a Rb+ as a tracer element. Employing the obtained parameters in the ion transport model, we predict temporal changes in the cytoplasm conductivity of CHO cells. We verify the model predictions by comparing its results with measured cytoplasm conductivity of healthy and pump-inhibited CHO cells using Ouabain[27,28]. The model is applicable to other mammalian cell lines with proper parameter adjustments

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