Population-Based Mathematical Modeling Facilitates the Interpretation of Dynamic Clamp Experiments in Cardiomyocytes

Abstract

Dynamic clamp (DC) is a powerful method that comprehensively probes how the AP responds to perturbations based on different currents intrinsic to cardiomyocytes. In this closed-loop method, a current is calculated based on the time course of measured voltage, and a scaled version of the calculated current is applied to the cell in real-time. However, since DC currents differ from endogenous currents in several ways, care needs to be taken in interpreting results of these experiments. Since our experiments found significant between-cell heterogeneity in the response to DC perturbations, in order to guide appropriate understanding of these experiments we performed population-based simulations of DC perturbations with different assumptions that reflect how DC currents differ from endogenous currents.DC currents lack the ionic selectivity of endogenous currents. Simulations of DC perturbations with and without ionic selectivity showed that a lack of ionic selectivity leads to overestimation of the effect of the L-type calcium current on APD, but that the effects of other perturbations were largely unaffected. Furthermore, while endogenous currents respond directly to intracellular ionic concentrations, these values are unknown in experiments and must instead be estimated for the calculation of DC currents. We performed simulations where DC currents were calculated using either true ionic concentrations or estimates thereof, and while we found only minor differences in the mean perturbation effect sizes between these two paradigms, the patterns of variability in cell response across a population of models differed significantly, with the latter method producing a closer approximation of experimental results.By illustrating the strengths and shortcomings of how well dynamic clamp perturbations approximate changes in endogenous currents, these simulations allow for more accurate interpretation of dynamic clamp results.