arxiv: 2605.01083 · v1 · submitted 2026-05-01 · 🧬 q-bio.TO · cs.NA· math.NA

Recognition: unknown

Modelling the electrophysiological interactions between human pluripotent cell-derived cardiomyocite grafts and host ventricular tissue

Suran Galappaththige , Vadim N Biktashev , Faisal J Alibhai , Michael Laflamme

Authors on Pith no claims yet

Pith reviewed 2026-05-09 14:27 UTC · model grok-4.3

classification 🧬 q-bio.TO cs.NAmath.NA

keywords cardiac cell therapygraft-host interfaceelectrophysiological modelingarrhythmogenesishPSC-CMcomputational frameworkventricular tissueectopic pacemaker

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The pith

A computational framework shows that electrical coupling strength at the graft-host boundary controls whether spontaneous activity in stem-cell grafts can trigger propagating excitation in host heart tissue.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces a modeling approach for studying how transplanted heart cells derived from pluripotent stem cells interact with the recipient's ventricular tissue. It treats the graft-host interface as a controllable boundary whose specific conductance can be varied to represent different degrees of electrical connection. Simulations in representative anatomical setups then track whether pacemaker-like activity inside the graft spreads to initiate waves in the surrounding host myocardium. This matters because such ectopic excitation is thought to drive the arrhythmias that limit current cell-therapy trials after heart attacks. The framework supplies a transparent, reproducible way to explore how changes at the interface might reduce that risk.

Core claim

The authors model the graft-host interface as an internal boundary possessing a defined specific conductance that directly corresponds to measurable tissue properties. With this parameterisation they implement the governing equations in both finite-difference and finite-element schemes. In chosen anatomical and physiological configurations they show that increasing interface conductance allows spontaneous graft activity to cross the boundary and initiate propagating excitation throughout the host tissue, whereas weaker coupling keeps the graft activity isolated.

What carries the argument

Graft-host interface represented as an internal boundary with a single specific conductance parameter that sets the strength of electrical coupling between graft and host.

If this is right

Graft activity remains confined when interface conductance falls below a threshold determined by the model geometry and cell properties.
Above that threshold the graft functions as an ectopic pacemaker capable of driving host excitation.
The same framework can be used to test how different graft sizes, shapes or locations alter the conductance threshold for arrhythmia initiation.
Strategies that deliberately modulate interface conductance become testable targets for reducing post-transplant arrhythmic risk.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

If the conductance threshold is confirmed, biomaterials or pharmacological agents that tune graft-host coupling could be developed to keep grafts electrically isolated until they mature.
The boundary-conductance approach may apply to other cell-replacement therapies where donor tissue risks generating ectopic rhythms in host organs.
Direct patch-clamp or optical mapping measurements of conductance at graft-host junctions in animal models would provide the most immediate test of the model's assumptions.

Load-bearing premise

The real graft-host contact can be represented accurately by a uniform boundary whose conductance is independent of other tissue properties and can be measured in the same units used in the model.

What would settle it

Experimental recordings from transplanted hearts that show no consistent relationship between measured interface conductance and the occurrence of graft-initiated propagating waves in host tissue.

Figures

Figures reproduced from arXiv: 2605.01083 by Faisal J Alibhai, Michael Laflamme, Suran Galappaththige, Vadim N Biktashev.

**Figure 1.** Figure 1: illustrates the result of the procedure of building the computational mesh, described in Subsection 2.2, for one of the representative histology images. We tried this procedure at different spatial resolutions to verify that the results are consistent across them view at source ↗

**Figure 2.** Figure 2: Test of approximation of the anisotropic spatially variable diffusion. view at source ↗

**Figure 3.** Figure 3: Work of “polishing” algorithm (a) Computatitonal grid (blue and green as in view at source ↗

**Figure 4.** Figure 4: Convergence test in 1D. (a) Initial condition for the exact solution. (b) Numerical convergence, log-log plot. Big symbols as defined by the legend correspond to the number of points in the grid divisible by 3, as opposed to those represented by the corresponding small symbols. ε1 means average absolute error of the numerical solution vs exact solution, ε2 is the root mean square error, and ε∞ is the maxim… view at source ↗

**Figure 5.** Figure 5: Convergence test in 2D. (a) Radial profile of the initial condition for the exact solution (t = 0, ϕ = 0). (b) Numerical convergence, log-log plot, notations the same as in view at source ↗

**Figure 6.** Figure 6: Stochastic decoupling. Upper row: 92% suppression is not sufficient to block propagation. Lower row: 93% suppression does block propagation. Here and below, the colour coding is: the red colour component represents V (excitation), green component represents the h, i.e. the fast sodium current inactivation gating variable (excitability), the blue component labels the graft tissue. This is for 5-fold reduced… view at source ↗

**Figure 7.** Figure 7: An illustration of the quarter-disk. A quarter-disk of radius R = 3 mm of graft tissue with border zone within host tissue box size L × L = 6 mm × 6 mm, border zone width W = 0.2 mm, spatial discretization hx = 0.05 mm. (a) BeatBox, colour coding representing distribution of the diffusivity, red for low, blue for high not to scale. (b) OpenCARP, standard visualization with colours representing tissue tags:… view at source ↗

**Figure 8.** Figure 8: Graft boundary radius vs conductivity parametric plots. view at source ↗

**Figure 9.** Figure 9: Period of oscillations. (a,b) as function of graft radius, at selected values of Σ (in mm/ms), and (c,d) as function of host/graft connectivity, at selected values of R (in mm). (a,c) Finite differences (BeatBox), zero-width inner boundary; (b,d) Finite elements (OpenCARP), border zone emulation. Large symbols indicate host oscillation periods; small symbols indicate graft oscillation periods. May 5, 2026 18/23 view at source ↗

**Figure 10.** Figure 10: First breaks in histology sections. (a,c,d) are snapshots from simulations, taken at times t with 5 ms after the moment of the excitation breakthrough from graft to host. (b) is the 1/R vs Σ diagram, filled green circles: graft excites host; open blue circles: graft oscillates alone; red crosses: graft oscillations suppressed, as in view at source ↗

read the original abstract

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are a promising therapy for regenerating myocardium after infarction, but their use is limited by graft-related arrhythmias that frequently occur shortly after transplantation. Experimental studies indicate that these arrhythmias can originate within the graft, which may act as an ectopic pacemaker, yet the mechanisms governing successful excitation of host tissue remain poorly understood. In particular, the role of electrical coupling at the graft-host interface is important, but difficult to measure directly or control. Computer modelling can help here. Here, we present a computational framework that enables systematic investigation of graft-host electrical interactions using a physiologically interpretable parameterisation. We model the graft-host interface as an internal boundary with a defined specific conductance, allowing direct control over coupling strength in units that correspond to measurable tissue properties. We formulate the governing equations and implement the computations using both finite-difference and finite-element discretisations in established cardiac modelling platforms. Using representative anatomical and physiological configurations, we demonstrate how variations in interface conductance influence the ability of spontaneous graft activity to initiate propagating excitation in host tissue. This framework provides a reproducible, mechanistically transparent tool for studying graft-related arrhythmogenesis and lays a foundation for evaluating strategies to mitigate arrhythmic risk in cardiac cell therapy.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This paper sets up a controllable specific conductance for the graft-host interface in cardiac regeneration models and implements it in two standard solvers, but shows no numerical outputs or validation.

read the letter

This paper sets up a modeling framework that treats the graft-host interface as an internal boundary with its own specific conductance parameter. You can set the coupling strength directly in units that match measurable tissue properties, rather than absorbing it into mesh or effective conductivity choices. The authors implement the same idea in both finite-difference and finite-element schemes on established cardiac platforms, which keeps the tool practical for people already running those codes. Using representative anatomical and physiological configurations to explore whether graft pacemaking spreads to the host is a straightforward way to illustrate the point without claiming patient-specific predictions. The approach is transparent and the parameter is independent, so it should let users run clean sweeps on coupling strength. The main limitation is the absence of any concrete simulation results, error checks, sensitivity tests, or comparison to experimental coupling data. The abstract describes how conductance variations affect propagation, but without numbers or figures the demonstration stays at the level of setup rather than findings. The assumption that a uniform conductance captures the real interface is reasonable for a first tool, yet it will need later testing against measured values. This work is aimed at computational researchers who study post-transplant arrhythmias in stem-cell therapies and already use bidomain or monodomain models. A reader who wants a ready parameterization to add graft-host studies will find the structure useful as a starting point. It deserves serious refereeing because the parameterization and dual implementation address a real gap in how these models handle the interface. Reviewers will probably ask for example outputs and basic validation, but the core idea is focused enough to merit the time. I would send it out for peer review.

Referee Report

0 major / 2 minor

Summary. The manuscript presents a computational modeling framework for studying electrophysiological interactions between human pluripotent stem cell-derived cardiomyocyte (hPSC-CM) grafts and host ventricular tissue. It models the graft-host interface as an internal boundary with a defined specific conductance parameter (in units corresponding to measurable tissue properties), formulates the governing equations, implements the model using both finite-difference and finite-element discretizations in established cardiac modeling platforms, and uses representative anatomical and physiological configurations to demonstrate how variations in interface conductance affect the ability of spontaneous graft activity to initiate propagating excitation in host tissue.

Significance. If the framework holds, it provides a reproducible, mechanistically transparent tool for investigating graft-related arrhythmogenesis in cardiac cell therapy. The physiologically interpretable parameterization of the interface conductance allows systematic control over coupling strength, addressing a key experimental challenge. Implementation in standard platforms and focus on representative configurations are strengths that could support future evaluation of strategies to mitigate arrhythmic risk.

minor comments (2)

The title contains a typographical error: 'cardiomyocite' should be spelled 'cardiomyocyte'.
The abstract and demonstration sections would benefit from a brief summary table of the key parameter values (including the range of interface conductances) used in the representative configurations to improve reproducibility.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their supportive summary of the manuscript and for recommending minor revision. The referee's description accurately reflects the framework's focus on modeling the graft-host interface via a controllable specific conductance parameter and its implementation in standard platforms. No specific major comments were provided in the report.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper introduces a computational framework by extending standard cardiac electrophysiology governing equations with an interface conductance parameter treated as an independent, controllable input (in units corresponding to measurable tissue properties). This parameter is not fitted to or derived from the demonstration outcomes; instead, the work implements the model in established finite-difference and finite-element platforms and runs simulations on representative anatomical/physiological configurations to explore its effects. No load-bearing steps reduce to self-definition, fitted-input predictions, self-citation chains for uniqueness, or smuggled ansatzes. The central contribution is the transparent parameterization and tool itself, which remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The framework rests on standard cardiac electrophysiology assumptions and introduces the interface conductance as the primary controllable element without new postulated entities.

free parameters (1)

interface specific conductance
Key parameter varied across values to demonstrate influence on excitation; chosen to correspond to measurable tissue properties but treated as an input for systematic study rather than fitted to a specific outcome.

axioms (2)

standard math Standard cardiac electrophysiology governing equations (monodomain or bidomain model) apply to both graft and host regions
The paper states it formulates the governing equations based on established cardiac modeling platforms.
domain assumption The graft exhibits spontaneous activity capable of acting as an ectopic pacemaker
Drawn from experimental studies referenced in the abstract as the basis for the modeling scenario.

pith-pipeline@v0.9.0 · 5541 in / 1457 out tokens · 23628 ms · 2026-05-09T14:27:13.655087+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

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