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Cell elongation from intrinsic shape preference drives a solid-to-solid transition rather than fluidization.

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2026-06-26 02:55 UTC pith:QH6GZ4XQ

load-bearing objection The paper shows that switching cell elongation to an autonomous elastic anisotropy in the vertex model produces a solid-to-solid transition instead of fluidization, and the distinction holds up as the load-bearing change.

arxiv 2606.26726 v1 pith:QH6GZ4XQ submitted 2026-06-25 cond-mat.soft physics.bio-ph

Solid-to-solid transition in dense assemblies of elongated cells

Shao-Zhen Lin , Jean-Fran\c{c}ois Rupprecht This is my paper
classification cond-mat.soft physics.bio-ph
keywords cell elongationtissue rheologysolid-to-solid transitionvertex modelanisotropic shapeyield stressshear rigidityconfluent tissues
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

The paper models dense cell assemblies where elongation arises from an internal elastic drive toward anisotropic shapes instead of an imposed target shape index. This change produces a transition from an ordered isotropic solid to a disordered anisotropic solid. Both phases retain finite yield stress and shear rigidity, unlike the fluidization seen in conventional models. The result separates cell morphology from tissue mechanical state.

Core claim

When cell elongation is generated by an autonomous, passive elastic preference for anisotropic shape rather than by an imposed target shape index, the tissue undergoes a solid-to-solid transition from an ordered isotropic solid to a disordered anisotropic solid. Finite yield stress and shear rigidity persist across the transition.

What carries the argument

The intrinsic passive elastic preference for anisotropic cell shape, which generates elongation autonomously and reverses the expected rheological response compared to standard target shape index control.

Load-bearing premise

Cell elongation must emerge from an internal elastic bias for anisotropic shapes rather than from an externally set target shape index.

What would settle it

A simulation or experiment in which autonomously elongated cells lose yield stress and fluidize under applied shear would falsify the solid-to-solid claim.

Watch this falsifier — get emailed when new claim-graph text bears on it.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

0 major / 2 minor

Summary. The manuscript modifies the standard vertex model by replacing the usual target shape index with an intrinsic, passive elastic preference for anisotropic cell shapes. The central claim is that this autonomous anisotropy drives a solid-to-solid transition: an ordered isotropic solid becomes a disordered anisotropic solid as the anisotropy strength increases, with finite yield stress and shear rigidity retained on both sides of the transition. This decouples cell elongation from tissue fluidization.

Significance. If robust, the result is significant for tissue mechanics because it reverses the conventional vertex-model outcome (elongation → fluidization) through a specific modeling choice and supplies a concrete counter-example to inferring rheology from morphology alone. The work is grounded in the energy formulation; the transition emerges directly from the autonomous anisotropy term without circular reduction to a fitted quantity.

minor comments (2)
  1. [Abstract] Abstract: the claim is stated clearly but the abstract supplies no implementation details, error analysis, or verification steps for the transition (e.g., how yield stress is measured or how the ordered/disordered states are identified).
  2. [§2] §2 (model definition): the precise functional form of the elastic anisotropy energy and its dependence on the single free parameter should be written explicitly alongside the standard vertex energy to allow direct comparison.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript, including the recognition that the autonomous anisotropy term produces a solid-to-solid transition while preserving yield stress and shear rigidity on both sides. We appreciate the recommendation for minor revision. No specific major comments appear in the report, so we have no individual points to address here. We will incorporate any editorial or minor clarifications in the revised version.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper's result follows directly from altering the vertex model energy to include an intrinsic passive elastic preference for anisotropic cell shape rather than the standard target shape index. This modeling distinction produces the solid-to-solid transition as a consequence of the defined energy functional, without any reduction of predictions to fitted inputs, self-definitional loops, or load-bearing self-citations. The abstract explicitly contrasts the two approaches and states the outcome as emerging from the energy term, confirming the derivation is self-contained against the model assumptions.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The claim rests on introducing an intrinsic elastic anisotropy term into the vertex model energy; this is the key addition beyond standard target-shape-index control.

free parameters (1)
  • elastic anisotropy strength
    Parameter that sets the magnitude of the passive preference for elongated cell shapes; its value controls the location of the reported transition.
axioms (1)
  • domain assumption Vertex model energy functional can be extended with an additional term encoding intrinsic passive elastic preference for anisotropic cell shape.
    This modeling choice is invoked to generate autonomous elongation and is the distinction from standard vertex models.

pith-pipeline@v0.9.1-grok · 5646 in / 1211 out tokens · 66559 ms · 2026-06-26T02:55:38.071511+00:00 · methodology

0 comments
read the original abstract

Cell shapes in confluent tissues range from nearly isotropic epithelial morphologies to highly elongated endothelial ones. In standard vertex models, tissue rigidity is controlled by a target shape index; increasing this index drives cell elongation and ultimate tissue fluidization. Here, we consider the case where cell elongation emerges autonomously by assigning an intrinsic, passive elastic preference for anisotropic shape. This distinction reverses the usual expectation: cell elongation does not fluidize the tissue, but drives a solid-to-solid transition from an ordered isotropic solid to a disordered anisotropic solid, with finite yield stress and shear rigidity on either side of the transition. These results decouple cell shape from tissue rheology and caution against inferring fluid-like mechanics from elongated cell morphologies alone.

Figures

Figures reproduced from arXiv: 2606.26726 by Jean-Fran\c{c}ois Rupprecht, Shao-Zhen Lin.

Figure 1
Figure 1. Figure 1: FIG. 1. Vertex model with cell elongation elasticity (CEE). [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. First-order phase transition on increasing [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Autonomous cell elongation drives a solid-to-solid [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Schematic of the CEE-mediated tissue solidification [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗

discussion (0)

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