REVIEW 3 major objections 4 minor 43 references
Theory of cell size regulation during migration in adhered cells
T0 review · 3 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read The paper argues that cell polarization is easier to establish over larger contact areas, so cell swelling drives faster migration once a critical contact area is crossed.
desk verdict Solid minimal framework uniting volume regulation, spreading, and polarization; the claimed critical-area prediction is currently fitted, not tested. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is the polarization expansion $p(\tilde u \cos\phi) \approx p_1 \tilde u + p_3 \tilde u^3 + p_5 \tilde u^5$ inserted into the force balance $2\pi\Gamma u = \int_0^{2\pi} f_a(\phi)\cos\phi\,d\phi$. It converts the advection-diffusion competition for polarity cues into a bifurcation for the Péclet number $\tilde u = uR/D$. The critical radius $R_c = \Gamma D/(f_0 p_1)$ is where the factor $\Gamma D/(f_0 R)$ crosses the linear gain $p_1$, and the signs of $p_3$ and $p_5$ decide whether the onset is continuous or abrupt. Supporting machinery includes the pump-leak volume relation $V = V_d + (V_m - V_d)/(1 - e^{\psi})$, a linear-response membrane potential $\psi(t)$, a contact-angle relaxation toward the force-balance value, and a spherical-cap area-volume relation that couple cell size to the active force $f_0$.
What would settle it
Measure polarity-cue profiles around the contact ring while perturbing actin flow, and check whether the force anisotropy really has the assumed fixed-coefficient form; or, holding volume fixed while changing only contact area through substrate adhesiveness, test whether persistent migration turns on exactly at $R_c = \Gamma D/(f_0 p_1)$ and follows the predicted $u(R)$ curve.
Extended reading notes
Core claim
The paper's central claim is that cell size regulates migration through a polarization mechanism, not through volume per se. The contact area sets how easily an asymmetry in polarity-cue concentration is maintained: advection of cues by retrograde cytoplasmic flow competes with diffusion, and the Péclet number $\tilde u = uR/D$ grows with the product of speed and contact radius. Expanding the force anisotropy $p(\tilde u \cos\phi)$ as $p_1 \tilde u + p_3 \tilde u^3 + p_5 \tilde u^5$, the steady-state force balance produces a bifurcation: for $R$ below $R_c = \Gamma D/(f_0 p_1)$ the unpolarized state $u=0$ is stable, while above $R_c$ a polarized branch $u(R)$ emerges, smoothly when $p_3<0$ and discontinuously when $p_3>0$. Because $u = \tilde u D/R$, the speed first rises with area and later falls at large radii. The same framework, with volume set by pump-leak ion transport and area by a spherical-cap force balance, reproduces the observed neutrophil sequence of fast spreading with slight volume loss followed by swelling that enlarges the contact area and lifts migration speed, and it matches the finding that velocity correlates more strongly with contact area than with volume.
Load-bearing premise
The velocity-area prediction hinges on treating the polarization response as a fixed polynomial whose first two coefficients are fitted to the same velocity data they are used to explain; if those coefficients vary with cell type or state, the predicted critical area is not an independent prediction.
Editorial extensions
If this is right
- Above the critical contact area, persistent migration switches on: cells below it diffuse randomly while cells above it move with a speed that initially grows with area.
- Migration speed is non-monotonic in contact area, peaking at $R = 3R_c/2$ in the smooth-onset case, so sufficiently large cells are predicted to slow down again.
- The sign of $p_3$ controls the transition type: $p_3<0$ gives a smooth supercritical onset, while $p_3>0$ gives an abrupt subcritical jump and bistability between resting and motile states.
- Swelling accelerates neutrophils by enlarging the contact area rather than by adding water, and the experimental data confirm that velocity correlates with area more strongly than with volume.
- Random motility below threshold is tied to the critical area through $\langle u_\xi^2\rangle \sim 1/A_c$, giving a measurable relation between a cell's random speed and the onset of directed motion.
Reading between the lines
- Beyond the paper, the same mechanism should apply to other motile cell types: modulating substrate adhesion at fixed volume should shift the onset of persistent migration and rescale the velocity-area curve.
- If the subcritical branch ($p_3>0$) is realized, the model predicts hysteresis, so a swollen cell would keep migrating when its area is reduced below $R_c$ until a lower threshold is reached; this can be tested in swelling-shrinking cycles.
- The theory suggests a design rule for synthetic motile cells: increasing contact area lowers the polarization threshold, while raising friction $\Gamma$ or cue diffusivity $D$ raises it.
- Fitting Eq. (10) to single-cell tracks during the swelling phase would turn the reported correlation into a dynamical prediction for how speed should track measured area.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents a minimal theoretical framework coupling cell volume, contact area, and migration velocity in adhered cells. Volume is described by a pump-leak model with mechanosensitive and activation-induced membrane-potential changes; contact area is obtained from a spherical-cap geometry with viscoelastic tension dynamics; migration emerges from a polarization feedback expressed as a phenomenological expansion of the active-force anisotropy in the Péclet number. The theory predicts a critical contact area above which persistent migration is possible, and a velocity–area curve with a maximum. The authors compare their predictions with neutrophil spreading/swelling and migration data from Nagy et al. and report good agreement, including a correlation analysis showing that velocity correlates more strongly with contact area than with volume.
Significance. If the central claims hold, the framework would provide a useful minimal explanation for how cell-size changes, particularly contact area, control the onset and speed of persistent migration, and it would organize existing observations of neutrophil swelling and motility into a single coupled dynamical picture. The analytic derivations in Appendices A–C are internally consistent, and the stability analysis in Appendix B correctly shows that δ1 > 0 stabilizes the volume–area coupling. The correlation analysis in Appendix D is a useful check of the proposed area–velocity link. However, the predictive content is weakened by the fact that the key polarization coefficients p1 and p3 are fitted to the same experimental velocity data used to validate the velocity–area curve; as a result, the critical area is a fitted threshold rather than an independent prediction.
major comments (3)
- [§III, Eq. (9), Fig. 4] The critical contact area Ac ≈ 1.2 A(0) is not an independent prediction because the coefficient p1 in Eq. (9) is fitted to the same velocity data that Eq. (10) is claimed to explain. With the reported post-activation values ΓD/f0 = 0.26 µm and p1 = 0.033, one obtains Rc = ΓD/(f0 p1) ≈ 7.9 µm and Ac = π Rc² ≈ 195 µm², which is about 1.27 A0; the stated value of 1.2 A0 is therefore set by the fit. The manuscript should either provide an independent determination of p1 (e.g., from measured polarity-cue profiles or a microscopic advection-diffusion model) or explicitly re-frame the critical-area statement as a fitted threshold rather than a prediction.
- [§III, Appendix C, Eq. (C13)] The parameter set reported for Fig. 4 (p1 = 0.033, p3 = 10⁻⁶) corresponds to the p3 > 0 case, which requires the fifth-order coefficient p5 in Eq. (C13) to specify the unstable branch and the threshold R*_c via Eq. (C16). However, p5 is not reported anywhere, so the subcritical branch and the jump velocity u*_c used in the experimental comparison are incompletely specified. Please report the value of p5 used to generate the curve in Fig. 4c, along with the resulting R*_c and u*_c.
- [§II, Eq. (9)] The expansion p(ũ cos φ) ≈ p1 ũ + p3 ũ³ + p5 ũ⁵ is introduced as a phenomenological step, with no derivation from the advection-diffusion feedback described in the text. Because this expansion directly determines the bifurcation threshold Rc = ΓD/(f0 p1) and the entire velocity–area curve, the sign and magnitude of p1 and p3 are load-bearing. The authors should either justify these coefficients from the underlying polarity-cue dynamics or clearly state that they are effective, cell-type-dependent parameters whose universality is untested.
minor comments (4)
- [General] There are several typographical errors that should be corrected, including 'polarzied' (Abstract/Introduction), 'electrnetruality' (Section II), 'charactarized' (Appendix C), and 'concnentrations' (Appendix A).
- [Fig. 3 caption] The caption reports only ΓD/f0 = 1.12 µm and p3 = ±1; the values of p1 and p5 used in the plotted curves are not given, which makes the figure difficult to reproduce.
- [Appendix D] The correlation coefficients r(x,y) in Fig. 5 are presented without confidence intervals or significance tests, so the claim that velocity correlates 'significantly' more strongly with area than with volume is not quantified.
- [§III] The phrase 'We consider a critical contact area of Ac ≈ 1.2 A(t = 0)' is presented as if it were a theoretical input, but the preceding text does not explain how this value arises from the model parameters; clarifying the derivation would avoid confusion.
Circularity Check
The critical-area and velocity-area predictions reduce to the fitted coefficients p1 and p3 of the phenomenological expansion in Eq. (9), so the central migration claim is interpolation rather than an independent prediction.
-
fitted input called prediction
[Section II 'Cell migration and polarization', Eq. (9); Section III 'Cell migration'; Fig. 4 caption]
"Due to the many arguments that enter p (such as the protein-membrane interaction, intracellular transport, and force generation description), we phenomenologically expand it in powers of ˜u, as follows: ... ≈ p1 ˜u + p3 ˜u3 + p5 ˜u5 (9) ... Explicitly, we consider a critical contact area of Ac ≈ 1.2 A(t = 0). Once this value is achieved, u smoothly increases with the contact area, explaining the observed behavior. Fig. 4 caption: p1, p3 = 0.033, 10−6."
The critical radius is Rc = ΓD/(f0 p1) (Eq. C11), and the velocity-area curve (Eq. 10) is obtained by solving the expansion (9) for fixed p1, p3, p5. The paper does not derive p1 and p3 from the advection-diffusion mechanism; it calls the expansion phenomenological. In the comparison with Nagy et al., the parameters are set to p1 = 0.033 and p3 = 10−6 (Fig. 4 caption) so that the theoretical velocity curve matches the measured rise, and the text then 'considers' Ac ≈ 1.2 A(0) as the activation threshold. Since the threshold location and the shape of the rise are controlled by these same fitted coefficients, the agreement in Fig. 4c is an interpolation, not an independent test of the predicted critical area. For the p3 > 0 branch actually used, the curve also depends on p5 (Eqs.
full rationale
The paper's volume/spreading dynamics (Eqs. 1–6) and the area-versus-volume correlation analysis (Appendix D) are self-contained against external data and do not involve circularity. The circularity is confined to the migration section. Eq. (9) is presented as a phenomenological expansion of the polarization function p in powers of the Péclet number, with coefficients pn left free. The bifurcation threshold Rc = ΓD/(f0 p1) and the velocity-area curve Eq. (10) are then solved from this expansion (Appendix C). In the experimental comparison, p1 and p3 are chosen (Fig. 4 caption) so that the velocity curve rises where the measured velocity rises, and the text then 'considers' Ac ≈ 1.2 A(0). Thus the critical contact area—the paper's headline prediction—is not an independent, out-of-sample prediction; it is a re-parameterization of the fitted coefficients. The qualitative statement that gradients are easier to establish over larger sizes is built into the assumption p1 > 0 and the R dependence of the prefactor, not derived from a molecular model. Nevertheless, the paper does not rely on a self-citation chain or on a uniqueness theorem; the volume-regulation and spreading parts have independent content. The deficiency is a fitted-input-called-prediction in the central migration claim, warranting a partial circularity score of 6 rather than a higher score.
Assumptions & free parameters
free parameters (15)
- p1 =
0.033
- p3 =
10^-6
- p5 =
assumed negative, not specified
- ψ0 =
-1.53
- δ1 =
0.75
- δ2 =
0.08
- τψ =
12 min
- τθ =
0.85 min
- τγ =
0.85 min
- f0/γ0 =
1.47 (pre), 1.96 (post activation)
- η/γ0 =
0.54 τγ/A0
- ΓD/f0 =
0.34, 0.26 µm
- Vd =
0.3 V0
- Vm =
2.5 Vd
- Ac =
1.2 A0
assumptions (10)
- standard math Pump-leak model with electroneutrality and osmotic balance
- standard math Cell shape is a spherical cap
- ad hoc to paper Linear response for potential dynamics
- ad hoc to paper Maxwell viscoelastic model for tension
- domain assumption Instantaneous channel adaptation
- ad hoc to paper Phenomenological expansion of p
- domain assumption Advection-diffusion feedback proportional to migration velocity
- domain assumption Anisotropy is small (p << 1)
- domain assumption δ1 > 0 and δ2 > 0
- domain assumption Cl- is passive and fast
invented entities (1)
-
Polarity cues
independent evidence
Cite this review
Pith. "Pith review of Theory of cell size regulation during migration in adhered cells." pith.science (2026). https://pith.science/paper/WEUCJQAA
@misc{pith2026250516750,
author = {Pith},
title = {Pith review of: Theory of cell size regulation during migration in adhered cells},
year = {2026},
howpublished = {\url{https://pith.science/paper/WEUCJQAA}},
note = {Machine review of arXiv:2505.16750}
}
read the original abstract
Cell migration is closely linked to cell shape, yet cell size is often assumed to remain constant. This assumption is challenged by recent experiments showing that cells undergo volume loss during spreading and swelling upon activation, with migration velocity correlated to cell size. In this Letter, we present a minimal theoretical framework for cellular size regulation and its influence on migration velocity. We connect cell size to membrane potential and active, actin-driven forces. Spatial inhomogeneities in these forces establish cell polarization and drive migration. Crucially, inhomogeneity is easier to establish over larger sizes, giving rise to a critical contact area, above which migration is possible. Our theory captures the coupled dynamics of cell volume, surface area, and motility and explains recent experiments on neutrophils.
Figures
Figures from the paper (2 more)
Reference graph
Works this paper leans on
-
[1]
P. Friedl and D. Gilmour, Collective cell migration in morphogenesis, regeneration and cancer, Nature reviews Molecular cell biology 10, 445 (2009)
work page 2009
-
[2]
P. Friedl and S. Alexander, Cancer invasion and the mi- croenvironment: plasticity and reciprocity, Cell 147, 992 (2011)
work page 2011
-
[3]
S. Nourshargh and R. Alon, Leukocyte migration into inflamed tissues, Immunity 41, 694 (2014)
work page 2014
-
[4]
V. Hakim and P. Silberzan, Collective cell migration: A physics perspective, Reports on Progress in Physics 80, 10.1088/1361-6633/aa65ef (2017)
-
[5]
J. E. Ron, P. Monzo, N. C. Gauthier, R. Voituriez, and N. S. Gov, One-dimensional cell motility patterns, Phys- ical review research 2, 033237 (2020)
work page 2020
-
[6]
J. E. Ron, M. Crestani, J. M. Kux, J. Liu, N. Al-Dam, P. Monzo, N. C. Gauthier, P. J. S´ aez, and N. S. Gov, Emergent seesaw oscillations during cellular directional decision-making, Nature Physics 20, 501 (2024)
work page 2024
-
[7]
J. Liu, J. Boix-Campos, J. E. Ron, J. M. Kux, N. S. Gov, and P. J. S´ aez, Shape dynamics and migration of branched cells on complex networks, arXiv preprint arXiv:2404.00118 (2024)
arXiv 2024
-
[8]
M. K. Driscoll, C. McCann, R. Kopace, T. Homan, J. T. Fourkas, C. Parent, and W. Losert, Cell shape dynamics: from waves to migration, PLoS computational biology 8, e1002392 (2012)
work page 2012
Show all 43 references
-
[9]
Blanch-Mercader and J
C. Blanch-Mercader and J. Casademunt, Spontaneous motility of actin lamellar fragments, Physical review let- ters 110, 078102 (2013)
2013
-
[10]
D. L. Bodor, W. P¨ onisch, R. G. Endres, and E. K. Paluch, Of cell shapes and motion: the physical basis of animal cell migration, Developmental cell 52, 550 (2020)
2020
-
[11]
I. Lavi, N. Meunier, R. Voituriez, and J. Casademunt, Motility and morphodynamics of confined cells, Physical Review E 101, 022404 (2020)
2020
-
[12]
R. K. Sadhu, A. Igliˇ c, and N. S. Gov, A minimal cell model for lamellipodia-based cellular dynamics and mi- gration, Journal of Cell Science 136, jcs260744 (2023)
2023
-
[13]
A. C. Callan-Jones and R. Voituriez, Active gel model of amoeboid cell motility, New Journal of Physics 15, 10.1088/1367-2630/15/2/025022 (2013)
2013 doi
-
[14]
Cadart, L
C. Cadart, L. Venkova, P. Recho, M. C. Lagomarsino, and M. Piel, The physics of cell-size regulation across timescales, Nature Physics 15, 993 (2019)
2019
-
[15]
K. Xie, Y. Yang, and H. Jiang, Controlling cellular vol- ume via mechanical and physical properties of substrate, Biophysical Journal 114, 675 (2018)
2018
-
[16]
M. Guo, A. F. Pegoraro, A. Mao, E. H. Zhou, P. R. Arany, Y. Han, D. T. Burnette, M. H. Jensen, K. E. Kasza, J. R. Moore, F. C. Mackintosh, J. J. Fredberg, D. J. Mooney, J. Lippincott-Schwartz, and D. A. Weitz, Cell volume change through water efflux impacts cell stiffness and ...
2017
-
[17]
Venkova, A
L. Venkova, A. S. Vishen, S. Lembo, N. Srivastava, B. Duchamp, A. Ruppel, A. Williart, S. Vassilopoulos, A. Deslys, J.-M. G. Arcos, et al., A mechano-osmotic feedback couples cell volume to the rate of cell deforma- tion, eLife 11, e72381 (2022)
2022
-
[18]
R. M. Adar and S. A. Safran, Active volume regulation in adhered cells, Proceedings of the National Academy of Sciences 117, 5604 (2020)
2020
-
[19]
R. M. Adar, A. S. Vishen, J.-F. Joanny, P. Sens, and S. A. Safran, Volume regulation in adhered cells: roles of surface tension and cell swelling, Biophysical Journal 122, 506 (2023)
2023
-
[20]
Delpire and K
E. Delpire and K. B. Gagnon, Water homeostasis and cell volume maintenance and regulation, Current topics in membranes 81, 3 (2018)
2018
-
[21]
Q. Ni, Z. Ge, Y. Li, G. Shatkin, J. Fu, A. Sen, K. Bera, Y. Yang, Y. Wang, Y. Wu, et al., Cytoskeletal activation of nhe1 regulates mechanosensitive cell volume adapta- tion and proliferation, Cell Reports 43 (2024)
2024
-
[22]
T. L. Nagy, E. Strickland, and O. D. Weiner, Neutrophils actively swell to potentiate rapid migration, Elife 12, RP90551 (2024)
2024
-
[23]
Tosteson and J
D. Tosteson and J. Hoffman, Regulation of cell volume by active cation transport in high and low potassium sheep red cells, The Journal of general physiology 44, 169 (1960)
1960
-
[24]
Keener and J
J. Keener and J. Sneyd, Mathematical physiology: I: 10 cellular physiology (Springer Science & Business Media, 2010)
2010
-
[25]
A. R. Kay, How cells can control their size by pumping ions, Frontiers in cell and developmental biology 5, 41 (2017)
2017
-
[26]
R. M. Adar, Separation of ionic timescales explains dynamics of cellular volume regulation, arXiv preprint arXiv:2411.01536 (2024)
2024 arXiv
-
[27]
Phillips, J
R. Phillips, J. Kondev, J. Theriot, et al., Physical biology of the cell(Garland Science, 2009)
2009
-
[28]
E. K. Hoffmann, I. H. Lambert, and S. F. Pedersen, Phys- iology of cell volume regulation in vertebrates, Physiolog- ical reviews 89, 193 (2009)
2009
-
[29]
Scita, S
G. Scita, S. Confalonieri, P. Lappalainen, and S. Suet- sugu, Irsp53: crossing the road of membrane and actin dynamics in the formation of membrane protrusions, Trends in cell biology 18, 52 (2008)
2008
-
[30]
Mukherjee, J
A. Mukherjee, J. E. Ron, H. T. Hu, T. Nishimura, K. Hanawa-Suetsugu, B. Behkam, N. S. Gov, S. Suet- sugu, and A. S. Nain, Actin filaments couple the protru- sive tips to the nucleus through the i-bar domain pro- tein irsp53 for migration of elongated cells on 1d fibers, bioRxi...
2022
-
[31]
I. Dang, R. Gorelik, C. Sousa-Blin, E. Derivery, C. Gu´ erin, J. Linkner, M. Nemethova, J. G. Dumortier, F. A. Giger, T. A. Chipysheva, et al., Inhibitory sig- nalling to the arp2/3 complex steers cell migration, Na- ture 503, 281 (2013)
2013
-
[32]
Maiuri, J.-F
P. Maiuri, J.-F. Rupprecht, S. Wieser, V. Ruprecht, O. B´ enichou, N. Carpi, M. Coppey, S. De Beco, N. Gov, C.-P. Heisenberg, et al., Actin flows mediate a univer- sal coupling between cell speed and cell persistence, Cell 161, 374 (2015)
2015
-
[33]
C. Yang, M. Pring, M. A. Wear, M. Huang, J. A. Cooper, T. M. Svitkina, and S. H. Zigmond, Mammalian carmil inhibits actin filament capping by capping protein, De- velopmental cell 9, 209 (2005)
2005
-
[34]
Machacek, L
M. Machacek, L. Hodgson, C. Welch, H. Elliott, O. Pertz, P. Nalbant, A. Abell, G. L. Johnson, K. M. Hahn, and G. Danuser, Coordination of rho gtpase activities during cell protrusion, Nature 461, 99 (2009)
2009
-
[35]
J. E. Ron, J. d’Alessandro, V. Cellerin, R. Voituriez, B. Ladoux, and N. S. Gov, Polarization and motility of one-dimensional multi-cellular trains, Biophysical Jour- nal 122, 4598 (2023)
2023
-
[36]
Bertrand, J
T. Bertrand, J. d’Alessandro, A. Maitra, S. Jain, B. Mercier, R.-M. M` ege, B. Ladoux, and R. Voituriez, Clustering and ordering in cell assemblies with generic asymmetric aligning interactions, Physical Review Re- search 6, 023022 (2024)
2024
-
[37]
A. C. Callan-Jones and R. Voituriez, Actin flows in cell migration: from locomotion and polarity to trajectories, Current opinion in cell biology 38, 12 (2016)
2016
-
[38]
R. J. Hawkins, R. Poincloux, O. B´ enichou, M. Piel, P. Chavrier, and R. Voituriez, Spontaneous contractility- mediated cortical flow generates cell migration in three- dimensional environments, Biophysical journal 101, 1041 (2011)
2011
-
[39]
C. A. Wilson, M. A. Tsuchida, G. M. Allen, E. L. Barn- hart, K. T. Applegate, P. T. Yam, L. Ji, K. Keren, G. Danuser, and J. A. Theriot, Myosin ii contributes to cell-scale actin network treadmilling through network dis- assembly, Nature 465, 373 (2010)
2010
-
[40]
Jurado, J
C. Jurado, J. R. Haserick, and J. Lee, Slipping or grip- ping? fluorescent speckle microscopy in fish keratocytes reveals two different mechanisms for generating a retro- grade flow of actin, Molecular biology of the cell 16, 507 (2005)
2005
-
[41]
Cadart, E
C. Cadart, E. Zlotek-Zlotkiewicz, L. Venkova, O. Thou- venin, V. Racine, M. L. Berre, S. Monnier, and M. Piel, Fluorescence exclusion measurement of volume in live cells, Methods in Cell Biology 139, 103 (2017)
2017
-
[42]
Rollin, J.-F
R. Rollin, J.-F. Joanny, and P. Sens, Cell size scaling laws: a unified theory, bioRxiv 10.1101/2022.08.01.502021 (2022)
2022 doi
-
[43]
Deviri and S
D. Deviri and S. Safran, Balance of osmotic pressures de- termines the volume of the nucleus, Biophysical Journal 121, 496a (2022)
2022
Reviewed August 7, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.