RESEARCH | Matej Krajnc

computational methods in tissue mechanics

We develop computational methods for studying the mechanics of tissues. One such method is the Graph vertex model (GVM), which stores the topology of the network of cell-cell junctions into a knowledge graph. Upon cell-rearrangement events, the knowledge graph gets locally transformed by well-defined graph transformations that are straight-forward to implement

RELATED PUBLICATIONS

T. Sarkar and M. Krajnc, Graph topological transformations in space-filling cell aggregates, https://arxiv.org/abs/2309.04818.

active dynamics of cell-cell junctions

(top) A schematic of the interplay between the elastic restoring force and active tension generated by the junctional myosin is shown. (bottom) The feedback loop between junctional contraction and tension is shown.

We develop theoretical models of the viscoelasticity and active dynamics of cell-cell interfaces so as to better understand active in-plane remodelling during morphogenesis and tissue repair. We study how active forces, generated at the cell-cortex level, drive cell-junction remodeling and how these dynamics are affected by the collective cell mechanics.

RELATED PUBLICATIONS

M. Krajnc, T. Stern, and C. Zankoc, Active instability and nonlinear dynamics of cell-cell junctions, Phys. Rev. Lett. 127, 198103 (2021).
C. Zankoc and M. Krajnc, Elasticity, Stability and Quasioscillations of Cell-Cell Junctions in Solid Confluent Epithelia, Biophys. J. 119, 1706 (2020).
M. Krajnc, Solid-fluid transition and cell sorting in epithelia with junctional tension fluctuations, Soft Matter 16, 3209 (2020).
M. Krajnc, S. Dasgupta, P. Ziherl, and J. Prost, Fluidization of epithelial sheets by active cell rearrangements, Phys. Rev. E 98, 022409 (2018).

mechanics of tissue folding and wrinkling

Schematic cross section of three epithelial waveforms in the discrete representation and the continuous waveform. Gray shading denotes the transition from the discrete to the continuum description.

We study physical mechanisms that govern the formation of three dimensional shape in epithelial monolayers focusing on the effects of finite thickness and the associated apico-basal surface-tension asymmetries. We are interested in minimal physical models that can explain the formation of nontrivial shapes such as wrinkles and folds.

RELATED PUBLICATIONS

U. Andrenšek, P. Ziherl, and M. Krajnc, Wrinkling instability in unsupported epithelial sheets, Phys. Rev. Lett. 130, 198401 (2023)
J. Rozman, M. Krajnc, and P. Ziherl, Morphologies of compressed active epithelial monolayers, Eur. Phys. J. E 44, 99 (2021).
J. Rozman, M. Krajnc, and P. Ziherl, Collective cell mechanics of epithelial sheets with organoid-like morphologies, Nat. Commun. 11, 3805 (2020).
N. Štorgel, M. Krajnc, P. Mrak, J. Štrus, and P. Ziherl, Quantitative morphology of epithelial folds, Biophys. J. 110, 269 (2016).
M. Rauzi, U. Krzic, T. E. Saunders, M. Krajnc, P. Ziherl, L. Hufnagel, and M. Leptin, Embryo-scale tissue mechanics during gastrulation movements, Nat. Commun. 6, 8677 (2015).

mechanics of tumor growth

Basal cell carcinoma (left) and squamous cell carcinoma (right) in mouse embryos.

We study physical mechanisms that govern shape transformation in malignant tissues. We are particularly interested in how a growing tumor mechanically interacts with healthy cells so as to form differently shaped lesions.

RELATED PUBLICATIONS

V. Fiore, M. Krajnc, F. G. Quiroz, J. Levorse, H. A. Pasolli, S. Y. Shvartsman, and E. Fuchs, Mechanics of a multilayer epithelium instruct tumour architecture and function, Nature 585, 433 (2020).