Phase transitions in biology: from bird flocks to population dynamics

Heffern, Elleard F. W.; Huelskamp, Holly; Bahar, Sonya; Inglis, R. Fredrik

doi:10.1098/rspb.2021.1111

Cited by 17 publications

(11 citation statements)

References 106 publications

(148 reference statements)

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“…Few studies have highlighted the potential of local cell-cell mechanical interactions to coordinate global effects such as contraction of bulk gels [53] or tissue-level processes such as fibrosis expansion [62] or tissue folding [63]. Thus, interactions between a multitude of cells may lead to exciting collective and global effects [53], as inspired by other natural systems, such as the coherent movement of birds or fish, where forces in the medium induce synchronization in the global movement of the group members without direct contact between its members [64,65]. Here we took advantage of our system to precisely pattern multicell arrays in precise spacing.…”

Section: Discussionmentioning

confidence: 99%

Micropatterning the organization of multicellular structures in 3D biological hydrogels; insights into collective cellular mechanical interactions

Ergaz,

Goren,

Lesman

2023

Biofabrication

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Control over the organization of cells at the microscale level within supporting biomaterials can push forward the construction of complex tissue architectures for tissue engineering applications and enable fundamental studies of how tissue structure relates to its function. While cells patterning on 2D substrates is a relatively established and available procedure, micropatterning cells in biomimetic 3D hydrogels has been more challenging, especially with micro-scale resolution, and currently relies on sophisticated tools and protocols. We present a robust and accessible ‘peel-off’ method to micropattern large arrays of individual cells or cell-clusters of precise sizes in biological 3D hydrogels, such as fibrin and collagen gels, with control over cell–cell separation distance and neighboring cells position. We further demonstrate partial control over cell position in the z-dimension by stacking two layers in varying distances between the layers. To demonstrate the potential of the micropatterning gel platform, we study the matrix-mediated mechanical interaction between array of cells that are accurately separated in defined distances. A collective process of intense cell-generated densified bands emerging in the gel between near neighbors was identified, along which cells preferentially migrate, a process relevant to tissue morphogenesis. The presented 3D gel micropatterning method can be used to reveal fundamental morphogenetic processes, and to reconstruct any tissue geometry with micrometer resolution in 3D biomimetic gel environments, leveraging the engineering of tissues in complex architectures.

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Section: Discussionmentioning

confidence: 99%

Micropatterning the organization of multicellular structures in 3D biological hydrogels; insights into collective cellular mechanical interactions

Ergaz,

Goren,

Lesman

2023

Biofabrication

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“…changes coinciding with axonal excitation were interpreted and modeled as manifestations of sudden structural transformations, or phase transitions, in the axonal membrane and/or intimately associated parts of the cytoskeleton ( Fernandes de Lima and Hanke, 2016 ). Within this context, phase transitions, most simply defined as a shift of a system from one identifiable state of order to another elicited by, often subtle, changes in a so-called control parameter ( Heffern et al, 2021 ), offer an especially attractive explanatory concept as they are well known to be accompanied by drastic changes in the material properties of the system of interest (including changes in compressibility, conductance and heat storage), are induced by relatively small variations in external conditions (like, electrical field, temperature, pH, calcium ions) and, similar to action potentials, can appear as on/off switches ( Kuklin et al, 2020 ; Heimburg, 2023 ).…”

Section: The “Electricity Only” Based Conception Of the Nerve Signal:...mentioning

confidence: 99%

Thinking about the action potential: the nerve signal as a window to the physical principles guiding neuronal excitability

Drukarch,

Wilhelmus

2023

Front. Cell. Neurosci.

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Ever since the work of Edgar Adrian, the neuronal action potential has been considered as an electric signal, modeled and interpreted using concepts and theories lent from electronic engineering. Accordingly, the electric action potential, as the prime manifestation of neuronal excitability, serving processing and reliable “long distance” communication of the information contained in the signal, was defined as a non-linear, self-propagating, regenerative, wave of electrical activity that travels along the surface of nerve cells. Thus, in the ground-breaking theory and mathematical model of Hodgkin and Huxley (HH), linking Nernst’s treatment of the electrochemistry of semi-permeable membranes to the physical laws of electricity and Kelvin’s cable theory, the electrical characteristics of the action potential are presented as the result of the depolarization-induced, voltage- and time-dependent opening and closure of ion channels in the membrane allowing the passive flow of charge, particularly in the form of Na+ and K+ -ions, into and out of the neuronal cytoplasm along the respective electrochemical ion gradient. In the model, which treats the membrane as a capacitor and ion channels as resistors, these changes in ionic conductance across the membrane cause a sudden and transient alteration of the transmembrane potential, i.e., the action potential, which is then carried forward and spreads over long(er) distances by means of both active and passive conduction dependent on local current flow by diffusion of Na+ ion in the neuronal cytoplasm. However, although highly successful in predicting and explaining many of the electric characteristics of the action potential, the HH model, nevertheless cannot accommodate the various non-electrical physical manifestations (mechanical, thermal and optical changes) that accompany action potential propagation, and for which there is ample experimental evidence. As such, the electrical conception of neuronal excitability appears to be incomplete and alternatives, aiming to improve, extend or even replace it, have been sought for. Commonly misunderstood as to their basic premises and the physical principles they are built on, and mistakenly perceived as a threat to the generally acknowledged explanatory power of the “classical” HH framework, these attempts to present a more complete picture of neuronal physiology, have met with fierce opposition from mainstream neuroscience and, as a consequence, currently remain underdeveloped and insufficiently tested. Here we present our perspective that this may be an unfortunate state of affairs as these different biophysics-informed approaches to incorporate also non-electrical signs of the action potential into the modeling and explanation of the nerve signal, in our view, are well suited to foster a new, more complete and better integrated understanding of the (multi)physical nature of neuronal excitability and signal transport and, hence, of neuronal function. In doing so, we will emphasize attempts to derive the different physical manifestations of the action potential from one common, macroscopic thermodynamics-based, framework treating the multiphysics of the nerve signal as the inevitable result of the collective material, i.e., physico-chemical, properties of the lipid bilayer neuronal membrane (in particular, the axolemma) and/or the so-called ectoplasm or membrane skeleton consisting of cytoskeletal protein polymers, in particular, actin fibrils. Potential consequences for our view of action potential physiology and role in neuronal function are identified and discussed.

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“…The catastrophic change includes a discontinuity in a trajectory thus giving place to a first-order phase transition (Sardanyé s et al, 2018). A first-order phase transition displays a sudden, discontinuous change in the order parameter at the critical point (Heffern et al, 2021). Figure 1 displays such change.…”

Section: Qualitative Events In the Growth Dynamicsmentioning

confidence: 99%

A Hybrid Analytical Model of Growth Regulation in Animals

Stass¹

2022

IJB

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The aim of this study was to build and analyse a model of ontogenetic growth of animals. The model was built based on experimental data and field observations. The growth of pigs was modelled by a non-local hybrid technique. This technique treats time as a discrete variable. In this study the growth of pigs was modelled beginning the stage of the rapid growth up to the maximum weight. The growth was modelled as a dynamic system. It was shown that the trajectory of the growth is neither smooth nor continuous. The main theme in this study is transition to a new growth phenotype. There are two results in this study. At a certain point in animal's ontogeny the trajectory of the growth undergoes a first-order phase transition. In the next stage, during bifurcation, new trajectories of growth emerge; this sequence of events has a biological meaning. The emerged trajectories differ from the initial trajectory, and from each other in essence. In the model, one trajectory of the growth emerges instantly. For other growth trajectory to emerge it takes half a year. In a population of animals, it is a general situation. Individual animals can take on only one of the emerged trajectories. In this study, a two-stage process of a transition to a new ontogenetic trajectory or a new phenotype was revealed. The transition to the new growth phenotype is to consider as the model of the pattern of the systemic regulation of growth.

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Phase transitions in biology: from bird flocks to population dynamics

Cited by 17 publications

References 106 publications

Micropatterning the organization of multicellular structures in 3D biological hydrogels; insights into collective cellular mechanical interactions

Micropatterning the organization of multicellular structures in 3D biological hydrogels; insights into collective cellular mechanical interactions

Thinking about the action potential: the nerve signal as a window to the physical principles guiding neuronal excitability

A Hybrid Analytical Model of Growth Regulation in Animals

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