Abstract
Multipolar spindles are very rare in normal tissues, but they are much more prevalent in many tumors, which might be induced by the mechanical confinements from overcrowding microenvironments in tumors. However, little is known about what the difference is between various forms of mechanical confinements that cells encounter in normal tissues and tumor tissues, and how they affect multipolarity and chromosome segregation fidelity. Here, we use microchannels with different heights and widths to mimic diverse forms and degrees of mechanical constraints within the tissue architecture. We find that multipolar spindles occur frequently under two-wall confinement but that they are rare under four-wall confinement, suggesting that multipolar-spindle assembly depends on the form of the three-dimensional mechanical confinement. We reveal that two-wall confinement leads to an increased fraction of multipolar spindles by pole splitting, while four-wall confinement restrains multipolarity by the enhancement of pole clustering and the inhibition of pole splitting. We further conduct numerical simulations and develop a theoretical model to investigate how mechanical confinement influences pole splitting and clustering. By exploring the energy landscape of pole-pole interactions and pole-cortex interactions and treating pole splitting and clustering as reversible reactions, we demonstrate that mechanical confinement controls cell shape and pole-cortex interactions, which, in turn, change the energy barriers of pole splitting and clustering as well as the probability of multipolar mitosis. Further experiments confirm the theoretical prediction that the pole-cortex interaction determines the probability of the multipolar spindles under various mechanical confinements. Our findings demonstrate the extent to which extracellular microenvironments and tissue architecture can affect complex cellular behaviors, indicating that normal tissue architecture may have the ability to suppress the progress of cancers. Thus, our findings would provide essential cues for cancer therapies targeting the tumor microenvironment.
6 More- Received 15 March 2022
- Revised 30 November 2022
- Accepted 26 January 2023
DOI:https://doi.org/10.1103/PhysRevX.13.011036
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Focus
Four Walls Good, Two Walls Bad for Confined Cells
Published 10 March 2023
Segregation of chromosomes in dividing cells can be disrupted if the cells are constrained by their surroundings.
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Popular Summary
All living organisms are products of continuous cell division. The bipolar spindle configuration of mitosis is an essential mechanism for the division and segmentation of chromosomes into the two daughter cells. Compared to normal tissues, many tumor tissues display much more multipolar mitosis, which may be induced by the highly crowded microenvironment that cancer cells encounter. However, little is known about the difference between various forms of mechanical confinements that cells encounter in normal tissues and tumor tissues, and how they affect multipolarity and chromosome segregation fidelity. Here, we show that confinement on two opposing sides encourages multipolarity while confinement on four sides inhibits it.
In our experiments, we grow cells in microchannels fabricated with various heights and widths to simulate different forms of mechanical confinement. Among unconstrained cells, about 12% exhibit multipolar spindles—a frequency that leaps as high as 60% under two-wall confinement. When constrained by four walls, the frequency falls to as low as 4%—much lower than even the free cells. We find that pole splitting and clustering can be regarded as reversible chemical reactions, and the mechanical confinement controls cell shape and pole-cortex interaction that in turn changes the energy barriers of pole splitting and clustering as well as the probability of multipolar mitosis.
The opposite consequences of two-wall and four-wall confinements indicate the sensitivity of cell behaviors to mechanical constraints from the extracellular microenvironment, implying that context matters. Our research provides insights into how extracellular microenvironments regulate cellular behaviors and may help with cancer diagnosis and therapies targeting the tumor microenvironment.