bims-ecemfi 2024-09-29 papers

EMBO Rep. 2024 Sep 27.

Robust tissue pattern formation by coupling morphogen signal and cell adhesion.

Kosuke Mizuno, Tsuyoshi Hirashima, Satoshi Toda.

Morphogens, locally produced signaling molecules, form a concentration gradient to guide tissue patterning. Tissue patterns emerge as a collaboration between morphogen diffusion and responsive cell behaviors, but the mechanisms through which diffusing morphogens define precise spatial patterns amidst biological fluctuations remain unclear. To investigate how cells respond to diffusing proteins to generate tissue patterns, we develop SYMPLE3D, a 3D culture platform. By engineering gene expression responsive to artificial morphogens, we observe that coupling morphogen signals with cadherin-based adhesion is sufficient to convert a morphogen gradient into distinct tissue domains. Morphogen-induced cadherins gather activated cells into a single domain, removing ectopically activated cells. In addition, we reveal a switch-like induction of cadherin-mediated compaction and cell mixing, homogenizing activated cells within the morphogen gradient to form a uniformly activated domain with a sharp boundary. These findings highlight the cooperation between morphogen gradients and cell adhesion in robust tissue patterning and introduce a novel method for tissue engineering to develop new tissue domains in organoids.

Keywords: Cadherin; Cell Adhesion; Morphogen; Pattern Formation; Synthetic Biology

DOI: https://doi.org/10.1038/s44319-024-00261-z

Proc Natl Acad Sci U S A. 2024 Oct;121(40): e2319310121

Intercellular friction and motility drive orientational order in cell monolayers.

Michael Chiang, Austin Hopkins, Benjamin Loewe, M Cristina Marchetti, Davide Marenduzzo.

Spatiotemporal patterns in multicellular systems are important to understanding tissue dynamics, for instance, during embryonic development and disease. Here, we use a multiphase field model to study numerically the behavior of a near-confluent monolayer of deformable cells with intercellular friction. Varying friction and cell motility drives a solid-liquid transition, and near the transition boundary, we find the emergence of local nematic order of cell deformation driven by shear-aligning cellular flows. Intercellular friction contributes to the monolayer's viscosity, which significantly increases the spatial correlation in the flow and, concomitantly, the extent of nematic order. We also show that local hexatic and nematic order are tightly coupled and propose a mechanical-geometric model for the colocalization of [Formula: see text] nematic defects and 5-7 disclination pairs, which are the structural defects in the hexatic phase. Such topological defects coincide with regions of high cell-cell overlap, suggesting that they may mediate cellular extrusion from the monolayer, as found experimentally. Our results delineate a mechanical basis for the recent observation of nematic and hexatic order in multicellular collectives in experiments and simulations and pinpoint a generic pathway to couple topological and physical effects in these systems.

Keywords: cellular extrusion; intercellular friction; nematic and hexatic order; solid–liquid transition; topological defects

DOI: https://doi.org/10.1073/pnas.2319310121

bioRxiv. 2024 Sep 15. pii: 2024.08.27.609782. [Epub ahead of print]

SCRATCH: A programmable, open-hardware, benchtop robot that automatically scratches cultured tissues to investigate cell migration, healing, and tissue sculpting.

Yubin Lin, Alexander Silverman-Dultz, Madeline Bailey, Daniel J Cohen.

Despite the widespread popularity of the ' scratch assay', where a pipette is dragged through cultured tissue to create an injury gap to study cell migration and healing, the manual nature of the assay carries significant drawbacks. So much of the process depends on individual manual technique, which can complicate quantification, reduce throughput, and limit the versatility and reproducibility of the approach. Here, we present a truly open-source, low-cost, accessible, and robotic scratching platform that addresses all of the core issues. Compatible with nearly all standard cell culture dishes and usable directly in a sterile culture hood, our robot makes highly reproducible scratches in a variety of complex cultured tissues with high throughput. Moreover, we demonstrate how scratching can be programmed to precisely remove areas of tissue to sculpt arbitrary tissue and wound shapes, as well as enable truly complex co-culture experiments. This system significantly improves the usefulness of the conventional scratch assay, and opens up new possibilities in complex tissue engineering and cell biological assays for realistic wound healing and migration research.

DOI: https://doi.org/10.1101/2024.08.27.609782

Langmuir. 2024 Sep 20.

Adhesion Mechanics and Detachment Dynamics of Vanishing Surface Layers on Hydrogels.

Md Mahmudul Hasan, Alison C Dunn.

Cross-linked hydrogel surfaces exhibit reduced stiffness when polymerized against polymeric hydrophobic surfaces. As such, these layers play a critical role in contact mechanics, particularly exhibiting strong relative adhesion with colloidal probes when the contact area is small. This prevents the use of continuum models of adhesive soft contact. To connect mechanisms of stretch to the force response, depth-controlled nanoindentation experiments were conducted on polyacrylamide (pAAM) hydrogel samples using colloidal probe atomic force microscopy (AFM). The pAAM sample had a high water content of >90% and was molded against polyoxymethylene (POM) to create a more dilute surface layer with thickness ∼0.5 μm. Indentations to multiple depths between 50 nm and 1.25 μm were repeated 10 times each. First, the force drops during the unloading, and separation segments of each indentation were characterized. This described the detachment progression for increasing areas of contact, revealing that the pull-off force for a single chain was in the single-pN range. Second, the stretched polymer network was modeled as an array of parallel, linear springs. Assuming a constant areal chain density of α = 100 chains/μm2, the maximum force of adhesion was plotted versus the volume of chains stretched upward, and the average chain stiffness was calculated from a linear fit to be 22.8 × 10-6 N/m. A Weibull distribution analysis of detachment events revealed a dependence of chain stiffness on maximum indentation depth (dmax), with higher stiffness at shallower depths approaching kchain ≈ 20 × 10-6 N/m. These findings on adhesion mechanics between a vanishing hydrogel surface and probe can guide the development of multifunctional hydrogels for various biomedical applications.

DOI: https://doi.org/10.1021/acs.langmuir.4c01740

Biomater Sci. 2024 Sep 27.

Influence of viscosity on adipogenic and osteogenic differentiation of mesenchymal stem cells during 2D culture.

Chengyu Lu, Tianjiao Zeng, Man Wang, Toru Yoshitomi, Naoki Kawazoe, Yingnan Yang, Guoping Chen.

Accumulatively, cellular behaviours triggered by biochemical cues have been widely explored and the focus of research is gradually shifting to biophysical cues. Compared to physical parameters such as stiffness, substrate morphology and viscoelasticity, the influence of viscosity on cellular behaviours is relatively unexplored and overlooked. Thus, in this study, the influence of viscosity on the adipogenic and osteogenic differentiation of human mesenchymal stem cells (hMSCs) was investigated by adjusting the viscosity of the culture medium. Viscosity exhibited different effects on adipogenic and osteogenic differentiation of hMSCs during two-dimensional (2D) culture. High viscosity facilitated osteogenic while inhibiting adipogenic differentiation. During adipogenic differentiation, the effect of viscosity on cell proliferation was negligible. However, during osteogenic differentiation, high viscosity decreased cell proliferation. The different influence of viscosity could be explained by the activation of mechanotransduction regulators of Yes-associated protein (YAP) and β-catenin. High viscosity could promote YAP and β-catenin nuclear translocation during osteogenic differentiation, which was responsible for the increased osteogenesis. High viscosity inhibited adipogenesis through promoting YAP nuclear translocation. This study could broaden the understanding of how viscosity can affect stem cell differentiation during 2D culture, which is valuable for tissue engineering.

DOI: https://doi.org/10.1039/d4bm00710g