An official website of the United States government
Eukaryotic cells in living tissues form dynamic patterns with spatially varying orientational order that affects important physiological processes such as apoptosis and cell migration. The challenge is how to impart a predesigned map of orientational order onto a growing tissue. Here, we demonstrate an approach to produce cell monolayers of human dermal fibroblasts with predesigned orientational patterns and topological defects using a photoaligned liquid crystal elastomer (LCE) that swells anisotropically in an aqueous medium. The patterns inscribed into the LCE are replicated by the tissue monolayer and cause a strong spatial variation of cells phenotype, their surface density, and number density fluctuations. Unbinding dynamics of defect pairs intrinsic to active matter is suppressed by anisotropic surface anchoring allowing the estimation of the elastic characteristics of the tissues. The demonstrated patterned LCE approach has potential to control the collective behavior of cells in living tissues, cell differentiation, and tissue morphogenesis.
more »
« less
Migration and division in cell monolayers on substrates with topological defects
Collective movement and organization of cell monolayers are important for wound healing and tissue development. Recent experiments highlighted the importance of liquid crystal order within these layers, suggesting that +1 topological defects have a role in organizing tissue morphogenesis. We study fibroblast organization, motion, and proliferation on a substrate with micron-sized ridges that induce +1 and −1 topological defects using simulation and experiment. We model cells as self-propelled deformable ellipses that interact via a Gay–Berne potential. Unlike earlier work on other cell types, we see that density variation near defects is not explained by collective migration. We propose instead that fibroblasts have different division rates depending on their area and aspect ratio. This model captures key features of our previous experiments: the alignment quality worsens at high cell density and, at the center of the +1 defects, cells can adopt either highly anisotropic or primarily isotropic morphologies. Experiments performed with different ridge heights confirm a prediction of this model: Suppressing migration across ridges promotes higher cell density at the +1 defect. Our work enables a mechanism for tissue patterning using topological defects without relying on cell migration.
more »
« less
- Award ID(s):
- 1915491
- PAR ID:
- 10565200
- Publisher / Repository:
- National Academy of Sciences USA
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 120
- Issue:
- 30
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)We investigated an in vitro model for mesothelial clearance, wherein ovarian cancer cells invade into a layer of mesothelial cells, resulting in mesothelial retraction combined with cancer cell disaggregation and spreading. Prior to the addition of tumor cells, the mesothelial cells had an elongated morphology, causing them to align with their neighbors into well-ordered domains. Flaws in this alignment, which occur at topological defects, have been associated with altered cell density, motion, and forces. Here we identified topological defects in the mesothelial layer, and showed how they affected local cell density by producing a net flow of cells inward or outward, depending on defect type. At locations of net inward flow, mesothelial clearance was impeded. Hence, the collective behavior of the mesothelial cells, as governed by the topological defects, affected tumor cell clearance and spreading. Importantly, our findings were consistent across multiple ovarian cancer cell types, suggesting a new physical mechanism that could impact ovarian cancer metastasis.more » « less
-
Bergstralh, D (Ed.)Abstract Collective cell migration is critical to embryonic development, wound healing, and the immune response, but also drives tumor dissemination. Understanding how cell collectives coordinate migration in vivo has been a challenge, with potential therapeutic benefits that range from addressing developmental defects to designing targeted cancer treatments. The small GTPase Rap1 has emerged as a regulator of both embryogenesis and cancer cell migration. How active Rap1 coordinates downstream signaling functions required for coordinated collective migration is poorly understood. Drosophila border cells undergo a stereotyped and genetically tractable in vivo migration within the developing egg chamber of the ovary. This group of 6–8 cells migrates through a densely packed tissue microenvironment and serves as an excellent model for collective cell migration during development and disease. Rap1, like all small GTPases, has distinct activity state switches that link extracellular signals to organized cell behaviors. Proper regulation of Rap1 activity is essential for successful border cell migration yet the signaling partners and other downstream effectors are poorly characterized. Using the known requirement for Rap1 in border cell migration, we conducted a dominant suppressor screen for genes whose heterozygous loss modifies the migration defects observed upon constitutively active Rap1V12 expression. Here, we identified 7 genomic regions on the X chromosome that interact with Rap1V12. We mapped three genomic regions to single Rap1-interacting genes, frizzled 4, Ubiquitin-specific protease 16/45, and strawberry notch. Thus, this unbiased screening approach identified multiple new candidate regulators of Rap1 activity with roles in collective border cell migration.more » « less
-
Cell migration is critical throughout a multicellular organism’s life from embryogenesis to immune response and tissue repair and can even go aberrantly wrong in diseases like metastatic cancer. In vitro, graded concentrations of diffusible chemoattractants can guide migrating cells, but less is known about chemoattractant distribution and chemotaxis within living organisms, which have complex tissue geometries. Using the border cells, which migrate collectively in the Drosophila egg chamber during oogenesis, we studied how tissue structure affects chemotaxis in vivo. Live-imaged border cells exhibited variations in their chemotactic migration, which correlated positionally within distinct tissue architectures, specifically acellular gaps at cell-cell intersections. To determine how different regions in the egg chamber’s geometry affect chemical cues, we developed a partial differential equation (PDE) model of chemoattractant distribution within a relevant in silico domain. Using a hybrid mathematical model that couples the chemoattractant PDE and an agent-based motion of the cluster, we found that larger extracellular volumes within intersections could locally dampen chemoattractant gradient magnitudes and slow cluster speed in simulations. In vivo, in response to genetically increasing the levels of a chemoattractant, PDGF- and VEGF-related factor 1, border cells exhibited delayed migration and behaved differently within specific architectural regions, consistent with results in silico. We next altered the architectural regions in the migration domain in half pint (hfp) mutant egg chambers and observed migration behaviors that still correlated with tissue features. Importantly, the abnormal tissue geometry was sufficient to rescue defects due to high levels of chemoattractant and resulted in punctual border cell migration indicating chemoattractant distribution can depend on tissue structure. Our modeling data indicate that chemoattractants are more concentrated in certain tissue architectures and dispersed in other regions, likely informing cell migration speeds and favoring clustered cell movements in tissue that contain varied architectures in vivo. Our results shed light on the intricate interplay between tissue geometry and the local distribution of important signaling molecules in orchestrating the essential process of cell migration.more » « less
-
Abstract Cells move in collective groups in biological processes such as wound healing, morphogenesis, and cancer metastasis. How active cell forces produce the motion in collective cell migration is still unclear. Many theoretical models have been introduced to elucidate the relationship between the cell’s active forces and different observations about the collective motion such as collective swirls, oscillations, and rearrangements. Though many models share the common feature of balancing forces in the cell layer, the specific relationships between force and motion vary among the different models, which can lead to different conclusions. Simultaneous experimental measurements of force and motion can aid in testing assumptions and predictions of the theoretical models. Here, we provide time-lapse images of cells in 1 mm circular islands, which are used to compute cell velocities, cell-substrate tractions, and monolayer stresses. Additional data are included from experiments that perturbed cell number density and actomyosin contractility. We expect this data set to be useful to researchers interested in force and motion in collective cell migration.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2301197120
