Biology subjects

Leggett, S. E.

Publications and source records attributed to Leggett, S. E..

5 recordsLinked to original sources

bioRxiv2026

Partial EMT Drives Persistent Collective Migration via Collision Guidance in Heterogeneous Populations

The epithelial-mesenchymal transition (EMT) alters cell-cell interactions to facilitate collective or individual migration during embryonic development, wound repair, or tumor invasion. Epithelial cells are typically cohesive and stationary while mesenchymal cells are individually dispersed and motile. Additional "partial" EMT states are thought to occur with distinct adhesive and migratory behaviors, but these functional phenotypes are poorly understood. Here, we show that cells treated with moderate TGF-{beta} concentration exhibit collective migration that is fast and directionally persistent despite heterogeneity in epithelial, partial, and mesenchymal states. We find cells coordinate their motility by reorienting in similar directions after transient contacts, a distinct "collision guidance" mechanism that differs from epithelial arrest or mesenchymal repulsion. Moreover, partial EMT cells sustain collision guidance when interacting with epithelial or mesenchymal cells, which otherwise have increased tendency to repel. We corroborate these experimental observations with a computational model using self-propelled interacting particles that align their motion or repel upon contact. Finally, we show that partial EMT enables tissue monolayer fronts to overwhelm and displace monolayers of other cell types after collision. Overall, these results reveal that partial EMT promotes coherent and emergent behaviors that bridge from cell to tissue length scales, with potential implications for shaping epithelial tissue formation, regeneration, or disorganization.

biophysics↗

bioRxiv2026

Endocytosis shapes extracellular chemical gradients in autonomous cell-cell attraction

Receptor-mediated ligand endocytosis is traditionally viewed as a negative feedback mechanism for signal attenuation. Here we show that ligand removal can paradoxically enhance directional information in autonomous cell-cell attraction. Many cell systems migrate toward one another in the absence of externally imposed gradients, implying that secretion, diffusion, and uptake must themselves generate usable directional cues. We develop a surface-resolved theory of a finite-sized detector exposed to a nearby source and derive analytical expressions for the steady-state ligand field. The resulting concentration profiles are governed by a single dimensionless Damkohler number that compares receptor-mediated endocytosis to diffusive ligand transport. Increasing ligand removal lowers extracellular ligand concentrations and reduces absolute concentration differences across the detector surface, but preferentially enhances relative surface anisotropy. Thus, destroying the signal can increase the usable information encoded in relative gradients. Incorporating nonlinear downstream processing reveals a tradeoff between contrast enhancement and signal depletion that yields a well-defined optimal endocytosis rate, in a regime consistent with experimentally measured receptor internalization kinetics. These results recast receptor-mediated endocytosis as an extracellular information-processing mechanism that reshapes self-generated gradients to enhance directional information.

biophysics↗

bioRxiv2025

High-fat circulating nutrients promote growth and invasion in a 3D microfluidic tumor model of triple-negative breast cancer

Diet influences the levels of small molecules that circulate in plasma and interstitial fluid, altering the biochemical composition of the tumor microenvironment (TME). These circulating nutrients have been associated with how tumors grow and respond to treatment, but it remains difficult to parse their direct effects on cancer cells. Here, we combine a three-dimensional (3D) microfluidic tumor model with physiologically relevant culture media to investigate how concentrations of circulating nutrients influence tumor growth, cancer cell invasion, and overall tumor metabolism. Human triple-negative breast cancer cells cultured in 2D under media conditions mimicking five different dietary states show no observable differences in proliferation or morphology. Nonetheless, those exposed to high-fat conditions exhibit increased metabolic activity and upregulate genes associated with motility and extracellular matrix remodeling. In the 3D microfluidic model, high-fat conditions accelerate tumor growth and invasion and induce the formation of hollow cavities. Surprisingly, the presence of these cavities does not correlate with an increase in apoptosis or ferroptosis. Instead, RNA-sequencing analysis revealed that high-fat conditions induce the expression of MMP1, consistent with cavitation via cell invasion. Mimicking the flow of circulating nutrients within the TME can thus be used to identify novel connections between metabolic states and tumor phenotype.

bioengineering↗

bioRxiv2025

3D Printed Molds for Organ-on-a-Chip and Fluidics: PDMS-Based Rapid and Accessible Prototyping

The ability to rapidly fabricate custom polydimethylsiloxane (PDMS) devices is central to advancing organ-on-a-chip (OoC) technologies and other biological microplatforms. However, traditional photolithography and the surface roughness of directly 3D printed molds limit their accessibility and scalability of PDMS-based systems. Photolithographic workflows are limited by their dependence on specialized equipment, technical expertise, dedicated fabrication infrastructure, and are typically restricted to planar geometries and microscale features, limiting their use for millifluidic or complex 3D device features. To address these challenges, we present a modular workflow for the robust fabrication of PDMS-based devices using stereolithography (SLA) or fused deposition modeling (FDM) printing combined with optimized epoxy coatings. Acetone-thinned epoxy formulations dramatically improve SLA printed mold smoothness, eliminate tearing during demolding, and yield PDMS replicas with clean, well-defined structural features. For FDM printed molds, a two-step epoxy coating strategy restores mold quality sufficient for robust replica molding. The resulting PDMS devices support irreversible glass bonding, fluid containment, and cell culture applications, validated using normal mammary epithelial and cancer cell lines. We further demonstrate the formation of perfusable tissue aggregates within 3D matrices and introduce a low-cost 3D printed imaging platform for parallel live-cell imaging across four PDMS devices, showcasing its use for monitoring 20 OoC channels under gravity- or pump-driven flow. This versatile and reproducible method lowers the barrier to entry for soft lithography, allowing researchers without prior microfabrication expertise to rapidly prototype functional PDMS devices for diverse biological applications. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/645830v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@bbf403org.highwire.dtl.DTLVardef@191249forg.highwire.dtl.DTLVardef@1fb7bf2org.highwire.dtl.DTLVardef@1865e4c_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2019

Mechanophenotyping of 3D Multicellular Clusters using Displacement Arrays of Rendered Tractions

Epithelial tissues mechanically deform the surrounding extracellular matrix during embryonic development, wound repair, and tumor invasion. Ex vivo measurements of such multicellular tractions within three-dimensional (3D) biomaterials could elucidate collective dissemination during disease progression, and enable preclinical testing of targeted anti-migration therapies. However, past 3D traction measurements have been low throughput due to the challenges of imaging and analyzing information-rich 3D material deformations. Here, we demonstrate a method to profile multicellular clusters in a 96-well plate format based on spatially heterogeneous contractile, protrusive, and circumferential tractions. As a case study, we profile multicellular clusters across varying states of the epithelial-mesenchymal transition, revealing a successive loss of protrusive and circumferential tractions, as well as the formation of localized contractile tractions with elongated cluster morphologies. These cluster phenotypes were biochemically perturbed using drugs, biasing towards traction signatures of different epithelial or mesenchymal states. This higher-throughput analysis is promising to systematically interrogate and perturb aberrant mechanobiology, which could be utilized with human patient samples to guide personalized therapies.

bioengineering↗