Biology subjects

Holle, A.

Publications and source records attributed to Holle, A..

4 recordsLinked to original sources

bioRxiv2026

A confining microfluidic platform for disparate density coculture reveals the dynamics of macrophage-mediated adipocyte clearance

Co-culturing cells with mismatched densities, where one cell type adheres to surfaces while the other floats, represents a fundamental challenge in cell biology. This is particularly evident in studying macrophage-adipocyte interactions, where macrophages must engage and clear lipid-rich apoptotic adipocytes, a process critical to understanding chronic inflammation in obesity and metabolic disease. The density disparity between macrophages, which sink and adhere to culture surfaces, and adipocytes, which float due to their lipid content, has prevented conventional co-culture approaches from achieving sustained cell-cell contact. To address this challenge, we developed a microfluidic system that confines adipocytes and lipid droplets in close proximity to macrophages. This platform features recessed micro-traps within the upper surface of a microfluidic chamber that trap buoyant objects while allowing media exchange and delivery of reagents for live-cell and immunofluorescence imaging. Time lapse imaging revealed that the dynamic process of macrophages-dead corpse interactions, showing that individual macrophages cannot engulf entire corpses but instead mechanically deform them. Furthermore, the platform successfully recapitulates the formation of Crown-Like Structures (CLS), clusters of macrophages surrounding dead adipocytes that are hallmarks of adipose tissue inflammation. Long-term culture revealed that CLS effectively clear lipids compared to partial macrophage engagement, providing mechanistic insights that were previously unattainable with standard histological approaches. Beyond the macrophage-lipid interaction, this platform has potential for studying interactions between adherent cells and buoyant targets, such as microplastics, opening new avenues for research where density mismatch poses a major barrier.

bioengineering↗

bioRxiv2026

Nondimensional nucleus shape parameters reveal mechanostasis during confined migration

Nucleus shape is a sensitive indicator of cell state, influenced by numerous bio-chemical and physiological factors. While prior work has cataloged how perturbations alter nucleus morphology, we address the inverse: inferring underlying molecular changes from nucleus shape alone. We previously developed a mechanical model yielding two nondimensional parameters: flatness index and scale factor, which are surrogate measures for cortical actin tension and nuclear envelope compliance respectively. In this study, we apply these parameters to investigate the dynamics in cellular mechanics during confined migration. We fabricated polydimethylsiloxane (PDMS) microchannels with widths of 3 {micro}m (high confinement) and 10 {micro}m (low confinement) and tracked cells migrating through them. We captured high-frequency 3D nucleus shapes via double fluorescence exclusion microscopy and custom image analysis. Fitting the model and estimating flatness index and scale factor to time-resolved shapes revealed dynamic regulation in 3 {micro}m channels: actin tension decreased and nucleus compliance increased immediately before nucleus entry into the constriction, with rapid restoration to baseline upon exit. No such changes occurred in 10 {micro}m channels, indicating active, confinement-dependent cytoskeletal adaptation. Immunostaining for YAP and lamin-A,C confirmed these model inferences. Our results uncover mechanostasis, active mechanical homeostasis, during confined migration and establish the combination of double fluorescence exclusion microscopy and nondimensional nucleus shape parameters as a powerful, non-invasive tool for single-cell mechanobiology studies.

biophysics↗

bioRxiv2025

Mechanical Memory Primes Cells for Confined Migration

When migratory cells move from one stiffness niche to another in vivo, they are exposed to highly confined spaces imposed by dense extracellular matrix (ECM) networks and inter-tissue boundaries. Cells that originate from one niche possess distinct mechanosensitive adaptations that influence their response to their new niche, a concept known as mechanical memory. However, the mechanisms by which this memory is acquired, and the degree to which it influences migratory potential and decision-making processes in confinement remain poorly understood. Here, we combine stiffness priming using polyacrylamide hydrogels with a confinement platform to screen mechanical memory across healthy and transformed cells. Using a dose-and- passage approach, we find that in stiffness-sensitive cells primed on soft substrates navigate confinement more efficiently. Bulk RNA sequencing identifies NFATC2 as a transcription factor that mediates mechanical memory by reprogramming gene expression in stiffness-sensitive cells. siRNA-induced knockdown of NFATC2 in memory-sensitive cells confirmed its necessity for mechanical memory acquisition and subsequent confined migration enhancement. Interestingly, highly invasive cancer cells exhibit minimal sensitivity to prior mechanical priming, suggesting differential adaptation strategies. These findings reveal mechanical memory as a cell-intrinsic property shaped by past mechanical environments and highlight potential implications for controlling migration in wound repair, fibrosis, and disease progression.

cell biology↗

bioRxiv2025

TRPM7 Annexin A1 Mechanosensitive Pathway Drives Capillary Infiltration by Circulating Tumor Cells

Successful metastatic dissemination requires tumor cells to overcome significant physical barriers. When circulating tumor cells (CTCs) become lodged in capillary beds, studies reveal that only a small subset can adapt to fluid shear stress (FSS) within the constricted vasculature. These rare, mechanically resilient cells may subsequently extravasate and form metastatic lesions, but details on this adaptation of the physical environment and its molecular basis are not well understood. Utilizing a microfluidics platform that mimics microcirculatory dynamics, we discover that only breast cancer cells with high metastatic potential maintain directional migration under physiologically relevant FSS conditions. This highlights the mechanical selection process of metastatic precursors during hematogenous dissemination. We identify the TRPM7-Annexin A1-actin signaling pathway as essential for overcoming physical barriers and regulating cell motility under capillary FSS. FSS prompts cytoskeletal reorganization and actin disassembly, restricting cell movement. Cancer cells respond to this by increasing mechanical loading, activating TRPM7 and triggering calcium influx, which then activates Annexin A1. This calcium-dependent protein, Annexin A1, interacts with the actin cortex to prevent FSS-induced actin disassembly, thus aiding migration. Experiments conducted in mouse liver capillaries validate the critical role of this pathway in cancer cell motility. Additionally, we propose a mechano-pharmacological strategy using FTY720 to target the TRPM7 pathway, highlighting its therapeutic potential to modify CTC receptor specificity and inhibit distant metastasis.

cancer biology↗