Biology subjects

Selhuber-Unkel, C.

Publications and source records attributed to Selhuber-Unkel, C..

7 recordsLinked to original sources

bioRxiv2026

Mechanophenotype of synovial fibroblasts correlates with patients' pathotypes and treatment response in Rheumatoid Arthritis

The mechanical features of synovial fibroblasts may encode clinically relevant information for the management of rheumatoid arthritis. Indeed, it remains poorly understood the links between cellular and microenvironment mechanics with patient stratification and therapeutic response. Here we show that combining organotypic synovial cultures with multimodal mechanophenotyping and transcriptomics identifies distinct ''soft'' and ''stiff'' fibroblast states. Healthy and rheumatoid arthritis fibroblasts were cultured in two or three dimensions (organotypic cell cultures), alone or with endothelial cells, and characterized by high-throughput nanoindentation, picobalance measurements, digital holographic microscopy, Brillouin microscopy and RNA sequencing. Three-dimensional culture reduced single-cell Young's modulus and total mass while increasing dry-mass surface density; endothelial co-culture increased fibroblast stiffness and the longitudinal modulus of intact organotypic cultures. Stiffness-based grouping revealed transcriptional programmes related to extracellular-matrix remodelling, cytoskeletal contractility, and TGF-beta, WNT, and Hippo signalling. Mapping these signatures to publicly available rheumatoid arthritis clinical transcriptomic datasets associated the ''stiff'' state with fibrotic and myeloid-fibrotic pathotypes and treatment-refractory programmes, whereas the ''soft'' state aligned with lymphoid pathotypes and rituximab- or tocilizumab-responsive programmes. These findings support mechanophenotype-associated transcriptional signatures as potential biomarkers for rheumatoid arthritis stratification.

biophysics↗

bioRxiv2026

Connecting adhesion dynamics and trail formation in malaria parasites by imaging the major surface antigens CSP and TRAP

Malaria infections are initiated by mosquito bites, during which Plasmodium sporozoites are injected into the host skin. Sporozoites migrate rapidly to find and enter blood capillaries and ultimately invade hepatocytes. Sporozoite migration and invasion is mediated by the transmembrane protein thrombospondin-related anonymous protein (TRAP), which links the extracellular substrate to the actomyosin complex powering gliding motility, while the abundant, GPI-anchored circumsporozoite protein (CSP) covers most of the parasite membrane and modulates adhesion. Both proteins are secreted onto the parasite surface and deposited in a membranous trail originating at the parasite rear. The surface dynamics of these essential sporozoite proteins and the mechanism of deposition, however, are not understood. Here, using orbital total internal reflection fluorescence microscopy (TIRF), we reveal the dynamics of TRAP adhesion site formation and disassembly as well as CSP and TRAP deposition rates. We find that TRAP assembles into distinct adhesion sites, which then undergo retrograde translocation as the sporozoite moves forward. Around half of the TRAP adhesins, together with CSP, remain associated in small membrane droplets on the substrate after the sporozoite has disengaged from the adhesion site. These droplets seem to originate from nanotubes, that presumably decay under high tension. Strikingly, we observe a change in actin filament accumulation if proteolytic cleavage of TRAP is inhibited, providing the first visual evidence for outside-in signaling in sporozoites. Our study reveals a relation between adhesion dynamics and trail formation in Plasmodium sporozoites that might also be relevant for other cell types.

cell biology↗

bioRxiv2026

Mechanotranscriptomic Profiling of Breast Cancer Cells Intravasated from Engineered Microtumors

Intravasation is the process by which cancer cells breach the physical boundaries of a primary tumor and enter blood or lymphatic vessels. In this work, MCF-7 breast cancer cells were cultured within polymer-based microcapsules (here referred to as artificial microtumors) to investigate the transcriptomic and morpho-mechanical changes occurring in cancer cells during their release from these matrices, mimicking in vitro the process of intravasation. Our results show that even confined and released cancer cells share approximately 95% of their global transcriptomic profiles, intravasation-like cells exhibited marked differences in the expression of pathogenic hallmarks, including pathways associated with cell proliferation, immunosurveillance, and dormancy. Notably, a clear upregulation of YAP/TAZ signaling was observed in released cells, a result further supported by single-cell traction force microscopy assays, demonstrating that those cells exhibit higher biomechanical activity compared to cells located within artificial microtumors or those cultured on conventional 2D flasks, as shown for intravasated cells in vivo. To further enrich our investigation, the mechanotranscriptomic activity of MCF-7 cells was compared with suspended spheroids cultured on non-adherent surfaces (i.e., agarose hydrogels). Our results show that released cells displayed increased biomechanical activity and elevated expression of malignant markers, indicating that mechanical stress, beyond cell-cell contact alone, is required to trigger malignant responses. These observations were further supported by co-culture studies of MCF-7 cells with human fibroblasts and endothelial cells, which showed reduced proliferative and invasive capacities under confinement. Overall, our findings demonstrate that shifts in mechanical and metabolic stress, as experienced during intravasation, act as critical stimuli driving mechanotranscriptomic programs associated with cancer progression.

cancer biology↗

bioRxiv2025

Model of integrin binding as a function of light-induced variations in forces exerted on cells via RGD-terminated, photoswitchable azobenzene surfaces

Photo-responsive biomaterials are attractive because of the ability to non-invasively alter and control the material properties, thus allowing control over the cell response at the interface with the bioamaterial surface. While in silico mathematical models have been implemented for simulating single-cell force spectroscopy (SCFS) experiments on static and some dynamic biomaterials, these models have yet to be extended to light-responsive biointerfaces. So here, we develop a mathematical model that describes and predicts the strength of integrin-mediated cell adhesions to a photoswitchable biomaterial surface. The fluctuating biomaterial comprises photoswitchable azobenzene attached to a glass surface and terminated with peptide c(RGDfK). Upon irradiation with light at 530 nm, the azobenzenes rapidly fluctuate between an extended and contracted conformation, leading to a change in the length of the azobenzene that stimulates integrins bound to c(RGDfK). The mathematical model mimics the nascent adhesion and spatial fluctuations in the extra-cellular matrix (ECM) and is calibrated using single-cell force microscopy retraction curves. It relies on spring-based mechanics to describe the stretch and deformation of a cell and ensembles of integrins when applied to a fluctuating biomaterial. We use the model to simulate retraction curves and the proportion of bound integrins on the surface as the material fluctuates. Additionally, we use the model to predict SCFS retraction curves for varying experimental conditions. This includes the length of time the cell (attached to the tip of the atomic force microscopy cantilever) is kept in contact with the biomaterial before retraction, and for varying frequency of light-induced movement of the azobenzene conformations. These model outcomes provide an attractive route to integrate and rigorously control certain experimental variables, thus accelerating experimental design of the study of cell adhesion to light-responsive biomaterials. Furthermore the model complements experiments by providing estimates of variables that are experimentally inaccessible. Thus, the outcomes of the model provide a valuable resource to aid in the interpretation and design of light-responsive biointerface functionalities.

biophysics↗

bioRxiv2024

Morphology-dependent entry kinetics and spread of influenza A virus

Influenza A viruses (IAV) display a broad variety of morphologies ranging from spherical to long filamentous virus particles. These diverse phenotypes are believed to allow the virus to overcome various immunological and pulmonary barriers during entry into the airway epithelium and influence the viral entry pathway. Remarkably, lab-adapted IAV strains lost this morphological variance and exhibit preferred spherical morphology. However, it remains unclear which factors lead to this lab-adapted preference and which pulmonary defense factors are responsible for the preferred filamentous morphology in physiological settings. In this study, we established fluorescent reporter viruses with spherical or filamentous morphology but with the same surface glycoproteins. We developed a correlative fluorescence and scanning electron microscopy workflow to analyze the impact of viral morphology on cell-to-cell spread and identify conditions under which IAV with either spherical or filamentous morphology confer an advantage. Our findings demonstrate that filamentous IAV cell-to-cell spread is significantly slower in various cell lines, which can explain the predominant spherical morphology in lab-adapted strains. This observation is consistent with delayed entry kinetics of filamentous viruses structurally analyzed by cellular cryo-electron tomography. We found that cellular junction integrity and mucin do not exert morphology-dependent inhibition of IAV cell-to-cell spread. On the other hand, filamentous virions confer an advantage under the pressure exerted by neutralizing antibodies against hemagglutinin.

microbiology↗

bioRxiv2023

2-photon laser printing to mechanically stimulate multicellular systems in 3D

Most biological activities take place in 3D environments, where cells communicate with each other in various directions and are located in a defined, often microstructured, space. To investigate the effect of defined cyclic mechanical forces on a multicellular system, we develop a sub-millimeter sized stretching device for mechanical stimulation of a structurally restricted, soft multicellular microenvironment. For the stretching device, a multimaterial 3D microstructure made of PDMS and gelatine-based hydrogel is printed via 2-photon polymerization (2PP) method. The printed structures are first characterized microscopically and mechanically to study the effect of different printing parameters. With 2PP, organotypic cell cultures are then directly printed into the hydrogel structures to achieve true 3D cell culture systems. These are mechanically stimulated with a cantilever by indenting the stretching device at a defined point. As a most important result, the cells in the 3D organotypic cell culture change morphology and actin orientation when exposed to cyclic mechanical stretch, even within short timescales of just 30 minutes. As a proof of concept, we encapsulated a Medaka retinal organoid in the same structure to demonstrate that even preformed organoids can be stimulated by our method. The results demonstrate the power of 2PP to manufacturing multifunctional soft devices for mechanically controlling multicellular systems at micrometer resolution and thus mimicking mechanical stress situations, as they occur in vivo.

biophysics↗

bioRxiv2023

Microbes as part of ancestral neuronal circuits: Bacterial produced signals affect neurons controlling eating behavior in Hydra

Although recent studies indicate the impact of microbes on the central nervous systems and behavior, it remains unclear how the relationship between the functionality of the nervous system, behavior and the microbiota arise. We studied the eating behavior of Hydra, a host that has a simple nervous system and a low-complexity microbiota. To identify the neuronal subpopulations involved, we used a subpopulation specific cell ablation system and calcium imaging. The role of the microbiota was uncovered by reducing the diversity of the natural microbiota. Here, we demonstrate that different neuronal subpopulations are functioning together to control the eating behavior. The microbiota participates in control of the eating behavior since germ-free or mono-colonized animals have drastic difficulties in mouth opening. This was restored by adding a full complement of the microbiota. In summary, we provide a mechanistic explanation of how the eating behavior is controlled in Hydra and how microbes can affect the neuronal circuit. Highlights- Multiple neuronal modules and their networks control complex behavior in an animal lacking a central nervous system. - Its associated microbes participate in these neuronal circuits and influence the eating behavior. - Disorganization of the microbiota negatively impacts this eating behavior. - Glutamate participates in an evolutionary ancient interkingdom language.

animal behavior and cognition↗