Biology subjects

Bosze, S.

Publications and source records attributed to Bosze, S..

4 recordsLinked to original sources

bioRxiv2025

Stress-induced switch in small extracellular vesicle secretion: from constitutive 'torn bag mechanism' to exocytosis

The biogenesis of small extracellular vesicles (sEVs) is only partially understood. Our recent findings provide evidence that a newly described sEV secretion pathway, the amphiectosome release and the "torn bag mechanism", is present in all tested cell lines and in mouse liver and kidney. Surprisingly, in in situ fixed steady-state cells, transmission electron microscopy did not reveal the classical exosome secretion route, the sEV release via exocytosis of multivesicular endosomes (MVEs). In the current study, we investigated which parameters influence the activation of the two distinct sEV release mechanisms. Our results show that under stress conditions (such as Ca{superscript 2} ionophore-induced membrane stress or metabolic stress-induced by serum starvation), exocytosis of MVEs is activated, while this process is absent in steady-state conditions. By silencing ATG5 (a key regulator of autophagy) and RAB27a (essential small GTPase for MVE exocytosis), we selectively modulated these two mechanisms. Amphiectosome release depended on both autophagy and ATG5, while exocytosis of MVE was autophagy-independent but RAB27a-dependent. Our findings suggest that sEV release via the "torn bag mechanism" is a general and essential secretion pathway in non-stressed, steady-state mammalian cells, while stress conditions induce the sEV release via MVE exocytosis.

cell biology↗

bioRxiv2025

Petasol Exhibits Rapid and Efficient Epithelial Transport in Epithelial Barrier Models

The epithelial permeability of petasol, a sesquiterpene derivative with reported antiviral properties, remains largely unexplored despite its potential as a therapeutic candidate. Here, we systematically characterize the transport of petasol across epithelial barriers using a combination of in vitro transwell models, automated millifluidic sampling, mathematical modeling, optical- and HPLC-mass spectroscopy. Vero E6 and Caco-2 cell layers were employed as epithelial barrier models, with transepithelial electrical resistance (TEER) measurements confirming the formation of functionally intact epithelial layers. Mathematical modeling of passive diffusion and cellular uptake allowed estimation of key transport parameters, including permeability coefficients and intracellular sequestration rates. Trans-barrier transport of petasol was compared to that of nitazoxanide, chloroquine, and FITC-dextran. Our results reveal that petasol exhibits efficient and rapid transport across both epithelial cell types without substantial intracellular accumulation or metabolic degradation, suggesting favorable properties for systemic delivery.

pharmacology and toxicology↗

bioRxiv2025

Barrier Function of the Vero E6 Cell Monolayer

Vero E6 cells are a standard model in virology research because of their broad susceptibility to viral infection. However, their ability to form functional barrier layers has received less attention. Here, we show that Vero E6 cells cultured on transwell inserts develop continuous monolayers with moderate transepithelial electrical resistance (TEER), reaching approximately 30 {Omega}{middle dot}cm2 in serum-containing medium and 45 {Omega}{middle dot}cm2 in virus production medium. The permeability coefficient (Papp) for 4 kDa FITC-dextran, a common measure for paracellular transport, is 3.7 x 10-6 cm/s, comparable to established endothelial models such as HUVEC or corneal endothelium. Immunofluorescence confirms the presence of tight junction (ZO-1) and adherens junction ({beta}-catenin) proteins. Chelation of calcium with EGTA causes a dose-dependent, reversible decrease in TEER and a marked increase in permeability, confirming the calcium sensitivity of the barrier. These findings suggest that Vero E6 cells serve as a valuable epithelial barrier model, facilitating studies on viral entry, immune evasion, and drug delivery.

cell biology↗

bioRxiv2025

Characterizing Solute Transport Across Cell Layers: Artifact Correction and Parameter Extraction from a Simplified Three-Compartment Model

Quantifying solute transport across epithelial cell layers grown on transwell inserts is a common approach in early-stage drug development to estimate pharmacokinetic properties such as absorption and bioavailability. To increase throughput and reduce variability, these assays are increasingly automated, including the use of robotic or microfluidic systems for time-resolved sampling. However, both automated and manual sampling can introduce systematic artifacts, such as residual volume retention and surface adsorption, that distort concentration time series and affect downstream analysis. To fully realize the potential precision of automated measurements, we propose a mathematical correction to account for sampling artifacts; then to fit the corrected data to a three-compartment model that captures membrane diffusion, cellular sequestration, and metabolic loss. The method is demonstrated on datasets from transwell epithelial barrier transport assays. We suggest that the considered three-compartment model yields mechanistically more meaningful parameters than the conventional apparent permeability (Papp) measure. The proposed approach thus enables more accurate characterization of analyte interactions with the barrier cell layer, supporting better-informed assessments of compound behavior in in vitro transport systems.

pharmacology and toxicology↗