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Biology subjects

Neubert, E.

Publications and source records attributed to Neubert, E..

5 recordsLinked to original sources

Informing agent-based models with spatial data using convolutional autoencoders

Spatial computational models such as agent-based models (ABMs) offer powerful in silico tools to study tumor dynamics, yet imaging data are still rarely used to inform these models directly. We present an ABM optimization framework that leverages convolutional encoders to compare spatial patterns between experimental imaging data and ABM-generated outputs within a shared latent space. This quantitative comparison was used to estimate ABM parameters across three datasets, ranging from synthetic data to 3D tumoroid-T cell co-culture microscopy and histopathology images from The Cancer Genome Atlas skin cutaneous melanoma samples. Estimated parameters were evaluated using data-derived features and experimental knowledge, including experimental conditions and gene expressions. Simulations using optimized parameters reproduced key spatial features of the training images, such as tumor boundary complexity and tumor-tumor neighborhood structure. Together, these results demonstrate a flexible framework for ABM parameter optimization using spatial data across modalities, enabling systematic investigation of how spatial architecture influences tumor progression and immune interactions.

systems biology↗

Rapid catecholamine trafficking regulates neutrophil functions and neutrophil-platelet interactions

Neutrophils are key effector cells of the innate immune system that respond to small signaling molecules regulating immune responses. For a long time, similarities between neuronal and immune cells have been discussed. Here, we show that human neutrophils rapidly take up, package and use catecholamine neurotransmitters such as dopamine or epinephrine via the machinery known from neurons. Uptake and release of catecholamines as well as trafficking and packaging into MPO/VMAT2-positive primary vesicles is visualized with false fluorescent neurotransmitters. We also directly image the fast (> 10 s) and transient release of catecholamines from neutrophils with near infrared fluorescent nanosensors. Serotonin or activated platelets trigger calcium (Ca2+) signaling and consequently exocytosis of catecholamines. They reduce NET-formation but increase platelet aggregation. Thus, we establish similarities between neurons and neutrophils and identify a paracrine neutrophil-platelet feedback loop relevant for inflammatory and coagulatory conditions.

immunology↗

Expansion microscopy of nuclear structure and dynamics in neutrophils

Neutrophils are key players of the immune system and possess an arsenal of effector functions, including the ability to form and expel neutrophil extracellular traps (NETs) in a process termed NETosis. During NETosis, the nuclear DNA/chromatin expands until it fills the whole cell and is released into the extracellular space. NETs are composed of DNA decorated with histones, proteins or peptides and NETosis is implicated in many diseases. Resolving the structure and dynamics of the nucleus in great detail is essential to understand the underlying processes but so far super-resolution methods have not been applied. Here, we developed an expansion microscopy-based method and determined the spatial distribution of chromatin/DNA, histone H1, and nucleophosmin (NPM1) with a 4.9-fold improved resolution (< 40 nm) and increased information content. It allowed us to identify the punctate localization of NPM1 in the nucleus and histone-rich domains in NETotic cells with a size of 54 nm. The technique could also be applied to components of the nuclear envelope (lamins B1 and B2) and myeloperoxidase (MPO) providing a complete picture of nuclear dynamics and structure. In conclusion, expansion microscopy enables super-resolved imaging of the highly dynamic structure of nuclei in immune cells. Why it mattersAccessibility to high-resolution imaging is critical to advancing research across various disciplines. However, conventionally this requires demanding optical hardware, special fluorophores or data analysis. Expansion microscopy is a technique adaptable to different cell and tissue types and is comparatively inexpensive and easy to perform. Applying this technique to cells and compartments such as the nucleus of immune cells that are difficult to image due to their size and morphology, yields valuable structural insights that would otherwise require more difficult super-resolution methods.

biophysics↗

Programmed transport and release of nanoscale cargo by immune cells

Transport and delivery of (nanoscale) materials are crucial for many applications in biomedicine. However, controlled uptake, transport and triggered release of such cargo remains challenging. In this study, we use human immune cells (neutrophilic granulocytes, neutrophils) and program them to perform these tasks in vitro. For this purpose, we let neutrophils phagocytose a nanoscale cargo. As an example, we used DNA-functionalized single-walled carbon nanotubes (SWCNT) that fluoresce in the near infrared (980 nm) and serve as sensors for small molecules. Cells still migrate, follow chemical gradients and respond to inflammatory signals after uptake of the cargo. To program release, we make use of neutrophil extracellular trap formation (NETosis), a novel cell death mechanism that leads to chromatin swelling and subsequent rupture of the cellular membrane and release of the cells whole content. By using the process of NETosis we can program the time point of cargo release via the initial concentration of stimuli such as phorbol 12-myristate-13-acetate (PMA) or lipopolysaccharide (LPS). At intermediate stimulation with LPS (100 g/ml), cells continue to migrate, follow gradients and surface cues for around 30 minutes and up to several hundred micrometers until they stop and release their cargo. The transported and released SWCNT sensor cargo is still functional as shown by subsequent detection of the neurotransmitter dopamine and reactive oxygen species (H2O2). In summary, we hijack a biological process (NETosis) and demonstrate how neutrophils can be used for programmed transport and delivery of functional nanomaterials.

biophysics↗

Effect of Adhesion and Substrate Elasticity on Neutrophil Extracellular Trap Formation

Neutrophils are the most abundant type of white blood cells. Upon stimulation, they are able to decondense and release their chromatin as neutrophil extracellular traps (NETs). This process (NETosis) is part of immune defense mechanisms but also plays an important role in many chronic and inflammatory diseases such as atherosclerosis, rheumatoid arthritis, diabetes and cancer. For this reason, much effort has been invested into understanding biochemical signaling pathways in NETosis. However, the impact of the mechanical micro-environment and adhesion on NETosis is not well understood. Here, we studied how adhesion and especially substrate elasticity affect NETosis. We employed polyacrylamide (PAA) gels with distinctly defined elasticities (Youngs modulus E) within the physiologically relevant range from 1 kPa to 128 kPa and coated the gels with integrin ligands (collagen I, fibrinogen). Neutrophils were cultured on these substrates and stimulated with potent inducers of NETosis: phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS). Interestingly, PMA-induced NETosis was neither affected by substrate elasticity nor by different integrin ligands. In contrast, for LPS stimulation, NETosis rates increased with increasing substrate elasticity (E > 20 kPa). LPS-induced NETosis increased with increasing cell contact area, while PMA-induced NETosis did not require adhesion at all. Furthermore, inhibition of phosphatidylinositide 3 kinase (PI3K), which is involved in adhesion signaling, completely abolished LPS-induced NETosis but only slightly decreased PMA-induced NETosis. In summary, we show that LPS-induced NETosis depends on adhesion and substrate elasticity while PMA-induced NETosis is completely independent of adhesion.

biophysics↗