Biology subjects

Bjorkoy, A.

Publications and source records attributed to Bjorkoy, A..

3 recordsLinked to original sources

bioRxiv2026

Label-free imaging of matrix mineralization in alginate-encapsulated bone spheroids using Coherent Raman Scattering microscopy

Three-dimensional (3D) cell cultures, such as spheroids, are increasingly used to perform advanced studies on bone matrix mineralization. However, their full characterization remains challenging. Traditional colorimetric and fluorescent assays using dyes, such as Alizarin Red S (ARS) and calcein, are effective in monolayer cell cultures, but fail to provide reliable information when used in complex 3D cell constructs. In this study, we investigated the application of Coherent Raman Scattering microscopy for label-free, comprehensive characterization of extracellular matrix (ECM) mineralization in alginate-encapsulated bone spheroids. After confirming that traditional staining techniques are unreliable for mineral detection in spheroids, Stimulated Raman Scattering (SRS) microscopy was used to detect phosphate-rich mineral deposits at a Raman shift of 960 cm-1, while Second Harmonic Generation (SHG) microscopy was used in association with SRS to provide complementary information on the deposition and organization of the collagenous matrix. SRS was used to detect lipid-rich regions at a Raman shift of 2857 cm-1 to perform cell localization. SRS imaging revealed the presence of phosphate-rich regions in the spheroids, including the core regions, usually challenging to characterize in intact 3D constructs. Raman spectral scans on SRS-positive regions confirmed the specificity of the phosphate signal. In addition, comparison of SRS and Coherent Anti-Stokes Raman Scattering (CARS) demonstrated the advantage of SRS in terms of reduced background compared to CARS for lipid imaging. Taken together, our results demonstrated that SRS, in combination with SHG, provides a promising and powerful approach to perform label-free, chemically specific characterization of intact 3D bone models.

biophysics↗

bioRxiv2025

The mechanical properties of Arabidopsis thaliana roots adapt dynamically during development and to stress

Mechanical properties of plant cells and tissues change dynamically, influencing plant growth, development, and interactions with the environment. Despite their central roles in plant life, current knowledge of how these properties change in vivo is very limited. Here we have combined Brillouin microscopy and molecular rotors to investigate stiffness, viscosity and porosity in living Arabidopsis thaliana seedling roots during differentiation and in response to stress and genetic manipulation. We found that mechanical properties change in a cell- and tissue-specific manner. The properties change dynamically during differentiation to support directional cell expansion. Cell-type-specific adaptations are induced within hours in response to stress or changes in cell wall metabolism. The findings form the foundation for future studies to characterize regulatory mechanisms linking biochemical signaling and mechanical properties.

plant biology↗

bioRxiv2022

Mechanical confinement and DDR1 signalling synergise to regulate collagen-induced apoptosis in rhabdomyosarcoma cells

Fibrillar collagens promote cell proliferation, migration, and survival in various epithelial cancers and are generally associated with tumour aggressiveness. However, the impact of fibrillar collagens on soft tissue sarcoma behaviour remains poorly understood. Unexpectedly, we find here that fibrillar collagen-related gene expression is associated with favourable patient prognosis in rhabdomyosarcoma. By developing and using collagen matrices with distinct stiffness and in vivo-like microarchitectures, we uncover that the activation of DDR1 has pro-apoptotic and integrin {beta}1 pro-survival function, specifically in 3D rhabdomyosarcoma cell cultures. We demonstrate that rhabdomyosarcoma cell-intrinsic or extrinsic matrix remodelling promotes cell survival. Mechanistically, we find that the 3D-specific collagen-induced apoptosis results from a dual DDR1-independent and a synergistic DDR1-dependent TRPV4-mediated response to mechanical confinement. Altogether, our results indicate that dense microfibrillar collagen-rich microenvironments are detrimental to rhabdomyosarcoma cells through an apoptotic response orchestrated by the induction of DDR1 signalling and mechanical confinement. This mechanism helps to explain the preference of rhabdomyosarcoma cells to grow in and metastasise to low fibrillar collagen microenvironments such as the lung.

cancer biology↗