Biology subjects

Bursa, N.

Publications and source records attributed to Bursa, N..

3 recordsLinked to original sources

bioRxiv2026

Vibration's frequency and intensity for optimal setup for enhancement bone response in small rodents: A systematic review and Bayesian network meta-analysis

Low-intensity vibration (LIV) is a non-invasive mechanical stimulus capable of regulating skeletal adaptation and cellular signaling pathways involved in bone remodeling. Despite growing interest in LIV, substantial methodological heterogeneity persists in the selection of experimental vibration parameters such as frequency, expressed in Hertz (Hz) and intensity, defined as earths gravitational field (g) (9.81 m/s2). Focusing on micro-computed tomography ({micro}CT) derived trabecular bone volume fraction (BV/TV) as the main outcome mesure, this study sought to synthesize the effects of different LIV frequency and intensity on BV/TV in small rodents (mice and rats) as they remain as the most studied pre-clinical model. To accomplish this, we performed a systematic review searching for publications in English on PubMed, Web of Science, CINAHL, and Embase databases. Two independent investigators followed inclusion criteria to select only peer-reviewed studies with mature mice, using whole-body vibration experiments without other co-variables. We further restricted to include studies that analyzed non-fractured bones and compared pre- and post-intervention or control values. In addition to these core criteria, a detailed hierarchical screening framework was applied during full-text review. The two independent investigators extracted data independently and considered the characteristics of the study, animals characteristics, intervention characteristics, and results. For this study we considered load-bearing hindlims, femur and tibia, separately but did not include vertebrae in the analysis. A Bayesian network meta-analysis and a revised SYRCLE risk of bias (RoB) tool were used to evaluate the risk of bias across included studies. Seven studies met the inclusion criteria. Results showed that an LIV regime applied at 45Hz at 2g presented higher chances to increase trabecular BV/TV of the mouse tibia (estimated effect 3.22 [CrI 1.98, 4.45]), while LIV regimes applied to the femur at 90Hz and 1.4g (estimated effect 3.08 [CrI -1.99, 7.97]) present better chances to increase trabecular BV/TV results compared to other interventions but with no significant differences. Finally, we applied 45Hz at 0.2g LIV to 5 month old male C57BL/6 for 5 weeks (n=10/group) which showed significantly increased Trabecular Thickness (Tb.Th) for both the tibia (10%, p<0.01) and femur (17%, p<0.001), with the femur showing further increaseses in trabecular BV/TV (32%, p<0.05) compared to non-LIV controls. We conclude that changes in the microarchitectures of the tibia and femur respond differently to the same application of LIV (45Hz, 0.2g) in mice and rats.

bioengineering↗

bioRxiv2025

Small Accelerations of the cell generate sufficient nuclear motion to modulate transcriptional activity, driving cellular response independent of matrix strain

The cells mechanical environment is a fundamental determinant of its activity. Ostensibly, the cellular response is dependent on interactions between extracellular matrix deformations and the cell adhesome. Low-intensity vibration (LIV) induces sinusoidal mechanical accelerations that stimulate mesenchymal stem cell (MSC) anabolism despite generating minimal matrix strain. In this study, we tested the hypothesis that accelerations of less than 1g cause nuclear motions relative to the cell membrane in adherent cells, resulting in elevated stresses in the cytoskeleton that promote transcriptional activity. Coupling a piezoelectric vibration platform with real-time microscopy, we applied a 0.7g, 90Hz LIV signal that oscillates the cell with displacements of up to {+/-}11 {micro}m. Live-cell tracking revealed that the sinusoidal vibrations caused the nucleus to move {+/-}1.27 {micro}m (17% of total displacement) out of phase with the cell membrane. Disruption of the LINC complex, which mechanically couples the nucleoskeleton to the cytoskeleton, doubled the magnitude of this relative motion, indicating that the nucleo-cytoskeletal configuration plays a major role in regulating nuclear motion. Consistent with a previously reported increase in nuclear stiffness caused by LIV, machine-learning-based image segmentation of confocal micrographs showed that LIV increased both apical and basal F-actin fiber numbers, generating a denser, more branched actin network near the nucleus. Following six 20 min bouts of LIV applied to MSC, RNA sequencing identified 372 differentially expressed genes. Upregulated gene sets were linked to F-actin assembly and focal adhesion pathways. Finite element simulations showed that nuclear stresses increased by LIV up to 18% were associated with nuclei flattening and a 30-50% increase in actin-generated forces. These findings demonstrate that low-intensity accelerations, independent of matrix strain, can directly activate a response of the nucleus, leading to cytoskeletal reorganization and heightened nuclear stresses. Thus, even very small oscillatory mechanical signals can markedly influence cell outcomes, establishing a mechanosensing pathway independent of extracellular strains.

bioengineering↗

bioRxiv2023

Data driven and cell specific determination of nuclei-associated actin structure

Quantitative and volumetric assessment of filamentous actin fibers (F-actin) remains challenging due to their interconnected nature, leading researchers to utilize threshold based or qualitative measurement methods with poor reproducibility. Here we introduce a novel machine learning based methodology for accurate quantification and reconstruction of nuclei-associated F-actin. Utilizing a Convolutional Neural Network (CNN), we segment actin filaments and nuclei from 3D confocal microscopy images and then reconstruct each fiber by connecting intersecting contours on cross-sectional slices. This allowed measurement of the total number of actin filaments and individual actin filament length and volume in a reproducible fashion. Focusing on the role of F-actin in supporting nucleocytoskeletal connectivity, we quantified apical F-actin, basal F-actin, and nuclear architecture in mesenchymal stem cells (MSCs) following the disruption of the Linker of Nucleoskeleton and Cytoskeleton (LINC) Complexes. Disabling LINC in mesenchymal stem cells (MSCs) generated F-actin disorganization at the nuclear envelope characterized by shorter length and volume of actin fibers contributing a less elongated nuclear shape. Our findings not only present a new tool for mechanobiology but introduce a novel pipeline for developing realistic computational models based on quantitative measures of F- actin.

bioengineering↗