Biology subjects

Nikitina, N.

Publications and source records attributed to Nikitina, N..

3 recordsLinked to original sources

bioRxiv2026

Chronological Aging Stiffens Cells, Alters Mitochondria, and Impairs Mitochondrial Mechanical Responsiveness in Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) can differentiate into osteoblasts and adipocytes, play a critical role for maintaining bone homeostasis. Although, aging impairs MSC function and contributes to several complications, the effects of aging on subcellular structure and related gene expression need further investigation. Here we established an in vitro system to study MSCs isolated from bones of 5, 12, and 24 months old mice which showed significantly decreased bone volume and exercise performance with age. RNA sequencing revealed downregulation of genes related to cell-matrix interactions, cell metabolism, and division. Functionally MSCs extracted from 24mo showed significantly increased adipogenesis and reduced osteogenesis compared to 5mo, which was accompanied by reduced levels of cell proliferative marker Ki67 and increased expression of senescence protein p16. Data-driven segmentation of F-actin architecture revealed no cell-wide or nuclei-associated alteration, while 24mo MSCs showed decreased nuclear volume and increased spreading and higher nuclear stiffness compared to 5mo. Mitochondria from 12mo and 24mo showed increased length and volume of fibers when compared to 5mo, which was accompanied by gene expression changes associated with mitochondrial inflammation and oxidative phosphorylation. To test the functional consequences, MSCs were subjected to mechanical stress for 72 hours using 90Hz, 07g low-intensity vibration (LIV). While 5mo MSCs showed a robust fusing of individual mitochondrial fibers, LIV response of 12mo and 24mo MSCs were progressively less, indicating an already stressed mitochondria compromised to mechanical challenge. In summary, this study has established an in vitro assay system, revealing age-associated impairments in differentiation, mitochondrial function, and mechanotransduction capacity.

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↗