Biology subjects

Zavala, A.

Publications and source records attributed to Zavala, A..

5 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↗

bioRxiv2024

Immune Checkpoint Inhibition-related Neuroinflammation Disrupts Cognitive Function

Combinatorial blockade of Cytotoxic T-lymphocyte associated protein 4 (CTLA-4) and Programmed Cell Death Protein 1 (PD-1) significantly improve the progression-free survival of individuals with metastatic cancers, including melanoma. In addition to unleashing anti-tumor immunity, combination immune checkpoint inhibition (ICI) disrupts immune-regulatory networks critical for maintaining homeostasis in various tissues, including the central nervous system (CNS). Although ICI- and cancer-related cognitive impairments (CRCI) in survivors are increasingly becoming evident, our understanding of ICI-induced immune-related adverse effects (IREA) in the CNS remains incomplete. Here, our murine melanoma model reveals that combination ICI impairs hippocampal-dependent learning and memory, as well as memory consolidation processes. Mechanistically, combination ICI disrupted synaptic integrity, and neuronal plasticity, reduced myelin, and further predisposed CNS for exaggerated experimental autoimmune encephalomyelitis. Combination ICI substantially altered both lymphoid and myeloid cells in the CNS. Neurogenesis was unaffected, however, microglial activation persisted for two-months post- ICI, concurrently with cognitive deficits, which parallels clinical observations in survivors. Overall, our results demonstrate that blockade of CTLA-4 and PD-1 alters neuro-immune homeostasis and activates microglia, promoting long-term neurodegeneration and driving cognitive impairments. Therefore, limiting microglial activation is a potential avenue to mitigate CNS IRAE while maintaining the therapeutic benefits of rapidly evolving ICIs and their combinations. SIGNIFICANCEDespite the superior therapeutic efficacy of immune checkpoint inhibition (ICI) for cancers, its undesired effects on brain function are not fully understood. Here, we demonstrate that combination ICI elevates neuroinflammation, activates microglia, leading to detrimental neurodegenerative and neurocognitive sequelae.

neuroscience↗

bioRxiv2023

Development and Characterization of a low intensity vibrational system for microgravity studies

The advent of extended-duration human spaceflight demands a better comprehension of the physiological impacts of microgravity. One primary concern is the adverse impact on the musculoskeletal system, including muscle atrophy and bone density reduction. Ground-based microgravity simulations have provided insights, with vibrational bioreactors emerging as potential mitigators of these negative effects. Despite the potential they have, the adaptation of vibrational bioreactors for space remains unfulfilled, resulting in a significant gap in microgravity research. This paper introduces the first automated low-intensity vibrational (LIV) bioreactor designed specifically for the International Space Station (ISS) environment. Our research covers the bioreactors design and characterization, the selection of an optimal linear guide for consistent 1-axis acceleration, a thorough analysis of its thermal and diffusion dynamics, and the pioneering use of BioMed Clear resin for enhanced scaffold design. This advancement sets the stage for more authentic space-based biological studies, vital for ensuring the safety of future space explorations.

bioengineering↗

bioRxiv2022

Depletion of Sun1/2 Induces Heterochromatin Accrual in Mesenchymal Stem Cells during Adipogenesis

Critical to the mechano-regulation of mesenchymal stem cells (MSC), Linker of the Nucleoskeleton and Cytoskeleton (LINC) complex transduces cytoskeletal forces to the nuclei. The LINC complex contains outer nuclear membrane Nesprin proteins that associate with the cytoskeleton and their inner nuclear membrane couplers, Sun proteins. In addition to coupling Nesprin-associated cytoskeletal elements to inner nuclear membrane, Sun proteins also function in regulating nuclear mechanics and chromatin tethering to inner nuclear membrane. This suggests that release of LINC-mediated cytoskeletal connections from cell nuclei may have different effects on chromatin organization and MSC differentiation than those due to ablation of intra-nuclear Sun proteins. To test this hypothesis we compared Sun1/2 depletion with expression of the dominant-negative KASH domain (dnKASH) that inhibits Nesprin-Sun association. In cells cultured under adipogenic conditions, disconnecting LINC from the cytoskeleton through dnKASH expression, increased adipogenic gene expression and fat droplet formation; heterochromatin H3K27 and H3K9 methylation was unaltered. In contrast, Sun1/2 depletion inhibited adipogenic gene expression and fat droplet formation; as well the anti-adipogenic effect of Sun1/2 depletion was accompanied by increased H3K9me3, which was enriched on Adipoq, silencing this fat locus. We conclude that releasing the nucleus from cytoskeletal constraints via dnKASH accelerates adipogenesis while depletion of Sun1/2 increases heterochromatin accrual on adipogenic genes in a fashion independent of LINC complex function. Therefore, while these two approaches both disable LINC functions, their divergent effects on the epigenetic landscape indicate they cannot be used interchangeably to study mechanical regulation of cell differentiation.

bioengineering↗

bioRxiv2017

T Cell Calcium Dynamics Visualized in a Ratiometric tdTomato-GCaMP6f Transgenic Reporter Mouse

Calcium is an essential cellular messenger that regulates numerous functions in living organisms. Here we describe development and characterization of \"Salsa6f\", a fusion of GCaMP6f and tdTomato optimized for cell tracking while monitoring cytosolic Ca2+, and a transgenic Ca2+ reporter mouse with Salsa6f floxed and targeted to the Rosa26 locus for expression in specific cell types. Using CD4-Cre-Salsa6f mice, we report normal development and function of T cells expressing Salsa6f and demonstrate Ca2+ signaling dynamics during T cell receptor engagement in naive T cells, helper Th17 T cells and regulatory T cells. Salsa6f expression also revealed functional expression of mechanosensitive Piezo1 channels in T cells. Transgenic expression of Salsa6f enables ratiometric imaging of Ca2+ signals in complex tissue environments found in vivo. Deep tissue two-photon imaging of T cells in the steady-state lymph node revealed a highly localized Ca2+ signaling behavior (\"sparkles\") as cells migrate.

cell biology↗