Biology subjects

Tsitsipatis, D.

Publications and source records attributed to Tsitsipatis, D..

8 recordsLinked to original sources

bioRxiv2026

A novel multicellular model of the adult mouse sinoatrial node retains spontaneous electrical activity and enables live investigation of the S100B-associated cell population

Approximately half of the adult sinoatrial node (SAN) consists of non-myocyte populations, indicating that cardiac pacemaking depends on interactions within a multicellular tissue rather than on pacemaker cardiomyocytes alone. Among these, an S100B-associated cell population has been implicated in pacemaker function, yet its identity and physiological roles remain poorly understood. These cells are rare and dispersed throughout the small, structurally complex SAN, making them difficult to observe repeatedly while preserving the native multicellular environment. Here, we established a dissociated multicellular culture of adult mouse SAN tissue on soft collagen-gelatin hydrogels that retains spontaneous electrical activity and permits longitudinal live imaging of S100B-associated cells. Using an S100B-EGFP+ reporter, we identified at least six reproducible morphological and behavioral phenotypes, including migration, proliferation, phagocytic behavior, and spontaneous self-organization into three-dimensional clusters. Cultures remained spontaneously electrically active for more than 10 days in vitro, with peak activity around day 10. This multicellular culture model bridges the gap between intact SAN preparations and isolated-cell cultures, allowing repeated observation of rare S100B-associated cells within a spontaneously active multicellular environment. HighlightsO_LIThe platform enables longitudinal live imaging of rare S100B-associated cells within an diverse multicellular SAN culture. C_LIO_LILive imaging reveals at least six reproducible morphological and behavioral phenotypes of S100B-associated cells. C_LIO_LIDissociated multicellular SAN cultures remain spontaneously electrically active for more than 10 days in vitro. C_LI

cell biology↗

bioRxiv2026

Reduced LANCL1-AS1 in old human skeletal muscle diminishes mitochondrial activity, shortens mt-mRNA poly(A) tails, and suppresses myogenesis

Regeneration of skeletal muscle preserves muscle mass and function, which decline with age. Here, we sought to identify long noncoding (lnc)RNAs involved in skeletal muscle myogenesis and potentially relevant to muscle aging. Cross-sectional analysis of skeletal muscle transcriptomes from healthy 22-through 89-year-old individuals revealed lncRNA LANCL1-AS1 among the top declining transcripts. Conversely, LANCL1-AS1 increased robustly during skeletal myogenesis and promoted myogenic differentiation in culture. Affinity pulldown by ChIRP followed by mass spectrometry revealed that LANCL1-AS1 associated with the mitochondrial protein LRPPRC, enhancing the formation of the chaperone complex LRPPRC-SLIRP, which maintains longer poly(A) tails of mitochondrial (mt-)mRNAs and stabilizes mt-mRNAs. Importantly, while myoblasts from old rhesus monkey muscle expressed lower levels of LANCL1-AS1 and mt-mRNAs, and displayed lower mitochondrial activity than young monkey myoblasts, overexpressing LANCL1-AS1 in old myoblasts restored mitochondrial activity and myogenesis. We propose that the age-associated reduction in LANCL1-AS1 contributes to impaired mitochondrial function and reduced myogenic capacity in aging skeletal muscle.

molecular biology↗

bioRxiv2026

SenCat: Cataloging human cell senescence through multiomic profiling of multiple senescent primary cell types

There is an urgent need to comprehensively catalog senescence markers across cell types in an organism in order to characterize senotypes and senescent cell heterogeneity. Here, we profiled the transcriptomes and proteomes in 14 different primary human cell types undergoing over 30 senescence paradigms to create a senescence catalog we termed SenCat. We found that, while senescent cells from all primary tissue types did not share a single unique marker, they did activate shared specific metabolic and damage-response pathways implicated in tissue repair. Machine learning analysis of the SenCat transcriptomic and proteomic datasets successfully identified independent sets of senescent human cells, and senescent-like cells in mouse lung and kidney. In sum, SenCat represents a much-needed resource to identify senescent cells across tissues in the body. HIGHLIGHTSO_LIIdentifying senescent cells in organisms in vivo remains a challenge C_LIO_LIWe created SenCat: a catalog transcriptomes and proteomes of senescent primary cells C_LIO_LIMachine learning (ML) analysis of SenCat identified robust senescence scores C_LIO_LIML-derived senescence scores uncovered senescent-like cell dynamics in vivo C_LI

molecular biology↗

bioRxiv2025

Senolytic treatment with fisetin reverses age-related endothelial dysfunction partially mediated by SASP factor CXCL12

BackgroundAdvancing age is the strongest risk factor for cardiovascular diseases (CVDs), primarily due to progressive vascular endothelial dysfunction. Cellular senescence and the senescence-associated secretory phenotype (SASP) contribute to age-related endothelial dysfunction by promoting mitochondrial oxidative stress and inflammation, which reduce nitric oxide (NO) bioavailability. However, the molecular changes in senescent endothelial cells and their role in endothelial dysfunction with aging remain incompletely unclear. As such, in this study we sought to identify the endothelial cell senescence-related signalling pathways, endothelial-derived SASP factors, and their impact on endothelial function with aging. MethodsSingle-cell transcriptomics was performed on aortas from young (6 months) and old (27 months) mice with and without in vivo senolytic treatment with fisetin (100 mg/kg/day administered in an intermittent dosing paradigm) to characterize endothelial cell senescence and transcript expression changes. Circulating levels of SASP factors were measured to validate transcriptional changes. Plasma exposure and protein addition and inhibiton experiments were conducted in isolated mouse arteries and cultured human endothelial cells to determine the causal role of the circulating SASP milieu and specific SASP factors in mediating endothelial dysfunction and underlying mechanisms-of-action. ResultsSenescent endothelial cells exhibited elevated expression of SASP factors, particularly Cxcl12, which was reversed by fisetin supplementation, with responses also reflected in circulating CXCL12 concentrations. Plasma from old mice impaired endothelial function by inducing vascular cell senescence, reducing NO, increasing mitochondrial oxidative stress, and promoting endothelial-to-mesenchymal transition--effects partially driven by CXCL12 and prevented by fisetin. ConclusionsThese results identify the SASP and CXCL12 as drivers of age-related endothelial dysfunction and establish mechanisms of senolytic intervention with fisetin supplementation. NOVELTY AND SIGNFICANCEO_ST_ABSWhat is known?C_ST_ABSO_LIAdvancing age is the primary risk factor for cardiovascular disease, in part due to progressive endothelial dysfunction. C_LIO_LICellular senescence contributes to age-related endothelial impairment through the secretion of a pro-inflammatory milieu known as the senescence-associated secretory phenotype (SASP), which can affect neighboring cells and tissue function. C_LIO_LISenolytic compounds selectively eliminate senescent cells and improve vascular function in preclinical models of aging. C_LI What new information does this article contribute?O_LIEndothelial cells are highly susceptible to senescence with aging in vivo and are selectively cleared by senolytic treatment with the natural compound fisetin. C_LIO_LISingle-cell transcriptomic profiling identifies CXCL12 as the most highly upregulated SASP factor in senescent endothelial cells and in circulation with aging, both of which are reversed by senolytic treatment with fisetin. C_LIO_LIWe identify a specific circulating SASP factor, CXCL12, as a partial mediator of endothelial dysfunction by inducing mitochondrial oxidative stress, impairing nitric oxide bioavailability, and promoting endothelial-to-mesenchymal transition (Endo, which is restored by senolytic treatment with fisetin. C_LI SummaryThis study provides novel mechanistic insight into how senescent endothelial cells and their secretory products--particularily CXCL12--contribute to age-related endothelial dysfunction. It further demonstrates that senolytic treatment with fisetin reverses these effects, highlighting a promising translational strategy for targeting vascular aging and preserving endothelial health. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=68 SRC="FIGDIR/small/670216v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@b49a8org.highwire.dtl.DTLVardef@110da92org.highwire.dtl.DTLVardef@17dbd54org.highwire.dtl.DTLVardef@1906c6_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Integrative single-cell analysis of neural stem/progenitor cells reveals epigenetically dysregulated interferon response in progressive multiple sclerosis

Progressive multiple sclerosis (PMS) is characterized by a primary smouldering pathological disease process associated with a superimposed inflammatory activity. Cellular and molecular processes sustaining the pathobiology of PMS remain to be identified. We previously discovered senescence signatures in neural stem/progenitor cells (NSCs) from people with PMS. Applying direct reprogramming to generate directly induced NSCs (iNSCs) from somatic fibroblasts, we retain epigenetic information and observe hypomethylation of genes associated with lipid metabolic processes and IFN signalling only in PMS lines. Single-cell/nucleus transcriptomic and epigenetic profiling reveal an inflammatory, senescent-like, IFN-responsive radial glia (RG)-like cell subcluster mainly in PMS iNSCs that is driven by IFN-associated transcription factors. Lastly, we identify a population of senescent, IFN-responsive, disease-associated RG-like cells (DARGs) in the PMS brain that share pseudotime trajectories with iNSCs in vitro. We describe the existence of a non-neurogenic, dysfunctional DARG population that has the potential to fuel smouldering inflammation in PMS.

neuroscience↗

bioRxiv2022

The YAP-TEAD complex promotes senescent cell survival by lowering endoplasmic reticulum stress

Sublethal cell damage can trigger a complex adaptive program known as senescence, characterized by growth arrest, resistance to apoptosis, and a senescence-associated secretory phenotype (SASP). As senescent cells accumulating in aging organs are linked to many age-associated diseases, senotherapeutic strategies are actively sought to eliminate them. Here, a whole-genome CRISPR knockout screen revealed that proteins in the YAP-TEAD pathway influenced senescent cell viability. Accordingly, treating senescent cells with a drug that inhibited this pathway, Verteporfin (VPF), selectively triggered apoptotic cell death and derepressed DDIT4, in turn inhibiting mTOR. Reducing mTOR function in senescent cells diminished endoplasmic reticulum (ER) biogenesis, causing ER stress and apoptosis due to high demands on ER function by the SASP. Importantly, VPF treatment decreased senescent cell numbers in the organs of old mice and mice exhibiting doxorubicin-induced senescence. We present a novel senolytic strategy that eliminates senescent cells by hindering ER activity required for SASP production.

cell biology↗

bioRxiv2022

Pleiotropic effects of BAFF on the senescence-associated secretome and growth arrest

Senescent cells release a variety of cytokines, proteases, and growth factors collectively known as the senescence-associated secretory phenotype (SASP). Sustained SASP contributes to a pattern of chronic inflammation associated with aging and implicated in many age-related diseases. Here, we investigated the expression and function of the immunomodulatory cytokine BAFF (B-cell activating factor), a SASP protein, in multiple senescence models. We first characterized BAFF production across different senescence models, including senescent human diploid fibroblasts (WI-38, IMR-90) and monocytic leukemia cells (THP-1), and tissues of mice induced to undergo senescence. We then identified IRF1 (interferon response factor 1) as a transcription factor required for promoting BAFF mRNA transcription in senescence. We discovered that suppressing BAFF production decreased the senescent phenotype of both fibroblasts and monocyte-derived THP-1 cells, overall reducing IL6 secretion, SA-{beta}-Gal staining, and {gamma}-H2AX accumulation. Importantly, however, the influence of BAFF on the senescence program was cell type-specific: in monocytes, BAFF promoted the early activation of NF-{kappa}B and general SASP secretion, while in fibroblasts, BAFF contributed to the production and function of TP53 (p53). We propose that BAFF is elevated across senescence models and is a potential target for senotherapy.

cell biology↗

bioRxiv2022

Single-cell analysis of skeletal muscle macrophages reveals age- associated functional subpopulations

Tissue-resident macrophages represent a group of highly responsive innate immune cells that acquire diverse functions by polarizing towards distinct subgroups. The subgroups of macrophages that reside in skeletal muscle (SKM) and their changes during aging are poorly characterized. By single-cell transcriptomic analysis, we found that mouse SKM macrophages primarily comprise two large populations, "healing" LYVE1+ and "proinflammatory" LYVE1-macrophages. SKM macrophages were further classified into four functional subgroups based on the expression levels of another cell-surface marker, MHCII: LYVE1+/MHCII-lo (similar to alternatively activated M2), LYVE1-/MHCII-hi (similar to classically activated M1), and two new subgroups, LYVE1+/MHCII-hi and LYVE1-/MHCII-lo. Notably, the new subgroup LYVE1+/MHCII-hi had traits of both M2 and M1 macrophages, while the other new subgroup, LYVE1-/MHCII-lo, expressed high levels of mRNAs encoding cytotoxicity proteins. Flow cytometric analysis validated the presence of the four macrophage subgroups in SKM. In old SKM, LYVE1-macrophages were more abundant than LYVE1+ macrophages. Furthermore, complementary unsupervised classification revealed the emergence of specific macrophage subclusters expressing abundant proinflammatory markers, including S100a8 and S100a9 in aged SKM. In sum, our study has identified dynamically polarized mouse SKM macrophages and further uncovered the contribution of specific macrophage subpopulations to the proinflammatory status in old SKM.

cell biology↗