Different Stages of Quiescence, Senescence, and Cell Stress Identified by Molecular Algorithm Based on the Expression of Ki67, RPS6, and Beta-Galactosidase Activity

How to make full use of dental pulp stem cells: an optimized cell culture method based on explant technology

Introduction

Dental pulp stem cells from humans possess self-renewal and versatile differentiation abilities. These cells, known as DPSC, are promising for tissue engineering due to their outstanding biological characteristics and ease of access without significant donor site trauma. Existing methods for isolating DPSC mainly include enzyme digestion and explant techniques. Compared with the enzymatic digestion technique, the outgrowth method is less prone to cell damage and loss during the operation, which is essential for DPSC with fewer tissue sources.

Methods

In order to maximize the amount of stem cells harvested while reducing the cost of DPSC culture, the feasibility of the optimized explant technique was evaluated in this experiment. Cell morphology, minimum cell emergence time, the total amount of cells harvested, cell survival, and proliferative and differentiation capacity of DPSC obtained with different numbers of explant attachments (A1-A5) were evaluated.

Results

There was a reduction in the survival rate of the cells in groups A2-A5, and the amount of harvested DPSC decreased in A3-A5 groups, but the DPSC harvested in groups A1-A4 had similar proliferative and differentiation abilities. However, starting from group A5, the survival rate, proliferation and differentiation ability of DPSC decreased significantly, and the adipogenic trend of the cells became more apparent, indicating that the cells had begun to enter the senescence state.

Discussion

The results of our study demonstrated that the DPSC obtained by the optimized explant method up to 4 times had reliable biological properties and is available for tissue engineering.

Dormancy of cutaneous melanoma

Many cancer-related deaths including melanoma result from metastases that develop months or years after the initial cancer therapy. Even the most effective drugs and immune therapies rarely eradicate all tumor cells. Instead, they strongly reduce cancer burden, permitting dormant cancer cells to persist in niches, where they establish a cellular homeostasis with their host without causing clinical symptoms. Dormant cancers respond poorly to most drugs and therapies since they do not proliferate and hide in niches. It therefore remains a major challenge to develop novel therapies for dormant cancers. In this review we focus on the mechanisms regulating the initiation of cutaneous melanoma dormancy as well as those which are involved in reawakening of dormant cutaneous melanoma cells. In recent years the role of neutrophils and niche components in reawakening of melanoma cells came into focus and indicate possible future therapeutic applications. Sophisticated in vitro and in vivo melanoma dormancy models are needed to make progress in this field and are discussed.

Effects of Blood-Derived Products on Cellular Senescence and Inflammatory Response: A Study on Skin Rejuvenation

Blood-derived products, such as citrate platelet-rich plasma (CPRP) and hyperacute serum (HAS), are recognized for their rich growth factor content. When human dermal fibroblast (HDF) cells are exposed to combined mitogenic and DNA-damaging stimuli, it can lead to an increased burden of senescent cells and a modified senescence-associated secretory phenotype. In this study, the senescent state was comprehensively assessed through various methods, including phosphorylated histone H2AX (γH2AX) staining, p21 and p16 q-PCR, p21-western blot, growth curves, and senescence-associated ß-galactosidase staining. Two primary treatments with blood products were administered, one early (immediately after etoposide) and the other late (11 days after etoposide treatment). The effects of the blood product treatment were evaluated by measuring interleukin 6 and 8 (IL-6 and IL-8) levels, as well as collagen 1 (COL1) and p21 mRNA expression. Additionally, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assays, cell size measurements, viability assays, and cell number calculations were conducted. The results revealed that cells treated with hyperacute serum in the early treatment phase exhibited the lowest observed IL-6 and IL-8 levels. In contrast, a clear inflammatory response for IL-8 was observed in cells treated with hyperacute serum and citrate platelet-rich plasma during the late treatment. Furthermore, an upregulation of COL1 expression was observed in the early treatment, while cells in the late treatment group remained unaffected. Notably, citrate platelet-rich plasma-treated cells showed a decrease in COL1 expression. Overall, the treatment with blood products appears to have slightly positive effects on skin rejuvenation.

Effect of Selected Antioxidants on the In Vitro Aging of Human Fibroblasts

The modification of the replicative lifespan (RLS) of fibroblasts is of interest both from a knowledge point of view and for the attenuation of skin aging. The effect of six antioxidants at a concentration of 1 μM on the replicative lifespan of human dermal fibroblasts was studied. The nitroxide 4-hydroxy-TEMPO (TEMPOL), ergothioneine, and Trolox extended the replicative lifespan (RLS) (40 ± 1 population doublings (PD)) by 7 ± 2, 4 ± 1, and 3 ± 1 PD and lowered the expression of p21 at late passages. Coumaric acid, curcumin and resveratrol did not affect the RLS . The level of reactive oxygen species (ROS) was decreased or not affected by the antioxidants although TEMPOL and coumaric acid decreased the level of glutathione. Only ergothioneine and resveratrol decreased the level of protein carbonylation. The antioxidants that could prolong the RLS elevated the mitochondrial membrane potential. Protecting the activity of mitochondria seems to be important for maintaining the replicative capacity of fibroblasts.

Tumor suppressor let-7 acts as a key regulator for pluripotency gene expression in Muse cells

In embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), the expression of an RNA-binding pluripotency-relevant protein, LIN28, and the absence of its antagonist, the tumor-suppressor microRNA (miRNA) let-7, play a key role in maintaining pluripotency. Muse cells are non-tumorigenic pluripotent-like stem cells residing in the bone marrow, peripheral blood, and organ connective tissues as pluripotent surface marker SSEA-3(+). They express pluripotency genes, differentiate into triploblastic-lineage cells, and self-renew at the single cell level. Muse cells do not express LIN28 but do express let-7 at higher levels than in iPSCs. In Muse cells, we demonstrated that let-7 inhibited the PI3K-AKT pathway, leading to sustainable expression of the key pluripotency regulator KLF4 as well as its downstream genes, POU5F1, SOX2, and NANOG. Let-7 also suppressed proliferation and glycolysis by inhibiting the PI3K-AKT pathway, suggesting its involvement in non-tumorigenicity. Furthermore, the MEK/ERK pathway is not controlled by let-7 and may have a pivotal role in maintaining self-renewal and suppression of senescence. The system found in Muse cells, in which the tumor suppressor let-7, but not LIN28, tunes the expression of pluripotency genes, might be a rational cell system conferring both pluripotency-like properties and a low risk for tumorigenicity.

The Binding of HSPA8 and Mitochondrial ALDH2 Mediates Oxygen-Glucose Deprivation-Induced Fibroblast Senescence

Cellular senescence refers to the permanent and irreversible cessation of the cell cycle. Recently, it has gained significant interest as a promising target for preventing cardiovascular diseases. Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that has been closely linked with an increased risk of cardiovascular diseases. In this study, bioinformatics analysis revealed that the signaling pathway for fibroblast senescence is significantly activated in mice after myocardial infarction (MI), and that ALDH2 might be a crucial molecule responsible for inducing this change. Therefore, we created an NIH3T3 fibroblast cell line oxygen-glucose deprivation (OGD) model to replicate the conditions of MI in vitro. We further revealed that decreased ALDH2 enzyme activity is a critical factor that affects fibroblast senescence after OGD, and the activation of ALDH2 can improve the mitochondrial damage caused by OGD. We identified Heat Shock 70-kDa Protein 8 (HSPA8) as an interacting protein of ALDH2 through co-immunoprecipitation (Co-IP) and mass spectrometry (MS) detection. Subsequently, our studies showed that HSPA8 translocates to the mitochondria after OGD, potentially binding to ALDH2 and inhibiting its enzyme activity. By transfecting siRNA to inhibit HSPA8 expression in cells, it was found that ALDH2 enzyme activity can be significantly increased, and the senescence characteristics induced by OGD in NIH3T3 cells can be improved. In conclusion, the data from this study suggest that HSPA8, in conjunction with ALDH2, could regulate fibroblast senescence after oxygen-glucose deprivation, providing a new direction and foundation for effectively intervening in fibroblast senescence after myocardial infarction.

M2-Macrophage-Induced Chronic Inflammation Promotes Reversible Mesenchymal Stromal Cell Senescence and Reduces Their Anti-Fibrotic Properties

Fibrosis and the associated decline in organ functionality lead to an almost 50% mortality rate in developed countries. Multipotent mesenchymal stromal cells (MSC) were shown to suppress the development and progression of fibrosis through secreted factors including specific non-coding RNAs transferred within extracellular vesicles (EV). However, age-associated chronic inflammation can provoke MSC senescence and change secretome composition, thereby affecting their antifibrotic properties. Alternatively activated macrophages (M2-type) are key players in chronic inflammation that may interact with MSC through paracrine mechanisms and decrease their antifibrotic functions. To confirm this hypothesis, we evaluated the M2-macrophage conditioned medium (CM-M2) effect on human adipose-tissue-derived MSC senescence in vitro. We found that CM-M2, as well as a pro-senescence agent, hydrogen peroxide (H2O2), increased p21+-MSC number and secretion of IL-6 and MCP-1, which are considered main senescence-associated secretory phenotype (SASP) components. Thus, both exposures led to the senescent phenotype acquisition of MSC. EV from both CM-M2 and H2O2-exposed MSC, which showed a decreased effect on the suppression of TGFβ-induced fibroblast-to-myofibroblast differentiation compared to EV from control MSC according to αSMA level and the αSMA+-stress fiber reduction. After two weeks of subsequent cultivation under standard conditions, MSC demonstrated a decrease in senescence hallmarks and fibroblast differentiation suppression via EV. These results suggest that M2-macrophage-induced chronic inflammation can reversibly induce MSC senescence, which reduces the MSC's ability to inhibit fibroblast-to-myofibroblast differentiation.

Multiparametric analysis of etoposide exposed mesenchymal stem cells and Fanconi anemia cells: implications in development of secondary myeloid malignancy

Secondary acute myeloid leukemia (sAML) may develop following a prior therapy or may evolve from an antecedent hematological disorder such as Fanconi Anemia (FA). Pathophysiology of leukemic evolution is not clear. Etoposide (Eto) is a chemotherapeutic agent implicated in development of sAML. FA is an inherited bone marrow (BM) failure disease characterized by genomic instability and xenobiotic susceptibility. Here, we hypothesized that alterations in the BM niche may play a critical/driver role in development of sAML in both conditions. Expression of selected genes involved in xenobiotic metabolism, DNA double-strand break response, endoplasmic reticulum (ER) stress, heat shock response and cell cycle regulation were determined in BM mesenchymal stem cells (MSCs) of healthy controls and FA patients at steady state and upon exposure to Eto at different concentrations and in recurrent doses. Expression of CYPA1, p53, CCNB1, Dicer1, CXCL12, FLT3L and TGF-Beta genes were significantly downregulated in FA-MSCs compared with healthy controls. Eto exposure induced significant alterations in healthy BM-MSCs with increased expression of CYP1A1, GAD34, ATF4, NUPR1, CXCL12, KLF4, CCNB1 and nuclear localization of Dicer1. Interestingly, FA-MSCs did not show significant alterations in these genes upon Eto exposure. As opposed to healthy MSCs DICER1 gene expression and intracellular localization was not altered on FA BM-MSCs after Eto treatment. These results showed that Eto is a highly potent molecule and has pleiotropic effects on BM-MSCs, FA cells show altered expression profile compared to healthy controls and Eto exposure on FA cells shows differential profile than healthy controls.

Microvesicles-hydrogel breaks the cycle of cellular senescence by improving mitochondrial function to treat osteoarthritis

BACKGROUND

Osteoarthritis (OA) is an age-related disease characterised by the accumulation of senescent chondrocytes, which drives its pathogenesis and progression. Senescent cells exhibit distinct features, including mitochondrial dysfunction and the excessive accumulation and release of reactive oxygen species (ROS), which are highly correlated and lead to a vicious cycle of increasing senescent cells. Stem cell therapy has proven effective in addressing cellular senescence, however, it still has issues such as immune rejection and ethical concerns. Microvesicles (MVs) constitute the primary mechanism through which stem cell therapy exerts its effects, offering a cell-free approach that circumvents these risks and has excellent anti-ageing potential. Nonetheless, MVs have a short in vivo half-life, and their secretion composition varies considerably under diverse conditions. This study aims to address these issues by constructing a ROS-responsive hydrogel loaded with pre-stimulant MVs. Through responding to ROS levels this hydrogel intelligently releases MVs, and enhancing mitochondrial function in chondrocytes to improving cellular senescence.

RESULT

We employed Interferon-gamma (IFN-γ) as a stem cell-specific stimulus to generate IFN-γ-microvesicles (iMVs) with enhanced anti-ageing effects. Simultaneously, we developed a ROS-responsive carrier utilising 3-aminophenylboronic acid (APBA)-modified silk fibroin (SF) and polyvinyl alcohol (PVA). This carrier served to protect MVs, prolong longevity, and facilitate intelligent release. In vitro experiments demonstrated that the Hydrogel@iMVs effectively mitigated cell senescence, improved mitochondrial function, and enhanced cellular antioxidant capacity. In vivo experiments further substantiated the anti-ageing capabilities of the Hydrogel@iMVs.

CONCLUSION

The effect of MVs can be significantly enhanced by appropriate pre-stimulation and constructing a suitable carrier. Therefore, we have developed a ROS-responsive hydrogel containing IFN-γ pre-stimulated iMVs to target the characteristics of ageing chondrocytes in OA for therapeutic purposes. Overall, this novel approach effectively improving mitochondrial dysfunction by regulating the balance between mitochondrial fission and fusion, and the accumulation of reactive oxygen species was reduced, finally, alleviates cellular senescence, offering a promising therapeutic strategy for OA.

Serum starvation-based method of ovarian cancer cell dormancy induction and termination in vitro

Awakening and growth reinitiation by dormant cells may contribute to epithelial ovarian cancer (EOC) relapse. The links between these phenomena are loose because of the limited stock of compelling models of EOC dormancy. Here, we show a simple and convenient dormancy research protocol based on serum starvation. This study was conducted on established EOC cell lines A2780, OVCAR-3, and SKOV-3, as well as on primary EOC cells. Cell growth arrest and proliferation were monitored by assessing the Ki67 antigen, PKH26 fluorescence, and cell cycle distribution. In addition, cells were tested for ERK1/2/p38 MAPK activity ratio, apoptosis, and senescence. The study showed that 72-h serum starvation induces G0/G1 growth arrest of a significant fraction of cells, accompanied by reduced Ki67 and ERK1/2/p38 MAPK activity ratio, without signs of apoptosis or cellular senescence. Moreover, providing cells with 72 h of a medium enriched in 5% serum allows the culture to regain its proliferative potential. At the same time, we attempted to induce and terminate dormancy with Mitomycin C addition and withdrawal, which were unsuccessful. In conclusion, serum starvation is a convenient way to reliably induce dormancy in EOC cells, allowing them to be efficiently awakened for further mechanistic research in vitro.

Premature senescence and cardiovascular disease following cancer treatments: mechanistic insights

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality, especially among the aging population. The "response-to-injury" model proposed by Dr. Russell Ross in 1999 emphasizes inflammation as a critical factor in atherosclerosis development, with atherosclerotic plaques forming due to endothelial cell (EC) injury, followed by myeloid cell adhesion and invasion into the blood vessel walls. Recent evidence indicates that cancer and its treatments can lead to long-term complications, including CVD. Cellular senescence, a hallmark of aging, is implicated in CVD pathogenesis, particularly in cancer survivors. However, the precise mechanisms linking premature senescence to CVD in cancer survivors remain poorly understood. This article aims to provide mechanistic insights into this association and propose future directions to better comprehend this complex interplay.

Metabolic regulation of endothelial senescence

Endothelial cell (EC) senescence is increasingly recognized as a significant contributor to the development of vascular dysfunction and age-related disorders and diseases, including cancer and cardiovascular diseases (CVD). The regulation of cellular senescence is known to be influenced by cellular metabolism. While extensive research has been conducted on the metabolic regulation of senescence in other cells such as cancer cells and fibroblasts, our understanding of the metabolic regulation of EC senescence remains limited. The specific metabolic changes that drive EC senescence are yet to be fully elucidated. The objective of this review is to provide an overview of the intricate interplay between cellular metabolism and senescence, with a particular emphasis on recent advancements in understanding the metabolic changes preceding cellular senescence. I will summarize the current knowledge on the metabolic regulation of EC senescence, aiming to offer insights into the underlying mechanisms and future research directions.

Endocrine pancreas-specific Gclc gene deletion causes a severe diabetes phenotype

Reduced glutathione (GSH) is an abundant antioxidant that regulates intracellular redox homeostasis by scavenging reactive oxygen species (ROS). Glutamate-cysteine ligase catalytic (GCLC) subunit is the rate-limiting step in GSH biosynthesis. Using the Pax6-Cre driver mouse line, we deleted expression of the Gclc gene in all pancreatic endocrine progenitor cells. Intriguingly, Gclc knockout (KO) mice, following weaning, exhibited an age-related, progressive diabetes phenotype, manifested as strikingly increased blood glucose and decreased plasma insulin levels. This severe diabetes trait is preceded by pathologic changes in islet of weanling mice. Gclc KO weanlings showed progressive abnormalities in pancreatic morphology including: islet-specific cellular vacuolization, decreased islet-cell mass, and alterations in islet hormone expression. Islets from newly-weaned mice displayed impaired glucose-stimulated insulin secretion, decreased insulin hormone gene expression, oxidative stress, and increased markers of cellular senescence. Our results suggest that GSH biosynthesis is essential for normal development of the mouse pancreatic islet, and that protection from oxidative stress-induced cellular senescence might prevent abnormal islet-cell damage during embryogenesis.

Progression of irradiated mesenchymal stromal cells from early to late senescence: Changes in SASP composition and anti-tumour properties

Genotoxic injuries converge on senescence-executive program that promotes production of a senescence-specific secretome (SASP). The study of SASP is particularly intriguing, since through it a senescence process, triggered in a few cells, can spread to many other cells and produce either beneficial or negative consequences for health. We analysed the SASP of quiescent mesenchymal stromal cells (MSCs) following stress induced premature senescence (SIPS) by ionizing radiation exposure. We performed a proteome analysis of SASP content obtained from early and late senescent cells. The bioinformatics studies evidenced that early and late SASPs, besides some common ontologies and signalling pathways, contain specific factors. In spite of these differences, we evidenced that SASPs can block in vitro proliferation of cancer cells and promote senescence/apoptosis. It is possible to imagine that SASP always contains core components that have an anti-tumour activity, the progression from early to late senescence enriches the SASP of factors that may promote SASP tumorigenic activity only by interacting and instructing cells of the immune system. Our results on Caco-2 cancer cells incubated with late SASP in presence of peripheral white blood cells strongly support this hypothesis. We evidenced that quiescent MSCs following SIPS produced SASP that, while progressively changed its composition, preserved the capacity to block cancer growth by inducing senescence and/or apoptosis only in an autonomous manner.

Progression of irradiated mesenchymal stromal cells from early to late senescence: Changes in SASP composition and anti-tumour properties

Genotoxic injuries converge on senescence-executive program that promotes production of a senescence-specific secretome (SASP). The study of SASP is particularly intriguing, since through it a senescence process, triggered in a few cells, can spread to many other cells and produce either beneficial or negative consequences for health. We analysed the SASP of quiescent mesenchymal stromal cells (MSCs) following stress induced premature senescence (SIPS) by ionizing radiation exposure. We performed a proteome analysis of SASP content obtained from early and late senescent cells. The bioinformatics studies evidenced that early and late SASPs, besides some common ontologies and signalling pathways, contain specific factors. In spite of these differences, we evidenced that SASPs can block in vitro proliferation of cancer cells and promote senescence/apoptosis. It is possible to imagine that SASP always contains core components that have an anti-tumour activity, the progression from early to late senescence enriches the SASP of factors that may promote SASP tumorigenic activity only by interacting and instructing cells of the immune system. Our results on Caco-2 cancer cells incubated with late SASP in presence of peripheral white blood cells strongly support this hypothesis. We evidenced that quiescent MSCs following SIPS produced SASP that, while progressively changed its composition, preserved the capacity to block cancer growth by inducing senescence and/or apoptosis only in an autonomous manner.

Brain-derived neurotrophic factor promotes orthodontic tooth movement by alleviating periodontal ligament stem cell senescence

Orthodontic treatment in older adults is more difficult than in younger adults, partially due to delayed osteogenesis caused by senescence of human periodontal ligament stem cells (hPDLSCs). The production of brain-derived neurotrophic factor (BDNF) which regulates the differentiation and survival of stem cells decreases with age. We aimed to investigate the relationship between BDNF and hPDLSC senescence and its effects on orthodontic tooth movement (OTM). We constructed mouse OTM models using orthodontic nickel‑titanium springs and compared the responses of wild-type (WT) and BDNF^+/- mice with or without addition of exogenous BDNF. In vitro, hPDLSCs subjected to the mechanical stretch were used to simulate the cell stretch environment during OTM. We extracted periodontal ligament cells from WT and BDNF^+/- mice to evaluate their senescence-related indicators. The application of orthodontic force increased BDNF expression in the periodontium of WT mice, while the mechanical stretch increased BDNF expression in hPDLSCs. Osteogenesis-related indicators, including RUNX2 and ALP decreased and cellular senescence-related indicators such as p16, p53 and β-galactosidase increased in BDNF^+/- mice periodontium. Furthermore, periodontal ligament cells extracted from BDNF^+/- mice exhibited more senescent compared with cells from WT mice. Application of exogenous BDNF decreased the expression of senescence-related indicators in hPDLSCs by inhibiting Notch3, thereby promoting osteogenic differentiation. Periodontal injection of BDNF decreased the expression of senescence-related indicators in periodontium of aged WT mice. In conclusion, our study showed that BDNF promotes osteogenesis during OTM by alleviating hPDLSCs senescence, paving a new path for future research and clinical applications.

SEMA6C: a novel adhesion-independent FAK and YAP activator, required for cancer cell viability and growth

Transmembrane semaphorins are signaling molecules, controlling axonal wiring and embryo development, which are increasingly implicated in human diseases. Semaphorin 6C (Sema6C) is a poorly understood family member and its functional role is still unclear. Upon targeting Sema6C expression in a range of cancer cells, we observed dramatic growth suppression, decreased ERK phosphorylation, upregulation of cell cycle inhibitor proteins p21, p27 and p53, and the onset of cell senescence, associated with activation of autophagy. These data are consistent with a fundamental requirement for Sema6C to support viability and growth in cancer cells. Mechanistically, we unveiled a novel signaling pathway elicited by Sema6C, and dependent on its intracellular domain, mediated by tyrosine kinases c-Abl and Focal Adhesion Kinase (FAK). Sema6C was found in complex with c-Abl, and induced its phosphorylation, which in turn led to FAK activation, independent of cell-matrix adhesion. Sema6C-induced FAK activity was furthermore responsible for increased nuclear localization of YAP transcriptional regulator. Moreover, Sema6C conferred YAP signaling-dependent long-term cancer cell survival upon nutrient deprivation. In conclusion, our findings demonstrate that Sema6C elicits a cancer promoting-signaling pathway sustaining cell viability and self-renewal, independent of growth factors and nutrients availability.

Reduced Fibroblast Activation on Electrospun Polycaprolactone Scaffolds

In vivo, quiescent fibroblasts reside in three-dimensional connective tissues and are activated in response to tissue injury before proliferating rapidly and becoming migratory and contractile myofibroblasts. When deregulated, chronic activation drives fibrotic disease. Fibroblasts cultured on stiff 2D surfaces display a partially activated phenotype, whilst many 3D environments limit fibroblast activation. Cell mechanotransduction, spreading, polarity, and integrin expression are controlled by material mechanical properties and micro-architecture. Between 3D culture systems, these features are highly variable, and the challenge of controlling individual properties without altering others has led to an inconsistent picture of fibroblast behaviour. Electrospinning offers greater control of mechanical properties and microarchitecture making it a valuable model to study fibroblast activation behaviour in vitro. Here, we present a comprehensive characterisation of the activation traits of human oral fibroblasts grown on a microfibrous scaffold composed of electrospun polycaprolactone. After over 7 days in the culture, we observed a reduction in proliferation rates compared to cells cultured in 2D, with low KI67 expression and no evidence of cellular senescence. A-SMA mRNA levels fell, and the expression of ECM protein-coding genes also decreased. Electrospun fibrous scaffolds, therefore, represent a tuneable platform to investigate the mechanisms of fibroblast activation and their roles in fibrotic disease.

β-Cryptoxanthin Maintains Mitochondrial Function by Promoting NRF2 Nuclear Translocation to Inhibit Oxidative Stress-Induced Senescence in HK-2 Cells

The mechanisms of acute kidney injury and chronic kidney disease remain incompletely revealed, and drug development is a pressing clinical challenge. Oxidative stress-induced cellular senescence and mitochondrial damage are important biological events in a variety of kidney diseases. As a type of carotenoid, β-Cryptoxanthin (BCX) has various biological functions, which means it is a potential therapeutic candidate for the treatment of kidney disease. However, the role of BCX in the kidney is unclear, and the effect of BCX on oxidative stress and cellular senescence in renal cells is also unknown. Therefore, we conducted a series of studies on human renal tubular epithelial (HK-2) cells in vitro. In the present study, we investigated the effect of BCX pretreatment on H₂O₂-induced oxidative stress and cellular senescence and explored the potential mechanism of BCX action. The results showed that BCX attenuated H₂O₂-induced oxidative stress and cellular senescence in HK-2 cells. Moreover, BCX promoted NRF2 nuclear expression, maintained mitochondrial function, and reduced mitochondrial damage in HK-2 cells. In addition, silencing NRF2 altered the protective effect of BCX on mitochondria and significantly reversed the anti-oxidative stress and anti-senescence effects of BCX in HK-2 cells. We concluded that BCX maintained mitochondrial function by promoting NRF2 nuclear translocation to inhibit oxidative stress-induced senescence in HK-2 cells. In light of these findings, the application of BCX might be a promising strategy for the prevention and treatment of kidney diseases.

Cell cycle exits and U-turns: Quiescence as multiple reversible forms of arrest

Cell proliferation control is essential during development and for maintaining adult tissues. Loss of that control promotes not only oncogenesis when cells proliferate inappropriately but also developmental abnormalities or degeneration when cells fail to proliferate when and where needed. To ensure that cells are produced at the right place and time, an intricate balance of pro-proliferative and anti-proliferative signals impacts the probability that cells undergo cell cycle exit to quiescence, or G₀ phase. This brief review describes recent advances in our understanding of how and when quiescence is initiated and maintained in mammalian cells. We highlight the growing appreciation for quiescence as a collection of context-dependent distinct states.

Aging of mesenchymal stem cell: machinery, markers, and strategies of fighting

Human mesenchymal stem cells (MSCs) are primary multipotent cells capable of differentiating into osteocytes, chondrocytes, and adipocytes when stimulated under appropriate conditions. The role of MSCs in tissue homeostasis, aging-related diseases, and cellular therapy is clinically suggested. As aging is a universal problem that has large socioeconomic effects, an improved understanding of the concepts of aging can direct public policies that reduce its adverse impacts on the healthcare system and humanity. Several studies of aging have been carried out over several years to understand the phenomenon and different factors affecting human aging. A reduced ability of adult stem cell populations to reproduce and regenerate is one of the main  contributors to the human aging process. In this context, MSCs senescence is a major challenge in front of cellular therapy advancement. Many factors, ranging from genetic and metabolic pathways to extrinsic factors through various cellular signaling pathways, are involved in regulating the mechanism of MSC senescence. To better understand and reverse cellular senescence, this review highlights the underlying mechanisms and signs of MSC cellular senescence, and discusses the strategies to combat aging and cellular senescence.

Environmental microplastics (EMPs) exposure alter the differentiation potential of mesenchymal stromal cells

Humans are exposed to environmental microplastic (MPs) that can be frequent in surrounding environment. The mesenchymal stromal cells are a heterogeneous population, which contain fibroblasts and stromal cells, progenitor cells and stem cells. They are part of the stromal component of most tissue and organs in our organisms. Any injury to their functions may impair tissue renewal and homeostasis. We evaluated the effects of different size MPs that could be present in water bottles on human bone marrow mesenchymal stromal cells (BMMSCs) and adipose mesenchymal stromal cells (AMSCs). MPs of polyethylene terephthalate (MPs-PET) (<1 μm and <2.6 μm) were tested in this study. PET treatments induced a reduction in proliferating cells (around 30%) associated either with the onset of senescence or increase in apoptosis. The AMSCs and BMMSCs exposed to PET showed an alteration of differentiation potential. AMSCs remained in an early stage of adipocyte differentiation as shown by high levels of mRNA for Peroxisome Proliferator Activated Receptor Gamma (PPARG) (7.51 vs 1.00) and reduction in Lipoprotein Lipase (LPL) mRNA levels (0.5 vs 1.0). A loss of differentiation capacity was also observed for the osteocyte phenotype in BMMSCs. In particular, we observed a reduction in Bone Gamma-Carboxy glutamate Protein (BGLAP) (0.4 for PET1 and 0.6 for PET2.6 vs 0.1 CTRL) and reduction in Osteopontin (SPP1) (0.3 for PET 1 and 0.64 for PET 2.6 vs 0.1 CTRL). This pioneering mesenchymal cell response study demonstrated that environmental microplastic could be bioavailable for cell uptake and may further lead to irreversible diseases.

Role of glycosphingolipid SSEA-3 and FGF2 in the stemness and lineage commitment of multilineage differentiating stress enduring (MUSE) cells

OBJECTIVES

Multilineage differentiating Stress Enduring (MUSE) cells are endogenous, stress-resistant stem cells, expressing pluripotency master genes and able to differentiate in cells of the three embryonic sheets. Stage-Specific Embryonic Antigen 3 (SSEA-3), a glycosphingolipid (GSL), is the marker for identifying MUSE cells and is used to isolate this population from mesenchymal stromal cells. GSLs modulate signal transduction by interacting with plasma membrane components. The growth factor FGF2, important for MUSE cells biology, may interact with GSLs. Specific cell surface markers represent an invaluable tool for stem cell isolation. Nonetheless their role, if any, in stem cell biology is poorly investigated. Functions of stem cells, however, depend on niche external cues, which reach cells through surface markers. We addressed the role of SSEA-3 in MUSE cell behaviour, trying to define whether SSEA-3 is just a marker or if it plays a functional role in this cell population by determining if it has any relationship with FGF2 activity.

RESULTS

We evidenced how the SSEA-3 and FGF2 cooperation affected the self-renewal and clonogenic capacity of MUSE cells. The block of SSEA-3 significantly reduced the multilineage potential of MUSE cells with production of nullipotent clones.

CONCLUSIONS

We contributed to dissecting the mechanisms underlying MUSE cell properties for establishing successful stem-cell-based therapies and the promotion of MUSE cells as a tool for the in vitro disease model.

The uniformity and stability of cellular mass density in mammalian cell culture

Cell dry mass is principally determined by the sum of biosynthesis and degradation. Measurable change in dry mass occurs on a time scale of hours. By contrast, cell volume can change in minutes by altering the osmotic conditions. How changes in dry mass and volume are coupled is a fundamental question in cell size control. If cell volume were proportional to cell dry mass during growth, the cell would always maintain the same cellular mass density, defined as cell dry mass dividing by cell volume. The accuracy and stability against perturbation of this proportionality has never been stringently tested. Normalized Raman Imaging (NoRI), can measure both protein and lipid dry mass density directly. Using this new technique, we have been able to investigate the stability of mass density in response to pharmaceutical and physiological perturbations in three cultured mammalian cell lines. We find a remarkably narrow mass density distribution within cells, that is, significantly tighter than the variability of mass or volume distribution. The measured mass density is independent of the cell cycle. We find that mass density can be modulated directly by extracellular osmolytes or by disruptions of the cytoskeleton. Yet, mass density is surprisingly resistant to pharmacological perturbations of protein synthesis or protein degradation, suggesting there must be some form of feedback control to maintain the homeostasis of mass density when mass is altered. By contrast, physiological perturbations such as starvation or senescence induce significant shifts in mass density. We have begun to shed light on how and why cell mass density remains fixed against some perturbations and yet is sensitive during transitions in physiological state.

Deubiquitinating Enzyme USP7 Is Required for Self-Renewal and Multipotency of Human Bone Marrow-Derived Mesenchymal Stromal Cells

Ubiquitin-specific protease 7 (USP7) is highly expressed in a variety of malignant tumors. However, the role of USP7 in regulating self-renewal and differentiation of human bone marrow derived mesenchymal stromal cells (hBMSCs) remains unknown. Herein, we report that USP7 regulates self-renewal of hBMSCs and is required during the early stages of osteogenic, adipogenic, and chondrogenic differentiation of hBMSCs. USP7, a deubiquitinating enzyme (DUB), was found to be downregulated during hBMSC differentiation. Furthermore, USP7 is an upstream regulator of the self-renewal regulating proteins SOX2 and NANOG in hBMSCs. Moreover, we observed that SOX2 and NANOG are poly-ubiquitinated and their expression is downregulated in USP7-deficient hBMSCs. Overall, this study showed that USP7 is required for maintaining self-renewal and multipotency in cultured hBMSCs. Targeting USP7 might be a novel strategy to preserve the self-renewal capacity of hBMSCs intended for stem cell therapy.

Monovalent ions and stress-induced senescence in human mesenchymal endometrial stem/stromal cells

Monovalent ions are involved in growth, proliferation, differentiation of cells as well as in their death. This work concerns the ion homeostasis during senescence induction in human mesenchymal endometrium stem/stromal cells (hMESCs): hMESCs subjected to oxidative stress (sublethal pulse of H₂O₂) enter the premature senescence accompanied by persistent DNA damage, irreversible cell cycle arrest, increased expression of the cell cycle inhibitors (p53, p21) cell hypertrophy, enhanced β-galactosidase activity. Using flame photometry to estimate K⁺, Na⁺ content and Rb⁺ (K⁺) fluxes we found that during the senescence development in stress-induced hMESCs, Na⁺/K⁺pump-mediated K⁺ fluxes are enhanced due to the increased Na⁺ content in senescent cells, while ouabain-resistant K⁺ fluxes remain unchanged. Senescence progression is accompanied by a peculiar decrease in the K⁺ content in cells from 800-900 to 500-600 µmol/g. Since cardiac glycosides are offered as selective agents for eliminating senescent cells, we investigated the effect of ouabain on ion homeostasis and viability of hMESCs and found that in both proliferating and senescent hMESCs, ouabain (1 nM-1 µM) inhibited pump-mediated K⁺ transport (ID₅₀ 5 × 10^-8 M), decreased cell K⁺/Na⁺ ratio to 0.1-0.2, however did not induce apoptosis. Comparison of the effect of ouabain on hMESCs with the literature data on the selective cytotoxic effect of cardiac glycosides on senescent or cancer cells suggests the ion pump blockade and intracellular K⁺ depletion should be synergized with target apoptotic signal to induce the cell death.

Translation of Cellular Senescence to Novel Therapeutics: Insights From Alternative Tools and Models

Increasing chronological age is the greatest risk factor for human diseases. Cellular senescence (CS), which is characterized by permanent cell-cycle arrest, has recently emerged as a fundamental mechanism in developing aging-related pathologies. During the aging process, senescent cell accumulation results in senescence-associated secretory phenotype (SASP) which plays an essential role in tissue dysfunction. Although discovered very recently, senotherapeutic drugs have been already involved in clinical studies. This review gives a summary of the molecular mechanisms of CS and its role particularly in the development of cardiovascular diseases (CVD) as the leading cause of death. In addition, it addresses alternative research tools including the nonhuman and human models as well as computational techniques for the discovery of novel therapies. Finally, senotherapeutic approaches that are mainly classified as senolytics and senomorphics are discussed.

CD44+ and CD133+ Non-Small Cell Lung Cancer Cells Exhibit DNA Damage Response Pathways and Dormant Polyploid Giant Cancer Cell Enrichment Relating to Their p53 Status

Cancer stem cells (CSCs) play a critical role in the initiation, progression and therapy relapse of many cancers including non-small cell lung cancer (NSCLC). Here, we aimed to address the question of whether the FACS-sorted CSC-like (CD44 + &CD133 +) vs. non-CSC (CD44-/CD133- isogenic subpopulations of p53wt A549 and p53null H1299 cells differ in terms of DNA-damage signaling and the appearance of "dormant" features, including polyploidy, which are early markers (predictors) of their sensitivity to genotoxic stress. X-ray irradiation (IR) at 5 Gy provoked significantly higher levels of the ATR-Chk1/Chk2-pathway activity in CD44-/CD133- and CD133+ subpopulations of H1299 cells compared to the respective subpopulations of A549 cells, which only excited ATR-Chk2 activation as demonstrated by the Multiplex DNA-Damage/Genotoxicity profiling. The CD44+ subpopulations did not demonstrate IR-induced activation of ATR, while significantly augmenting only Chk2 and Chk1/2 in the A549- and H1299-derived cells, respectively. Compared to the A549 cells, all the subpopulations of H1299 cells established an increased IR-induced expression of the γH2AX DNA-repair protein. The CD44-/CD133- and CD133+ subpopulations of the A549 cells revealed IR-induced activation of ATR-p53-p21 cell dormancy signaling-mediated pathway, while none of the CD44+ subpopulations of either cell line possessed any signs of such activity. Our data indicated, for the first time, the transcription factor MITF-FAM3C axis operative in p53-deficient H1299 cells, specifically their CD44+ and CD133+ populations, in response to IR, which warrants further investigation. The p21-mediated quiescence is likely the predominant surviving pathway in CD44-/CD133- and CD133+ populations of A549 cells as indicated by single-cell high-content imaging and analysis of Ki67- and EdU-coupled fluorescence after IR stress. SA-beta-galhistology revealed that cellular-stress-induced premature senescence (SIPS) likely has a significant influence on the temporary dormant state of H1299 cells. For the first time, we demonstrated polyploid giant and/or multinucleated cancer-cell (PGCC/MGCC) fractions mainly featuring the progressively augmenting Ki67^low phenotype in CD44+ and CD133+ A549 cells at 24-48 h after IR. In contrast, the Ki67^high phenotype enrichment in the same fractions of all the sorted H1299 cells suggested an increase in their cycling/heterochromatin reorganization activity after IR stress. Our results proposed that entering the "quiescence" state rather than p21-mediated SIPS may play a significant role in the survival of p53wt CSC-like NSCLC cells after IR. The results obtained are important for the selection of therapeutic schemes for the treatment of patients with NSCLC, depending on the functioning of the p53 system in tumor cells.

Molecular dissection on inhibition of Ras-induced cellular senescence by small t antigen of SV40

Simian virus 40 (SV40) is a potentially oncogenic virus of monkey origin. Transmission, prevalence, and pathogenicity rates of SV40 are unclear, but infection can occur in humans, for example individuals with high contact with rhesus macaques and individuals that received contaminated early batches of polio vaccines in 1950-1963. In addition, several human polyomaviruses, proven carcinogenic, are also highly common in global populations. Cellular senescence is a major mechanism of cancer prevention in vivo. Hyperactivation of Ras usually induces cellular senescence rather than cell transformation. Previous studies suggest small t antigen (ST) of SV40 may interfere with cellular senescence induced by Ras. In the current study, ST was demonstrated to inhibit Ras-induced cellular senescence (RIS) and accumulation of DNA damage in Ras-activated cells. In addition, ST suppressed the signal transmission from BRaf to MEK and thus blocked the downstream transmission of the activated Ras signal. B56γ knockdown mimicked the inhibitory effects of ST overexpression on RIS. Furthermore, KSR1 knockdown inhibited Ras activation and the subsequent cellular senescence. Further mechanism studies indicated that the phosphorylation level of KSR1 rather than the levels of the total protein regulates the activation of Ras signaling pathway. In sum, ST inhibits the continuous hyperactivation of Ras signals by interfering with the normal functions of PP2A-B56γ of dephosphorylating KSR1, thus inhibiting the occurrence of cellular senescence. Although the roles of SV40 in human carcinogenesis are controversial so far, our study has shown that ST of polyomaviruses has tumorigenic potential by inhibiting oncogene-induced senescence (OIS) as a proof of concept.

WNT/beta-catenin signalling interrupts a senescence-induction cascade in human mesenchymal stem cells that restricts their expansion

Senescence, the irreversible cell cycle arrest of damaged cells, is accompanied by a deleterious pro-inflammatory senescence-associated secretory phenotype (SASP). Senescence and the SASP are major factors in aging, cancer, and degenerative diseases, and interfere with the expansion of adult cells in vitro, yet little is known about how to counteract their induction and deleterious effects. Paracrine signals are increasingly recognized as important senescence triggers and understanding their regulation and mode of action may provide novel opportunities to reduce senescence-induced inflammation and improve cell-based therapies. Here, we show that the signalling protein WNT3A counteracts the induction of paracrine senescence in cultured human adult mesenchymal stem cells (MSCs). We find that entry into senescence in a small subpopulation of MSCs triggers a secretome that causes a feed-forward signalling cascade that with increasing speed induces healthy cells into senescence. WNT signals interrupt this cascade by repressing cytokines that mediate this induction of senescence. Inhibition of those mediators by interference with NF-κB or interleukin 6 signalling reduced paracrine senescence in absence of WNT3A and promoted the expansion of MSCs. Our work reveals how WNT signals can antagonize senescence and has relevance not only for expansion of adult cells but can also provide new insights into senescence-associated inflammatory and degenerative diseases.

Annexin A1 promotes the progression of bladder cancer via regulating EGFR signaling pathway

BACKGROUND

Bladder cancer (BLCA) is one of the most common malignancies worldwide. One of the main reasons for the unsatisfactory management of BLCA is the complex molecular biological mechanism. Annexin A1 (ANXA1), a Ca²⁺-regulated phospholipid-binding protein, has been demonstrated to be implicated in the progression and prognosis of many cancers. However, the expression pattern, biological function and mechanism of ANXA1 in BLCA remain unclear.

METHODS

The clinical relevance of ANXA1 in BLCA was investigated by bioinformatics analysis based on TCGA and GEO datasets. Immunohistochemical (IHC) analysis was performed to detect the expression of ANXA1 in BLCA tissues, and the relationships between ANXA1 and clinical parameters were analyzed. In vitro and in vivo experiments were conducted to study the biological functions of ANXA1 in BLCA. Finally, the potential mechanism of ANXA1 in BLCA was explored by bioinformatics analysis and verified by in vitro and in vivo experiments.

RESULTS

Bioinformatics and IHC analyses indicated that a high expression level of ANXA1 was strongly associated with the progression and poor prognosis of patients with BLCA. Functional studies demonstrated that ANXA1 silencing inhibited the proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) of BLCA cells in vitro, and suppressed the growth of xenografted bladder tumors in vivo. Mechanistically, loss of ANXA1 decreased the expression and phosphorylation level of EGFR and the activation of downstream signaling pathways. In addition, knockdown of ANXA1 accelerated ubiquitination and degradation of P-EGFR to downregulate the activation of EGFR signaling.

CONCLUSIONS

These findings indicate that ANXA1 is a reliable clinical predictor for the prognosis of BLCA and promotes proliferation and migration by activating EGFR signaling in BLCA. Therefore, ANXA1 may be a promising biomarker for the prognosis of patients with BLCA, thus shedding light on precise and personalized therapy for BLCA in the future.

A senolysis-based theragnostic prodrug strategy towards chronic renal failure

Selective elimination of senescent cells (senolysis) has become a promising therapeutic strategy for the management of chronic renal failure (CRF), but the senolytic molecular pathways towards CRF therapy are limited. Here, we present for the first time a senescence-associated β-galactosidase (SA-β-gal) activatable theragnostic prodrug strategy to pertinently and effectively treat CRF in mice with the aid of fluorescence-guided senolysis. The signs of premature senescence, including the overexpression of β-gal, have been found in kidneys of mice with CRF, making this enzyme particularly suitable as a trigger of prodrugs for CRF therapy. With this unique design, our pioneering prodrug TSPD achieved the activation of a fluorophore for tracking and the specific release of the parent drug, gemcitabine, in β-gal-enriched cells after activation with SA-β-gal. In mice with CRF, abdominal administration of TSPD was effective for improvement of the kidney functions, supporting the feasibility of the SA-β-gal-dependent senolysis therapy towards CRF.

Here, we report a senescence-associated β-galactosidase activatable theragnostic prodrug to pertinently treat chronic renal failure (CRF) in mice with the aid of fluorescence-guided senolysis, providing a creative molecular approach to CRF therapy.

Telomere Shortening and Its Association with Cell Dysfunction in Lung Diseases

Telomeres are localized at the end of chromosomes to provide genome stability; however, the telomere length tends to be shortened with each cell division inducing a progressive telomere shortening (TS). In addition to age, other factors, such as exposure to pollutants, diet, stress, and disruptions in the shelterin protein complex or genes associated with telomerase induce TS. This phenomenon favors cellular senescence and genotoxic stress, which increases the risk of the development and progression of lung diseases such as idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, SARS-CoV-2 infection, and lung cancer. In an infectious environment, immune cells that exhibit TS are associated with severe lymphopenia and death, whereas in a noninfectious context, naïve T cells that exhibit TS are related to cancer progression and enhanced inflammatory processes. In this review, we discuss how TS modifies the function of the immune system cells, making them inefficient in maintaining homeostasis in the lung. Finally, we discuss the advances in drug and gene therapy for lung diseases where TS could be used as a target for future treatments.

Age-related exacerbation of hematopoietic organ damage induced by systemic hyper-inflammation in senescence-accelerated mice

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening systemic hyper-inflammatory disorder. The mortality of HLH is higher in the elderly than in young adults. Senescence-accelerated mice (SAMP1/TA-1) exhibit characteristic accelerated aging after 30 weeks of age, and HLH-like features, including hematopoietic organ damage, are seen after lipopolysaccharide (LPS) treatment. Thus, SAMP1/TA-1 is a useful model of hematological pathophysiology in the elderly with HLH. In this study, dosing of SAMP1/TA-1 mice with LPS revealed that the suppression of myelopoiesis and B-lymphopoiesis was more severe in aged mice than in young mice. The bone marrow (BM) expression of genes encoding positive regulators of myelopoiesis (G-CSF, GM-CSF, and IL-6) and of those encoding negative regulators of B cell lymphopoiesis (TNF-α) increased in both groups, while the expression of genes encoding positive-regulators of B cell lymphopoiesis (IL-7, SDF-1, and SCF) decreased. The expression of the GM-CSF-encoding transcript was lower in aged mice than in young animals. The production of GM-CSF by cultured stromal cells after LPS treatment was also lower in aged mice than in young mice. The accumulation of the TNF-α-encoding transcript and the depletion of the IL-7-encoding transcript were prolonged in aged mice compared to young animals. LPS dosing led to a prolonged increase in the proportion of BM M1 macrophages in aged mice compared to young animals. The expression of the gene encoding p16^INK4a and the proportion of β-galactosidase- and phosphorylated ribosomal protein S6-positive cells were increased in cultured stromal cells from aged mice compared to those from young animals, while the proportion of Ki67-positive cells was decreased in stromal cells from aged mice. Thus, age-related deterioration of stromal cells probably causes the suppression of hematopoiesis in aged mice. This age-related latent organ dysfunction may be exacerbated in elderly people with HLH, resulting in poor prognosis.