DNA damage repair response in mesenchymal stromal cells: From cellular senescence and aging to apoptosis and differentiation ability

PM2.5-induced cellular senescence drives brown adipose tissue impairment in middle-aged mice

Airborne fine particulate matter (PM2.5) exposure is closely associated with metabolic disturbance, in which brown adipose tissue (BAT) is one of the main contributing organs. However, knowledge of the phenotype and mechanism of PM2.5 exposure-impaired BAT is quite limited. In the study, male C57BL/6 mice at three different life phases (young, adult, and middle-aged) were simultaneously exposed to concentrated ambient PM2.5 or filtered air for 8 weeks using a whole-body inhalational exposure system. H&E staining and high-resolution respirometry were used to assess the size of adipocytes and mitochondrial function. Transcriptomics was performed to determine the differentially expressed genes in BAT. Quantitative RT-PCR, immunohistochemistry staining, and immunoblots were performed to verify the transcriptomics and explore the mechanism for BAT mitochondrial dysfunction. Firstly, PM2.5 exposure caused altered BAT morphology and mitochondrial dysfunction in middle-aged but not young or adult mice. Furthermore, PM2.5 exposure increased cellular senescence in BAT of middle-aged mice, accompanied by cell cycle arrest, impaired DNA replication, and inhibited AKT signaling pathway. Moreover, PM2.5 exposure disrupted apoptosis and autophagy homeostasis in BAT of middle-aged mice. Therefore, BAT in middle-aged mice was more vulnerable to PM2.5 exposure, and the cellular senescence-initiated apoptosis, autophagy, and mitochondrial dysfunction may be the mechanism of PM2.5 exposure-induced BAT impairment.

Mechanical Rejuvenation of Mesenchymal Stem Cells from Aged Patients

Mesenchymal stem cells (MSC) are an appealing therapeutic cell type for many diseases. However, patients with poor health or advanced age often have MSCs with poor regenerative properties. A major limiter of MSC therapies is cellular senescence, which is marked by limited proliferation capability, diminished multipotency, and reduced regenerative properties. In this work, we explored the ability of applied mechanical forces to reduce cellular senescence in MSCs. Our studies revealed that mechanical conditioning caused a lasting enhancement in proliferation, overall cell culture expansion potential, multipotency, and a reduction of senescence in MSCs from aged donors. Mechanistic studies suggested that these functional enhancements were mediated by oxidative stress and DNA damage repair signaling with mechanical load altering the expression of proteins of the sirtuin pathway, the DNA damage repair protein ATM, and antioxidant proteins. In addition, our results suggest a biophysical mechanism in which mechanical stretch leads to improved recognition of damaged DNA in the nucleus. Analysis of the cells through RNA-seq and ATAC-seq, demonstrated that mechanical loading alters the cell's genetic landscape to cause broad shifts in transcriptomic patterns that related to senescence. Overall, our results demonstrate that mechanical conditioning can rejuvenate mesenchymal stem cells derived from aged patients and improve their potential as a therapeutic cell type.

GRAPHICAL ABSTRACT

The effect of mesenchymal stem cells administration on DNA repair gene expressions in critically ill COVID-19 patients: prospective controlled study

When the studies are evaluated, immunomodulatory effect of MSCs, administration in critically ill patients, obstacle situations in use and side effects, pulmonary fibrosis prevention, which stem cells and their products, regeneration effect, administration route, and dosage are listed under the main heading like. The effect of MSC administration on DNA repair genes in COVID-19 infection is unknown. Our aim is to determine the effect of mesenchymal stem cells (MSCs) therapy applied in critically ill patients with coronavirus infection on DNA repair pathways and genes associated with those pathways. Patients (n = 30) divided into two equal groups. Group-1: Patients in a critically ill condition, Group-2: Patients in critically ill condition and transplanted MSCs. The mechanism was investigated in eleven genes of five different pathways; Base excision repair: PARP1, Nucleotide excision repair (NER): RAD23B and ERCC1, Homologous recombinational repair (HR): ATM, RAD51, RAD52 and WRN, Mismatch repair (MMR): MLH1, MSH2, and MSH6, Direct reversal repair pathway: MGMT. It was found that MSCs application had a significant effect on 6 genes located in 3 different DNA damage response pathways. These are NER pathway genes; RAD23 and ERCC1, HR pathway genes; ATM and RAD51, MMR pathway genes; MSH2 and MSH6 (p < 0.05). Two main points were shown. First, as a result of cellular damage in critical patients with COVID-19, DNA damage occurs and then DNA repair pathways and genes are activated in reaction to this situation. Second, administration of MSC to patients with COVID-19 infection plays a positive role by increasing the expression of DNA repair genes located in DNA damage pathways.

Stem Leydig cells support macrophage immunological homeostasis through mitochondrial transfer in mice

As testicular mesenchymal stromal cells, stem Leydig cells (SLCs) show great promise in the treatment of male hypogonadism. The therapeutic functions of mesenchymal stromal cells are largely determined by their reciprocal regulation by immune responses. However, the immunoregulatory properties of SLCs remain unclear. Here, we observe that SLCs transplantation restore male fertility and testosterone production in an ischemia‒reperfusion injury mouse model. SLCs prevent inflammatory cascades through mitochondrial transfer to macrophages. Reactive oxygen species (ROS) released from activated macrophages inducing mitochondrial transfer from SLCs to macrophages in a transient receptor potential cation channel subfamily member 7 (TRPM7)-mediated manner. Notably, knockdown of TRPM7 in transplanted SLCs compromised therapeutic outcomes in both testicular ischemia‒reperfusion and testicular aging mouse models. These findings reveal a new mechanism of SLCs transplantation that may contribute to preserve testis function in male patients with hypogonadism related to immune disorders.

Cellular microenvironment: a key for tuning mesenchymal stem cell senescence

Mesenchymal stem cells (MSCs) possess the ability to self-renew and differentiate into multiple cell types, making them highly suitable for use as seed cells in tissue engineering. These can be derived from various sources and have been found to play crucial roles in several physiological processes, such as tissue repair, immune regulation, and intercellular communication. However, the limited capacity for cell proliferation and the secretion of senescence-associated secreted phenotypes (SASPs) pose challenges for the clinical application of MSCs. In this review, we provide a comprehensive summary of the senescence characteristics of MSCs and examine the different features of cellular microenvironments studied thus far. Additionally, we discuss the mechanisms by which cellular microenvironments regulate the senescence process of MSCs, offering insights into preserving their functionality and enhancing their effectiveness.

Mesenchymal stromal cell biotherapy for Parkinson's disease premotor symptoms

Parkinson's disease (PD) is a neurodegenerative disorder with motor deficits due to nigrostriatal dopamine depletion and with the non-motor/premotor symptoms (NMS) such as anxiety, cognitive dysfunction, depression, hyposmia, and sleep disorders. NMS is presented in at least one-fifth of the patients with PD. With the histological information being investigated, stem cells are shown to provide neurotrophic supports and cellular replacement in the damaging brain areas under PD conditions. Pathological change of progressive PD includes degeneration and loss of dopaminergic neurons in the substantia nigra of the midbrain. The current stem cell beneficial effect addresses dopamine boost for the striatal neurons and gliovascular mechanisms as competing for validated PD drug targets. In addition, there are clinical interventions for improving the patient's NMS and targeting their autonomic dysfunction, dementia, mood disorders, or sleep problems. In our and many others' research using brain injury models, multipotent mesenchymal stromal cells demonstrate an additional and unique ability to alleviate depressive-like behaviors, independent of an accelerated motor recovery. Intranasal delivery of the stem cells is discussed for it is extensively tested in rodent animal models of neurological and psychiatric disorders. In this review, we attempt to discuss the repairing potentials of transplanted cells into parkinsonism pathological regions of motor deficits and focus on preventive and treatment effects. From new approaches in the PD biological therapy, it is believed that it can as well benefit patients against PD-NMS.

m6A contributes to a pro-survival state in GC-2 cells by facilitating DNA damage repair: Novel perspectives on the mechanism underlying DEHP genotoxicity in male germ cells

Di(2-ethyl-hexyl) phthalate (DEHP), an environmental endocrine disruptor, can destroy the sperm genomic integrity and impairs spermatogenesis. N6-methyladenosine (m6A) is involved in the cellular effects of DEHP. However, the genotoxic effect of DEHP on spermatocytes and the possible role of m6A in this process remain unclear. This study demonstrated that m6A alleviates DEHP genotoxicity in GC-2 cells. In DEHP-treated mice, DNA double-strand breaks (DSBs) were induced in the testis and spermatocytes. To further explore the molecular mechanism of DEHP genotoxicity on spermatocytes, GC-2 cells were exposed to DEHP. DEHP produced distinct genotoxicity and caused DSBs, which led to the inhibition of DNA synthesis and cell cycle arrest. The DNA damage response (DDR) was initiated to repair the DSBs induced by environmentally relevant levels of DEHP (100 μM and 200 μM). During this process, METTL3 upregulated m6A, which facilitated the DDR via stabilizing the DNA damage repair factors (Rad51 and Xrcc5) mRNA to maintain the pro-survival state. Moreover, Mettl3 knockdown partially inhibited DDR. Interestingly, high-dose DEHP (400 μM and 600 μM) directly induced apoptosis rather than the pro-survival state. Altogether: METTL3-mediated m6A participates in maintaining the pro-survival state by upregulating DDR, providing guidance for mitigating the genotoxicity of environment-related level DEHP exposure.

Chronic stress in solid tumor development: from mechanisms to interventions

Chronic stress results in disturbances of body hormones through the neuroendocrine system. Cancer patients often experience recurrent anxiety and restlessness during disease progression and treatment, which aggravates disease progression and hinders treatment effects. Recent studies have shown that chronic stress-regulated neuroendocrine systems secret hormones to activate many signaling pathways related to tumor development in tumor cells. The activated neuroendocrine system acts not only on tumor cells but also modulates the survival and metabolic changes of surrounding non-cancerous cells. Current clinical evidences also suggest that chronic stress affects the outcome of cancer treatment. However, in clinic, there is lack of effective treatment for chronic stress in cancer patients. In this review, we discuss the main mechanisms by which chronic stress regulates the tumor microenvironment, including functional regulation of tumor cells by stress hormones (stem cell-like properties, metastasis, angiogenesis, DNA damage accumulation, and apoptotic resistance), metabolic reprogramming and immune escape, and peritumor neuromodulation. Based on the current clinical treatment framework for cancer and chronic stress, we also summarize pharmacological and non-pharmacological therapeutic approaches to provide some directions for cancer therapy.

Mesenchymal stem cells support human vascular endothelial cells to form vascular sprouts in human platelet lysate-based matrices

During tissue regeneration, mesenchymal stem cells can support endothelial cells in the process of new vessel formation. For a functional interaction of endothelial cells with mesenchymal stem cells a vascular inductive microenvironment is required. Using a cellular model for neo-vessel formation, we could show that newly formed vascular structures emanated from the embedded aggregates, consisting of mesenchymal stem cells co-cultured with autologous human umbilical vein endothelial cells, into avascular human platelet lysate-based matrices, bridging distances up to 5 mm to join with adjacent aggregates with the same morphology forming an interconnected network. These newly formed vascular sprouts showed branch points and generated a lumen, as sign of mature vascular development. In two-dimensional culture, we detected binding of mesenchymal stem cells to laser-damaged endothelial cells under flow conditions, mimicking the dynamics in blood vessels. In conclusion, we observed that mesenchymal stem cells can support human umbilical vein endothelial cells in their vitality and functionality. In xeno-free human platelet lysate-based matrices, endothelial cells form complex vascular networks in a primarily avascular scaffold with the aid of mesenchymal stem cells, when co-cultured in three-dimensional spherical aggregates. Under dynamic conditions, representing the flow rate of venous vessel, mesenchymal stem cells preferably bind to damaged endothelial cells presumably assisting in the healing process.

Acute cytotoxicity test of PM2.5, NNK and BPDE in human normal bronchial epithelial cells: A comparison of a co-culture model containing macrophages and a mono-culture model

BACKGROUND

Based on extensive research on cytotoxicity of exogenous compounds in vitro, it is essential to develop a cell model that better mimics environment in vivo to explore cytotoxic mechanisms of exogenous compounds.

METHODS

A co-culture system was established using a transwell system with Beas-2B and U937 cells. Cells were treated with fine particulate matter (PM2.5; 25, 50 and 100 μg/mL), nicotine-derived nitrosamine ketone (NNK; 50, 100 and 200 μg/mL) and benzo(a)pyrene diol epoxide (BPDE; 0.5, 2 and 8 μM) for 24 h. Cell proliferation, apoptosis and cell cycle, DNA damage were detected by CCK-8 and EdU, flow cytometry, and comet assay, respectively. Differentially expressed transcript and cytokine concentrations were determined by transcriptome sequencing and Cytokine Array, respectively.

RESULTS

Compared with mono-culture, cell proliferation increased, apoptosis decreased, and DNA damage decreased in a dose-response relationship in co-culture. Gene expression profile was significantly different in co-culture, with significantly increased expression levels of 48 cytokines in co-culture.

CONCLUSION

Cytotoxic damage to Beas-2B cells induced by exogenous carcinogens, including PM2.5, NNK and BPDE, was significantly reduced in a co-culture system compared with a mono-culture system. The mechanism may be related to changes in expression of cytokines, such as LIF, and activation of related pathways, such as TNF signaling pathway. Cytotoxic damage to Beas-2B induced by PM2.5, NNK and BPDE, was significantly reduced in co-culture. The mechanism may be related to changes in expression of cytokines and activation of related pathways. These findings provide new insights into cytotoxicity and experimental basis for safety evaluations of exogenous carcinogens.

Improving the immunomodulatory function of mesenchymal stem cells by defined chemical approach

Mesenchymal stem cell (MSC) is a potential therapeutic material that has self-renewal, multilineage differentiation, and immunomodulation properties. However, the biological function of MSCs may decline due to the influence of donor differences and the in vitro expansion environment, which hinders the advancement of MSC-based clinical therapy. Here, we investigated a method for improving the immunomodulatory function of MSCs with the help of small-molecule compounds, A-83-01, CHIR99021, and Y27632 (ACY). The results showed that small-molecule induced MSCs (SM-MSCs) could enhance their immunosuppressive effects on T cells and macrophages. In vivo studies showed that, in contrast to control MSCs (Ctrl-MSCs), SM-MSCs could inhibit the inflammatory response in mouse models of delayed hypersensitivity and acute peritonitis more effectively. In addition, SM-MSCs showed the stronger ability to inhibit the infiltration of pro-inflammatory T cells and macrophages. Thus, small-molecule compounds ACY could better promote the immunomodulatory effect of MSCs, indicating it could be a potential improving method in MSC culture.

Endothelial cells regulated by RNF20 orchestrate the proliferation and differentiation of neural precursor cells during embryonic development

The intimate communication between the vascular and nervous systems is critical for maintaining central nervous system (CNS) development. However, whether cerebrovascular endothelial cells (ECs) can orchestrate neural precursor cell (NPC) proliferation and differentiation, and the identity of the signals involved therein, is unclear. Here, we find that the development of ECs is often accompanied by DNA damage. RNF20, an E3 ubiquitin ligase, is required for the DNA damage response (DDR). The deletion of RNF20 causes the accumulation of DNA damage in ECs, which fails to secrete cartilage intermediate layer protein 2 (CILP2). Moreover, the loss of endothelium-derived CILP2 alters the downstream cascade signaling of Wnt signaling pathways through the interaction with Wnt3a, which disturbs the NPC fate and causes autism-like behaviors in mice. Therefore, the close and refined controlled neurovascular interactions ensure the normal operation of neurogenesis during embryonic development.

Fullerenol protects cornea from ultraviolet B exposure

The eyes are highly susceptible to the oxidative stress induced by ultraviolet B (UVB, wavelength between 280 ∼ 320 nm), which could cause severe damage to the cornea. Fullerenols are effective antioxidants to alleviate UVB-induced injury, while their application for the eyes is still rare. In present study, we investigated the protective performance and mechanism of fullerenols on cornea under UVB radiation in vivo and in vitro. The synthesized fullerenols exhibited broad-spectrum free radical scavenging properties (applicable to both reactive oxygen species (ROS) and reactive nitrogen species (RNS)) and photo-stability. When compared with another widely used antioxidant glutathione (GSH), the administration of fullerenols markedly decreased the injured area, corneal edema, cell death, and increased the cell proliferation in UVB-induced rat cornea. The effects of fullerenols were confirmed in UVB-exposed human corneal epithelial cells (hCECs), where elevated cell viability and proliferation, decreased oxidative free radical production, repaired mitochondrial dysfunction and DNA lesions were observed. RNA sequencing (RNA-Seq) analysis demonstrated that fullerenol alleviated UVB-induced corneal injury through down-regulation of oxidative stress-related genes and up-regulation of proliferation-associated genes. Our results demonstrate the suitability of fullerenols as a potential exogenous treatment in ameliorating UVB-induced cornea damage.

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Fullerenol produces significant precaution on UVB-induced corneal damage.

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Fullerenol exhibits broader spectrum free radical scavenging properties than GSH.

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Fullerenol mitigates the LSCs loss in the cornea caused by UVB.

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Fullerenol down-regulates oxidative stress genes and up-regulates proliferation-related genes.

The role of senescence in cellular plasticity: Lessons from regeneration and development and implications for age-related diseases

Senescence is a cellular state which involves cell cycle arrest and a proinflammatory phenotype, and it has traditionally been associated with cellular and organismal aging. However, increasing evidence suggests key roles in tissue growth and regrowth, especially during development and regeneration. Conversely, cellular plasticity-the capacity of cells to undergo identity change, including differentiation and dedifferentiation-is associated with development and regeneration but is now being investigated in the context of age-related diseases such as Alzheimer disease. Here, we discuss the paradox of the role for cellular senescence in cellular plasticity: senescence can act as a cell-autonomous barrier and a paracrine driver of plasticity. We provide a conceptual framework for integrating recent data and use the interplay between cellular senescence and plasticity to provide insight into age-related diseases. Finally, we argue that age-related diseases can be better deciphered when senescence is recognized as a core mechanism of regeneration and development.

A Small-Molecule Cocktails-Based Strategy in Culture of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have a variety of unique properties, such as stem cell multipotency and immune regulation, making them attractive for use in cell therapy. Before infusion therapy, MSCs are required to undergo tissue separation, purification, and expansion in vitro for a certain duration. During the process of in vitro expansion of MSCs, the influence of culture time and environment can lead to cell senescence, increased heterogeneity, and function attenuation, which limits their clinical applications. We used a cocktail of three small-molecule compounds, ACY (A-83–01, CHIR99021, and Y-27632), to increase the proliferation activity of MSCs in vitro and reduce cell senescence. ACY inhibited the increase in heterogeneity of MSCs and conserved their differentiation potential. Additionally, ACY maintained the phenotype of MSCs and upregulated the expression of immunomodulatory factors. These results suggest that ACY can effectively improve the quantity and quality of MSCs.

Exploring microenvironment strategies to delay mesenchymal stem cell senescence

Mesenchymal stem cells (MSCs) have recently emerged as an important candidate for cell therapy and tissue regeneration. However, some limitations in translational research and therapies still exist, such as insufficient cell supply, inadequate differentiation potential, and decreased immune capacity, all of which result from replicative senescence during long-term in vitro culture. In vitro, stem cells lack a protective microenvironment owing to the absence of physical and biochemical cues compared with the in vivo niche, which provides dynamic physicochemical and biological cues. This difference results in accelerated aging after long-term in vitro culture. Therefore, it remains a great challenge to delay replicative senescence in culture. Constructing a microenvironment to delay replicative senescence of MSCs by maintaining their phenotypes, properties, and functions is a feasible strategy to solve this problem and has made measurable progress both in preclinical studies and clinical trials. Here, we review the current knowledge on the characteristics of senescent MSCs, explore the molecular mechanisms of MSCs senescence, describe the niche of MSCs, and discuss some current microenvironment strategies to delay MSCs replicative senescence that can broaden their range of therapeutic applications.

Molecular Targets and Emerging Therapies for Advanced Gallbladder Cancer

Biliary tract cancers (BTCs), for their low incidence, have been often considered together. Gallbladder cancer (GBC) is the most common biliary tract malignancy, characterized by late diagnosis and poor prognosis, and although it is considered a rare tumor in western countries, other areas of the world show considerable incidence rates. In 2010, results from the large phase III ABC-02 clinical trial on GBC identified the gemcitabine and cisplatin combination as the most effective first-line regimen for both GBC and other BTCs. Since then, various systemic therapies have proven active in BTCs in both first- and second-line settings. Molecular profiling has highlighted important genetic differences between GBC and other BTCs, opening new ways for targeted therapy in advanced disease where standard chemotherapies show marginal benefit. Genome-wide data analysis have shown that GBC molecular landscape offer possible strategies for precision medicine approaches, and a better molecular understanding of the GBC is needed to better stratify patients for treatment. In this review, we discuss the molecular targetable agents for GBC, including the results that emerged by clinical trials exploring new treatment strategies.

Tumorigenic Aspects of MSC Senescence-Implication in Cancer Development and Therapy

As an organism ages, many physiological processes change, including the immune system. This process, called immunosenescence, characterized by abnormal activation and imbalance of innate and adaptive immunity, leads to a state of chronic low-grade systemic inflammation, termed inflammaging. Aging and inflammaging are considered to be the root of many diseases of the elderly, as infections, autoimmune and chronic inflammatory diseases, degenerative diseases, and cancer. The role of mesenchymal stromal/stem cells (MSCs) in the inflammaging process and the age-related diseases is not completely established, although numerous features of aging MSCs, including altered immunomodulatory properties, impeded MSC niche supporting functions, and senescent MSC secretory repertoire are consistent with inflammaging development. Although senescence has its physiological function and can represent a mechanism of tumor prevention, in most cases it eventually transforms into a deleterious (para-)inflammatory process that promotes tumor growth. In this review we are going through current literature, trying to explore the role of senescent MSCs in making and/or sustaining a microenvironment permissive to tumor development and to analyze the therapeutic options that could target this process.

Dysregulation of Caveolin-1 Phosphorylation and Nuclear Translocation Is Associated with Senescence Onset

We recently reported that the inability of osteoarthritic (OA) chondrocytes to repair oxidative stress (OS) induced DNA damage is linked to Cav-1 overexpression/improper localization. We speculated that the senescent status of OA cells was responsible for this Cav-1 dysregulation. Here, to further investigate this hypothesis, we used Wharton Jelly derived mesenchymal stem cells (WJ-MSCs) and investigated Cav-1 function as cells reached replicative senescence or upon stress induced senescence (SIPS). We showed that Cav-1 is upregulated, phosphorylated and translocated to the nucleus in young WJ-MSCs upon acute exogenous OS, and that it returns back to basal/nonphosphorylated levels and exports the nucleus in the recovery phase. However, as cells reach senescence, this regulation is lost. OS did not induce any Cav-1-mediated response, which is concomitant with the inability of older cells to restore DNA damage. Furthermore, downregulation of Cav-1 resulted in persistent OS-induced DNA damage and subsequent onset of senescence. We also report that the establishment of senescence is mediated by autophagy stimulation, since downregulation of autophagy key molecule Atg5, simultaneously with Cav-1 downregulation, was found to inhibit SIPS. Basically, we propose that Cav-1 involvement in DNA damage response can lead to senescence, either because the damage is extensive or because Cav-1 is absent/unable to perform its homeostatic role.

Role of mismatch repair in aging

A common feature of aging is the accumulation of genetic damage throughout life. DNA damage can lead to genomic instability. Many diseases associated with premature aging are a result of increased accumulation of DNA damage. In order to minimize these damages, organisms have evolved a complex network of DNA repair mechanisms, including mismatch repair (MMR). In this review, we detail the effects of MMR on genomic instability and its role in aging emphasizing on the association between MMR and the other hallmarks of aging, serving to drive or amplify these mechanisms. These hallmarks include telomere attrition, epigenetic alterations, mitochondrial dysfunction, altered nutrient sensing and cell senescence. The close relationship between MMR and these markers may provide prevention and treatment strategies, to reduce the incidence of age-related diseases and promote the healthy aging of human beings.

Bone marrow mesenchymal stem cells derived from juvenile macaques reversed ovarian ageing in elderly macaques

BACKGROUND

Female sex hormone secretion and reproductive ability decrease with ageing. Bone marrow mesenchymal stem cells (BMMSCs) have been postulated to play a key role in treating ovarian ageing.

METHODS

We used macaque ovarian ageing models to observe the structural and functional changes after juvenile BMMSC treatment. Moreover, RNA-seq was used to analyse the ovarian transcriptional expression profile and key pathways through which BMMSCs reverse ovarian ageing.

RESULTS

In the elderly macaque models, the ovaries were atrophied, the regulation ability of sex hormones was reduced, the ovarian structure was destroyed, and only local atretic follicles were observed, in contrast with young rhesus monkeys. Intravenous infusion of BMMSCs in elderly macaques increased ovarian volume, strengthened the regulation ability of sex hormones, reduced the degree of pulmonary fibrosis, inhibited apoptosis, increased density of blood vessels, and promoted follicular regeneration. In addition, the ovarian expression characteristics of ageing-related genes of the elderly treatment group reverted to that of the young control group, 1258 genes that were differentially expressed, among which 415 genes upregulated with age were downregulated, 843 genes downregulated with age were upregulated after BMMSC treatment, and the top 20 differentially expressed genes (DEGs) in the protein-protein interaction (PPI) network were significantly enriched in oocyte meiosis and progesterone-mediated oocyte maturation pathways.

CONCLUSION

The BMMSCs derived from juvenile macaques can reverse ovarian ageing in elderly macaques.

Dependence of mitochondrial function on the filamentous actin cytoskeleton in cultured mesenchymal stem cells treated with cytochalasin B

Owing to their self-renewal and multi-lineage differentiation capability, mesenchymal stem cells (MSCs) hold enormous potential in regenerative medicine. A prerequisite for a successful MSC therapy is the rigorous investigation of their function after in vitro cultivation. Damages introduced to mitochondria during cultivation adversely affect MSCs function and can determine their fate. While it has been shown that microtubules and vimentin intermediate filaments are important for mitochondrial dynamics and active mitochondrial transport within the cytoplasm of MSCs, the role of filamentous actin in this process has not been fully understood yet. To gain a deeper understanding of the interdependence between mitochondrial function and the cytoskeleton, we applied cytochalasin B to disturb the filamentous actin-based cytoskeleton of MSCs. In this study we combined conventional functional assays with a state-of-the-art oxygen sensor-integrated microfluidic device to investigate mitochondrial function. We demonstrated that cytochalasin B treatment at a dose of 16 μM led to a decrease in cell viability with high mitochondrial membrane potential, increased oxygen consumption rate, disturbed fusion and fission balance, nuclear extrusion and perinuclear accumulation of mitochondria. Treatment of MSCs for 48 h ultimately led to nuclear fragmentation, and activation of the intrinsic pathway of apoptotic cell death. Importantly, we could show that mitochondrial function of MSCs can efficiently recover from the damage to the filamentous actin-based cytoskeleton over a period of 24 h. As a result of our study, a causative connection between the filamentous actin-based cytoskeleton and mitochondrial dynamics was demonstrated.

The biogenesis and biological function of PIWI-interacting RNA in cancer

Small non-coding RNAs (ncRNAs) are vital regulators of biological activities, and aberrant levels of small ncRNAs are commonly found in precancerous lesions and cancer. PIWI-interacting RNAs (piRNAs) are a novel type of small ncRNA initially discovered in germ cells that have a specific length (24-31 nucleotides), bind to PIWI proteins, and show 2'-O-methyl modification at the 3'-end. Numerous studies have revealed that piRNAs can play important roles in tumorigenesis via multiple biological regulatory mechanisms, including silencing transcriptional and posttranscriptional gene processes and accelerating multiprotein interactions. piRNAs are emerging players in the malignant transformation of normal cells and participate in the regulation of cancer hallmarks. Most of the specific cancer hallmarks regulated by piRNAs are involved in sustaining proliferative signaling, resistance to cell death or apoptosis, and activation of invasion and metastasis. Additionally, piRNAs have been used as biomarkers for cancer diagnosis and prognosis and have great potential for clinical utility. However, research on the underlying mechanisms of piRNAs in cancer is limited. Here, we systematically reviewed recent advances in the biogenesis and biological functions of piRNAs and relevant bioinformatics databases with the aim of providing insights into cancer diagnosis and clinical applications. We also focused on some cancer hallmarks rarely reported to be related to piRNAs, which can promote in-depth research of piRNAs in molecular biology and facilitate their clinical translation into cancer treatment.

Cellular senescence in vascular wall mesenchymal stromal cells, a possible contribution to the development of aortic aneurysm

Cellular senescence is a hallmark of ageing and it plays a key role in the development of age-related diseases. Abdominal aortic aneurysm (AAA) is an age related degenerative vascular disorder, characterized by a progressive dilatation of the vascular wall and high risk of rupture over time. Nowadays, no pharmacological therapies are available and the understanding of the molecular mechanisms that lead to AAA onset and development are poorly defined. In this study we investigated the cellular features of senescence in vascular mesenchymal stromal cells, isolated from pathological (AAA - MSCs) and healthy (h - MSCs) segments of human abdominal aorta and their implication in impairing the vascular repair ability of MSCs. Cell proliferation, ROS production, cell surface area, the expression of cyclin dependent kinase inhibitors p21^CIP1 and p16^INK4a, the activation of the DNA damage response and a dysregulated autophagy showed a senescent state in AAA - MSCs compared to h-MSCs. Moreover, a reduced ability to differentiate toward endothelial cells was observed in AAA - MSCs. All these data suggest that the accumulation of senescent vascular MSCs over time impairs their remodeling ability during ageing. This condition could support the onset and development of AAA.

Role of Hyperglycemia in the Senescence of Mesenchymal Stem Cells

The regenerative and immunomodulatory properties of mesenchymal stem cells (MSCs) have laid a sound foundation for their clinical application in various diseases. However, the clinical efficiency of MSC treatments varies depending on certain cell characteristics. Among these, the roles of cell aging or senescence cannot be excluded. Despite their stemness, evidence of senescence in MSCs has recently gained attention. Many factors may contribute to the senescence of MSCs, including MSC origin (biological niche), donor conditions (age, obesity, diseases, or unknown factors), and culture conditions in vitro. With the rapidly increasing prevalence of diabetes mellitus (DM) and gestational diabetes mellitus (GDM), the effects of hyperglycemia on the senescence of MSCs should be evaluated to improve the application of autologous MSCs. This review aims to present the available data on the senescence of MSCs, its relationship with hyperglycemia, and the strategies to suppress the senescence of MSCs in a hyperglycemic environment.

Timolol induces necroptosis, apoptosis and senescence concentration-dependently in rabbit Limbal stem cells in vitro

Limbal stem cells (LSCs) are crucial for corneal transparency and vision. Any damages to LSCs might lead to limbal stem cell deficiency resulting in corneal opacification and even blindness. Here, we investigated the cytotoxicity of timolol and its underlying mechanisms in rabbit LSCs (rLSCs) in vitro. High concentrations of 0.5% and 0.25% timolol induced necroptosis in rLSCs to upregulate receptor interacting protein kinase (RIPK)1, RIPK3, mixed lineage kinase domain-like (MLKL) and phosphorylated MLKL along with downregulation of caspase-8 and caspase-2 within 4 h. While, median concentrations of 0.125% to 0.0625% timolol induced apoptosis in the rLSCs within 28 h. The apoptotic mechanism in the median-concentration timolol-treated rLSCs is probably via extrinsic apoptosis pathway by activating caspase-2, caspase-8 and caspase-3 and intrinsic apoptosis pathway triggered by excessive generation of ROS and subsequent DNA damage to upregulate Bax and Bad, downregulate Bcl-2 and Bcl-xL, subsequently disrupt mitochondrial membrane potential, cytosolically translocate cytochrome c and apoptosis-inducing factor, and activate caspase-9. In addition, low concentration of 0.03125% timolol induced senescence in the rLSCs by elevating ROS level and increasing number of senescence associated β-galactosidase positive cells at 28 h. Our findings reveal that timolol induces necroptosis, apoptosis and senescence concentration-dependently in rLSCs in vitro.

The Valproate Mediates Radio-Bidirectional Regulation Through RFWD3-Dependent Ubiquitination on Rad51

Ionizing radiation (IR) can induce DNA double-strand breaks (DSBs) in tumor cells during radiotherapy (RT), but the efficiency of RT is limited because of the toxicity to normal cells. Locating an adjuvant treatment to alleviate damage in normal cells while sensitizing tumor cells to IR has attracted much attention. Here, using the 7,12-dimethylbenz[α]anthracene (DMBA)-induced malignant transformed MCF10A cells, we found that valproate (VPA), a histone deacetylase inhibitor (HDACi), radiosensitized transformed cells while alleviated IR-induced damage in normal cells at a safe dose (0.5 mM). We further demonstrated the decrease of homologous recombination (HR)-associated Rad51 in the transformed cells was related to the increase of its ubiquitination regulated by E3 ligase RFWD3 for the radiosensitization, which was opposite to normal cells, indicating that RFWD3-dependent ubiquitination on Rad51 was involved in the VPA-mediated radio-bidirectional effect. Through DMBA-transformed breast cancer rat model, VPA at 200 mg/kg radiosensitized tumor tissue cells by increasing RFWD3 and inhibited Rad51, while radioprotected normal tissue cells by decreasing RFWD3 and enhanced Rad51. In addition, we found high-level Rad51 was associated with tumorigenesis and poor prognosis in breast cancer patients. Our findings uncovered RFWD3-dependent Rad51 ubiquitination was the novel mechanism of VPA-mediated radio-bidirectional effect, VPA is a potential adjuvant treatment for tumor RT.

Evidence and perspectives of cell senescence in neurodegenerative diseases

Increased life expectancies have significantly increased the number of individuals suffering from geriatric neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). The financial cost for current and future patients with these diseases is overwhelming, resulting in substantial economic and societal costs. Unfortunately, most recent high-profile clinical trials for neurodegenerative diseases have failed to obtain efficacious results, indicating that novel approaches are desperately needed to treat these pathologies. Cell senescence, characterized by permanent cell cycle arrest, resistance to apoptosis, mitochondrial alterations, and secretion of senescence-associated secretory phenotype (SASP) components, has been extensively studied in mitotic cells such as fibroblasts, which is considered a hallmark of aging. Furthermore, multiple cell types in the senescent state in the brain, including neurons, microglia, astrocytes, and neural stem cells, have recently been observed in the context of neurodegenerative diseases, suggesting that these senescent cells may play an essential role in the pathological processes of neurodegenerative diseases. Therefore, this review begins by outlining key aspects of cell senescence constitution followed by examining the evidence implicating senescent cells in neurodegenerative diseases. In the final section, we review how cell senescence may be targeted as novel therapeutics to treat pathologies associated with neurodegenerative diseases.

Theoretical insight into 7,8-dihydrogen-8-oxoguanine radical cation deprotonation

The pK_a values of reactive protons in 8-oxoG˙⁺ and potential energy profiles for 8-oxoG radical cation deprotonation reaction (N1–H and N7–H) were firstly calculated.

The role of Nrf2 in neural stem/progenitors cells: From maintaining stemness and self-renewal to promoting differentiation capability and facilitating therapeutic application in neurodegenerative disease

Neurodegenerative diseases (NDs) cause progressive loss of neurons in nervous system. NDs are categorized as acute NDs such as stroke and head injury, besides chronic NDs including Alzheimer's, Parkinson's, Huntington's diseases, Friedreich's Ataxia, Multiple Sclerosis. The exact etiology of NDs is not understood but oxidative stress, inflammation and synaptic dysfunction are main hallmarks. Oxidative stress leads to free radical attack on neural cells which contributes to protein misfolding, glia cell activation, mitochondrial dysfunction, impairment of DNA repair system and subsequently cellular death. Neural stem cells (NSCs) support adult neurogenesis in nervous system during injuries which is limited to certain regions in brain. NSCs can differentiate into the neurons, astrocytes or oligodendrocytes. Impaired neurogenesis and inadequate induction of neurogenesis are the main obstacles in treatment of NDs. Protection of neural cells from oxidative damages and supporting neurogenesis are promising strategies to treat NDs. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a transcriptional master regulator that maintains the redox homeostasis in cells by provoking expression of antioxidant, anti-inflammatory and cytoprotective genes. Nrf2 can strongly influence the NSCs function and fate determination by reducing levels of reactive oxygen species in benefit of NSC survival and neurogenesis. In this review we will summarize the role of Nrf2 in NSC function, and exogenous and endogenous therapeutic strategies in treatment of NDs.

Overview of current targeted therapy in gallbladder cancer

Gallbladder cancer (GBC) is rare, but is the most malignant type of biliary tract tumor. Unfortunately, only a small population of cancer patients is acceptable for the surgical resection, the current effective regimen; thus, the high mortality rate has been static for decades. To substantially circumvent the stagnant scenario, a number of therapeutic approaches owing to the creation of advanced technologic measures (e.g., next-generation sequencing, transcriptomics, proteomics) have been intensively innovated, which include targeted therapy, immunotherapy, and nanoparticle-based delivery systems. In the current review, we primarily focus on the targeted therapy capable of specifically inhibiting individual key molecules that govern aberrant signaling cascades in GBC. Global clinical trials of targeted therapy in GBC are updated and may offer great value for novel pathologic and therapeutic insights of this deadly disease, ultimately improving the efficacy of treatment.