The inflammatory cytokine TNF-α promotes the premature senescence of rat nucleus pulposus cells via the PI3K/Akt signaling pathway

Advances in the study of the glymphatic system and aging

The glymphatic system is cerebrospinal fluid-brain tissue fluid exchange flow mediated by aquaporin-4 (AQP4) on the end feet of astrocytes for a system, which is capable of rapidly removing brain metabolites and thus maintaining brain homeostasis, and is known as the central immune system. Dysfunction of the glymphatic system causes accumulation of misfolded and highly phosphorylated proteins (amyloid-β and Tau proteins), which destabilizes the proteins, and the body's neuroinflammatory factors are altered causing aging of the immune system and leading to neurodegenerative diseases. Damage to the glymphatic system and aging share common manifestations, as well as unstudied biological mechanisms that are also linked, such as mitochondria, oxidative stress, chronic inflammation, and sleep. In this paper, we first summarize the structure, function, and research methods of the glymphatic system and the relationship between the glymphatic system and the peripheral immune system, and second, sort out and summarize the factors of the glymphatic system in removing metabolites and resolving aging-related diseases and factors affecting aging, to explore its related biological mechanisms, and moreover, to provide a new way of thinking for treating or intervening aging-related diseases.

Palm Kernel Cake Extracts Obtained from the Combination of Bacterial Fermentation and Enzymic Hydrolysis Promote Swine Small Intestine IPEC-J2 Cell Proliferation and Alleviate LPS-Induced Inflammation In Vitro

Co-fermentation with bacteria and enzymes can reduce sugar content in palm kernel cake (PKC); however, the chemical changes and their effects on cell functionality are unclear. This study investigated the active components in pre-treated PKC extracts and their effects on pig small intestine IPEC-J2 cell proliferation and LPS-induced inflammation. The extracts contained 60.75% sugar, 36.80% mannose, 1.75% polyphenols and 0.59% flavone, as determined by chemical analyses, suggesting that the extracts were palm kernel cake oligosaccharides (PKCOS). Then, we found that 1000 µg/mL PKCOS counteracted the decrease in cell viability (CCK8 kit) caused by LPS induction by 5 µg/mL LPS (p < 0.05). Mechanistic studies conducted by RNA-seq and qPCR analyses suggested PKCOS promoted cell proliferation through the upregulation of TNF-α, PI3KAP1, MAP3K5 and Fos in the PI3K/MAPK signalling pathway; alleviated inflammation caused by LPS via the downregulation of the target genes Casp3 and TNF-α in association with apoptosis; and regulated the expression of the antioxidant genes SOD1, SOD2 and GPX4 to exert positive antioxidant effects (p < 0.05). Furthermore, PKCOS upregulated SLC5A1 (encoding SLGT1), HK and MPI in the glycolytic pathway (p < 0.05), suggesting cell survival. In summary, PKCOS has positive effects on promoting swine intestine cell proliferation against inflammation.

Joint Effects of Exercise and Ramadan Fasting on Telomere Length: Implications for Cellular Aging

Aging is a fundamental biological process that progressively impairs the functionality of the bodily systems, leading to an increased risk of diseases. Telomere length is one of the most often used biomarkers of aging. Recent research has focused on developing interventions to mitigate the effects of aging and improve the quality of life. The objective of this study was to investigate the combined effect of exercise and Ramadan fasting on telomere length. Twenty-nine young, non-obese, healthy females were randomized into two groups: the control group underwent a 4-week exercise training program, and the second group underwent a 4-week exercise training program while fasting during Ramadan. Blood samples were collected, and measurements of clinical traits, cytokines, oxidative stress, and telomere length were performed before and after intervention. Telomere length increased significantly from baseline in the exercise-while-fasting group, but showed no significant change in the exercise control group. This increase was accompanied by a reduction in TNF-α, among other cytokines. Additionally, a significant positive correlation was observed between the mean change in telomere length and HDL in the exercise-while-fasting group only. This study is the first to report an increase in telomere length after combining Ramadan fasting with training, suggesting that exercising while fasting may be an effective tool for slowing down the aging rate. Further studies using larger and more diverse cohorts are warranted.

Senescent response in inner annulus fibrosus cells in response to TNFα, H2O2, and TNFα-induced nucleus pulposus senescent secretome

Senescence, particularly in the nucleus pulposus (NP) cells, has been implicated in the pathogenesis of disc degeneration, however, the mechanism(s) of annulus fibrosus (AF) cell senescence is still not well understood. Both TNFα and H2O2, have been implicated as contributors to the senescence pathways, and their levels are increased in degenerated discs when compared to healthy discs. Thus, the objective of this study is to identify factor(s) that induces inner AF (iAF) cell senescence. Under TNFα exposure, at a concentration previously shown to induce senescence in NP cells, bovine iAF cells did not undergo senescence, indicated by their ability to continue to proliferate as demonstrated by Ki67 staining and growth curves and lack of expression of the senescent markers, p16 and p21. The lack of senescent response occurred even though iAF express higher levels of TNFR1 than NP cells. Interestingly, iAF cells showed no increase in intracellular ROS or secreted H2O2 in response to TNFα which contrasted to NP cells that did. Following TNFα treatment, only iAF cells had increased expression of the superoxide scavengers SOD1 and SOD2 whereas NP cells had increased NOX4 gene expression, an enzyme that can generate H2O2. Treating iAF cells with low dose H2O2 (50 μM) induced senescence, however unlike TNFα, H2O2 did not induce degenerative-like changes as there was no difference in COL2, ACAN, MMP13, or IL6 gene expression or number of COL2 and ACAN immunopositive cells compared to untreated controls. The latter result suggests that iAF cells may have distinct degenerative and senescent phenotypes. To evaluate paracrine signalling by senescent NP cells, iAF and TNFα-treated NP cells were co-cultured. In contact co-culture the NP cells induced iAF senescence. Thus, senescent NP cells may secrete soluble factors that induce degenerative and senescent changes within the iAF. This may contribute to a positive feedback loop of disc degeneration. It is possible these factors may include H2O2 and cytokines (such as TNFα). Further studies will investigate if human disc cells respond similarly.

TIM-3 regulates the proliferation by BDNF-mediated PI3K/AKT axis in the process of endometriosis

BACKGROUND

T cell immunoglobulin and mucin domain-containing molecule-3 (TIM-3) initially discovered on the surface of Th1 cells, negatively regulates immune responses and mediates apoptosis of Th1 cells. An increasing number of studies have since shown that TIM-3 is crucial in the genesis and development of immune diseases, cancers, and chronic infectious illnesses. However, the effect of TIM-3 on endometriosis is still unknown.

METHODS

Quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry were used to measure TIM-3 levels in endometriosis. Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine, colony-forming, Transwell® migration, Matrigel® invasion, and flow cytometry assays were used to explore the function of TIM-3 in vitro, and xenograft experiments in nude mice were used to assess its role in vivo. According to the RNA seq, brain-derived neurotrophic factor (BDNF) was screened. The involvement of specific proliferation-related signaling molecules was determined by transfecting a plasmid and adding an inhibitor in vivo and in vitro.

RESULTS

TIM-3 mRNA and protein expression levels were significantly higher in eutopic and ectopic endometrial tissues than in normal endometrial tissues. By examining the effects of TIM-3 overexpression and knockdown on cell proliferation, migration, and invasion in vitro, and lesions formation in vivo, we found that the expression of TIM-3 was positively correlated with cell proliferation and clone formation in vitro, as well as lesions growth in nude mice. By adding the phosphatidylinositol 3 kinase/protein kinase B(PI3K/AKT) pathway inhibitor LY294002 and knocking down PI3K, we further verified that TIM-3 promotes proliferation in vivo and in vitro via the PI3K pathway. By transfecting the plasmid into ESC cells and gave inhibitors to endometriotic rats models, we tested that TIM-3 regulates the proliferation by BDNF-mediated PI3K/AKT axis.

CONCLUSION

TIM-3 can promote the proliferation of endometriosis by BDNF-mediated PI3K/AKT axis in vivo and in vitro, which may provide a new therapeutic target for the treatment of endometriosis.

Non-Intrinsic, Systemic Mechanisms of Cellular Senescence

Cellular senescence is believed to contribute to aging and disease through the activity of secreted factors that promote inflammation, remodel the extracellular matrix, and adversely modify the behavior of non-senescent cells. While the markers and properties of senescent cells are still under investigation, it is postulated that cellular senescence manifests in vivo as the consequence of cellular damage that accumulates and becomes exacerbated with time. Yet, the notions that senescence has a solely intrinsic and time-dependent nature are questioned by the rapid induction of senescence in young mice and young cells in vitro by exposure to blood from aged animals. Here, we review some of the research on the systemically present factors that increase with age and may contribute to extrinsically induced senescence or "bystander senescence". These include proteins, reactive oxygen species, lipids, and nucleic acids, which may be present in individual soluble form, in vesicles, and in non-membranous multi-component macromolecules.

In Vitro Models of Cell Senescence: A Systematic Review on Musculoskeletal Tissues and Cells

Ageing is an irreversible and inevitable biological process and a significant risk factor for the development of various diseases, also affecting the musculoskeletal system, resulting from the accumulation of cell senescence. The aim of this systematic review was to collect the in vitro studies conducted over the past decade in which cell senescence was induced through various methods, with the purpose of evaluating the molecular and cellular mechanisms underlying senescence and to identify treatments capable of delaying senescence. Through three electronic databases, 22 in vitro studies were identified and included in this systematic review. Disc, cartilage, or muscle cells or tissues and mesenchymal stem cells were employed to set-up in vitro models of senescence. The most common technique used to induce cell senescence was the addition to the culture medium of tumor necrosis factor (TNF)α and/or interleukin (IL)1β, followed by irradiation, compression, hydrogen peroxide (H2O2), microgravity, in vitro expansion up to passage 10, and cells harvested from damaged areas of explants. Few studies evaluated possible treatments to anti-senescence effects. The included studies used in vitro models of senescence in musculoskeletal tissues, providing powerful tools to evaluate age-related changes and pathologies, also contributing to the development of new therapeutic approaches.

Protein-Bound Uremic Toxins in Senescence and Kidney Fibrosis

Chronic kidney disease (CKD) is a progressive condition of kidney dysfunction due to diverse causes of injury. In healthy kidneys, protein-bound uremic toxins (PBUTs) are cleared from the systemic circulation by proximal tubule cells through the concerted action of plasma membrane transporters that facilitate their urinary excretion, but the endogenous metabolites are hardly removed with kidney dysfunction and may contribute to CKD progression. Accumulating evidence suggests that senescence of kidney tubule cells influences kidney fibrosis, the common endpoint for CKD with an excessive accumulation of extracellular matrix (ECM). Senescence is a special state of cells characterized by permanent cell cycle arrest and limitation of proliferation, which promotes fibrosis by releasing senescence-associated secretory phenotype (SASP) factors. The accumulation of PBUTs in CKD causes oxidative stress and increases the production of inflammatory (SASP) factors that could trigger fibrosis. Recent studies gave some clues that PBUTs may also promote senescence in kidney tubular cells. This review provides an overview on how senescence contributes to CKD, the involvement of PBUTs in this process, and how kidney senescence can be studied. Finally, some suggestions for future therapeutic options for CKD while targeting senescence are given.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Cellular Senescence in Intervertebral Disc Aging and Degeneration: Molecular Mechanisms and Potential Therapeutic Opportunities

Closely associated with aging and age-related disorders, cellular senescence (CS) is the inability of cells to proliferate due to accumulated unrepaired cellular damage and irreversible cell cycle arrest. Senescent cells are characterized by their senescence-associated secretory phenotype that overproduces inflammatory and catabolic factors that hamper normal tissue homeostasis. Chronic accumulation of senescent cells is thought to be associated with intervertebral disc degeneration (IDD) in an aging population. This IDD is one of the largest age-dependent chronic disorders, often associated with neurological dysfunctions such as, low back pain, radiculopathy, and myelopathy. Senescent cells (SnCs) increase in number in the aged, degenerated discs, and have a causative role in driving age-related IDD. This review summarizes current evidence supporting the role of CS on onset and progression of age-related IDD. The discussion includes molecular pathways involved in CS such as p53-p21CIP1, p16INK4a, NF-κB, and MAPK, and the potential therapeutic value of targeting these pathways. We propose several mechanisms of CS in IDD including mechanical stress, oxidative stress, genotoxic stress, nutritional deprivation, and inflammatory stress. There are still large knowledge gaps in disc CS research, an understanding of which will provide opportunities to develop therapeutic interventions to treat age-related IDD.

The mechanisms and functions of TNF-α in intervertebral disc degeneration

Low back pain (LBP) is one of the most common health problems in people's lives, which brings a massive burden to clinicians, and the leading cause of LBP is intervertebral disc degeneration (IDD). IDD is mainly caused by factors such as aging, mechanical stress, and lack of nutrition. The pathological mechanism of IDD is very complex, involving inflammatory response, cell metabolism disorder, and so on. Unfortunately, in the current treatment of IDD, only relieving symptoms as the primary means of relieving a patient's pain cannot effectively inhibit or reverse the progression of IDD. Tumor necrosis factor-α (TNF-α) is a multifunctional pro-inflammatory factor involved in many diseases' pathological processes. With the in-depth study of the pathological mechanism of IDD, more and more evidence has shown that TNF-α is an essential activator of IDD, which is related to the metabolic disorder, inflammatory responses, apoptosis, and other pathological processes of extracellular dissociation in the intervertebral disc. Therefore, anti-TNF-α therapy is an effective therapeutic target for alleviating IDD, especially in inhibiting extracellular matrix degradation and reducing inflammatory responses. This article reviews the pathological role of TNF-α in IDD and the latest research progress of TNF-α inhibitors in treating IDD.

The Uremic Toxin Indoxyl Sulfate Accelerates Senescence in Kidney Proximal Tubule Cells

Kidney fibrosis is the common final pathway of nearly all chronic and progressive nephropathies. One cause may be the accumulation of senescent cells that secrete factors (senescence associated secretory phenotype, SASP) promoting fibrosis and inflammation. It has been suggested that uremic toxins, such as indoxyl sulfate (IS), play a role in this. Here, we investigated whether IS accelerates senescence in conditionally immortalized proximal tubule epithelial cells overexpressing the organic anion transporter 1 (ciPTEC-OAT1), thereby promoting kidney fibrosis. Cell viability results suggested that the tolerance of ciPTEC-OAT1 against IS increased in a time-dependent manner at the same dose of IS. This was accompanied by SA-β-gal staining, confirming the accumulation of senescent cells, as well as an upregulation of p21 and downregulation of laminB1 at different time points, accompanied by an upregulation in the SASP factors IL-1β, IL-6 and IL-8. RNA-sequencing and transcriptome analysis revealed that IS accelerates senescence, and that cell cycle appears to be the most relevant factor during the process. IS accelerates senescence via TNF-α and NF-ĸB signalling early on, and the epithelial-mesenchymal transition process at later time points. In conclusion, our results suggest that IS accelerates cellular senescence in proximal tubule epithelial cells.

TNFα/TNFR1 signal induces excessive senescence of decidua stromal cells in recurrent pregnancy loss

Defects in decidual response are associated with adverse pregnancy outcomes which includes recurrent pregnancy loss (RPL). It is reported that cellular senescence happens during decidualization and pro-senescent decidual response in the luteal phase endometrium is related to RPL. However, the underlying mechanisms of how excessive decidual senescence takes place in RPL decidua cells remain largely unexplored. The senescent phenotype of RPL decidua and tumor necrosis factor receptor 1(TNFR1) expression were analyzed by using our previously published single-cell sequencing dataset of decidua cells from 6 RPL and 5 matched normal decidua, which were further verified by PCR and WB in decidual tissues. Effects of TNFα on the decidual stromal cells (DSCs) senescence and underlying molecular pathways were analyzed using the in vitro decidualization model of human endometrial stromal cells (HESCs). We showed that decidual stroma cells from RPL patients exhibited transcriptomic features of cellular senescence by analysis of single-cell datasets. The TNFα level and TNFR1 expression were increased in RPL decidua tissues. Furthermore, in vitro cell model demonstrated that increased TNFα induced excessive senescence during decidualization and TNFR1/p53/p16 pathway mediates TNFα-induced stromal senescence. In addition, we also found that the expression of IGFBP1 was regulated by TNFα-TNFR1 interaction during decidualization. Taken together, the present findings suggest that the increased secretion of TNFα induced stromal cell excessive senescence in RPL decidua, which is mediated via TNFR1, and thus provide a possible therapeutic target for the treatment of RPL.

Eupatilin attenuates the senescence of nucleus pulposus cells and mitigates intervertebral disc degeneration via inhibition of the MAPK/NF-κB signaling pathway

Intervertebral disc degeneration (IDD) is the main cause of low back pain. An increasing number of studies have suggested that inflammatory response or the senescence of nucleus pulposus (NP) cells is strongly associated with the progress of IDD. Eupatilin, the main flavonoid extracted from Artemisia, was reported to be associated with the inhibition of the intracellular inflammatory response and the senescence of cells. However, the relationship between eupatilin and IDD is still unknown. In this study, we explored the role of eupatilin in tumor necrosis factor-α (TNF-α)-induced activation of inflammatory signaling pathways and NP cell senescence, in the anabolism and catabolism of NP cell extracellular matrix (ECM) and in the effect of the puncture-induced model of caudal IDD in the rat. In vitro, eupatilin significantly inhibited TNF-α-induced ECM degradation, downregulated the expression of related markers of NP cells (MMP3, MMP9, and MMP13), and upregulated the expression of SOX9 and COL2A1. Furthermore, eupatilin reduced TNF-α-induced cell senescence by inhibiting the expression of the senescence of NP cell-related markers (p21 and p53). Mechanistically, ECM degradation and cell senescence were reduced by eupatilin, which inhibited the activation of MAPK/NF-κB signaling pathways. Consistent with the in vitro data, eupatilin administration ameliorated the puncture-induced model of caudal IDD in the rat. In conclusion, eupatilin can inhibit the inflammatory response and the senescence of NP cells, which may be a novel treatment strategy for IDD.

Inhibition of the extracellular signal-regulated kinase pathway reduces the inflammatory component in nucleus pulposus cells

Intervertebral disc (IVD) degeneration is a spinal disorder that triggers an inflammatory response and subsequent development of spinal pseudoarthrosis. The aim of the present study is to elucidate the role of the extracellular signal-regulated kinase (ERK) pathway in inflammation-induced IVD cells. Inflammatory human nucleus pulposus (NP) cells (NPCs) were induced using tumor necrosis factor-α and the ERK pathway was blocked using a selective molecule-based inhibitor U0126. Gene expression of catabolic and anabolic markers, proinflammatory, and NPCs markers was investigated. The enzymatic activity of matrix metalloproteinases (MMP)2/MMP9 was determined by gelatin zymography and nitrite production was assessed by Griess reaction. The NPC metabolic activity and viability were assessed using resazurin sodium-salt and live/dead assays, and subsequently, the specificity of U0126 on ERK1/2 signaling was determined. The catabolic enzyme MMP3 (p = 0.0001) and proinflammatory cytokine interleukin 6 (p = 0.036) were downregulated by U0126 in NPCs under inflammatory conditions. A significant increase of the cytokeratin 19 (p = 0.0031) was observed, suggesting a partial and possible recovery of the NP phenotype. U0126 does not seem to have an effect on prostaglandin production, aggrecanases, or other anabolic genes. We confirmed that U0126 selectively blocks the ERK phosphorylation and only affects the cell metabolic activity without the reduction of viable cells. Inhibition of ERK signaling downregulates important metalloproteinases and proinflammatory cytokines, and upregulates some NP markers, suggesting its potential to treat IVD degeneration.

Effects and Mechanism of Particulate Matter on Tendon Healing Based on Integrated Analysis of DNA Methylation and RNA Sequencing Data in a Rat Model

Exposure to particulate matter (PM) has been linked with the severity of various diseases. To date, there is no study on the relationship between PM exposure and tendon healing. Open Achilles tenotomy of 20 rats was performed. The animals were divided into two groups according to exposure to PM: a PM group and a non-PM group. After 6 weeks of PM exposure, the harvest and investigations of lungs, blood samples, and Achilles tendons were performed. Compared to the non-PM group, the white blood cell count and tumor necrosis factor-alpha expression in the PM group were significantly higher. The Achilles tendons in PM group showed significantly increased inflammatory outcomes. A TEM analysis showed reduced collagen fibrils in the PM group. A biomechanical analysis demonstrated that the load to failure value was lower in the PM group. An upregulation of the gene encoding cyclic AMP response element-binding protein (CREB) was detected in the PM group by an integrated analysis of DNA methylation and RNA sequencing data, as confirmed via a Western blot analysis showing significantly elevated levels of phosphorylated CREB. In summary, PM exposure caused a deleterious effect on tendon healing. The molecular data indicate that the action mechanism of PM may be associated with upregulated CREB signaling.

Stem cell-homing hydrogel-based miR-29b-5p delivery promotes cartilage regeneration by suppressing senescence in an osteoarthritis rat model

Osteoarthritis (OA) is a common joint disease characterized by progressive loss of cartilage and reduction in lubricating synovial fluid, which lacks effective treatments currently. Here, we propose a hydrogel-based miRNA delivery strategy to rejuvenate impaired cartilage by creating a regenerative microenvironment to mitigate chondrocyte senescence that mainly contributes to cartilage breakdown during OA development. An aging-related miRNA, miR-29b-5p, was first found to be markedly down-regulated in OA cartilage, and their up-regulation suppressed the expression of matrix metalloproteinases and senescence-associated genes (P16^INK4a/P21) via ten-eleven-translocation enzyme 1 (TET1). An injectable bioactive self-assembling peptide nanofiber hydrogel was applied to deliver agomir-29b-5p, which was functionalized by conjugating a stem cell-homing peptide SKPPGTSS for endogenous synovial stem cell recruitment simultaneously. Sustained miR-29b-5p delivery and recruitment of synovial stem cells and their subsequent differentiation into chondrocytes led to successful cartilage repair and chondrocyte rejuvenation. This strategy enables miRNA-based therapeutic modality to become a viable alternative for surgery in OA treatment.

Tiaojing Cuyun Recipe Enhances Pregnancy Outcome via the VEGF/PI3K/AKT/eNOS Signaling Pathway in EID Mice

Purpose. In this study, we evaluated the effect of Tiaojing Cuyun Recipe (TJCYR) on embryo implantation dysfunction- (EID-) induced damage of endometrial receptivity in mice and investigated the mechanisms underlying the effect. Methods. The main compounds of TJCYR were identified by high-performance liquid chromatography (HPLC). One hundred and twenty pregnant mice were randomly divided into six groups: control, EID only, progesterone (Prog)+EID, TJCYR-low-dose+EID, TJCYR-medium-dose+EID, and TJCYR-high-dose+EID. Mifepristone was injected to make the EID model. On the fourth day of pregnancy, serum was obtained to analyze hormone level by radioimmunoassay, the uterus was collected to analyze morphology by hematoxylin and eosin (H&E) and scanning electron microscopy (SEM), and a combination of immunofluorescence and Western blot was used to identify the related proteins. On the eighth day of pregnancy, the mice were sacrificed and the number of uterus-implanted blastocysts was counted. Results. Treatment with TJCYR significantly improved the number of implanted sites, the number of well-developed pinopodes, and microvascular formation in the mice. Moreover, TJCYR significantly activated PI3K/Akt/eNOS signaling pathways to promote angiogenesis, resulting in significantly improved endometrial receptivity and fertility outcomes when compared to the model group. Conclusion. These findings demonstrate that TJCYR was able to protect embryo implantation of EID mice due to TJCYR-mediated improvement in endometrial receptivity by promoting endometrial angiogenesis.

Platelet-Derived Growth Factor-BB Inhibits Intervertebral Disc Degeneration via Suppressing Pyroptosis and Activating the MAPK Signaling Pathway

Platelet-derived growth factor-BB (PDGF-BB) is a cytokine involved in tissue repair and tumor progression. It has been found to have expression differences between normal and degenerative intervertebral discs. However, it is not clear whether PDGF-BB has a protective effect on intervertebral disc degeneration (IDD). In this experiment, we treated nucleus pulposus cells (NPCs) with IL-1β to simulate an inflammatory environment and found that the extracellular matrix (ECM) anabolic function of NPCs in an inflammatory state was inhibited. Moreover, the induction of IL-1β also enhanced the expression of NLRP3 and the cleavage of caspase-1 and IL-1β, which activated the pyroptosis of NPCs. In this study, we studied the effect of PDGF-BB on IL-1β-treated NPCs and found that PDGF-BB not only significantly promotes the ECM anabolism of NPCs, but also inhibits the occurrence of pyroptosis and the production of pyroptosis products of NPCs. Consistent with this, when we used imatinib to block the PDGF-BB receptor, the above-mentioned protective effect disappeared. In addition, we found that PDGF-BB can also promote the ECM anabolism of NPCs by regulating the ERK, JNK, PI3K/AKT signaling pathways, but not the P38 signaling pathway. In vivo studies, mice that blocked PDGF-BB receptors showed more severe histological manifestations of intervertebral disc degeneration. In summary, our results indicate that PDGF-BB participates in inhibiting the occurrence and development of IDD by inhibiting pyroptosis and regulating the MAPK signaling pathway.

Melatonin Inhibits Annulus Fibrosus Cell Senescence through Regulating the ROS/NF-κB Pathway in an Inflammatory Environment

Inflammation response is an important reason for disc cell senescence during disc degeneration. Recently, melatonin is suggested to protect against disc degeneration. However, the effects of melatonin on annulus fibrosus (AF) cell senescence are not fully studied. The main purpose of this study was to investigate the effects of melatonin on AF cell senescence in an inflammatory environment and the underlying mechanism. Rat disc AF cells were cultured in a medium with tumor necrosis factor-α (TNF-α). Melatonin was added along with the medium to observe its protective effects. Compared with the control AF cells, TNF-α significantly declined cell proliferation potency and telomerase activity, elevated senescence-associated β-galactosidase (SA-β-Gal) activity, upregulated protein expression of senescence markers (p16 and p53), and increased reactive oxygen species (ROS) content and activity of the NF-κB pathway. However, when the TNF-α-treated AF cells were incubated with melatonin, ROS content and activity of the NF-κB pathway were decreased, and those parameters reflecting cell senescence indicated that AF cell senescence was also partly alleviated. Together, melatonin suppresses AF cell senescence through regulating the ROS/NF-κB pathway in an inflammatory environment. This study sheds a new light that melatonin may be promising to retard inflammation-caused disc degeneration.

Induced senescence of healthy nucleus pulposus cells is mediated by paracrine signaling from TNF-α-activated cells

Intervertebral disc degeneration is an irreversible process associated with accumulation of senescent nucleus pulposus (NP) cells. This study investigates the hypothesis that Tumor necrosis factor-α (TNF-α)-treated senescent NP cells propagate senescence of neighboring healthy cells via a paracrine effect that involves p-Stat3 signaling and the cytokine interleukin-6 (IL-6). NP cells isolated from bovine caudal intervertebral disc (IVD) were treated with TNF-α to induce senescence which was confirmed by demonstrating upregulation of senescence-associated β-galactosidase and p16. This was correlated with downregulation of NP-associated markers, Aggrecan, Col2A1, and Sox9. Direct contact and non-contact co-culture of healthy and senescent cells showed that TNF-α-treated cells increased the senescence in healthy cells via a paracrine effect. The senescent cells have a secretory phenotype as indicated by increased gene and protein levels of IL-6. Phosphorylated Signal Transducer and Activator of Transcription 3 (pStat3) levels were also high in treated cells and appeared to upregulate IL-6 as inhibition of Stat3 phosphorylation by StatticV downregulated IL-6 mRNA expression in cells and protein levels in the culture media. All trans retinoic acid, an IL-6 inhibitor, also decreased the secretion of IL-6 and reduced the paracrine effect of senescent cells on healthy cells. Decreased pStat3 levels and inhibition of IL-6 secretion did not fully restore NP gene expression of Col2A1 but importantly, appeared to cause senescent cells to undergo apoptosis and cell death. This study demonstrated the paracrine effect of senescent NP cells which involves Stat3 and IL-6 and may explain why senescent NP cells accumulate in IVD with age. The role of pSTAT3 and IL-6 in mediating NP senescence requires further study as it may be a novel strategy for modulating the senescent-inducing effects of TNF-α.

Premature Senescence of T-cells Favors Bone Loss During Osteolytic Diseases. A New Concern in the Osteoimmunology Arena

Cellular senescence is a biological process triggered in response to time-accumulated DNA damage, which prioritizes cell survival over cell function. Particularly, senescent T lymphocytes can be generated prematurely during chronic inflammatory diseases regardless of chronological aging. These senescent T lymphocytes are characterized by the loss of CD28 expression, a co-stimulatory receptor that mediates antigen presentation and effective T-cell activation. An increased number of premature senescent CD4+CD28- T lymphocytes has been frequently observed in osteolytic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, ankylosing spondylitis, osteopenia, osteoporosis, and osteomyelitis. Indeed, CD4+CD28- T lymphocytes produce higher levels of osteoclastogenic molecular mediators directly related to pathologic bone loss, such as tumor necrosis factor (TNF)-α, interleukin (IL)-17A, and receptor-activator of nuclear factor κB ligand (RANKL), as compared with regular CD4+CD28+ T lymphocytes. In addition, premature senescent CD8+CD28- T lymphocytes have been negatively associated with bone healing and regeneration by inhibiting osteoblast differentiation and mesenchymal stromal cell survival. Therefore, accumulated evidence supports the role of senescent T lymphocytes in osteoimmunology. Moreover, premature senescence of T-cells seems to be associated with the functional imbalance between the osteolytic T-helper type-17 (Th17) and bone protective T regulatory (Treg) lymphocytes, as well as the phenotypic instability of Treg lymphocytes responsible for its trans-differentiation into RANKL-producing exFoxp3Th17 cells, a key cellular phenomenon directly related to bone loss. Herein, we present a framework for the understanding of the pathogenic characteristics of T lymphocytes with a premature senescent phenotype; and particularly, we revise and discuss their role in the osteoimmunology of osteolytic diseases.

Suramin attenuates intervertebral disc degeneration by inhibiting NF-κB signalling pathway

Aims

Interleukin (IL)-1β is one of the major pathogenic regulators during the pathological development of intervertebral disc degeneration (IDD). However, effective treatment options for IDD are limited. Suramin is used to treat African sleeping sickness. This study aimed to investigate the pharmacological effects of suramin on mitigating IDD and to characterize the underlying mechanism.

Methods

Porcine nucleus pulposus (NP) cells were treated with vehicle, 10 ng/ml IL-1β, 10 μM suramin, or 10 μM suramin plus IL-1β. The expression levels of catabolic and anabolic proteins, proinflammatory cytokines, mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-κB-related signalling molecules were assessed by Western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), and immunofluorescence analysis. Flow cytometry was applied to detect apoptotic cells. The ex vivo effects of suramin were examined using IDD organ culture and differentiation was analyzed by Safranin O-Fast green and Alcian blue staining.

Results

Suramin inhibited IL-1β-induced apoptosis, downregulated matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and ADAMTS-5, and upregulated collagen 2A (Col2a1) and aggrecan in IL-1β-treated NP cells. IL-1β-induced inflammation, assessed by IL-1β, IL-8, and tumour necrosis factor α (TNF-α) upregulation, was alleviated by suramin treatment. Suramin suppressed IL-1β-mediated proteoglycan depletion and the induction of MMP-3, ADAMTS-4, and pro-inflammatory gene expression in ex vivo experiments.

Conclusion

Suramin administration represents a novel and effectively therapeutic approach, which could potentially alleviate IDD by reducing extracellular matrix (ECM) deposition and inhibiting apoptosis and inflammatory responses in the NP cells.

Cite this article: Bone Joint Res 2021;10(8):498–513.

Vinpocetine Effect on the Juncture of Diabetes and Aging: An in-vitro study

BACKGROUND

The rapid-growing population of diabetic patients and the elderly are among the direst challenges that the science of medicine is facing today. Targeting these two challenges can shed light on new means to control and ideally reverse this trend. In this experiment, Vinpocetine's effect on aged pancreatic beta-cell functions in correlation with oxidative stress was studied.

METHODS

Islet cells were isolated from the pancreas of aged rats and exposed to Vinpocetine, dissolved in acetone and RPMI, for 48 h. Then, senescence-associated molecular parameters, including P16 and P38 gene expressions and β-galactosidase activity, were investigated along with diabetic and inflammation markers.

RESULTS

Experimental results showed that Vinpocetine could significantly increase aged islets insulin secretion and also make a meaningful reduction in oxidative stress markers. This drug can also decrease expression levels of P16 and P38, the primary genes responsible for the aging pathway. TNF-α, IL-6, and NF-κB expressions were also reduced noticeably after treatment with Vinpocetine.

CONCLUSION

The current study showed that Vinpocetine, a derivative of the secondary plant metabolite called Vincamine, could break this vicious cycle of oxidative stress and aging by reducing oxidative stress and inflammation, thus inhibiting cellular aging.

Role of PI3K/AKT Signaling Pathway in Nucleus Pulposus Cells

OBJECTIVE

To investigate the role of PI3K/AKT signaling pathway in nucleus pulposus (NP) cells.

METHODS

Nucleus pulposus (NP) cells were isolated from SD rat, and thereafter, passage three (P3) NP cells were divided into the following experimental groups: control, PI3K/AKT agonist IGF-1 (25 ng/ml, 50 ng/ml, and 100 ng/ml), and PI3K/AKT inhibitor LY294002 (5 μM, 10 μM, and 20 μM). Flow cytometry and BrdU cell proliferation assays were performed to assess apoptosis and the proliferation rate of NP cells. Western blot analysis was performed to examine the protein expression level of Col II, Col X, Aggrecan, and MMP13.

RESULTS

PI3K/AKT inhibitor LY294002 increased the rate of apoptosis in NP cells when compared to the control and decreased the proliferation rate when compared to control. Moreover, LY294002 decreased the protein expression level of Col-II and Aggrecan in NP cells. At the same time, LY294002 increased the protein expression level of MMP13 and Col-X in NP cells. Through activating PI3K/AKT, IGF-1 increased the proliferation rate when compared to control and decreased the rate of apoptosis when compared to control. Additionally, IGF-1 decreased the protein expression level of MMP13 and Col-X and increased Col-II and Aggrecan in NP cells.

CONCLUSION

The inhibition of PI3K/AKT signaling pathway accelerated the apoptosis of NP cells and facilitated the extracellular matrix degradation. However, the activation of PI3K/AKT pathway partly prevented the NP cell from apoptosis and promoted their proliferation. Meanwhile, its activation also delayed the loss of extracellular matrix.

Blocking TNFα attenuates progressive cartilage matrix degradation in inflammatory arthritis

Because damage to hyaline cartilage is irreversible, relieving progressive cartilage destruction is an important therapeutic approach for inflammatory arthritis. In the present study, human hyaline chondrocytes were isolated from total knee replacements of 15 patients with osteoarthritis (OA) and three with rheumatoid arthritis (RA). Synovial fluid of OA (n=25) and RA (n=34) were collected to measure tumor necrosis factor α (TNFα) using ELISA. Consistent with previous studies, the synovial fluid exhibited high TNFα levels and hyaline cartilage was severely destroyed in patients with RA. TNFα-treated chondrocytes were used as model for inflammatory arthritis. TNFα did not influence proliferation or extracellular matrix expression in chondrocytes, but induced matrix metalloproteinase (MMP)1, 3 and 13 expression levels in chondrocytes, which was accompanied by activation of nuclear factor-κB signaling. During chondrogenic differentiation, TNFα attenuated mRNA expression levels of anabolic factors (collagen type 2 and aggrecan) and enhanced mRNA expression of catabolic factors (MMP1, MMP3 and MMP13) in chondrocytes. Moreover, anti-TNFα agents (Golimumab) inhibited the TNFα-induced metabolic shift in chondrocytes and chondrogenic differentiation. The present study revealed a mechanism by which TNFα may induce metabolic shift in chondrocytes, leading to progressive chondrocyte destruction.

Artemisinin protects DPSC from hypoxia and TNF-α mediated osteogenesis impairments through CA9 and Wnt signaling pathway

Dental pulp stem cells (DPSCs) possess the ability of multi-lineage differentiation, and are excellent sources of tissue engineering and regenerative medicine. Oxygen concentration and inflammation are two critical environmental factors that affect the osteogenic differentiation of DPSCs. We aimed to study the role of the antimalarial drug artemisinin on the osteogenic differentiation of human DPSCs under the hypoxia and inflammation conditions. We demonstrated that hypoxia (5% O₂) and inflammation (20 ng/mL TNF-α), alone or in combination, significantly diminished in vitro cell survival and increased apoptotic rates. Notably, hypoxia and TNF-α exerted accumulative effect in suppressing the osteogenic differentiation of DPSCs, as evidenced by reduced expression levels of osteogenesis-associated genes including ALP, RUNX2 and OCN in osteogenic condition, as well as reduced mineral nodules formation as indicated by alizarin red staining. Artemisinin at the dose of 40 μM markedly reversed the suppression in cell survival caused by hypoxia or inflammation, and reduced apoptotic rates and the expressions of pro-apoptotic proteins. Additionally, artemisinin restored osteogenic differentiation of DPSCs under the hypoxia or/and inflammation conditions. Moreover, the beneficial effect of artemisinin was dependent on upregulated expression of CA9 and CA9-mediated antioxidant responses, as CA9 knockdown abolished the protective role of artemisinin on DPSC osteogenesis. Furthermore, while hypoxia or/and inflammation significantly inactivated the Wnt/β-catenin signaling in DPSCs, additional exposure to artemisinin re-activated this pathway to promote osteogenic differentiation of DPSCs. Our results provide novel insight on the link between artemisinin and DPSC osteogenesis, and suggest promising artemisinin-based strategies for better dentin/pulp tissue engineering.

Transforming growth factor-β1-regulated Fas/FasL pathway activation suppresses nucleus pulposus cell apoptosis in an inflammatory environment

Background: During disc degeneration, inflammatory cytokine tumor necrosis factor (TNF)-α is correlated with nucleus pulposus (NP) cell apoptosis. Transforming growth factor (TGF)-β1 has the potential to regenerate degenerative disc.

Objective: To investigate the protective role of TGF-β1 against TNF-α-mediated NP cell apoptosis and the underlying mechanism.

Methods: Rat NP cells were treated with TNF-α (100 ng/ml) for 48 h. TGF-β1 was added into the culture medium to investigate its protective effects against TNF-α-induced NP cell apoptosis. Exogenous FasL was used to investigate the potential role of the Fas/FasL pathway in this process. Flow cytometry assay was used to analyze NP cell apoptosis. Real-time PCR and Western blotting were used to analyze gene and protein expression of apoptosis-related molecules.

Results: In TNF-α-treated NP cells, TGF-β1 significantly decreased NP cell apoptosis, declined caspase-3 and -8 activity, and decreased expression of Bax and caspase-3 (cleaved-caspase-3) but increased expression of Bcl-2. However, exogenous FasL partly reversed these effects of TGF-β1 in NP cells treated with TNF-α. Additionally, expression of Fas and FasL in TNF-α-treated NP cells partly decreased by TGF-β1, whereas exogenous FasL increased expression of Fas and FasL in NP cells treated with TGF-β1 and TNF-α.

Conclusion: TGF-β1 helps to inhibit TNF-α-induced NP cell apoptosis and the Fas/FasL pathway may be involved in this process. The present study suggests that TGF-β1 may be effective to retard inflammation-mediated disc degeneration.

N6-Methyladenosine Induced miR-34a-5p Promotes TNF-α-Induced Nucleus Pulposus Cell Senescence by Targeting SIRT1

Low back pain is tightly associated with intervertebral disc degeneration (IVDD) and aberrant nucleus pulposus (NP) is a critical cause. miRNAs N6-methyladenosine (m6A) modification accounts for the TNF-α-induced senescence of NP cells. The aim of this study was to investigate whether m6A modification regulates TNF-α-mediated cell viability, cell cycle arrest, and cell senescence and how it works. The results showed that METTL14 expression positively correlated with m6A and TNF-α expression in HNPCs. The knockdown of METTL14 led to the inhibition of the TNF-α-induced cell senescence. METTL14 overexpression promoted cell senescence. METTL14 regulated the m6A modification of miR-34a-5p and interacted with DGCR8 to process miR-34a-5p. The miR-34a-5p inhibitor inhibited the cell cycle senescence of HNPCs. miR-34a-5p was predicted to interact with the SIRT1 mRNA. SIRT1 overexpression counteracted the miR-34a-5p-promoted cell senescence. METTL14 participates in the TNF-α-induced m6A modification of miR-34a-5p to promote cell senescence in HNPCs and NP cells of IVDD patients. Downregulation of either METTL14 expression or miR-34a-5p leads to the inhibition of cell cycle arrest and senescence. SIRT1 mRNA is an effective binding target of miR-34a-5p, and SIRT1 overexpression mitigates the cell cycle arrest and senescence caused by miR-34a-5p.

Enhancing mitochondrial activity in neurons protects against neurodegeneration in a mouse model of multiple sclerosis

While transcripts of neuronal mitochondrial genes are strongly suppressed in central nervous system inflammation, it is unknown whether this results in mitochondrial dysfunction and whether an increase of mitochondrial function can rescue neurodegeneration. Here, we show that predominantly genes of the electron transport chain are suppressed in inflamed mouse neurons, resulting in impaired mitochondrial complex IV activity. This was associated with post-translational inactivation of the transcriptional co-regulator proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). In mice, neuronal overexpression of Ppargc1a, which encodes for PGC-1α, led to increased numbers of mitochondria, complex IV activity, and maximum respiratory capacity. Moreover, Ppargc1a-overexpressing neurons showed a higher mitochondrial membrane potential that related to an improved calcium buffering capacity. Accordingly, neuronal deletion of Ppargc1a aggravated neurodegeneration during experimental autoimmune encephalomyelitis, while neuronal overexpression of Ppargc1a ameliorated it. Our study provides systemic insights into mitochondrial dysfunction in neurons during inflammation and commends elevation of mitochondrial activity as a promising neuroprotective strategy.

Silencing p53 inhibits interleukin 10-induced activated hepatic stellate cell senescence and fibrotic degradation in vivo

Activated hepatic stellate cells are reported to play a significant role in liver fibrogenesis. Beside the phenotype reversion and apoptosis of activated hepatic stellate cells, the senescence of activated hepatic stellate cells limits liver fibrosis. Our previous researches have demonstrated that interleukin-10 could promote hepatic stellate cells senescence via p53 signaling pathway in vitro. However, the relationship between expression of p53 and senescence of activated hepatic stellate cells induced by interleukin-10 in fibrotic liver is unclear. The purpose of present study was to explore whether p53 plays a crucial role in the senescence of activated hepatic stellate cells and degradation of collagen mediated by interleukin-10. Hepatic fibrosis animal model was induced by carbon tetrachloride through intraperitoneal injection and transfection of interleukin-10 gene to liver was performed by hydrodynamic-based transfer system. Depletions of p53 in vivo and in vitro were carried out by adenovirus-based short hairpin RNA against p53. Regression of fibrosis was assessed by liver biopsy and collagen staining. Cellular senescence in the liver was observed by senescence-associated beta-galactosidase (SA-β-Gal) staining. Immunohistochemistry, immunofluorescence double staining, and Western blot analysis were used to evaluate the senescent cell and senescence-related protein expression. Our data showed that interleukin-10 gene treatment could lighten hepatic fibrosis induced by carbon tetrachloride and induce the aging of activated hepatic stellate cells accompanied by up-regulating the expression of aging-related proteins. We further demonstrated that depletion of p53 could abrogate up-regulation of interleukin-10 on the expression of senescence-related protein in vivo and vitro. Moreover, p53 knockout in fibrotic mice could block not only the senescence of activated hepatic stellate cells, but also the degradation of fibrosis induced by interleukin-10 gene intervention. Taken together, our results suggested that interleukin-10 gene treatment could attenuate carbon tetrachloride-induced hepatic fibrosis by inducing senescence of activated hepatic stellate cells in vivo, and this induction was closely related to p53 signaling pathway.

RICK regulates the odontogenic differentiation of dental pulp stem cells through activation of TNF-α via the ERK and not through NF-κB signaling pathway

Dental pulp stem cells (DPSCs) are capable of both self-renewal and multilineage differentiation, which play a positive role in dentinogenesis. Studies have shown that tumor necrosis factor-α (TNF-α) is involved in the differentiation of DPSCs under pro-inflammatory stimuli, but the mechanism of action of TNF-α is unknown. Rip-like interacting caspase-like apoptosis-regulatory protein kinase (RICK) is a biomarker of an early inflammatory response that plays a key role in modulating cell differentiation, but the role of RICK in DPSCs is still unclear. In this study, we identified that RICK regulates TNF-α-mediated odontogenic differentiation of DPSCs via the ERK signaling pathway. The expression of the biomarkers of odontogenic differentiation dental matrix protein-1 (DMP-1), dentin sialophosphoprotein (DSPP), biomarkers of odontogenic differentiation, increased in low concentration (1-10 ng/ml) of TNF-α and decreased in high concentration (50-100 ng/ml). Odontogenic differentiation increased over time in the odontogenic differentiation medium. In the presence of 10 ng/L TNF-α, the expression of RICK increased gradually over time, along with odontogenic differentiation. Genetic silencing of RICK expression reduced the expression of odontogenic markers DMP-1 and DSPP. The ERK, but not the NF-κB signaling pathway, was activated during the odontogenic differentiation of DPSCs. ERK signaling modulators decreased when RICK expression was inhibited. PD98059, an ERK inhibitor, blocked the odontogenic differentiation of DPSCs induced by TNF-α. These results provide a further theoretical and experimental basis for the potential use of RICK in targeted therapy for dentin regeneration.

New insights into the interplay between miRNAs and autophagy in the aging of intervertebral discs

Intervertebral disc degeneration (IDD) has been widely known as a main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate gene expression and serve key roles in the ageing process of intervertebral disc. Autophagy is an evolutionarily conserved process that maintains cellular homeostasis through recycling of nutrients and degradation of damaged or aged cytoplasmic organelles. Autophagy has been proposed as a "double-edged sword" and autophagy dysfunction of IVD cells is considered as a crucial reason of IDD. A rapidly growing number of recent studies demonstrate that both miRNAs and autophagy play important roles in the progression of IDD. Furthermore, accumulated research has indicated that miRNAs target autophagy-related genes and influence the onset and development of IDD. Hence, this review focuses mainly on the current findings regarding the correlations between miRNA, autophagy, and IDD and provides new insights into the role of miRNA-autophagy pathway involved in IDD pathophysiology.

Notch1-mediated inflammation is associated with endothelial dysfunction in human brain microvascular endothelial cells upon particulate matter exposure

Exposure to atmospheric particulate matter (PM) is an emerging risk factor for the pathogenesis of several diseases in humans, including cerebrovascular diseases. However, the mechanisms underlying PM-induced endothelial dysfunction are currently unclear. In this study, we examined how PM leads to endothelial dysfunction in human brain microvascular endothelial cells (HBMECs). We demonstrated that PM₁₀ exposure (up to 25 μg/mL) increase Notch1 cleavage, and it regulates endothelial dysfunction through NICD-mediated inflammation and senescence. PM₁₀-induced NICD signaling causes increased expression of interleukin-1 beta (IL-1β) and enhances characteristics of cellular senescence, which leads to increased endothelial permeability in HBMECs. Knockdown of Notch1 by siRNA blocks PM₁₀-induced endothelial dysfunction via the suppression of inflammation and senescence. Furthermore, we found that Notch1-mediated inflammation accelerates endothelial senescence, which eventually leads to endothelial dysfunction. Altogether, our data suggest that Notch1 and NICD are potential target regulators for the prevention of cerebrovascular endothelial dysfunction induced by ambient air pollutants such as PM.

SIRT1 Activation Using CRISPR/dCas9 Promotes Regeneration of Human Corneal Endothelial Cells through Inhibiting Senescence

Human corneal endothelial cells (hCECs) are restricted in proliferative capacity in vivo. Reduction in the number of hCEC leads to persistent corneal edema requiring corneal transplantation. This study demonstrates the functions of SIRT1 in hCECs and its potential for corneal endothelial regeneration. Cell morphology, cell growth rates and proliferation-associated proteins were compared in normal and senescent hCECs. SIRT1 was activated using the CRISPR/dCas9 activation system (SIRT1a). The plasmids were transfected into CECs of six-week-old Sprague–Dawley rats using electroporation and cryoinjury was performed. Senescent cells were larger, elongated and showed lower proliferation rates and lower SIRT1 levels. SIRT1 activation promoted the wound healing of CECs. In vivo transfection of SIRT1a promoted the regeneration of CECs. The proportion of the S-phase cells was lower in senescent cells and elevated upon SIRT1a activation. SIRT1 regulated cell proliferation, proliferation-associated proteins, mitochondrial membrane potential, and oxidative stress levels. In conclusion, corneal endothelial senescence is related with a decreased SIRT1 level. SIRT1a promotes the regeneration of CECs by inhibiting cytokine-induced cell death and senescence. Gene function activation therapy using SIRT1a may serve as a novel treatment strategy for hCEC diseases.

A small-molecule inhibitor of the Wnt pathway, lorecivivint (SM04690), as a potential disease-modifying agent for the treatment of degenerative disc disease

BACKGROUND CONTEXT

Abnormal Wnt signaling in intervertebral discs (IVDs) progresses degenerative disc disease (DDD) pathogenesis by impairing nucleus pulposus cell function, decreasing matrix deposition, and accelerating fibrosis.

PURPOSE

This study was conducted to evaluate the effects of lorecivivint (LOR; SM04690), a small-molecule Wnt pathway inhibitor, on IVD cells and in an animal model of DDD.

STUDY DESIGN

We used in vitro assays and a rat model of DDD to test the effects of LOR on nucleus pulposus cell senescence and viability, annulus fibrosus (AF) cell fibrosis, and cartilage regeneration and protection.

METHODS

Wnt pathway gene expression was measured in human NP and AF cell cultures treated with LOR or DMSO (vehicle). Chondrocyte-like differentiation of rat and human NP cells, NP cell senescence and protection, and AF cell fibrosis were assessed using gene expression and immunocytochemistry. Disc and plasma pharmacokinetics were analyzed following intradiscal LOR injection in rats. In vivo effects of LOR and vehicle on AF integrity, AF/NP junction, NP cellularity and matrix, and disc height were compared using histopathology and radiography in a rat coccygeal IVD needle-puncture model of DDD.

RESULTS

In NP and AF cell cultures, LOR-inhibited Wnt pathway gene expression compared with vehicle. In NP cells, LOR inhibited senescence, decreased catabolism, and induced differentiation into chondrocyte-like cells; in AF cells, LOR decreased catabolism and inhibited fibrosis. A single intradiscal LOR injection in rats resulted in therapeutic disc concentrations (~30 nM) for >180 days and minimal systemic exposure. DDD-model rats receiving LOR qualitatively demonstrated increased cartilage matrix and reduced AF lamellar disorganization and fragmentation with significantly (p<.05) improved histology scores and increased disc height compared with vehicle.

CONCLUSIONS

LOR showed beneficial effects on IVD cells in vitro and reduced disease progression in a rat model of DDD compared with vehicle, suggesting that LOR may have disease-modifying therapeutic potential.

CLINICAL SIGNIFICANCE

The current therapeutic options for DDD are pain management and surgical intervention; there are no approved therapies that alter the progression of DDD. Our data support advancing LOR into clinical development as an injectable, small-molecule, potential disease-modifying treatment for DDD in humans.

A single-cell transcriptomic atlas characterizes ageing tissues in the mouse

Ageing is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death1. Despite rapid advances over recent years, many of the molecular and cellular processes that underlie the progressive loss of healthy physiology are poorly understood2. To gain a better insight into these processes, here we generate a single-cell transcriptomic atlas across the lifespan of Mus musculus that includes data from 23 tissues and organs. We found cell-specific changes occurring across multiple cell types and organs, as well as age-related changes in the cellular composition of different organs. Using single-cell transcriptomic data, we assessed cell-type-specific manifestations of different hallmarks of ageing-such as senescence3, genomic instability4 and changes in the immune system2. This transcriptomic atlas-which we denote Tabula Muris Senis, or 'Mouse Ageing Cell Atlas'-provides molecular information about how the most important hallmarks of ageing are reflected in a broad range of tissues and cell types.

A20 of nucleus pulposus cells plays a self-protection role via the nuclear factor-kappa B pathway in the inflammatory microenvironment

Aims

Inflammatory response plays a pivotal role in the pathophysiological process of intervertebral disc degeneration (IDD). A20 (also known as tumour necrosis factor alpha-induced protein 3 (TNFAIP3)) is a ubiquitin-editing enzyme that restricts nuclear factor-kappa B (NF-κB) signalling. A20 prevents the occurrence of multiple inflammatory diseases. However, the role of A20 in the initiation of IDD has not been elucidated. The aim of the study was to investigate the effect of A20 in senescence of TNF alpha (TNF-α)-induced nucleus pulposus cells (NPCs).

Methods

Immunohistochemical staining was performed to observe the expression of A20 in normal and degenerated human intervertebral discs. The NPCs were dissected from the tail vertebrae of healthy male Sprague-Dawley rats and were cultured in the incubator. In the experiment, TNF-α was used to mimic the inflammatory environment of IDD. The cell viability and senescence were examined to investigate the effect of A20 on TNF-α-treated NPCs. The expression of messenger RNA (mRNA)-encoding proteins related to matrix macromolecules (collagen II, aggrecan) and senescence markers (p53, p16). Additionally, NF-κB/p65 activity of NPCs was detected within different test compounds.

Results

The expression of A20 was upregulated in degenerate human intervertebral discs. The A20 levels of NPCs in TNF-α inflammatory microenvironments were dramatically higher than those of the control group. TNF-α significantly decreased cell proliferation potency but increased senescence-associated beta-galactosidase (SA-β-Gal) activity, the expression of senescence-associated proteins, the synthesis of extracellular matrix, and G1 cycle arrest. The senescence indicators and NF-κB/p65 expression of A20 downregulated group treated with TNF-α were significantly upregulated compared to TNF-α-treated normal NPCs.

Conclusion

A20 has a self-protective effect on the senescence of NPCs induced by TNF-α. The downregulation of A20 in NPCs exacerbated the senescence of NPCs induced by TNF-α.

Cite this article:Bone Joint Res. 2020;9(5):225–235.

Epigallocatechin-3-Gallate Protects H2O2-Induced Nucleus Pulposus Cell Apoptosis and Inflammation by Inhibiting cGAS/Sting/NLRP3 Activation

Background

Intervertebral disc degeneration (IDD) is the most common diagnosis of patients with lower back pain. IDD is the underlying lesion of many spinal degenerative diseases; however, the role of cGAS/Sting/NLRP3 pathway and epigallocatechin gallate (EGCG) in the development of IDD remained unclear.

Methods

The expressions of cGAS, Sting and NLRP3 mRNA of intervertebral disc (IVD) samples from IDD patients and controls were detected by RT-PCR. The nucleus pulposus cells (NPCs) were induced by hydrogen peroxide (H₂O₂) and used as an in-vitro model. Both 5 μM and 25 μM EGCG treatment were used to detect the effect of EGCG on the in-vitro model. Cell viability was detected by the MTT method, and cell apoptosis and cell cycle would be detected by flow cytometry. Western blot was used in the detection of the expression of cGAS/Sting/NLRP3 as well as apoptosis-related protein level. ELISA was used in the detection of pro-inflammatory factors, including IL-1β, TNF-α, IL-6 and IL-10.

Results

The expressions of cGAS, Sting and NLRP3 mRNA were significantly increased in the IVD samples from IDD patients and NLRP3 was associated with cGAS and Sting. Advanced in-vitro study showed that H₂O₂ significantly increased the expression of cGAS, Sting and NLRP3 protein levels. Advanced experiments showed that EGCG treatment demonstrated significant protective effects in cell viability, apoptosis, cell cycle arrest and inflammatory status through down-regulation of cGAS/Sting/NLRP3 pathway.

Conclusion

It was shown that the cGAS, Sting and NLRP3 up-regulation was associated with the incidence of IDD. Our findings also suggest that EGCG treatment would provide anti-apoptosis, anti-inflammation and promote cell viability in H₂O₂ treatment-incubated NPCs through inhibiting cGAS/Sting/NLRP3 pathway.

Long non-coding RNA PART1 promotes intervertebral disc degeneration through regulating the miR‑93/MMP2 pathway in nucleus pulposus cells

The aim of the present study was to investigate the role of the long non‑coding (lnc)RNA PART1 in nucleus pulposus (NP) cells derived from patients with intervertebral disc degeneration (IDD). The level of PART1 in degenerative NP tissues from patients with IDD, bulging and herniated discs was measured by reverse transcription‑quantitative PCR (RT‑qPCR) analysis. NP cells were isolated from patients with IDD and transfected with siPART1, after which time the growth ability of the NP cells was evaluated by Cell Counting Kit‑8 and colony formation assays, and cell apoptosis was measured by flow cytometry. The levels of the cell proliferation marker Ki‑67 and the apoptosis marker cleaved caspase‑3, and the levels of genes related to extracellular matrix (ECM) synthesis and degradation, were also evaluated by western blotting and RT‑qPCR, as appropriate. Bioinformatics methods predicted that miR‑93 was sponged by PART1, and matrix metallopeptidase (MMP)2 was targeted by miR‑93, which was further confirmed by dual‑luciferase reporter assay. The levels of miR‑93 and MMP2 were also measured in NP tissues, and further rescue experiments were performed to confirm the role of the PART1/miR‑93/MMP2 pathway in NP cells. PART1 was found to be upregulated in degenerative NP tissues, and siPART1 caused an increase in cell growth ability and ECM synthesis, whereas it decreased cell apoptosis and ECM degradation in NP cells. miR‑93 was downregulated and MMP2 was upregulated in degenerative NP tissues. Rescue experiments indicated that the effects of miR‑93 inhibitor on NP cells were abolished by siPART1, and the effect of miR‑93 mimic on NP cells was rescued by MMP2 overexpression. Thus, the results of the present study demonstrated that PART1 may regulate NP cell degeneration through the miR‑93/MMP2 pathway. These findings indicate a novel signaling axis in NP cells that may be explored for the treatment of IDD.

End-stage renal disease is different from chronic kidney disease in upregulating ROS-modulated proinflammatory secretome in PBMCs - A novel multiple-hit model for disease progression

Background

The molecular mechanisms underlying chronic kidney disease (CKD) transition to end-stage renal disease (ESRD) and CKD acceleration of cardiovascular and other tissue inflammations remain poorly determined.

Methods

We conducted a comprehensive data analyses on 7 microarray datasets in peripheral blood mononuclear cells (PBMCs) from patients with CKD and ESRD from NCBI-GEO databases, where we examined the expressions of 2641 secretome genes (SG).

Results

1) 86.7% middle class (molecular weight >500 Daltons) uremic toxins (UTs) were encoded by SGs; 2) Upregulation of SGs in PBMCs in patients with ESRD (121 SGs) were significantly higher than that of CKD (44 SGs); 3) Transcriptomic analyses of PBMC secretome had advantages to identify more comprehensive secretome than conventional secretomic analyses; 4) ESRD-induced SGs had strong proinflammatory pathways; 5) Proinflammatory cytokines-based UTs such as IL-1β and IL-18 promoted ESRD modulation of SGs; 6) ESRD-upregulated co-stimulation receptors CD48 and CD58 increased secretomic upregulation in the PBMCs, which were magnified enormously in tissues; 7) M1-, and M2-macrophage polarization signals contributed to ESRD- and CKD-upregulated SGs; 8) ESRD- and CKD-upregulated SGs contained senescence-promoting regulators by upregulating proinflammatory IGFBP7 and downregulating anti-inflammatory TGF-β1 and telomere stabilizer SERPINE1/PAI-1; 9) ROS pathways played bigger roles in mediating ESRD-upregulated SGs (11.6%) than that in CKD-upregulated SGs (6.8%), and half of ESRD-upregulated SGs were ROS-independent.

Conclusions

Our analysis suggests novel secretomic upregulation in PBMCs of patients with CKD and ESRD, act synergistically with uremic toxins, to promote inflammation and potential disease progression. Our findings have provided novel insights on PBMC secretome upregulation to promote disease progression and may lead to the identification of new therapeutic targets for novel regimens for CKD, ESRD and their accelerated cardiovascular disease, other inflammations and cancers. (Total words: 279).

Transforming Growth Factor β Enhances Tissue Formation by Passaged Nucleus Pulposus Cells In Vitro

The nucleus pulposus (NP) is composed of NP and notochord cell. It is a paucicellular tissue and if it is to be used as a source of cells for tissue engineering the cell number will have to be expanded by cell passaging. The hypothesis of this study is that passaged NP and notochordal cells grown in three-dimensional (3D) culture in the presence of transforming growth factor β (TGFβ) will show enhanced NP tissue formation compared with cells grown in the absence of this growth factor. Bovine NP cells isolated by sequential enzymatic digestion from caudal intervertebral discs were either placed directly in 3D culture (P0) or serially passaged up to passage 3 (P3) prior to placement in 3D culture. Serial cell passage in monolayer culture led to de-differentiation, increased senescence and oxidative stress and decreases in the gene expression of NP and notochordal associated markers and increases in de-differentiation markers. The NP tissue regeneration capacity of cells in 3D culture decreases with passaging as indicated by diminished tissue thickness and total collagen content when compared with tissues formed by P0 cells. Immunohistochemical studies showed that type II collagen accumulation appeared to decrease. TGFβ1 or TGFβ3 treatment enhanced the ability of cells at each passage to form tissue, in part by decreasing cell death. However, neither TGFβ1 nor TGFβ3 were able to restore the notochordal phenotype. Although TGFβ1/3 recovered NP tissue formation by passaged cells, to generate NP in vitro that resembles the native tissue will require identification of conditions facilitating retention of notochordal cell differentiation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:438-449, 2020.

A positive feedback loop between EZH2 and NOX4 regulates nucleus pulposus cell senescence in age-related intervertebral disc degeneration

Background

The senescence of nucleus pulposus (NP) cells plays a vital role in the pathogenesis of intervertebral disc (IVD) degeneration (IDD). NADPH oxidase 4 (NOX4)-associated oxidative stress has been shown to induce premature NP cell senescence. Enhancer of zeste homolog 2 (EZH2) is a crucial gene regulating cell senescence. The aim of this study was to investigate the roles of EZH2 in NOX4-induced NP cell senescence and a feedback loop between EZH2 and NOX4.

Results

The down-regulation of EZH2 and the up-regulation of NOX4 and p16 were observed in the degenerative discs of aging rats. EZH2 regulated NP cell senescence via the H3K27me3-p16 pathway. Also, EZH2 regulated the expression of NOX4 in NP cells through the histone H3 lysine 27 trimethylation (H3K27me3) in the promoter of NOX4 gene. Furthermore, NOX4 down-regulated EZH2 expression in NP cells via the canonical Wnt/β-catenin pathway.

Conclusions

A positive feedback loop between EZH2 and NOX4 is involved in regulating NP cell senescence, which provides a novel insight into the mechanism of IDD and a potential therapeutic target for IDD.

Salicin prevents TNF-α-induced cellular senescence in human umbilical vein endothelial cells (HUVECs)

Cellular senescence is strongly tied to vascular disease. The current study aims to examine ways that endothelial cellular senescence can be prevented and the mechanisms by which prevention of senescence occurs. Human umbilical vein endothelial cells were exposed to TNF-α to induce senescence; then salicin was administered in two doses - 50 and 100 µM - to establish a dose-dependent effect of salicin on SA-β-Gal, G1 cell cycle arrest, expression of p21 and PAI-1, p53 acetylation at K382, NRF2 and oxidative stress. NRF2 was examined as a mediating mechanism of salicin's impact on cellular senescence and was found to account for salicin's impact on SA-β-Gal, p21, PAI-1 and p53. Together, these results provide a compelling case that salicin has a substantial impact on numerous factors tied to cellular senescence in human endothelial cells. Thus, treatment with salicin may hold promise as a means of preventing aging-related vascular disease. Furthermore, salicin appears to operate via a functional pathway that is different from that affected by anti-inflammatory drugs (e.g. aspirin).

The inflammatory mediators TNFα and nitric oxide arrest spermatogonia GC-1 cell cycle

During an inflammatory process of the testis, the network of somatic, immune, and germ cell interactions is altered leading to organ dysfunction. In testicular biopsies of infertile men, spermatogenesis impairment is associated with reduced spermatogonia proliferation, increased number of immune cells, and content of pro-inflammatory cytokines. TNFα-TNFR and nitric oxide (NO)-NO synthase systems are up-regulated in models of testicular damage and in human testis with maturation arrest. The purpose of this study was to test the hypothesis that TNFα-TNFR system and NO alter the function of spermatogonia in the inflamed testis. We studied the effect of TNFα and NO on GC-1 spermatogonia cell cycle progression and death by flow cytometry. GC-1 cells expressed TNFR1 and TNFR2 (immunofluorescence). TNFα (10 and 50 ng/ml) and DETA-Nonoate (0.5 and 2 mM), a NO releaser, increased the percentage of cells in S-phase of the cell cycle and reduced the percentage in G1, inducing also cell apoptosis. TNFα effect was not mediated by oxidative stress unlike NO, since the presence of N-acetyl-l-cysteine (2.5 and 5.0 mM) prevented NO induced cell cycle arrest and death. GC-1 spermatogonia overpass NO induced cell cycle arrest but no TNFα, since after removal of NO, spermatogonia progressed through the cell cycle. We propose TNFα and NO might contribute to impairment of spermatogenesis by preventing adequate functioning of the spermatogonia population. Our results showed that TNFα and NO impaired spermatogonia cell cycle, inducing GC-1 arrest in the S phase.

The Post-amyloid Era in Alzheimer's Disease: Trust Your Gut Feeling

The amyloid hypothesis, the assumption that beta-amyloid toxicity is the primary cause of neuronal and synaptic loss, has been the mainstream research concept in Alzheimer's disease for the past two decades. Currently, this model is quietly being replaced by a more holistic, “systemic disease” paradigm which, like the aging process, affects multiple body tissues and organs, including the gut microbiota. It is well-established that inflammation is a hallmark of cellular senescence; however, the infection-senescence link has been less explored. Microbiota-induced senescence is a gradually emerging concept promoted by the discovery of pathogens and their products in Alzheimer's disease brains associated with senescent neurons, glia, and endothelial cells. Infectious agents have previously been associated with Alzheimer's disease, but the cause vs. effect issue could not be resolved. A recent study may have settled this debate as it shows that gingipain, a Porphyromonas gingivalis toxin, can be detected not only in Alzheimer's disease but also in the brains of older individuals deceased prior to developing the illness. In this review, we take the position that gut and other microbes from the body periphery reach the brain by triggering intestinal and blood-brain barrier senescence and disruption. We also surmise that novel Alzheimer's disease findings, including neuronal somatic mosaicism, iron dyshomeostasis, aggressive glial phenotypes, and loss of aerobic glycolysis, can be explained by the infection-senescence model. In addition, we discuss potential cellular senescence targets and therapeutic strategies, including iron chelators, inflammasome inhibitors, senolytic antibiotics, mitophagy inducers, and epigenetic metabolic reprograming.

Vaspin Prevents Tumor Necrosis Factor-α-Induced Apoptosis in Cardiomyocytes by Promoting Autophagy

Visceral adipose tissue-derived serine protease inhibitor (Vaspin) is an adipocytokine that has been shown to exert anti-inflammatory effects and inhibits apoptosis under diabetic conditions. This study was designed to investigate the impact of vaspin on autophagy in tumor necrosis factor (TNF)-α-induced injury in cardiomyocytes and its cardioprotective effects in the pathogenesis of diabetic cardiomyopathy (DCM). H9C2 cells were treated with TNF-α with or without vaspin in vitro. Tumor necrosis factor-α treatment inhibited autophagy and promoted apoptosis in H9C2 cells after stimulating for 24 hours. Pretreatment with vaspin significantly mitigated apoptosis induced by TNF-α partly because of augment effects of vaspin on autophagy as demonstrated by a higher ratio of LC3-II/LC3-I, higher expression of Beclin-1, and increased autophagosomes formation. Furthermore, the AKT agonist IGF-1 significantly reversed the effect of vaspin on autophagy. In vivo DCM model was also developed by treating rats with streptozotocin followed by intraperitoneal injection with vaspin. In DCM rats, upregulation of vaspin reversed cardiac dysfunction, as identified by increased left ventricular ejection fractions and fractional shortening levels, a higher Em/Am ratio, and lower levels of TNF-α, lactate dehydrogenase, creatine kinase, and creatine kinase-myocardial isoenzyme. In conclusion, vaspin attenuated the TNF-α-induced apoptosis by promoting autophagy probably through inhibiting the PI3K/AKT/mTOR pathway and further ameliorated the cardiac dysfunction in DCM rats.

Resveratrol attenuates inflammation environment-induced nucleus pulposus cell senescence in vitro

Intervertebral disc degeneration is a disease identified as an inflammation response-participated pathological process. As a classical cellular feature, disc cell senescence is reported to be closely related with disc cell senescence. Resveratrol has a protective role against inflammation in some cells. However, its biological effects on disc cells remain largely unclear. The present study was aimed to study the effects of resveratrol on disc nucleus pulposus (NP) cell senescence in an inflammation environment. Isolated NP cells were cultured in cultured medium with (control group) or without (inflammation group) inflammatory cytokine TNF-α and IL-1β for 14 days. Resveratrol was added along with the NP cells treated with inflammatory cytokines to investigate its effects. NP cell senescence was analyzed by senescence-associated β-Galactosidase (SA-β-Gal) staining, cell proliferation, G0/1 cell cycle arrest, telomerase activity, gene/protein expression of senescence markers (p16 and p53) and NP matrix biosynthesis. In addition, the intracellular reactive oxygen species (ROS) was also analyzed. Compared with the control group, inflammation group significantly increased SA-β-Gal activity and ROS content, decreased cell proliferation and telomerase activity, promoted G0/1 cell cycle arrest, up-regulated gene/protein expression of senescence markers (p16 and p53) and matrix catabolism enzymes (MMP-3, MMP-13 and ADAMTS-4), and down-regulated gene/protein expression of NP matrix macromolecules (aggrecan and collagen II). However, resveratrol partly reversed the effects of inflammatory cytokine on these cell senescence-associated parameters. Together, resveratrol was effective to suppress cell senescence in an inflammatory environment. The present study shows new knowledge on how to retard inflammation response-initiated disc degeneration.