Leptin changes differentiation fate and induces senescence in chondrogenic progenitor cells

Thigh muscle and fat volumes are associated with knee cartilage abnormalities and bone marrow edema-like lesions: data from the osteoarthritis initiative

OBJECTIVE

To investigate the associations of thigh muscle and fat volumes with structural abnormalities on MRI related to knee osteoarthritis.

MATERIALS AND METHODS

MRI studies of the thighs and knees from 100 individuals were randomly selected from the Osteoarthritis Initiative Cohort. Whole Organ MR Scoring (WORMS) and effusion-synovitis scoring were performed in all knee MRI. Thigh muscles, intermuscular fat, and subcutaneous fat were manually segmented in 15 consecutive MR thigh images. Radiographic Kellgren-Lawrence grades (KLG) were also obtained in all knee radiographs. Independent t-tests were used to investigate the associations between thigh muscle and fat volumes, and sex. Mixed-effects analyses were obtained to investigate the associations between thigh muscle and fat volumes, KLG, WOMAC pain score, cartilage and bone marrow WORMS, as well as effusion-synovitis scores.

RESULTS

Women had higher subcutaneous fat volume than men (616.82 vs. 229.13 cm3, p < 0.01) and men had higher muscle volumes than women (p < 0.01). Quadriceps (coef = -2.15, p = 0.01) and vastus medialis (coef = -1.84, p = 0.03) volumes were negatively associated with the WORMS cartilage scores. Intermuscular fat volume (coef = 0.48, p = 0.01) was positively associated with WORMS bone marrow edema-like lesion (BMEL) scores. The quadriceps (coef = -0.99, p < 0.01) and hamstring (coef = -0.59, p = 0.01) volumes were negatively associated with WORMS BMEL scores. No evidence of an association was found between thigh muscle and fat volumes with KLG and effusion-synovitis grading (p > 0.05).

CONCLUSION

Increased quadriceps and hamstring volumes were negatively associated with cartilage lesion and BMEL scores while no evidence of an association was found between thigh muscle and fat volumes, and radiographic knee osteoarthritis or effusion-synovitis grading.

P53: A Key Target in the Development of Osteoarthritis

Osteoarthritis (OA), a chronic degenerative disease characterized mainly by damage to the articular cartilage, is increasingly relevant to the pathological processes of senescence, apoptosis, autophagy, proliferation, and differentiation of chondrocytes. Clinical strategies for osteoarthritis can only improve symptoms and even along with side effects due to age, sex, disease, and other factors. Therefore, there is an urgent need to identify new ideas and targets for current clinical treatment. The tumor suppressor gene p53, which has been identified as a potential target for tumor therapeutic intervention, is responsible for the direct induction of the pathological processes involved in OA modulation. Consequently, deciphering the characteristics of p53 in chondrocytes is essential for investigating OA pathogenesis due to p53 regulation in an array of signaling pathways. This review highlights the effects of p53 on senescence, apoptosis, and autophagy of chondrocytes and its role in the development of OA. It also elucidates the underlying mechanism of p53 regulation in OA, which may help provide a novel strategies for the clinical treatment of OA.

Articular Cartilage Regeneration via Induced Chondrocyte Autophagy by Sustained Release of Leptin Inhibitor from Thermo-Sensitive Hydrogel through STAT3/REDD1/mTORC1 Cascade

The pathophysiology of osteoarthritis (OA) is closely linked to autophagy abnormalities in articular chondrocytes, the sole mature cell type in healthy cartilage. Nevertheless, the precise molecular mechanism remains uncertain. Previous research has demonstrated that leptin activates mTORC1 , thereby inhibiting chondrocyte autophagy during the progression of OA. In this study, it is demonstrated that the presence of leptin induces a substantial increase in the expression of STAT3, leading to a notable decrease in REDD1 expression and subsequent phosphorylation of p70S6K, a recognized downstream effector of mTORC1. Conversely, inhibition of leptin yields contrasting effects. Additionally, the potential advantages of utilizing a sustained intra-articular release of a leptin inhibitor (LI) via an injectable, thermosensitive poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (PDLLA-PEG-PDLLA: PLEL) hydrogel delivery system for the purpose of investigating its impact on cartilage repair are explored. The study conducted on LI-loaded PLEL (PLEL@LI) demonstrates remarkable efficacy in inhibiting OA and displays encouraging therapeutic advantages in the restoration of subchondral bone and cartilage. These findings establish a solid foundation for the advancement of a pioneering treatment approach utilizing PLEL@LI for OA.

Adipokines in Rheumatoid Arthritis: Emerging Biomarkers and Therapeutic Targets

Rheumatoid arthritis (RA) is a chronic inflammatory disease manifested by joint involvement, extra-articular manifestations, and general symptoms. Adipose tissue, previously perceived as an inert energy storage organ, has been recognised as a significant contributor to RA pathophysiology. Adipokines modulate immune responses, inflammation, and metabolic pathways in RA. Although most adipokines have a pro-inflammatory and aggravating effect on RA, some could counteract this pathological process. The coexistence of RA and sarcopenic obesity (SO) has gained attention due to its impact on disease severity and outcomes. Sarcopenic obesity further contributes to the inflammatory milieu and metabolic disturbances. Recent research has highlighted the intricate crosstalk between adipose tissue and skeletal muscle, suggesting potential interactions between these tissues in RA. This review summarizes the roles of adipokines in RA, particularly in inflammation, immune modulation, and joint destruction. In addition, it explores the emerging role of adipomyokines, specifically irisin and myostatin, in the pathogenesis of RA and their potential as therapeutic targets. We discuss the therapeutic implications of targeting adipokines and adipomyokines in RA management and highlight the challenges and future directions for research in this field.

Mitochondria pleiotropism in stem cell senescence: Mechanisms and therapeutic approaches

Aging is a complex biological process characterized by a progressive decline in cellular and tissue function, ultimately leading to organismal aging. Stem cells, with their regenerative potential, play a crucial role in maintaining tissue homeostasis and repair throughout an organism's lifespan. Mitochondria, the powerhouses of the cell, have emerged as key players in the aging process, impacting stem cell function and contributing to age-related tissue dysfunction. Here are discuss the mechanisms through which mitochondria influence stem cell fate decisions, including energy production, metabolic regulation, ROS signalling, and epigenetic modifications. Therefore, this review highlights the role of mitochondria in driving stem cell senescence and the subsequent impact on tissue function, leading to overall organismal aging and age-related diseases. Finally, we explore potential anti-aging therapies targeting mitochondrial health and discuss their implications for promoting healthy aging. This comprehensive review sheds light on the critical interplay between mitochondrial function, stem cell senescence, and organismal aging, offering insights into potential strategies for attenuating age-related decline and promoting healthy longevity.

Mechanical Signal-Tailored Hydrogel Microspheres Recruit and Train Stem Cells for Precise Differentiation

The aberrant mechanical microenvironment in degenerated tissues induces misdirection of cell fate, making it challenging to achieve efficient endogenous regeneration. Herein, a hydrogel microsphere-based synthetic niche with integrated cell recruitment and targeted cell differentiation properties via mechanotransduction is constructed . Through the incorporation of microfluidics and photo-polymerization strategies, fibronectin (Fn) modified methacrylated gelatin (GelMA) microspheres are prepared with the independently tunable elastic modulus (1-10Kpa) and ligand density (2 and 10 µg mL-1 ), allowing a wide range of cytoskeleton modulation to trigger the corresponding mechanobiological signaling. The combination of the soft matrix (2Kpa) and low ligand density (2 µg mL-1 ) can support the nucleus pulposus (NP)-like differentiation of intervertebral disc (IVD) progenitor/stem cells by translocating Yes-associated protein (YAP), without the addition of inducible biochemical factors. Meanwhile, platelet-derived growth factor-BB (PDGF-BB) is loaded onto Fn-GelMA microspheres (PDGF@Fn-GelMA) via the heparin-binding domain of Fn to initiate endogenous cell recruitment. In in vivo experiments, hydrogel microsphere-niche maintained the IVD structure and stimulated matrix synthesis. Overall, this synthetic niche with cell recruiting and mechanical training capabilities offered a promising strategy for endogenous tissue regeneration.

PSD95 as a New Potential Therapeutic Target of Osteoarthritis: A Study of the Identification of Hub Genes through Self-Contrast Model

Osteoarthritis (OA) is a worldwide joint disease. However, the precise mechanism causing OA remains unclear. Our primary aim was to identify vital biomarkers associated with the mechano-inflammatory aspect of OA, providing potential diagnostic and therapeutic targets for OA. Thirty OA patients who underwent total knee arthroplasty were recruited, and cartilage samples were obtained from both the lateral tibial plateau (LTP) and medial tibial plateau (MTP). GO and KEGG enrichment analyses were performed, and the protein-protein interaction (PPI) assessment was conducted for hub genes. The effect of PSD95 inhibition on cartilage degeneration was also conducted and analyzed. A total of 1247 upregulated and 244 downregulated DEGs were identified. Significant differences were observed between MTP and LTP in mechanical stress-related genes and activated sensory neurons based on a self-contrast model of human knee OA. Cluster analysis identified DLG4 as the hub gene. Cyclic loading stress increased PSD95 (encoded by DLG4) expression in LTP cartilage, and PSD95 inhibitors could alleviate OA progression. This study suggests that inhibiting PSD95 could be a potential therapeutic strategy for preventing articular cartilage degradation.

Achieving Nasal Septal Cartilage In Situ Regeneration: Focus on Cartilage Progenitor Cells

The nasal septal cartilage plays an important role in preventing the collapse of the nasal bones and maintaining the appearance of the nose. In the context of inherent difficulties regarding septal cartilage repair and the shortage of cartilage graft resources for regeneration, tissue engineering, especially the in situ strategy based on scaffolds, has become a new prospect and become one of the most promising approaches. Given that it is difficult for chondrocytes to achieve directional migration and secrete matrix components to participate in tissue repair after cartilage injury, cartilage progenitor cells (CPCs), with great migratory ability and stem cell characteristics, have caught the attention of researchers and brought hope for nasal septal cartilage in situ regeneration. In this review, we first summarized the distribution, characteristics, isolation, and culture methods of nasal septal CPCs. Subsequently, we described the roles of migratory CPCs in cartilage regeneration. Finally, we reviewed the existing studies on CPCs-based cartilage tissue engineering and summarized the strategies for promoting the migration and chondrogenesis of CPCs so as to provide ideas for achieving nasal septal cartilage in situ regeneration.

Sirtuins in osteoarthritis: current understanding

Osteoarthritis (OA) is a common disease characterized by severe chronic joint pain, that imposes a large burden on elderly people. OA is a highly heterogeneous disease, and multiple etiologies contribute to its progression. Sirtuins (SIRTs) are Class III histone deacetylases (HDACs) that regulate a comprehensive range of biological processes such as gene expression, cell differentiation, and organism development, and lifespan. Over the past three decades, increasing evidence has revealed that SIRTs are not only important energy sensors but also protectors against metabolic stresses and aging, and an increasing number of studies have focused on the functions of SIRTs in OA pathogenesis. In this review, we illustrate the biological functions of SIRTs in OA pathogenesis from the perspectives of energy metabolism, inflammation, autophagy and cellular senescence. Moreover, we offer insights into the role played by SIRTs in regulating circadian rhythm, which has recently been recognized to be crucial in OA development. Here, we provide the current understanding of SIRTs in OA to guide a new direction for OA treatment exploration.

Senescence in osteoarthritis: from mechanism to potential treatment

Osteoarthritis (OA) is an age-related cartilage degenerative disease, and chondrocyte senescence has been extensively studied in recent years. Increased numbers of senescent chondrocytes are found in OA cartilage. Selective clearance of senescent chondrocytes in a post-traumatic osteoarthritis (PTOA) mouse model ameliorated OA development, while intraarticular injection of senescent cells induced mouse OA. However, the means and extent to which senescence affects OA remain unclear. Here, we review the latent mechanism of senescence in OA and propose potential therapeutic methods to target OA-related senescence, with an emphasis on immunotherapies. Natural killer (NK) cells participate in the elimination of senescent cells in multiple organs. A relatively comprehensive discussion is presented in that section. Risk factors for OA are ageing, obesity, metabolic disorders and mechanical overload. Determining the relationship between known risk factors and senescence will help elucidate OA pathogenesis and identify optimal treatments.

Adipokines as targets in musculoskeletal immune and inflammatory diseases

Adipokines are the principal mediators in adipose signaling. Nevertheless, besides their role in energy storage, these molecules can be produced by other cells, such as immune cells or chondrocytes. Given their pleiotropic effects, research over the past few years has also focused on musculoskeletal diseases, showing that these adipokines might have relevant roles in worsening the disease or improving the treatment response. In this review, we summarize recent advances in our understanding of adipokines and their role in the most prevalent musculoskeletal immune and inflammatory disorders.

From regeneration to osteoarthritis in the knee joint: The role shift of cartilage-derived progenitor cells

A mount of growing evidence has proven that cartilage-derived progenitor cells (CPCs) harbor strong proliferation, migration, andmultiple differentiation potentials over the past 2 decades. CPCs in the stage of immature tissue play an important role in cartilage development process and injured cartilage repair in the young and active people. However, during maturation and aging, cartilage defects cannot be completely repaired by CPCs in vivo. Recently, tissue engineering has revealed that repaired cartilage defects with sufficient stem cell resources under good condition and bioactive scaffolds in vitro and in vivo. Chronic inflammation in the knee joint limit the proliferation and chondrogenesis abilities of CPCs, which further hampered cartilage healing and regeneration. Neocartilage formation was observed in the varus deformity of osteoarthritis (OA) patients treated with offloading technologies, which raises the possibility that organisms could rebuild cartilage structures spontaneously. In addition, nutritionmetabolismdysregulation, including glucose and free fatty acid dysregulation, could influence both chondrogenesis and cartilage formation. There are a few reviews about the advantages of CPCs for cartilage repair, but few focused on the reasons why CPCs could not repair the cartilage as they do in immature status. A wide spectrum of CPCs was generated by different techniques and exhibited substantial differences. We recently reported that CPCs maybe are as internal inflammation sources during cartilage inflammaging. In this review, we further streamlined the changes of CPCs from immature development to maturation and from healthy status to OA advancement. The key words including “cartilage derived stem cells”, “cartilage progenitor cells”, “chondroprogenitor cells”, “chondroprogenitors” were set for latest literature searching in PubMed and Web of Science. The articles were then screened through titles, abstracts, and the full texts in sequence. The internal environment including long-term inflammation, extendedmechanical loading, and nutritional elements intake and external deleterious factors were summarized. Taken together, these results provide a comprehensive understanding of the underlying mechanism of CPC proliferation and differentiation during development, maturation, aging, injury, and cartilage regeneration in vivo.

A single-cell mass cytometry platform to map the effects of preclinical drugs on cartilage homeostasis

No disease-modifying drug exists for osteoarthritis (OA). Despite success in animal models, candidate drugs continue to fail in clinical trials owing to the unmapped interpatient heterogeneity and disease complexity. We used a single-cell platform based on cytometry by time-of-flight (cyTOF) to precisely outline the effects of candidate drugs on human OA chondrocytes. OA chondrocytes harvested from patients undergoing total knee arthroplasty were treated with 2 drugs, an NF-κB pathway inhibitor, BMS-345541, and a chondroinductive small molecule, kartogenin, that showed preclinical success in animal models for OA. cyTOF conducted with 30 metal isotope-labeled antibodies parsed the effects of the drugs on inflammatory, senescent, and chondroprogenitor cell populations. The NF-κB pathway inhibition decreased the expression of p-NF-κB, HIF2A, and inducible NOS in multiple chondrocyte clusters and significantly depleted 4 p16ink4a-expressing senescent populations, including NOTCH1+STRO1+ chondroprogenitor cells. While kartogenin also affected select p16ink4a-expressing senescent clusters, there was a less discernible effect on chondroprogenitor cell populations. Overall, BMS-345541 elicited a uniform drug response in all patients, while only a few responded to kartogenin. These studies demonstrate that a single-cell cyTOF-based drug screening platform can provide insights into patient response assessment and patient stratification.

Adipokine Signaling Pathways in Osteoarthritis

Osteoarthritis (OA) is a debilitating joint disease that affects millions of individuals. The pathogenesis of OA has not been fully elucidated. Obesity is a well-recognized risk factor for OA. Multiple studies have demonstrated adipokines play a key role in obesity-induced OA. Increasing evidence show that various adipokines may significantly affect the development or clinical course of OA by regulating the pro/anti-inflammatory and anabolic/catabolic balance, matrix remodeling, chondrocyte apoptosis and autophagy, and subchondral bone sclerosis. Several signaling pathways are involved but still have not been systematically investigated. In this article, we review the cellular and molecular mechanisms of adipokines in OA, and highlight the possible signaling pathways. The review suggested adipokines play important roles in obesity-induced OA, and exert downstream function via the activation of various signaling pathways. In addition, some pharmaceuticals targeting these pathways have been applied into ongoing clinical trials and showed encouraging results. However, these signaling pathways are complex and converge into a common network with each other. In the future work, more research is warranted to further investigate how this network works. Moreover, more high quality randomised controlled trials are needed in order to investigate the therapeutic effects of pharmaceuticals against these pathways for the treatment of OA. This review may help researchers to better understand the pathogenesis of OA, so as to provide new insight for future clinical practices and translational research.

Mitochondrially targeted tamoxifen alleviates markers of obesity and type 2 diabetes mellitus in mice

Type 2 diabetes mellitus represents a major health problem with increasing prevalence worldwide. Limited efficacy of current therapies has prompted a search for novel therapeutic options. Here we show that treatment of pre-diabetic mice with mitochondrially targeted tamoxifen, a potential anti-cancer agent with senolytic activity, improves glucose tolerance and reduces body weight with most pronounced reduction of visceral adipose tissue due to reduced food intake, suppressed adipogenesis and elimination of senescent cells. Glucose-lowering effect of mitochondrially targeted tamoxifen is linked to improvement of type 2 diabetes mellitus-related hormones profile and is accompanied by reduced lipid accumulation in liver. Lower senescent cell burden in various tissues, as well as its inhibitory effect on pre-adipocyte differentiation, results in lower level of circulating inflammatory mediators that typically enhance metabolic dysfunction. Targeting senescence with mitochodrially targeted tamoxifen thus represents an approach to the treatment of type 2 diabetes mellitus and its related comorbidities, promising a complex impact on senescence-related pathologies in aging population of patients with type 2 diabetes mellitus with potential translation into the clinic.

Senescent cells play a role in pathogenesis of diabetes, and senolytic agents can improve obesity- and diabetes-related pathologies. Here the authors report that mitochondrially targeted tamoxifen, a potential anti-cancer agent with senolytic activity, alleviates symptoms of obesity and prediabetes in mice, potentially via reduction of food intake and elimination of senescent cells.

Pondering the Potential of Hyaline Cartilage-Derived Chondroprogenitors for Tissue Regeneration: A Systematic Review

OBJECTIVE

Chondroprogenitors have recently gained prominence due to promising results seen in in vitro and animal studies as a potential contender in cell-based therapy for cartilage repair. Lack of consensus regarding nomenclature, isolation techniques, and expansion protocols create substantial limitations for translational research, especially given the absence of distinct markers of identification. The objective of this systematic review was to identify and collate information pertaining to hyaline cartilage-derived chondroprogenitors, with regard to their isolation, culture, and outcome measures.

DESIGN

As per Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a web-based search of Scopus and PubMed databases was performed from January 2000 to May 2020, which yielded 509 studies. A total of 65 studies were identified that met the standardized inclusion criteria which comprised of, but was not limited to, progenitors derived from fibronectin adhesion, migrated subpopulation from explant cultures, and single-cell sorting.

RESULT

Literature search revealed that progenitors demonstrated inherent chondrogenesis and minimal tendency for hypertrophy. Multiple sources also demonstrated significantly better outcomes that bone marrow-derived mesenchymal stem cells and comparable results to chondrocytes. With regard to progenitor subgroups, collated evidence points to better and consistent outcomes with the use of migratory progenitors when compared to fibronectin adhesion assay-derived progenitors, although a direct comparison between the two cell populations is warranted.

CONCLUSION

Since chondroprogenitors exhibit favorable properties for cartilage repair, efficient characterization of progenitors is imperative, to complete their phenotypic profile, so as to optimize their use in translational research for neocartilage formation.

The Adipokine Component in the Molecular Regulation of Cancer Cell Survival, Proliferation and Metastasis

A hormonal imbalance may disrupt the rigorously monitored cellular microenvironment by hampering the natural homeostatic mechanisms. The most common example of such hormonal glitch could be seen in obesity where the uprise in adipokine levels is in virtue of the expanding bulk of adipose tissue. Such aberrant endocrine signaling disrupts the regulation of cellular fate, rendering the cells to live in a tumor supportive microenvironment. Previously, it was believed that the adipokines support cancer proliferation and metastasis with no direct involvement in neoplastic transformations and tumorigenesis. However, the recent studies have reported discrete mechanisms that establish the direct involvement of adipokine signaling in tumorigenesis. Moreover, the individual adipokine profile of the patients has never been considered in the prognosis and staging of the disease. Hence, the present manuscript has focused on the reported extensive mechanisms that culminate the basis of poor prognosis and diminished survival rate in obese cancer patients.

Causal association of adipokines with osteoarthritis: a Mendelian randomization study

OBJECTIVE

This two-sample Mendelian randomization study aimed to delve into the effects of genetically predicted adipokine levels on OA.

METHODS

Summary statistic data for OA originated from a meta-analysis of a genome-wide association study with an overall 50 508 subjects of European ancestry. Publicly available summary data from four genome-wide association studies were exploited to respectively identify instrumental variables of adiponectin, leptin, resistin, chemerin and retinol-blinding protein 4. Subsequently, Mendelian randomization analyses were conducted with inverse variance weighted (IVW), weighted median and Mendelian randomization-Egger regression. Furthermore, sensitivity analyses were then conducted to assess the robustness of our results.

RESULTS

The positive causality between genetically predicted leptin level and risk of total OA was indicated by IVW [odds ratio (OR): 2.40, 95% CI: 1.13-5.09] and weighted median (OR: 2.94, 95% CI: 1.23-6.99). In subgroup analyses, evidence of potential harmful effects of higher level of adiponectin (OR: 1.28, 95% CI: 1.01-1.61 using IVW), leptin (OR: 3.44, 95% CI: 1.18-10.03 using IVW) and resistin (OR: 1.18, 95% CI: 1.03-1.36 using IVW) on risk of knee OA were acquired. However, the mentioned effects on risk of hip OA were not statistically significant. Slight evidence was identified supporting causality of chemerin and retinol-blinding protein 4 for OA. The findings of this study were verified by the results from sensitivity analysis.

CONCLUSIONS

An association between genetically predicted leptin level and risk of total OA was identified. Furthermore, association of genetically predicted levels of adiponectin, leptin and resistin with risk of knee OA were reported.

Joint-adjacent Adipose Tissue by MRI is Associated With Prevalence and Progression of Knee Degenerative Changes: Data from the Osteoarthritis Initiative

BACKGROUND

Adipose tissue has recently gained interest as an independent imaging biomarker for osteoarthritis.

PURPOSE

To explore 1) cross-sectional associations between local subcutaneous fat (SCF) thickness at the knee and the extent of degenerative changes in overweight and obese individuals and 2) associations between local fat distribution and progression of osteoarthritis over 4 years.

STUDY TYPE

Retrospective cohort study.

POPULATION

338 obese and overweight participants from the Osteoarthritis Initiative cohort without radiographic evidence of osteoarthritis.

FIELD STRENGTH

3T: 3D-FLASH-WE; 3D-DESS-WE; T1w-SE; MSME.

ASSESSMENT

Baseline SCF thickness was measured in standardized locations medial, lateral and anterior to the knee and the average joint-adjacent SCF (ajSCF) was calculated. Right thigh SCF cross-sectional area was assessed. Quantitative cartilage T₂ relaxation times and semi-quantitative whole organ MRI scores (WORMS) were obtained at baseline and 4-year follow-up. WORMS_sum was calculated as sum of cartilage, bone marrow edema, subchondral cyst, and meniscal scores.

STATISTICAL TESTS

Associations of SCF measures with baseline, and 4-year change in T₂ and WORMS were analyzed using regression models. SCF measurements were standardized using the equation Value Participant - Mean Cohort Standard deviation . Analyses were adjusted for age, sex, physical activity, and BMI.

RESULTS

Cross-sectionally, significant associations between lateral SCF, lateral compartment WORMS and T₂ were found ( Δ WORMS sum 1 SD change in lateral SCF , [95% CI]: 0.53, [0.12-0.95], P < 0.05; ΔT₂ : 0.50, [0.02-0.98], P < 0.05). Moreover, greater lateral SCF was associated with faster progression of lateral WORMS_sum gradings (OR = 1.50, [1.05-2.15], P < 0.05). No significant positive associations were found for thigh SCF and WORMS_sum (P = 0.44) or T₂ measurements (medial: P = 0.15, lateral: 0.39, patellar: P = 0.75).

DATA CONCLUSION

Joint-adjacent SCF thickness was associated with imaging parameters of knee osteoarthritis, both cross-sectionally and longitudinally, while thigh SCF was not, suggesting a spatial association of SCF and knee osteoarthritis. Based on these findings, joint-adjacent SCF may play a role in the development and progression of knee osteoarthritis.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY: Stage 5.

An Update on the Role of Leptin in the Immuno-Metabolism of Cartilage

Since its discovery in 1994, leptin has been considered as an adipokine with pleiotropic effects. In this review, we summarize the actual information about the impact of this hormone on cartilage metabolism and pathology. Leptin signalling depends on the interaction with leptin receptor LEPR, being the long isoform of the receptor (LEPRb) the one with more efficient intracellular signalling. Chondrocytes express the long isoform of the leptin receptor and in these cells, leptin signalling, alone or in combination with other molecules, induces the expression of pro-inflammatory molecules and cartilage degenerative enzymes. Leptin has been shown to increase the proliferation and activation of immune cells, increasing the severity of immune degenerative cartilage diseases. Leptin expression in serum and synovial fluid are related to degenerative diseases such as osteoarthritis (OA), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Inhibition of leptin signalling showed to have protective effects in these diseases showing the key role of leptin in cartilage degeneration.

Age-Related Changes in the Inflammatory Status of Human Mesenchymal Stem Cells: Implications for Cell Therapy

Human mesenchymal stem/stromal cell (hMSC)-based cell therapies are promising for treating a variety of diseases. The unique immunomodulatory properties of hMSCs have extended their therapeutic potential beyond tissue regeneration. However, extensive pre-clinical culture expansion inevitably drives cells toward replicative “aging” and a consequent decline in quality. These “in vitro-aged” hMSCs resemble biologically aged cells, which have been reported to show senescence signatures, diminished immunosuppressive capacity, and weakened regenerative potential as well as pro-inflammatory features. In this review, we have surveyed the literature to explore the intimate relationship between the inflammatory status of hMSCs and their in vitro aging process. We posit that a shift from an anti-inflammatory to a pro-inflammatory phenotype of culture-expanded hMSCs contributes to a deterioration in their therapeutic efficacy. Potential molecular and cellular mechanisms underpinning this phenomenon have been discussed. We have also highlighted studies that leverage these mechanisms to make culture-expanded hMSCs more amenable for clinical use.

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Aged MSCs have reduced immunosuppressive potential

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Chronic inflammatory microenvironments can exacerbate MSC senescence and aging

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The immunomodulatory potential of MSCs should be assessed prior to clinical use

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MSC immunomodulatory properties may be modified in vitro by bioengineering means

Cartilage tissue engineering for obesity-induced osteoarthritis: Physiology, challenges, and future prospects

Osteoarthritis (OA) is a multifactorial joint disease with pathological changes that affect whole joint tissue. Obesity is acknowledged as the most influential risk factor for both the initiation and progression of OA in weight-bearing and non-weight-bearing joints. Obesity-induced OA is a newly defined phenotypic group in which chronic low-grade inflammation has a central role. Aside from persistent chronic inflammation, abnormal mechanical loading due to increased body weight on weight-bearing joints is accountable for the initiation and progression of obesity-induced OA. The current therapeutic approaches for OA are still evolving. Tissue-engineering-based strategy for cartilage regeneration is one of the most promising treatment breakthroughs in recent years. However, patients with obesity-induced OA are often excluded from cartilage repair attempts due to the abnormal mechanical demands, altered biomechanical and biochemical activities of cells, persistent chronic inflammation, and other obesity-associated factors. With the alarming increase in the number of obese populations globally, the need for an innovative therapeutic approach that could effectively repair and restore the damaged synovial joints is of significant importance for this sub-population of patients. In this review, we discuss the involvement of the systemic and localized inflammatory response in obesity-induced OA and the impact of altered mechanical loading on pathological changes in the synovial joint. Moreover, we examine the current strategies in cartilage tissue engineering and address the critical challenges of cell-based therapies for OA. Besides, we provide examples of innovative ways and potential strategies to overcome the obstacles in the treatment of obesity-induced OA.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Altogether, this review delivers insight into obesity-induced OA and offers future research direction on the creation of tissue engineering-based therapies for obesity-induced OA.

Neuromodulation of bone: Role of different peptides and their interactions (Review)

Our understanding of the skeletal system has been expanded upon the recognition of several neural pathways that serve important roles in bone metabolism and skeletal homeostasis, as bone tissue is richly innervated. Considerable evidence provided by in vitro, animal and human studies have further elucidated the importance of a host of hormones and local factors, including neurotransmitters, in modulating bone metabolism and osteo-chondrogenic differentiation, both peripherally and centrally. Various cells of the musculoskeletal system not only express receptors for these neurotransmitters, but also influence their endogenous levels in the skeleton. As with a number of physiological systems in nature, a neuronal pathway regulating bone turnover will be neutralized by another pathway exerting an opposite effect. These neuropeptides are also critically involved in articular cartilage homeostasis and pathogenesis of degenerative joint disorders, such as osteoarthritis. In the present Review, data on the role of several neuronal populations in nerve-dependent skeletal metabolism is examined, and the molecular events involved are explored, which may reveal broader relationships between two apparently unrelated organs.

Senescence-Associated Secretory Phenotype Determines Survival and Therapeutic Response in Cervical Cancer

Simple Summary

Cervical cancer is the most common gynecological cancer caused by persistent infections with human papilloma viruses. Over time, this infection leads to secretion of inflammatory proteins in the cervix, which exacerbates the neoplastic and senescent changes to the cervical epithelial lining. We measured nineteen serum proteins in retrospectively collected samples from cervical cancer patients. We show here that 10 out of 19 proteins are associated with senescence phenotype in cervical cancer patients. This senescence associated protein signature influences how cervical cancer patients responds to therapy.

Abstract

Molecular biomarkers that can predict survival and therapeutic outcome are still lacking for cervical cancer. Here we measured a panel of 19 serum proteins in sera from 565 patients with stage II or III cervical cancer and identified 10 proteins that have an impact on disease specific survival (DSS) (Hazzard’s ratio; HR = 1.51–2.1). Surprisingly, all ten proteins are implicated in senescence-associated secreted phenotype (SASP), a hallmark of cellular senescence. Machine learning using Ridge regression of these SASP proteins can robustly stratify patients with high SASP, which is associated with poor survival, and patients with low SASP associated with good survival (HR = 3.09–4.52). Furthermore, brachytherapy, an effective therapy for cervical cancer, greatly improves survival in SASP-high patients (HR = 3.3, p < 5 × 10⁻⁵) but has little impact on survival of SASP-low patients (HR = 1.5, p = 0.31). These results demonstrate that cellular senescence is a major determining factor for survival and therapeutic response in cervical cancer and suggest that senescence reduction therapy may be an efficacious strategy to improve the therapeutic outcome of cervical cancer.

Eliminating senescent chondrogenic progenitor cells enhances chondrogenesis under intermittent hydrostatic pressure for the treatment of OA

Background

Osteoarthritis (OA) is a major cause of limb dysfunction, and distraction arthroplasty which generates intermittent hydrostatic pressure (IHP) is an effective approach for OA treatment. However, the result was not always satisfactory and the reasons remained unresolved. Because aging is recognized as an important risk factor for OA and chondrogenic progenitor cells (CPCs) could acquire senescent phenotype, we made a hypothesis that CPCs senescence could have harmful effect on chondrogenesis and the outcome of distraction arthroplasty could be improved by eliminating senescent CPCs pharmacologically.

Methods

The role of senescent CPCs on distraction arthroplasty was first determined by comparing the cartilage samples from the failure and non-failure patients. Next, the biological behaviors of senescent CPCs were observed in the in vitro cell culture and IHP model. Finally, the beneficial effect of senescent CPCs clearance by senolytic dasatinib and quercetin (DQ) on cartilage regeneration was observed in the in vitro and in vivo IHP model.

Results

Larger quantities of senescent CPCs along with increased IL-1 β secretion were demonstrated in the failure patients of distraction arthroplasty. Senescent CPCs revealed impaired proliferation and chondrogenic capability and also had increased IL-1 β synthesis, typical of senescence-associated secretory phenotype (SASP). CPCs senescence and SASP formation were mutually dependent in vitro. Greater amounts of senescent CPCs were negatively correlated with IHP-induced chondrogenesis. In contrast, chondrogenesis could be significantly improved by DQ pretreatment which selectively induced senescent CPCs into apoptosis in the in vitro and in vivo IHP model. Mechanistically, senescent CPCs elimination could decrease SASP formation and therefore promote the proliferation and chondrogenic regeneration capacity of the surrounding survived CPCs under IHP stimulation.

Conclusions

Eliminating senescent CPCs by senolytics could decrease SASP formation and improve the result of joint distraction arthroplasty effectively. Our study provided a novel CPCs senescence-based therapeutic target for improving the outcome of OA treatment.

An update on the association between metabolic syndrome and osteoarthritis and on the potential role of leptin in osteoarthritis

Metabolic syndrome (MetS) has been associated with osteoarthritis (OA). Leptin, which is one of the markers of MetS, has been associated with OA pathophysiology. This study aimed to provide an update on the association between MetS and OA and on the potential role of leptin in OA. In this review, we summarized the current knowledge of the association between MetS and OA and updated the evidence on the potential role of leptin in OA. Clinical studies have investigated the epidemiologic association between MetS or its components and OA. Results suggested strong epidemiologic associations between MetS and OA, especially in the Asian population. Animal studies also indicated that metabolic dysregulation may lead to OA pathogenesis. The systemic role of MetS in OA pathophysiology is associated with obesity-related inflammation, the beneficial role of n-3 polyunsaturated fatty acids and deleterious role of cholesterol, physical inactivity, hypertension-induced subchondral ischemia, dyslipidemia-induced ectopic lipid deposition in chondrocytes, hyperglycemia-induced local effects of oxidative stress and advanced glycation end-products, low-grade systemic inflammation, and obesity-related adipokines by inducing the expression of proinflammtory factors. Leptin levels in serum/plasma and synovial fluid were associated with joint pain, radiographic progression, bone formation biomarkers, cartilage volume, knee OA incidence, and total joint arthroplasty in OA patients. Elevated leptin expression and increased effect of leptin on infrapatellar fat pad, synovium, articular cartilage, and bone were also involved in the pathogenesis of OA. Current knowledge indicates a convincing epidemiologic association between MetS and OA, especially in the Asian population. Animal studies have also shown that metabolic dysregulation may lead to OA pathogenesis. Accumulating evidence suggests that leptin may play a potential role in OA pathogenesis. Therefore, leptin and its receptor may be an emerging target for intervention in metabolic-associated OA.

Overexpression of Pitx1 attenuates the senescence of chondrocytes from osteoarthritis degeneration cartilage-A self-controlled model for studying the etiology and treatment of osteoarthritis

To explore the role of low expression of Pitx1 in degenerative cartilage tissue. A cartilage injury model was established by using the cartilage scratch method. The newly generated tissue by BrdU labeled in injured cartilage region expressed SOX-9 and Col2A1 in 5-week-old rats. Compared with that, the number of BrdU-positive cells was lower in 4-month-old cartilage injury model rats. Compared with that in lateral cartilage, the expression of Pitx1 was lower in medial cartilage. Compared with chondrocytes derived from the lateral cartilage, chondrocytes derived from the medial cartilage exhibited significantly increased cell aging, as determined by SA-β-GAL staining; downregulated Pitx1 expression; reduced autophagy levels; and decreased Col2A1 expression in a chondrogenic differentiation assay. Inhibition of Pitx1 expression in chondrocytes from the lateral cartilage significantly increased the ratio of cell senescence. Overexpression of Pitx1 in chondrocytes derived from the medial cartilage decreased the cell senescence ratio. In a luciferase assay, Pitx1 was found to promote Sirt1 gene transcription. Decreased Pitx1 expression is an essential cause of cartilage degeneration in the medial tibial plateau. The described self-controlled model is an excellent way to study OA etiology and screen therapeutic drugs for OA.

The burden of metabolic syndrome on osteoarthritic joints

Background

The prevalence of osteoarthritis (OA) increases with obesity, with up to two thirds of the elderly obese population affected by OA of the knee. The metabolic syndrome (MetS), frequently associated with central obesity and characterised by elevated waist circumference, raised fasting plasma glucose concentration, raised triglycerides, reduced high-density lipoproteins, and/or hypertension, is implicated in the pathogenesis of OA. This narrative review discusses the mechanisms involved in the influence of MetS on OA, with a focus on the effects on macrophages and chondrocytes.

Main text

A skewing of macrophages towards a pro-inflammatory M1 phenotype within synovial and adipose tissues is thought to play a role in OA pathogenesis. The metabolic perturbations typical of MetS are important drivers of pro-inflammatory macrophage polarisation and activity. This is mediated via alterations in the levels and activities of the cellular nutrient sensors 5′ adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin complex 1 (mTORC1), intracellular accumulation of metabolic intermediates such as succinate and citrate, and increases in free fatty acids (FFAs) and hyperglycaemia-induced advanced glycation end-products (AGEs) that bind to receptors on the macrophage surface. Altered levels of adipokines, including leptin and adiponectin, further influence macrophage polarisation. The metabolic alterations in MetS also affect the cartilage through direct effects on chondrocytes by stimulating the production of pro-inflammatory and catabolic factors and possibly by suppressing autophagy and promoting cellular senescence.

Conclusions

The influence of MetS on OA pathogenesis involves a wide range of metabolic alterations that directly affect macrophages and chondrocytes. The relative burden of intra-articular versus systemic adipose tissue in the MetS-associated OA remains to be clarified. Understanding how altered metabolism interacts with joints affected by OA is crucial for the development of further strategies for treating this debilitating condition, such as supplementing existing therapies with metformin and utilising ω-3 fatty acid derivatives to restore imbalances in ω-3 and ω-6 fatty acids.

Increased renal cellular senescence in murine high-fat diet: effect of the senolytic drug quercetin

Obesity and dyslipidemia can be associated with cellular senescence, and may impair kidney function. However, whether senescence contributes to renal dysfunction in these conditions remains unclear. Quercetin is an abundant dietary flavonoid that selectively clears inhibiting PI3K/AKT and p53/p21/serpines and inducing apoptosis. We hypothesized that high-fat-diet-induced obesity causes renal senescence, which would be mitigated by quercetin. C57BL/6J mice fed either standard chow or high-fat diets (HFDs) were treated with quercetin (50 mg/kg) or vehicle 5-days biweekly via oral gavage for 10 weeks. Subsequently, renal function was studied in vivo using magnetic resonance imaging, and renal senescence and histology were evaluated ex vivo. Mice fed with a HFD developed obesity and hypercholesterolemia, whereas renal size remained unchanged. Murine obesity impaired renal function and cortical oxygenation, and induced glomerulomegaly. Renal markers of senescence (eg, expression of p16, p19, and p53) and its secretory phenotype were upregulated in the obese hypercholesterolemic compared to lean mice in renal tubular cells, but attenuated in quercetin-treated murine kidneys, as was renal fibrosis. Quercetin treatment also increased renal cortical oxygenation and decreased plasma creatinine levels in obese mice, whereas body weight and cholesterol levels were unaltered. Therefore, murine obesity and dyslipidemia induce renal tissue senescence and impairs kidney function, which is alleviated by chronic senolytic treatment. These findings implicate senescence in loss of kidney function in murine dyslipidemia and obesity, and support further studies of senolytic therapy in obesity.

Adipose Tissue Senescence and Inflammation in Aging is Reversed by the Young Milieu

Visceral adipose tissue (VAT) inflammation plays a central role in longevity and multiple age-related disorders. Cellular senescence (SEN) is a fundamental aging mechanism that contributes to age-related chronic inflammation and organ dysfunction, including VAT. Recent studies using heterochronic parabiosis models strongly suggested that circulating factors in young plasma alter the aging phenotypes of old animals. Our study investigated if young plasma rescued SEN phenotypes in the VAT of aging mice. With heterochronic parabiosis model using young (3 months) and old (18 months) mice, we found significant reduction in the levels of pro-inflammatory cytokines and altered adipokine profile that are protective of SEN in the VAT of old mice. These data are indicative of protection from SEN of aging VAT by young blood circulation. Old parabionts also exhibited diminished expression of cyclin-dependent kinase inhibitors (CDKi) genes p16 (Cdkn2a) and p21 (Cdkn1a/Cip1) in the VAT. In addition, when exposed to young serum condition in an ex vivo culture system, aging adipose tissue-derived stromovascular fraction cells produced significantly lower amounts of pro-inflammatory cytokines (MCP-1 and IL-6) compared to old condition. Expressions of p16 and p21 genes were also diminished in the old stromovascular fraction cells under young serum condition. Finally, in 3T3-preadipocytes culture system, we found reduced pro-inflammatory cytokines (Mcp-1 and Il-6) and diminished expression of cyclin-dependent kinase inhibitor genes in the presence of young serum compared to old serum. In summary, this study demonstrates that young milieu is capable of protecting aging adipose tissue from SEN and thereby inflammation.

Activation of the leptin pathway by high expression of the long form of the leptin receptor (Ob-Rb) accelerates chondrocyte senescence in osteoarthritis

Objectives

Activation of the leptin pathway is closely correlated with human knee cartilage degeneration. However, the role of the long form of the leptin receptor (Ob-Rb) in cartilage degeneration needs further study. The aim of this study was to determine the effect of increasing the expression of Ob-Rb on chondrocytes using a lentiviral vector containing Ob-Rb.

Methods

The medial and lateral cartilage samples of the tibial plateau from 12 osteoarthritis (OA) patients were collected. Ob-Rb messenger RNA (mRNA) was detected in these samples. The Ob-Rb-overexpressing chondrocytes and controls were treated with different doses of leptin for two days. The activation of the p53/p21 pathway and the number of senescence-associated β-galactosidase (SA-β-gal)-positive cells were evaluated. The mammalian target of rapamycin (mTOR) signalling pathway and autophagy were detected after the chondrocytes were treated with a high dose of leptin.

Results

In total, 12 cases were found to have severe medial cartilage wear compared with the lateral cartilage. Immunofluorescence showed that the expression of Ob-Rb in the medial cartilage of the tibial plateau was high. High levels of leptin led to cell cycle arrest and inhibited autophagy. After overexpression of Ob-Rb, the physiological dose of leptin induced cell senescence in the chondrocytes. High doses of leptin inhibited autophagy by activating the mTOR signalling pathway. Blockade of the mTOR signalling pathway could restore autophagy and partially reverse senescence induced by leptin in chondrocytes.

Conclusion

In summary, the present study demonstrated that high doses of leptin induce cell senescence by activating the mTOR pathway in chondrocytes from OA cartilage. Highly expressed Ob-Rb accelerates chondrocyte senescence by activating the leptin pathway in OA.

Cite this article: X. Zhao, P. Huang, G. Li, L. Zhendong, G. Hu, Q. Xu. Activation of the leptin pathway by high expression of the long form of the leptin receptor (Ob-Rb) accelerates chondrocyte senescence in osteoarthritis. Bone Joint Res 2019;8:425–436. DOI: 10.1302/2046-3758.89.BJR-2018-0325.R2.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

Low-Dose Pesticide Mixture Induces Accelerated Mesenchymal Stem Cell Aging In Vitro

The general population is chronically exposed to multiple environmental contaminants such as pesticides. We have previously demonstrated that human mesenchymal stem cells (MSCs) exposed in vitro to low doses of a mixture of seven common pesticides showed a permanent phenotype modification with a specific induction of an oxidative stress-related senescence. Pesticide mixture also induced a shift in MSC differentiation toward adipogenesis. Thus, we hypothesized that common combination of pesticides may induce a premature cellular aging of adult MSCs. Our goal was to evaluate if the prolonged exposure to pesticide mixture could accelerate aging-related markers and in particular deteriorate the immunosuppressive properties of MSCs. MSCs exposed to pesticide mixture, under long-term culture and obtained from aging donor, were compared by bulk RNA sequencing analysis. Aging, senescence, and immunomodulatory markers were compared. The protein expression of cellular aging-associated metabolic markers and immune function of MSCs were analyzed. Functional analysis of the secretome impacts on immunomodulatory properties of MSCs was realized after 21 days' exposure to pesticide mixture. The RNA sequencing analysis of MSCs exposed to pesticide showed some similarities with cells from prolonged culture, but also with the MSCs of an aged donor. Changes in the metabolic markers MDH1, GOT and SIRT3, as well as an alteration in the modulation of active T cells and modifications in cytokine production are all associated with cellular aging. A modified functional profile was found with similarities to aging process. Stem Cells 2019;37:1083-1094.

Obesity, Fat Mass and Immune System: Role for Leptin

Obesity is an epidemic disease characterized by chronic low-grade inflammation associated with a dysfunctional fat mass. Adipose tissue is now considered an extremely active endocrine organ that secretes cytokine-like hormones, called adipokines, either pro- or anti-inflammatory factors bridging metabolism to the immune system. Leptin is historically one of most relevant adipokines, with important physiological roles in the central control of energy metabolism and in the regulation of metabolism-immune system interplay, being a cornerstone of the emerging field of immunometabolism. Indeed, leptin receptor is expressed throughout the immune system and leptin has been shown to regulate both innate and adaptive immune responses. This review discusses the latest data regarding the role of leptin as a mediator of immune system and metabolism, with particular emphasis on its effects on obesity-associated metabolic disorders and autoimmune and/or inflammatory rheumatic diseases.

Adipokines and inflammation: is it a question of weight?

Obesity has reached epidemic proportions in the Western society and is increasing in the developing world. It is considered as one of the major contributors to the global burden of disability and chronic diseases, including autoimmune, inflammatory and degenerative diseases. Research conducted on obesity and its complications over the last two decades has transformed the outdated concept of white adipose tissue (WAT) merely serving as an energy depot. WAT is now recognized as an active and inflammatory organ capable of producing a wide variety of factors known as adipokines. These molecules participate through endocrine, paracrine, autocrine or juxtacrine crosstalk mechanisms in a great variety of physiological or pathophysiological processes, regulating food intake, insulin sensitivity, immunity and inflammation. Although initially restricted to metabolic activities (regulation of glucose and lipid metabolism), adipokines currently represent a new family of proteins that can be considered key players in the complex network of soluble mediators involved in the pathophysiology of immune/inflammatory diseases. However, the complexity of the adipokine network in the pathogenesis and progression of inflammatory diseases has posed, since the beginning, the important question of whether it may be possible to target the mechanism(s) by which adipokines contribute to disease selectively without suppressing their physiological functions. Here, we explore in depth the most recent findings concerning the involvement of adipokines in inflammation and immune responses, in particular in rheumatic, inflammatory and degenerative diseases. We also highlight several possible strategies for therapeutic development and propose that adipokines and their signalling pathways may represent innovative therapeutic strategies for inflammatory disorders.

The role of cellular senescence in aging through the prism of Koch-like criteria

Since Hayflick's discovery of cellular senescence (CS), a great volume of knowledge in the field has been accumulated and intensively discussed. Here, we attempted to organize the evidence "for" and "against" the hypothesized causal role of CS in aging. For that purpose, we utilized robust Koch-like logical criteria, based on the assumption that some quantitative relationships between the accumulation of senescent cells and aging rate should exist. If so, it could be expected that (i) the "CS load" would be greater in the premature aging phenotype and lesser in longevity phenotype; (ii) CS would promote age-related diseases, and (iii) the interventions that modulate the levels of senescent cells should also modulate health/lifespan. The analysis shows that CS can be considered a causal factor of aging and an important player in various age-related diseases, though its contribution may greatly vary across species. While the relative impact of senescent cells to aging could overall be rather limited and their elimination is hardly expected to be the "fountain of youth", the potential benefits of the senolytic strategy seems a promising option in combating age-related diseases and extending healthspan.

Increasing UCP2 expression and decreasing NOX1/4 expression maintain chondrocyte phenotype by reducing reactive oxygen species production

The aim of this study is to demonstrate that improving the mitochondrial function can inhibite the loss of chondrocyte phenotype by regulating the expression of uncoupling protein 2(UCP2) and NADPH oxidase1/4(NOX1/4) to reduce the production of reactive oxygen species(ROS). The effects of mitochondrial biogenesis “master regular” peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), mitochondrial transcriptional factor A (TFAM), UCP2, and NOX1/4 on chondrocyte phenotype was examined. It was found that when the chondrocyte phenotype was lost, PGC-1α, UCP2, and TFAM expression decreased, while NOX1/4 expression increased. Inhibiting UCP2 expression promoted the loss of chondrocyte phenotype, and inhibiting NOX1/4 relieved the loss of the chondrocyte phenotype. After activating the PGC-1α-TFAM pathway, UCP2 increased and NOX1/4 decreased, which suppressed loss of the chondrocyte phenotype. After inhibiting NOX1/4, UCP2 expression increased. Increasing and decreasing UCP2 and NOX1/4 expression, respectively, helps maintain the chondrocyte phenotype and improve mitochondrial functioning by reducing reactive oxygen species production.

Arterial ageing: from endothelial dysfunction to vascular calcification

Complex structural and functional changes occur in the arterial system with advancing age. The aged artery is characterized by changes in microRNA expression patterns, autophagy, smooth muscle cell migration and proliferation, and arterial calcification with progressively increased mechanical vessel rigidity and stiffness. With age the vascular smooth muscle cells modify their phenotype from contractile to 'synthetic' determining the development of intimal thickening as early as the second decade of life as an adaptive response to forces acting on the arterial wall. The increased permeability observed in intimal thickening could represent the substrate on which low-level atherosclerotic stimuli can promote the development of advanced atherosclerotic lesions. In elderly patients the atherosclerotic plaques tend to be larger with increased vascular stenosis. In these plaques there is a progressive accumulation of both lipids and collagen and a decrease of inflammation. Similarly the plaques from elderly patients show more calcification as compared with those from younger patients. The coronary artery calcium score is a well-established marker of adverse cardiovascular outcomes. The presence of diffuse calcification in a severely stenotic segment probably induces changes in mechanical properties and shear stress of the arterial wall favouring the rupture of a vulnerable lesion in a less stenotic adjacent segment. Oxidative stress and inflammation appear to be the two primary pathological mechanisms of ageing-related endothelial dysfunction even in the absence of clinical disease. Arterial ageing is no longer considered an inexorable process. Only a better understanding of the link between ageing and vascular dysfunction can lead to significant advances in both preventative and therapeutic treatments with the aim that in the future vascular ageing may be halted or even reversed.

Adipokine Contribution to the Pathogenesis of Osteoarthritis

Recent studies have shown that overweight and obesity play an important role in the development of osteoarthritis (OA). However, joint overload is not the only risk factor in this disease. For instance, the presence of OA in non-weight-bearing joints such as the hand suggests that metabolic factors may also contribute to its pathogenesis. Recently, white adipose tissue (WAT) has been recognized not only as an energy reservoir but also as an important secretory organ of adipokines. In this regard, adipokines have been closely associated with obesity and also play an important role in bone and cartilage homeostasis. Furthermore, drugs such as rosuvastatin or rosiglitazone have demonstrated chondroprotective and anti-inflammatory effects in cartilage explants from patients with OA. Thus, it seems that adipokines are important factors linking obesity, adiposity, and inflammation in OA. In this review, we are focused on establishing the physiological mechanisms of adipokines on cartilage homeostasis and evaluating their role in the pathophysiology of OA based on evidence derived from experimental research as well as from clinical-epidemiological studies.

Leptin in the interplay of inflammation, metabolism and immune system disorders

Leptin is one of the most relevant factors secreted by adipose tissue and the forerunner of a class of molecules collectively called adipokines. Initially discovered in 1994, its crucial role as a central regulator in energy homeostasis has been largely described during the past 20 years. Once secreted into the circulation, leptin reaches the central and peripheral nervous systems and acts by binding and activating the long form of leptin receptor (LEPR), regulating appetite and food intake, bone mass, basal metabolism, reproductive function and insulin secretion, among other processes. Research on the regulation of different adipose tissues has provided important insights into the intricate network that links nutrition, metabolism and immune homeostasis. The neuroendocrine and immune systems communicate bi-directionally through common ligands and receptors during stress responses and inflammation, and control cellular immune responses in several pathological situations including immune-inflammatory rheumatic diseases. This Review discusses the latest findings regarding the role of leptin in the immune system and metabolism, with particular emphasis on its effect on autoimmune and/or inflammatory rheumatic diseases, such as rheumatoid arthritis and osteoarthritis.

Therapeutic role of sirtuins in neurodegenerative disease and their modulation by polyphenols

Searching for effective therapeutic agents‏‎ to ‎‏prevent‏ ‏neurodegeneration ‎is a challenging task due ‎to ‎the growing list of neurodegenerative disorders associated with a multitude of inter-related pathways.‎ The induction and inhibition of several different signaling pathways has been shown to slow down and/or attenuate ‎neurodegeneration and decline in cognition and locomotor function. Among these signaling pathways, a new class of enzymes known as sirtuins or silent information regulators of gene transcription has been shown to play important regulatory roles in the ageing process. SIRT1, a nuclear sirtuin, has received ‎particular interest due to its role as a deacetylase for several metabolic and signaling proteins involved in stress response, apoptosis, mitochondrial function, self-renewal, and ‎neuroprotection. ‎A new strategy to treat ‎neurodegenerative diseases is targeted therapy. In ‎this ‎paper, we‎ ‎ reviewed up-to-date findings regarding the targeting of ‎SIRT1 by polyphenolic ‎compounds,‎ ‎as a ‎new ‎‏approach in the search for novel, safe and effective treatments for ‎ ‎neurodegenerative ‎diseases. ‎.