Long-term treatment with senolytic drugs Dasatinib and Quercetin ameliorates age-dependent intervertebral disc degeneration in mice

S1P regulates intervertebral disc aging by mediating endoplasmic reticulum-mitochondrial calcium ion homeostasis

As the aging process progresses, age-related intervertebral disc degeneration (IVDD) is becoming an emerging public health issue. Site-1 protease (S1P) has recently been found to be associated with abnormal spinal development in patients with mutations and has multiple biological functions. Here, we discovered a reduction of S1P in degenerated and aging intervertebral discs, primarily regulated by DNA methylation. Furthermore, through drug treatment and siRNA-mediated S1P knockdown, nucleus pulposus cells were more prone to exhibit degenerative and aging phenotypes. Conditional KO of S1P in mice resulted in spinal developmental abnormalities and premature aging. Mechanistically, S1P deficiency impeded COP II-mediated transport vesicle formation, which leads to protein retention in the endoplasmic reticulum (ER) and subsequently ER distension. ER distension increased the contact between the ER and mitochondria, disrupting ER-to-mitochondria calcium flow and resulting in mitochondrial dysfunction and energy metabolism disturbance. Finally, using 2-APB to inhibit calcium ion channels and the senolytic drug dasatinib and quercetin (D + Q) partially rescued the aging and degenerative phenotypes caused by S1P deficiency. In conclusion, our findings suggest that S1P is a critical factor in causing IVDD in the process of aging and highlight the potential of targeting S1P as a therapeutic approach for age-related IVDD.

Therapeutic targeting of senescent cells in the CNS

Senescent cells accumulate throughout the body with advanced age, diseases and chronic conditions. They negatively impact health and function of multiple systems, including the central nervous system (CNS). Therapies that target senescent cells, broadly referred to as senotherapeutics, recently emerged as potentially important treatment strategies for the CNS. Promising therapeutic approaches involve clearing senescent cells by disarming their pro-survival pathways with 'senolytics'; or dampening their toxic senescence-associated secretory phenotype (SASP) using 'senomorphics'. Following the pioneering discovery of first-generation senolytics dasatinib and quercetin, dozens of additional therapies have been identified, and several promising targets are under investigation. Although potentially transformative, senotherapies are still in early stages and require thorough testing to ensure reliable target engagement, specificity, safety and efficacy. The limited brain penetrance and potential toxic side effects of CNS-acting senotherapeutics pose challenges for drug development and translation to the clinic. This Review assesses the potential impact of senotherapeutics for neurological conditions by summarizing preclinical evidence, innovative methods for target and biomarker identification, academic and industry drug development pipelines and progress in clinical trials.

Hypoxia and aging: molecular mechanisms, diseases, and therapeutic targets

Aging is a complex biological process characterized by the gradual decline of cellular functions, increased susceptibility to diseases, and impaired stress responses. Hypoxia, defined as reduced oxygen availability, is a critical factor that influences aging through molecular pathways involving hypoxia-inducible factors (HIFs), oxidative stress, inflammation, and epigenetic modifications. This review explores the interconnected roles of hypoxia in aging, highlighting how hypoxic conditions exacerbate cellular damage, promote senescence, and contribute to age-related pathologies, including cardiovascular diseases, neurodegenerative disorders, cancer, metabolic dysfunctions, and pulmonary conditions. By examining the molecular mechanisms linking hypoxia to aging, we identify key pathways that serve as potential therapeutic targets. Emerging interventions such as HIF modulators, antioxidants, senolytics, and lifestyle modifications hold promise in mitigating the adverse effects of hypoxia on aging tissues. However, challenges such as the heterogeneity of aging, lack of reliable biomarkers, and safety concerns regarding hypoxia-targeted therapies remain. This review emphasizes the need for personalized approaches and advanced technologies to develop effective antiaging interventions. By integrating current knowledge, this review provides a comprehensive framework that underscores the importance of targeting hypoxia-induced pathways to enhance healthy aging and reduce the burden of age-related diseases.

Melatonin mitigates matrix stiffness-induced intervertebral disk degeneration by inhibiting reactive oxygen species and melatonin receptors mediated PI3K/AKT/NF-κB pathway

Intervertebral disk degeneration (IVDD) may lead to an increase in extracellular matrix (ECM) stiffness, potentially contributing to the progression of the disease. Melatonin reportedly mitigates IVDD; however, its potential to attenuate elevated matrix stiffness-induced IVDD remains unexplored. Therefore, we aimed to investigate whether melatonin can alleviate the progression of IVDD triggered by increased matrix stiffness and elucidate its underlying mechanisms. Nucleus pulposus (NP) tissues were collected from patients, and ECM stiffness, reactive oxygen species (ROS) levels, apoptosis rates, and P65 expression in these tissues with varying Pfirrmann scores were determined. In vitro experiments were conducted to investigate the effects of melatonin on various pathophysiological mechanisms within the NP cells cultured on soft substrates with differing stiffness levels. Our findings revealed a positive correlation between ECM stiffness in human NP tissue and degree of IVDD. In addition, phosphorylation of P65 exhibited a strong association with matrix stiffness. Enhanced levels of ROS and cellular apoptosis were observed within degenerated intervertebral disks. In vitro experiments demonstrated that melatonin significantly inhibited catabolism and apoptosis induced by stiff matrices, along with elevated ROS levels. Furthermore, we observed that melatonin inhibited NP cell catabolism and apoptosis by reducing the melatonin receptors mediated activation of the PI3K/AKT and nuclear factor-kappa B (NF-κB) pathways. Also, we found that the reduction of ROS by melatonin can assist in inhibiting the activation of the NF-κB pathway. The outcomes of the in vivo experiments corroborated the results of the in vitro experiments, illustrating that melatonin treatment could alleviate the compression-induced upregulation of matrix stiffness in NP and IVDD. Collectively, melatonin can potentially alleviate high matrix stiffness-induced IVDD by reducing intracellular ROS levels and inhibiting the PI3K/AKT/NF-κB pathway.NEW & NOTEWORTHY Melatonin mitigates intervertebral disk degeneration (IVDD) induced by matrix stiffness through reactive oxygen species (ROS) reduction. Matrix stiffness is related to increased nucleus pulposus cell ROS, apoptosis, and degeneration. Melatonin inhibits PI3K/AKT/NF-κB pathways via melatonin receptors in a stiff matrix environment. In vivo, melatonin restores disk height and alleviates IVDD progression.

Targeting FAP-positive chondrocytes in osteoarthritis: a novel lipid nanoparticle siRNA approach to mitigate cartilage degeneration

BACKGROUND

Osteoarthritis (OA) is a common joint disease that leads to chronic pain and functional limitations. Recent research has revealed soluble fibroblast activation protein (FAP) secreted from OA synovium could degrade type II collagen (Col2) in cartilage to promote the progression of OA. This study aimed to reveal the role of FAP from chondrocytes in OA and develop a novel lipid nanoparticle (LNP)-FAP siRNA delivery system for OA treatment.

METHODS

The expression of FAP in the cartilage of knee OA patients was investigated using [68 Ga]Ga-FAPI-04 PET in vivo and immunofluorescence, western blotting, and RT-qPCR in vitro. Cell senescence was determined by senescence-associated β-galactosidase (SA-β-Gal) assay after FAP overexpressing or knockdown in chondrocytes. An OA model with chondrocyte-specific FAP knockout mice was applied to investigate the role of FAP in chondrocyte senescence and OA development. The therapeutic effects of lipid nanoparticle (LNP) @FAP siRNA on cartilage degeneration were evaluated in the rat OA model.

RESULTS

Our study found that higher [68 Ga]Ga-FAPI-04 uptake was detected in knee OA patients by PET/CT scan. FAP mRNA and protein levels were highly expressed in OA-damaged cartilage. Moreover, we found that overexpression of FAP promotes chondrocyte senescence, and the genetic knockout of FAP in chondrocytes alleviates OA. Knockdown FAP by siRNA could alleviate chondrocyte senescence and suppress the NF-κB pathway to reduce the senescence-associated secretory phenotype (SASP). In the rat model of OA, intraarticular injection of LNP@FAP siRNA can reduce senescent cells and ameliorate cartilage destruction.

CONCLUSION

FAP-positive chondrocytes play a significant role in the pathogenesis of OA. Targeting these cells selectively has the potential to mitigate the progression of the disease. Our study provides valuable insights into the intraarticular injection of LNP@FAP siRNA as a promising strategy for the treatment of OA.

Protective effects of PDGF-AB/BB against cellular senescence in human intervertebral disc

Cellular senescence, characterized by a permanent state of cell cycle arrest and a secretory phenotype contributing to inflammation and tissue deterioration, has emerged as a target for age-related interventions. Accumulation of senescent cells is closely linked with intervertebral disc (IVD) degeneration, a prevalent age-dependent chronic disorder causing low back pain. Previous studies have highlighted that platelet-derived growth factor (PDGF) mitigated IVD degeneration through anti-apoptosis, anti-inflammation, and pro-anabolism. However, its impact on IVD cell senescence remains elusive. In this study, human NP and AF cells derived from aged, degenerated IVDs were treated with recombinant human (rh) PDGF-AB/BB for 5 days and changes of transcriptome profiling were examined through mRNA sequencing. NP and AF cells demonstrated similar but distinct responses to the treatment. However, the effects of PDGF-AB and BB on human IVD cells were comparable. Specifically, PDGF-AB/BB treatment resulted in downregulation of gene clusters related to neurogenesis and response to mechanical stimulus in AF cells while the downregulated genes in NP cells were mainly associated with metabolic pathways. In both NP and AF cells, PDGF-AB and BB treatment upregulated the expression of genes involved in cell cycle regulation, mesenchymal cell differentiation, and response to reduced oxygen levels, while downregulating the expression of genes related to senescence associated phenotype, including oxidative stress, reactive oxygen species (ROS), and mitochondria dysfunction. Network analysis revealed that PDGFRA and IL6 were the top hub genes in treated NP cells. Furthermore, in irradiation-induced senescent NP cells, PDGFRA gene expression was significantly reduced compared to non-irradiated cells. However, rhPDGF-AB/BB treatment increased PDGFRA expression and mitigated the senescence progression through increased cell population in the S phase, reduced SA-β-Gal activity, and decreased expression of senescence related regulators including P21, P16, IL6, and NF-κB. Our findings reveal a novel anti-senescence role of PDGF in the IVD, demonstrating its ability to alleviate the senescent phenotype and protect against the progression of senescence. This makes it a promising candidate for preventing or treating IVD degeneration by targeting cellular senescence.

Roles of chromatin and genome instability in cellular senescence and their relevance to ageing and related diseases

Ageing is a complex biological process in which a gradual decline in physiological fitness increases susceptibility to diseases such as neurodegenerative disorders and cancer. Cellular senescence, a state of irreversible cell-growth arrest accompanied by functional deterioration, has emerged as a pivotal driver of ageing. In this Review, we discuss how heterochromatin loss, telomere attrition and DNA damage contribute to cellular senescence, ageing and age-related diseases by eliciting genome instability, innate immunity and inflammation. We also discuss how emerging therapeutic strategies could restore heterochromatin stability, maintain telomere integrity and boost the DNA repair capacity, and thus counteract cellular senescence and ageing-associated pathologies. Finally, we outline current research challenges and future directions aimed at better comprehending and delaying ageing.

Single-cell RNA sequencing reveals the MIF/ACKR3 receptor-ligand interaction between neutrophils and nucleus pulposus cells in intervertebral disc degeneration

OBJECTIVES

To unravel the heterogeneity and function of microenvironmental neutrophils during intervertebral disc degeneration (IDD).

METHODS

Single-cell RNA sequencing (scRNA-seq) was utilized to dissect the cellular landscape of neutrophils in intervertebral disc (IVD) tissues and their crosstalk with nucleus pulposus cells (NPCs). The expression levels of macrophage migration inhibitory factor (MIF) and ACKR3 in IVD tissues were detected. The MIF/ACKR3 axis was identified and its effects on IDD were investigated in vitro and in vivo.

RESULTS

We sequenced here 71520 single cells from 5 control and 9 degenerated IVD samples using scRNA-seq. We identified a unique cluster of neutrophils abundant in degenerated IVD tissues that highly expressed MIF and was functionally enriched in extracellular matrix organization (ECMO). Cell-to-cell communication analyses showed that this ECMO-neutrophil subpopulation was closely interacted with an effector NPCs subtype, which displayed high expression of ACKR3. Further analyses revealed that MIF was positively correlated with ACKR3 and functioned via directly binding to ACKR3 on effector NPCs. MIF inhibition attenuated degenerative changes of NPCs and extracellular matrix, which could be partially reversed by ACKR3 overexpression. Clinically, a significant correlation of high MIF/ACKR3 expression with advanced IDD grade was observed. Furthermore, we also found a positive association between MIF+ ECMO-neutrophil counts and ACKR3+ effector NPCs density as well as higher expression of the MIF/ACKR3 signaling in areas where these two cell types were neighbors.

CONCLUSIONS

These data suggest that ECMO-neutrophil promotes IDD progression by their communication with NPCs via the MIF/ACKR3 axis, which may shed light on therapeutic strategies.

Quercetin Regulates Microglia M1/M2 Polarization and Alleviates Retinal Inflammation via ERK/STAT3 Pathway

Retinal inflammation is a pivotal characteristic observed in various retinal degenerative disorders, notably age-related macular degeneration (AMD), primarily orchestrated by the activation of microglia. Targeting the inhibition of microglial activation has emerged as a therapeutic focal point. Quercetin (Qu), ubiquitously present in dietary sources and tea, has garnered attention for its anti-neuroinflammatory properties. However, the impact of Qu on retinal inflammation and the associated mechanistic pathways remains incompletely elucidated. In this study, retinal inflammation was induced in adult male C57BL/6 J mice through intraperitoneal administration of LPS. The results revealed that Qu pre-treatment induces a phenotypic shift in microglia from M1 phenotype to M2 phenotype. Furthermore, Qu attenuated retinal inflammation and stabilized the integrity of the blood-retina barrier (BRB). In vitro experiments revealed that Qu impedes microglial activation, proliferation, and migration, primarily via modulation the ERK/STAT3 signaling pathway. Notably, these actions of Qu significantly contributed to the preservation of photoreceptors. Consequently, Qu pre-treatment holds promise as an effective strategy for controlling retinal inflammation and preserving visual function.

Dietary Polyphenols as Anti-Aging Agents: Targeting the Hallmarks of Aging

Background: Aging is a natural biological process influenced by multiple factors and is a significant contributor to various chronic diseases. Slowing down the aging process and extending health span have been pursuits of the scientific field. Methods: Examination of the effects of dietary polyphenols on hallmarks of aging such as genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, disabled macroautophagy, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, chronic inflammation, and dysbiosis. Results: Polyphenols, abundant in nature, exhibit numerous biological activities, including antioxidant effects, free radical scavenging, neuroprotection, and anti-aging properties. These compounds are generally safe and effective in potentially slowing aging and preventing age-related disorders. Conclusions: The review encourages the development of novel therapeutic strategies using dietary polyphenols to create holistic anti-aging therapies and nutritional supplements.

Senolytics cocktail dasatinib and quercetin alleviate chondrocyte senescence and facet joint osteoarthritis in mice

BACKGROUND CONTEXT

Low back pain (LBP) is a pervasive issue, causing substantial economic burden and physical distress worldwide. Facet joint osteoarthritis (FJ OA) is believed to be a significant contributor to this problem. However, the precise role of chondrocyte senescence in FJ OA remains unclear, as does whether the clearance of chondrocyte senescence can alleviate the progression of FJ OA.

PURPOSE

The goal of this study was to understand the potential of Dasatinib (D) and Quercetin (Q) as a treatment to clear chondrocyte senescence during the progression of FJ OA.

STUDY DESIGN

We used a preclinical bipedal standing mice model with the administration of Dasatinib (D) (5 mg/kg) and Quercetin (Q) (50 mg/kg) after 10 weeks of bipedal standing.

MATERIALS AND METHODS

Human degenerative lumbar facet joint (LFJ) samples were obtained to investigate the relationship between chondrocyte cellular senescence and LFJ osteoarthritis (OA). Subsequently, we established an in vitro model of excessive mechanical stress on chondrocytes and an in vivo bipedal standing mice model to induce LFJ OA. IHC (immunohistochemistry) staining in vivo and SA-β-gal staining, qRT-PCR and Western blot analysis were applied to test the senolytic effect of the combination of Dasatinib (D) and Quercetin (Q). IHC staining and X-ray microscope were also performed to examine the contribution of D+Q to the anabolism in cartilage and subchondral bone recoupling. Immunofluorescence and Western blot analysis in vitro and IHC staining in vivo were conducted to assess the impact of D+Q on the regulation of the NF-κB pathway activation during chondrocyte senescence.

RESULTS

We observed that facet joint cartilage degeneration is associated with chondrocyte cellular senescence in both human and mouse degenerative samples. Following treatment with D+Q in vitro, cellular senescence was significantly reduced. Upon oral gavage administration of D+Q in the bipedal standing mice model, decreased cellular senescence and reversed chondrocyte anabolism were observed. Furthermore, administration of D+Q maintained subchondral bone remodeling homeostasis and potentially reversed the activation of the NF-κB pathway in chondrocytes of the lumbar facet joint.

CONCLUSIONS

In summary, our investigation unveiled a significant correlation between chondrocyte senescence and LFJOA. Treatment with the senolytic combination of D+Q in FJ OA yielded a notable reduction in chondrocyte senescence, along with a decrease in the release of SASP factors. Additionally, it facilitated the promotion of cartilage anabolism, maintenance of subchondral bone coupling, and amelioration of NF-κB pathway activation.

CLINICAL SIGNIFICANCE

Our outcomes revealed that D+Q, the renowned combination used for senolytic treatment, alleviate the progression of LFJ OA. The utilization of D+Q as a senolytic demonstrates a novel and promising alternative for LFJ OA treatment.

Chemical Recording of Pump-Specific Drug Efflux in Living Cells

Drug efflux-a process primarily facilitated by efflux pumps such as multidrug resistance proteins (MRPs)-plays a pivotal role in cellular resistance to chemotherapies. Conventional approaches to assess drug efflux are predominantly conducted in vitro and often lack pump specificity. Here we report the bioorthogonal reporter inhibiting efflux (BRIEF) strategy, which enables the recording of pump-specific drug efflux in living cells. In BRIEF, a specific substrate is engineered as a bioorthogonal efflux probe (BEP) for specific pumps. The cellular concentration and protein labeling level of the probe can be augmented when the test drug is transported by the same pumps. Serendipitously, we discovered that per-O-acetylated unnatural monosaccharides, initially designed for metabolic glycan labeling, are exported by some MRPs. Using Ac4GlcNAl as a BEP, we studied the structure-efflux relationship of flavonoids and identified small molecules, including tannic acid, cholesterol and gallic acid, as novel MRP substrates in high-throughput screening. Tannic acid, known for anti-tumor and anti-SARS-CoV-2 properties, showed increased efficacy upon MRP inhibition. Additionally, BRIEF was adapted to assess p-glycoprotein-mediated efflux using Rhodamine 123 as a BEP, leveraging its light-activatable proximity labeling ability. BRIEF provides a versatile approach to investigate drug efflux and enhance chemotherapy strategies.

Aged bone marrow macrophages drive systemic aging and age-related dysfunction via extracellular vesicle-mediated induction of paracrine senescence

The accumulation and systemic propagation of senescent cells contributes to physiological aging and age-related pathology. However, which cell types are most susceptible to the aged milieu and could be responsible for the propagation of senescence has remained unclear. Here we found that physiologically aged bone marrow monocytes/macrophages (BMMs) propagate senescence to multiple tissues, through extracellular vesicles (EVs), and drive age-associated dysfunction in mice. We identified peroxisome proliferator-activated receptor α (PPARα) as a target of microRNAs within aged BMM-EVs that regulates downstream effects on senescence and age-related dysfunction. Demonstrating therapeutic potential, we report that treatment with the PPARα agonist fenofibrate effectively restores tissue homeostasis in aged mice. Suggesting conservation to humans, in a cohort study of 7,986 participants, we found that fenofibrate use is associated with a reduced risk of age-related chronic disease and higher life expectancy. Together, our findings establish that BMMs can propagate senescence to distant tissues and cause age-related dysfunction, and they provide supportive evidence for fenofibrate to extend healthy lifespan.

Apoptotic metabolites ameliorate bone aging phenotypes via TCOF1/FLVCR1-mediated mitochondrial homeostasis

Over 50 billion cells undergo apoptosis each day in an adult human to maintain tissue homeostasis by eliminating damaged or unwanted cells. Apoptotic deficiency can lead to age-related diseases with reduced apoptotic metabolites. However, whether apoptotic metabolism regulates aging is unclear. Here, we show that aging mice and apoptosis-deficient MRL/lpr (B6.MRL-Faslpr/J) mice exhibit decreased apoptotic levels along with increased aging phenotypes in the skeletal bones, which can be rescued by the treatment with apoptosis inducer staurosporine (STS) and stem cell-derived apoptotic vesicles (apoVs). Moreover, embryonic stem cells (ESC)-apoVs can significantly reduce senescent hallmarks and mtDNA leakage to rejuvenate aging bone marrow mesenchymal stem cells (MSCs) and ameliorate senile osteoporosis when compared to MSC-apoVs. Mechanistically, ESC-apoVs use TCOF1 to upregulate mitochondrial protein transcription, resulting in FLVCR1-mediated mitochondrial functional homeostasis. Taken together, this study reveals a previously unknown role of apoptotic metabolites in ameliorating bone aging phenotypes and the unique role of TCOF1/FLVCR1 in maintaining mitochondrial homeostasis.

Musculoskeletal imaging of senescence

Senescent cells play a vital role in the pathogenesis of musculoskeletal (MSK) diseases, such as chronic inflammatory joint disorders, rheumatoid arthritis (RA), and osteoarthritis (OA). Cellular senescence in articular joints represents a response of local cells to persistent stress that leads to cell-cycle arrest and enhanced production of inflammatory cytokines, which in turn perpetuates joint damage and leads to significant morbidities in afflicted patients. It has been recently discovered that clearance of senescent cells by novel "senolytic" therapies can attenuate the chronic inflammatory microenvironment of RA and OA, preventing further disease progression and supporting healing processes. To identify patients who might benefit from these new senolytic therapies and monitor therapy response, there is an unmet need to identify and map senescent cells in articular joints and related musculoskeletal tissues. To fill this gap, new imaging biomarkers are being developed to detect and characterize senescent cells in human joints and musculoskeletal tissues. This review article will provide an overview of these efforts. New imaging biomarkers for senescence cells are expected to significantly improve the specificity of state-of-the-art imaging technologies for diagnosing musculoskeletal disorders.

Pip5k1γ promotes anabolism of nucleus pulposus cells and intervertebral disc homeostasis by activating CaMKII-Ampk pathway in aged mice

Degenerative disc disease (DDD) represents a significant global health challenge, yet its underlying molecular mechanisms remain elusive. This study aimed to investigate the role of type 1 phosphatidylinositol 4-phosphate 5-kinase (Pip5k1) in intervertebral disc (IVD) homeostasis and disease. All three Pip5k1 isoforms, namely Pip5k1α, Pip5k1β, and Pip5k1γ, were detectable in mouse and human IVD tissues, with Pip5k1γ displaying a highest expression in nucleus pulposus (NP) cells. The expression of Pip5k1γ was significantly down-regulated in the NP cells of aged mice and patients with severe DDD. To determine whether Pip5k1γ expression is required for disc homeostasis, we generated a Pip5k1γfl/fl; AggrecanCreERT2 mouse model for the conditional knockout of the Pip5k1γ gene in aggrecan-expressing IVD cells. Our findings revealed that the conditional deletion of Pip5k1γ did not affect the disc structure or cellular composition in 5-month-old adult mice. However, in aged (15-month-old) mice, this deletion led to several severe degenerative disc defects, including decreased NP cellularity, spontaneous fibrosis and cleft formation, and a loss of the boundary between NP and annulus fibrosus. At the molecular level, the absence of Pip5k1γ reduced the anabolism of NP cells without markedly affecting their catabolic or anti-catabolic activities. Moreover, the loss of Pip5k1γ significantly dampened the activation of the protective Ampk pathway in NP cells, thereby accelerating NP cell senescence. Notably, Pip5k1γ deficiency blunted the effectiveness of metformin, a potent Ampk activator, in activating the Ampk pathway and mitigating lumbar spine instability (LSI)-induced disc lesions in mice. Overall, our study unveils a novel role for Pip5k1γ in promoting anabolism and maintaining disc homeostasis, suggesting it as a potential therapeutic target for DDD.

Preserving the Immune-Privileged Niche of the Nucleus Pulposus: Safeguarding Intervertebral Discs from Degeneration after Discectomy with Synthetic Mucin Hydrogel Injection

Intervertebral disc (IVD) herniation is a prevalent spinal disorder, often necessitating surgical intervention such as microdiscectomy for symptomatic relief and nerve decompression. IVDs comprise a gel-like nucleus pulposus (NP) encased by an annulus fibrosus (AF), and their avascular nature renders them immune-privileged. Microdiscectomy exposes the residual NP to the immune system, precipitating an immune cell infiltration and attack that exacerbates IVD degeneration. While many efforts in the tissue engineering field are directed toward IVD regeneration, the inherently limited regenerative capacity due to the avascular and low-cellularity nature of the disc and the challenging mechanical environment of the spine often impedes success. This study, aiming to prevent IVD degeneration post-microdiscectomy, utilizes mucin-derived gels (Muc-gels) that form a gel at the surgical site, inspired by the natural mucin coating on living organisms to evade immune reorganization. It is shown that type I macrophages are present in severely degenerated human discs. Encapsulating IVDs within Muc-gels prevents fibrous encapsulation and macrophage infiltration in a mouse subcutaneous model. The injection of Muc-gels prevents IVD degeneration in a rat tail IVD degeneration model up to 24 weeks post-operation. Mechanistic investigations indicate that Muc-gels attenuate immune cell infiltration into NPs, offering durable protection against immune attack post-microdiscectomy.

The paravertebral lymphatic system is involved in the resorption of the herniated nucleus pulposus and the regression of inflammation associated with disc herniation

OBJECTIVE

To investigate the role of the paravertebral lymphatic system in the nucleus pulposus herniation (NPH) resorption and the inflammation regression.

DESIGN

Clinical specimens (n = 10) from patients with lumbar disc herniation (LDH) were collected, C57BL/6 (n = 84) and conditional Vegfr3 knockout mice (n = 14) were used. Immunofluorescence staining detected lymphatic vessels (LVs) and NP cells. Near-infrared imaging assessed lymphatic drainage function, and Alcian Blue/Orange determined inflammation.

RESULTS

Lymphangiogenesis was observed in the herniated NP of patients with LDH, and the proportion of capillary LVs was higher than that of collecting LVs (mean 68.2% [95% confidence interval: 59.4, 77.1]). In NPH mice, NP cells were detected in paravertebral tissue (38.6 [32.0, 45.2]) and draining lymph nodes (dLN) at 4 h (76.9 [54.9, 98.8]). A significant increase of NP cells in dLNs was observed at 24 h (157.1 [113.7, 200.6]). Most of the herniated NP cells were cleared in paravertebral tissue after 1 week (7.5 [4.4, 10.6]), but disc inflammation peaked at 1 week (19.9% [14.7, 25.1]), along with persistent lymphangiogenesis (9.5 [7.2, 11.8]). However, conditional Vegfr3 knockout mice exhibited impaired lymphangiogenesis (5.7 [4.4, 7.0]) and herniated NP cell clearance (6.1 [1.8, 10.5]) during NPH, leading to exacerbated disc inflammation (23.7% [19.3, 28.2]).

CONCLUSION

The paravertebral lymphatic system is involved in the NPH resorption and inflammation regression. Promoting lymphangiogenesis may be a novel strategy for facilitating NPH resorption and inflammation regression in patients with LDH.

Active Magnesium Boride/Alginate Hydrogels Rejuvenate Senescent Cells

The clearance of senescent cells may be detrimental to low cell density diseases, such as intervertebral disc degeneration (IVDD), and rejuvenating these cells presents a formidable obstacle. In this study, we investigate a mild-alkalization strategy employing magnesium boride-alginate (MB-ALG) hydrogels to rejuvenate senescent cells associated with age-related diseases. MB-ALG hydrogels proficiently ensnare senescent cells owing to their surface roughness. The hydrolysis of MB-ALG hydrogels liberates hydroxide ions (OH-), effecting a transition from an acidic microenvironment (pH ∼ 6.2) to a mildly alkaline state (pH ∼ 8.0), thereby fostering senescent cell proliferation via activation of the PI3K/Akt/mTOR pathway. Additionally, H2 aids in ROS clearance, which reduces cellular oxidative stress. And, Mg2+ rejuvenates senescent cells by inhibiting Ca2+ influx and fine-tuning the sirt1-p53 signaling pathways. Both in vitro and in vivo experiments conducted on rat intervertebral discs corroborate the sustained antisenescence and rejuvenation properties of MB-ALG hydrogels, with effects persisting for up to 12 weeks postoperation. These discoveries elucidate the role of mild-alkalization in dictating cellular destiny and provide key insights for addressing age-related diseases.

Cellular Senescence: The Driving Force of Musculoskeletal Diseases

The aging of the world population is closely associated with an increased prevalence of musculoskeletal disorders, such as osteoporosis, sarcopenia, and osteoarthritis, due to common genetic, endocrine, and mechanical risk factors. These conditions are characterized by degeneration of bone, muscle, and cartilage tissue, resulting in an increased risk of fractures and reduced mobility. Importantly, a crucial role in the pathophysiology of these diseases has been proposed for cellular senescence, a state of irreversible cell cycle arrest induced by factors such as DNA damage, telomere shortening, and mitochondrial dysfunction. In addition, senescent cells secrete pro-inflammatory molecules, called senescence-associated secretory phenotype (SASP), which can alter tissue homeostasis and promote disease progression. Undoubtedly, targeting senescent cells and their secretory profiles could promote the development of integrated strategies, including regular exercise and a balanced diet or the use of senolytics and senomorphs, to improve the quality of life of the aging population. Therefore, our review aimed to highlight the role of cellular senescence in age-related musculoskeletal diseases, summarizing the main underlying mechanisms and potential anti-senescence strategies for the treatment of osteoporosis, sarcopenia, and osteoarthritis.

Targeting multiple hallmarks of mammalian aging with combinations of interventions

Aging is currently viewed as a result of multiple biological processes that manifest themselves independently, reinforce each other and in their totality lead to the aged phenotype. Genetic and pharmaceutical approaches targeting specific underlying causes of aging have been used to extend the lifespan and healthspan of model organisms ranging from yeast to mammals. However, most interventions display only a modest benefit. This outcome is to be expected if we consider that even if one aging process is successfully treated, other aging pathways may remain intact. Hence solving the problem of aging may require targeting not one but many of its underlying causes at once. Here we review the challenges and successes of combination therapies aimed at increasing the lifespan of mammals and propose novel directions for their development. We conclude that both additive and synergistic effects on mammalian lifespan can be achieved by combining interventions that target the same or different hallmarks of aging. However, the number of studies in which multiple hallmarks were targeted simultaneously is surprisingly limited. We argue that this approach is as promising as it is understudied.

TNKS1BP1 mediates AECII senescence and radiation induced lung injury through suppressing EEF2 degradation

BACKGROUND

Although recent studies provide mechanistic understanding to the pathogenesis of radiation induced lung injury (RILI), rare therapeutics show definitive promise for treating this disease. Type II alveolar epithelial cells (AECII) injury in various manner results in an inflammation response to initiate RILI.

RESULTS

Here, we reported that radiation (IR) up-regulated the TNKS1BP1, causing progressive accumulation of the cellular senescence by up-regulating EEF2 in AECII and lung tissue of RILI mice. Senescent AECII induced Senescence-Associated Secretory Phenotype (SASP), consequently activating fibroblasts and macrophages to promote RILI development. In response to IR, elevated TNKS1BP1 interacted with and decreased CNOT4 to suppress EEF2 degradation. Ectopic expression of EEF2 accelerated AECII senescence. Using a model system of TNKS1BP1 knockout (KO) mice, we demonstrated that TNKS1BP1 KO prevents IR-induced lung tissue senescence and RILI.

CONCLUSIONS

Notably, this study suggested that a regulatory mechanism of the TNKS1BP1/CNOT4/EEF2 axis in AECII senescence may be a potential strategy for RILI.

Sdc4 deletion perturbs intervertebral disc matrix homeostasis and promotes early osteopenia in the aging mouse spine

Syndecan 4 (SDC4), a cell surface heparan sulfate proteoglycan, is known to regulate matrix catabolism by nucleus pulposus cells in an inflammatory milieu. However, the role of SDC4 in the aging spine has never been explored. Here we analyzed the spinal phenotype of Sdc4 global knockout (KO) mice as a function of age. Micro-computed tomography showed that Sdc4 deletion severely reduced vertebral trabecular and cortical bone mass, and biomechanical properties of vertebrae were significantly altered in Sdc4 KO mice. These changes in vertebral bone were likely due to elevated osteoclastic activity. The histological assessment showed subtle phenotypic changes in the intervertebral disc. Imaging-Fourier transform-infrared analyses showed a reduced relative ratio of mature collagen crosslinks in young adult nucleus pulposus (NP) and annulus fibrosus (AF) of KO compared to wildtype discs. Additionally, relative chondroitin sulfate levels increased in the NP compartment of the KO mice. Transcriptomic analysis of NP tissue using CompBio, an AI-based tool showed biological themes associated with prominent dysregulation of heparan sulfate GAG degradation, mitochondria metabolism, autophagy, endoplasmic reticulum (ER)-associated misfolded protein processes and ER to Golgi protein processing. Overall, this study highlights the important role of SDC4 in fine-tuning vertebral bone homeostasis and extracellular matrix homeostasis in the mouse intervertebral disc.

Senolytic Treatment Improve Small Intestine Regeneration in Aging

Aging induces a series of alterations, specifically a decline in the stature and number of villi and crypts in the small intestine, thus compromising the absorbent capability of the villi. This investigation employed a senolytic combination of dasatinib and quercetin (D+Q) to examine its impact on the intestinal tract of elderly mice. Our findings demonstrate that D+Q treatment leads to a decrease in the expression of p21, p16, and Ki67, while concurrently triggering removal of apoptotic cells within the villi. Additionally, D+Q treatment exhibits the ability to promote growth in both the height and quantity of villi and crypts, along with stimulating nitric oxide (NO) production in aged mice. The study presented a model to assess strategies to alleviate age-related senescence in the intestinal tract of elderly mice. Importantly, D+Q showcases promising potential in enhancing intestinal functionality within the aging.

Therapy-Induced Cellular Senescence: Potentiating Tumor Elimination or Driving Cancer Resistance and Recurrence?

Cellular senescence has been increasingly recognized as a hallmark of cancer, reflecting its association with aging and inflammation, its role as a response to deregulated proliferation and oncogenic stress, and its induction by cancer therapies. While therapy-induced senescence (TIS) has been linked to resistance, recurrence, metastasis, and normal tissue toxicity, TIS also has the potential to enhance therapy response and stimulate anti-tumor immunity. In this review, we examine the Jekyll and Hyde nature of senescent cells (SnCs), focusing on how their persistence while expressing the senescence-associated secretory phenotype (SASP) modulates the tumor microenvironment through autocrine and paracrine mechanisms. Through the SASP, SnCs can mediate both resistance and response to cancer therapies. To fulfill the unmet potential of cancer immunotherapy, we consider how SnCs may influence tumor inflammation and serve as an antigen source to potentiate anti-tumor immune response. This new perspective suggests treatment approaches based on TIS to enhance immune checkpoint blockade. Finally, we describe strategies for mitigating the detrimental effects of senescence, such as modulating the SASP or targeting SnC persistence, which may enhance the overall benefits of cancer treatment.

Senolytic combination of dasatinib and quercetin attenuates renal damage in diabetic kidney disease

BACKGROUND

Senolytic combination of dasatinib and quercetin (DQ) is the most studied senolytics drugs used to treat various age-related diseases. However, its protective activity against diabetic kidney disease (DKD) and underlying mechanisms are uncertain.

PURPOSE

To investigate the functions and potential mechanisms of the senolytics DQ on DKD.

METHODS

Diabetic db/db mice were administrated DQ or transfected with over-expressed PPARα or shPPARα vector. The positive control group was administered irbesartan. Renal function and fibrotic changes in kidney tissue were tested. Single-cell RNA-seq (scRNA-seq) was conducted to analyze the differential transcriptome between the diabetic and control mice. Molecular docking simulation was used to assess the combination of DQ and potential factors. Moreover, tubular epithelial cells under high-glucose (HG) conditions were incubated with DQ and transfected with or without over-expressed PPARα/siPPARα vector.

RESULTS

DQ significantly improved renal function, histopathological and fibrotic changes, alleviated lipid deposition, and increased ATP levels in mice with DKD. DQ reduced multiple fatty acid oxidation (FAO) pathway-related proteins and up-regulated PPARα in db/db mice. Overexpression of PPARα upregulated the expression of PPARα-targeting downstream FAO pathway-related proteins, restored renal function, and inhibited renal fibrosis in vitro and in vivo. Moreover, molecular docking and dynamics simulation analyses indicated the nephroprotective effect of DQ via binding to PPARα. Knockdown of PPARα reversed the effect of DQ on the FAO pathway and impaired the protective effect of DQ during DKD.

CONCLUSION

For the first time, DQ was found to exert a renal protective effect by binding to PPARα and attenuating renal damage through the promotion of FAO in DKD.

EZH2-H3K27me3-Mediated Epigenetic Silencing of DKK1 Induces Nucleus Pulposus Cell Pyroptosis in Intervertebral Disc Degeneration by Activating NLRP3 and NAIP/NLRC4

Nucleus pulposus (NP) cell pyroptosis is crucial for intervertebral disc degeneration (IDD). However, the precise mechanisms underlying pyroptosis in IDD remain elusive. Therefore, this study aimed to investigate how dickkopf-1 (DKK1) influences NP cell pyroptosis and delineate the regulatory mechanisms of IDD. Behavioral tests and histological examinations were conducted in rat IDD models to assess the effect of DKK1 on the structure and function of intervertebral discs. Detected pyroptosis levels using Hoechst 33,342/propidium iodide (PI) double staining, and determined pyroptosis-related protein expression via western blotting. The cellular mechanisms of DKK1 in pyroptosis were explored in interleukin (IL)-1β-induced NP cells transfected with or without DKK1 overexpression plasmids (oe-DKK1). In addition, IL-1β-treated NP cells transfected with sh-EZH2 and/or sh-DKK1 were utilized to clarify the interplay between the enhancer of zeste homologue 2 (EZH2) and DKK1 in pyroptosis. Additionally, the epigenetic regulation of DKK1 by EZH2 was explored in NP cells treated with the EZH2 inhibitors GSK126/DZNep. DKK1 expression decreased in IDD rats. Transfection with oe-DKK1 reduced pro-inflammatory factors and extracellular matrix markers in IDD rats. In IL-1β-induced NP cells, DKK1 overexpression suppressed pyroptosis and inhibited the NLRP3 and NAIP/NLRC4 inflammasome activation. EZH2 knockdown increased DKK1 expression and reduced pyroptosis-related proteins. Conversely, DKK1 downregulation reversed the inhibitory effects of EZH2 knockdown on pyroptosis. Furthermore, EZH2 suppressed DKK1 expression via H3K27 methylation at the DKK1 promoter. EZH2 negatively regulates DKK1 expression via H3K27me3 methylation, promoting NP cell pyroptosis in IDD patients. This regulatory effect involves the activation of NLRP3 and NAIP/NLRC4 inflammasomes.

Rescue of nucleus pulposus cells from an oxidative stress microenvironment via glutathione-derived carbon dots to alleviate intervertebral disc degeneration

The senescence of nucleus pulposus (NP) cells (NPCs), which is induced by the anomalous accumulation of reactive oxygen species (ROS), is a major cause of intervertebral disc degeneration (IVDD). In this research, glutathione-doped carbon dots (GSH-CDs), which are novel carbon dot antioxidant nanozymes, were successfully constructed to remove large amounts of ROS for the maintenance of NP tissue at the physical redox level. After significantly scavenging endogenous ROS via exerting antioxidant activities, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant capacity, GSH-CDs with good biocompatibility have been demonstrated to effectively improve mitochondrial dysfunction and rescue NPCs from senescence, catabolism, and inflammatory factors in vivo and in vitro. In vivo imaging data and histomorphological indicators, such as the disc height index (DHI) and Pfirrmann grade, demonstrated prominent improvements in the progression of IVDD after the topical application of GSH-CDs. In summary, this study investigated the GSH-CDs nanozyme, which possesses excellent potential to inhibit the senescence of NPCs with mitochondrial lesions induced by the excessive accumulation of ROS and improve the progression of IVDD, providing potential therapeutic options for clinical treatment.

Combination of Dasatinib and Quercetin alleviates heat stress-induced cognitive deficits in aged and young adult male mice

OBJECTIVE

Dasatinib and quercetin (D & Q) have demonstrated promise in improving aged-related pathophysiological dysfunctions in humans and mice. Herein we aimed to ascertain whether the heat stress (HS)-induced cognitive deficits in aged or even young adult male mice can be reduced by D & Q therapy.

METHODS

Before the onset of HS, animals were pre-treated with D & Q or placebo for 3 consecutive days every 2 weeks over a 10-week period. Cognitive function, intestinal barrier permeability, and blood-brain barrier permeability were assessed.

RESULTS

Compared to the non-HS young adult male mice, the HS young adult male mice or the aged male mice had significantly lesser extents of the exacerbated stress reactions, intestinal barrier disruption, endotoxemia, systemic inflammation and oxidative stress, blood-brain barrier disruption, hippocampal inflammation and oxidative stress, and cognitive deficits evaluated at 7 days post-HS. All the cognitive deficits and other syndromes that occurred in young adult HS mice or in aged HS mice were significantly attenuated by D & Q therapy (P < 0.01). Compared to the young adult HS mice, the aged HS mice had significantly (P < 0.01) higher severity of cognitive deficits and other related syndromes.

CONCLUSIONS

First, our data show that aged male mice are more vulnerable to HS-induced cognitive deficits than those of the young adult male mice. Second, we demonstrate that a combination of D and Q therapy attenuates cognitive deficits in heat stressed aged or young adult male mice via broad normalization of the brain-gut-endotoxin axis function.

Engineered extracellular vesicle-based gene therapy for the treatment of discogenic back pain

Painful musculoskeletal disorders such as intervertebral disc (IVD) degeneration associated with chronic low back pain (termed "Discogenic back pain", DBP), are a significant socio-economic burden worldwide and contribute to the growing opioid crisis. Yet there are very few if any successful interventions that can restore the tissue's structure and function while also addressing the symptomatic pain. Here we have developed a novel non-viral gene therapy, using engineered extracellular vesicles (eEVs) to deliver the developmental transcription factor FOXF1 to the degenerated IVD in an in vivo model. Injured IVDs treated with eEVs loaded with FOXF1 demonstrated robust sex-specific reductions in pain behaviors compared to control groups. Furthermore, significant restoration of IVD structure and function in animals treated with FOXF1 eEVs were observed, with significant increases in disc height, tissue hydration, proteoglycan content, and mechanical properties. This is the first study to successfully restore tissue function while modulating pain behaviors in an animal model of DBP using eEV-based non-viral delivery of transcription factor genes. Such a strategy can be readily translated to other painful musculoskeletal disorders.

Thread-structural microneedles loaded with engineered exosomes for annulus fibrosus repair by regulating mitophagy recovery and extracellular matrix homeostasis

Low back pain is among the most grave public health concerns worldwide and the major clinical manifestation of intervertebral disc degeneration (IVDD). The destruction of annulus fibrosus (AF) is the primary cause of IVDD. A sustainable and stable treatment system for IVDD is lacking because of the special organizational structure and low nutrient supply of AF. We here found that IVDD results in the impaired mitochondrial function of AF tissue, and mitochondrial autophagy (mitophagy) plays a protective role in this process. We therefore reported a thread-structural microneedle (T-MN) matching the ring structure of AF. Based on the adsorption effect of laminin, our T-MN could load with bone marrow mesenchymal stem cell-derived exosomes to envelope the regulating mitophagy microRNA (miRNA 378), named as T-MN@EXO@miR-378. In general, we offered in situ locking in the defect site of AF to prevent nucleus pulposus leakage and promoted AF repair. The design of the thread structure was aimed at bionically matching the layered AF structure, thereby providing stronger adhesion. The T-MN@EXO@miR-378 effectively attached to AF and slowly released therapeutic engineered exosomes, and prevented IVDD progression by restoring mitophagy, promoting AF cell proliferation and migration, and inhibiting the pathological remodeling of the extracellular matrix. This functional system can be used as an excellent tool for sustained drug release and has a certain prospect in substituting the conventional treatment of IVDD.

Looking for the philosopher's stone: Emerging approaches to target the hallmarks of aging in the skin

Senescence and epigenetic alterations are two important hallmarks of cellular aging. During aging, cells subjected to stress undergo many cycles of damage and repair before finally entering either apoptosis or senescence, a permanent state of cell cycle arrest. The first biomarkers of senescence to be identified were increased ß-galactosidase activity and induction of p16INK4a. Another feature of senescent cells is the senescence-associated secretory phenotype (SASP), a complex secretome containing more than 80 pro-inflammatory factors including metalloproteinases, growth factors, chemokines and cytokines. The secretome is regulated through a dynamic process involving a self-amplifying autocrine feedback loop and activation of the immune system. Senescent cells play positive and negative roles depending on the composition of their SASP and may participate in various processes including wound healing and tumour suppression, as well as cell regeneration, embryogenesis, tumorigenesis, inflammation and finally aging. The SASP is also a biomarker of age, biological aging and age-related diseases. Recent advances in anti-age research have shown that senescence can be now prevented or delayed by clearing the senescent cells or mitigating the effects of SASP factors, which can be achieved by a healthy lifestyle (exercise and diet), and senolytics and senomorphics, respectively. An alternative is tissue rejuvenation, which can be achieved by stimulating aged stem cells and reprogramming deprogrammed aged cells. These non-clinical findings will open up new avenues of clinical research into the development of treatments capable of preventing or treating age-related pathologies in humans.

Towards Healthy Longevity: Comprehensive Insights from Molecular Targets and Biomarkers to Biological Clocks

Aging is a complex and time-dependent decline in physiological function that affects most organisms, leading to increased risk of age-related diseases. Investigating the molecular underpinnings of aging is crucial to identify geroprotectors, precisely quantify biological age, and propose healthy longevity approaches. This review explores pathways that are currently being investigated as intervention targets and aging biomarkers spanning molecular, cellular, and systemic dimensions. Interventions that target these hallmarks may ameliorate the aging process, with some progressing to clinical trials. Biomarkers of these hallmarks are used to estimate biological aging and risk of aging-associated disease. Utilizing aging biomarkers, biological aging clocks can be constructed that predict a state of abnormal aging, age-related diseases, and increased mortality. Biological age estimation can therefore provide the basis for a fine-grained risk stratification by predicting all-cause mortality well ahead of the onset of specific diseases, thus offering a window for intervention. Yet, despite technological advancements, challenges persist due to individual variability and the dynamic nature of these biomarkers. Addressing this requires longitudinal studies for robust biomarker identification. Overall, utilizing the hallmarks of aging to discover new drug targets and develop new biomarkers opens new frontiers in medicine. Prospects involve multi-omics integration, machine learning, and personalized approaches for targeted interventions, promising a healthier aging population.

PGC1α-Inducing Senomorphic Nanotherapeutics Functionalized with NKG2D-Overexpressing Cell Membranes for Intervertebral Disc Degeneration

Cellular senescence is a significant contributor to intervertebral disc aging and degeneration. However, the application of senotherapies, such as senomorphics targeting senescence markers and the senescence-associated secretory phenotype (SASP), remains limited due to challenges in precise delivery. Given that the natural killer group 2D (NKG2D) ligands are increased on the surface of senescent nucleus pulposus (NP) cells, the NKG2D-overexpressing NP cell membranes (NNPm) are constructed, which is expected to achieve a dual targeting effect toward senescent NP cells based on homologous membrane fusion and the NKG2D-mediated immunosurveillance mechanism. Then, mesoporous silica nanoparticles carrying a peroxisome proliferator-activated receptor-ɣ coactivator 1α (PGC1α)inducer (SP) are coated with NNPm (SP@NNPm) and it is found that SP@NNPm selectively targets senescent NP cells, and the SP cores exhibit pH-responsive drug release. Moreover, SP@NNPm effectively induces PGC1α-mediated mitochondrial biogenesis and mitigates senescence-associated markers induced by oxidative stress and the SASP, thereby alleviating puncture-induced senescence and disc degeneration. This dual-targeting nanotherapeutic system represents a novel approach to delivery senomorphics for disc degeneration treatment.

Apigetrin alleviates intervertebral disk degeneration by regulating nucleus pulposus cell autophagy

Background

Intervertebral disk degeneration (IVDD) is a common spine disease, and inflammation is considered to be one of its main pathogenesis. Apigetrin (API) is a natural bioactive flavonoid isolated from various herbal medicines and shows attractive anti-inflammatory and antioxidative properties; whereas, there is no exploration of the therapeutic potential of API on IVDD. Here, we aim to explore the potential role of API on IVDD in vivo and in vitro.

Methods

In vitro, western blotting, real-time quantitative polymerase chain reaction, and immunofluorescence analysis were implemented to explore the bioactivity of API on interleukin-1 beta (IL-1β)-induced inflammatory changes in nucleus pulposus cells (NPCs). In vivo, histological staining and immunohistochemistry were employed to investigate the histological changes of intervertebral disk sections on puncture-induced IVDD rat models.

Results

In vitro, API played a crucial role in anti-inflammation and autophagy enhancement in IL-1β-induced NPCs. API improved inflammation by inhibiting the nuclear factor-kappaB and mitogen-activated protein kinas pathways, whereas it promoted autophagy via the phosphatidylinositol 3-kinase/AKT/mammalian target of the rapamycin pathway. Furthermore, in vivo experiment illustrated that API mitigates the IVDD progression in puncture-induced IVDD model.

Conclusions

API inhibited degenerative phenotypes and promoted autophagy in vivo and in vitro IVDD models. Those suggested that API might be a potential drug or target for IVDD.

Identifying the protective effects of miR-874-3p/ATF3 axis in intervertebral disc degeneration by single-cell RNA sequencing and validation

Intervertebral disc degeneration (IVDD) severely affects the work and the quality of life of people. We previously demonstrated that silencing activation transcription factor 3 (ATF3) blocked the IVDD pathological process by regulating nucleus pulposus cell (NPC) ferroptosis, apoptosis, inflammation, and extracellular matrix (ECM) metabolism. Nevertheless, whether miR-874-3p mediated the IVDD pathological process by targeting ATF3 remains unclear. We performed single-cell RNA sequencing (scRNA-seq) and bioinformatics analysis to identify ATF3 as a key ferroptosis gene in IVDD. Then, Western blotting, flow cytometry, ELISA, and animal experiments were performed to validate the roles and regulatory mechanisms of miR-874-3p/ATF3 signalling axis in IVDD. ATF3 was highly expressed in IVDD patients and multiple cell types of IVDD rat, as revealed by scRNA-seq and bioinformatics analysis. GO analysis unveiled the involvement of ATF3 in regulating cell apoptosis and ECM metabolism. Furthermore, we verified that miR-874-3p might protect against IVDD by inhibiting NPC ferroptosis, apoptosis, ECM degradation, and inflammatory response by targeting ATF3. In vivo experiments displayed the protective effect of miR-874-3p/ATF3 axis on IVDD. These findings propose the potential of miR-874-3p and ATF3 as biomarkers of IVDD and suggest that targeting the miR-874-3p/ATF3 axis may be a therapeutic target for IVDD.

Chronological and Biological Aging in Amyotrophic Lateral Sclerosis and the Potential of Senolytic Therapies

Amyotrophic Lateral Sclerosis (ALS) is a group of sporadic and genetic neurodegenerative disorders that result in losses of upper and lower motor neurons. Treatment of ALS is limited, and survival is 2-5 years after disease onset. While ALS can occur in younger individuals, the risk significantly increases with advancing age. Notably, both sporadic and genetic forms of ALS share pathophysiological features overlapping hallmarks of aging including genome instability/DNA damage, mitochondrial dysfunction, inflammation, proteostasis, and cellular senescence. This review explores chronological and biological aging in the context of ALS onset and progression. Age-related muscle weakness and motor unit loss mirror aspects of ALS pathology and coincide with peak ALS incidence, suggesting a potential link between aging and disease development. Hallmarks of biological aging, including DNA damage, mitochondrial dysfunction, and cellular senescence, are implicated in both aging and ALS, offering insights into shared mechanisms underlying disease pathogenesis. Furthermore, senescence-associated secretory phenotype and senolytic treatments emerge as promising avenues for ALS intervention, with the potential to mitigate neuroinflammation and modify disease progression.

Modulation of tumor plasticity by senescent cells: Deciphering basic mechanisms and survival pathways to unravel therapeutic options

Senescence is a cellular state in which the cell loses its proliferative capacity, often irreversibly. Physiologically, it occurs due to a limited capacity of cell division associated with telomere shortening, the so-called replicative senescence. It can also be induced early due to DNA damage, oncogenic activation, oxidative stress, or damage to other cellular components (collectively named induced senescence). Tumor cells acquire the ability to bypass replicative senescence, thus ensuring the replicative immortality, a hallmark of cancer. Many anti-cancer therapies, however, can lead tumor cells to induced senescence. Initially, this response leads to a slowdown in tumor growth. However, the longstanding accumulation of senescent cells (SnCs) in tumors can promote neoplastic progression due to the enrichment of numerous molecules and extracellular vesicles that constitutes the senescence-associated secretory phenotype (SASP). Among other effects, SASP can potentiate or unlock the tumor plasticity and phenotypic transitions, another hallmark of cancer. This review discusses how SnCs can fuel mechanisms that underlie cancer plasticity, like cell differentiation, stemness, reprogramming, and epithelial-mesenchymal transition. We also discuss the main molecular mechanisms that make SnCs resistant to cell death, and potential strategies to target SnCs. At the end, we raise open questions and clinically relevant perspectives in the field.

Effective delivery of miR-150-5p with nucleus pulposus cell-specific nanoparticles attenuates intervertebral disc degeneration

BACKGROUND

The use of gene therapy to deliver microRNAs (miRNAs) has gradually translated to preclinical application for the treatment of intervertebral disc degeneration (IDD). However, the effects of miRNAs are hindered by the short half-life time and the poor cellular uptake, owing to the lack of efficient delivery systems. Here, we investigated nucleus pulposus cell (NPC) specific aptamer-decorated polymeric nanoparticles that can load miR-150-5p for IDD treatment.

METHODS

The role of miR-150-5p during disc development and degeneration was examined by miR-150-5p knockout (KO) mice. Histological analysis was undertaken in disc specimens. The functional mechanism of miR-150-5p in IDD development was investigated by qRT-PCR assay, Western blot, coimmunoprecipitation and immunofluorescence. NPC specific aptamer-decorated nanoparticles was designed, and its penetration, stability and safety were evaluated. IDD progression was assessed by radiological analysis including X-ray and MRI, after the annulus fibrosus needle puncture surgery with miR-150-5p manipulation by intradiscal injection of nanoparticles. The investigations into the interaction between aptamer and receptor were conducted using mass spectrometry, molecular docking and molecular dynamics simulations.

RESULTS

We investigated NPC-specific aptamer-decorated polymeric nanoparticles that can bind to miR-150-5p for IDD treatment. Furthermore, we detected that nanoparticle-loaded miR-150-5p inhibitors alleviated NPC senescence in vitro, and the effects of the nanoparticles were sustained for more than 3 months in vivo. The microenvironment of NPCs improves the endo/lysosomal escape of miRNAs, greatly inhibiting the secretion of senescence-associated factors and the subsequent degeneration of NPCs. Importantly, nanoparticles delivering miR-150-5p inhibitors attenuated needle puncture-induced IDD in mouse models by targeting FBXW11 and inhibiting TAK1 ubiquitination, resulting in the downregulation of NF-kB signaling pathway activity.

CONCLUSIONS

NPC-targeting nanoparticles delivering miR-150-5p show favorable therapeutic efficacy and safety and may constitute a promising treatment for IDD.

The potential for senotherapy as a novel approach to extend life quality in veterinary medicine

Cellular senescence, a condition where cells undergo arrest and can assume an inflammatory phenotype, has been associated with initiation and perpetuation of inflammation driving multiple disease processes in rodent models and humans. Senescent cells secrete inflammatory cytokines, proteins, and matrix metalloproteinases, termed the senescence associated secretory phenotype (SASP), which accelerates the aging processes. In preclinical models, drug interventions termed "senotherapeutics" selectively clear senescent cells and represent a promising strategy to prevent or treat multiple age-related conditions in humans and veterinary species. In this review, we summarize the current available literature describing in vitro evidence for senotheraputic activity, preclinical models of disease, ongoing human clinical trials, and potential clinical applications in veterinary medicine. These promising data to date provide further justification for future studies identifying the most active senotherapeutic combinations, dosages, and routes of administration for use in veterinary medicine.

Failure of senolytic treatment to prevent cognitive decline in a female rodent model of aging

There are sex differences in vulnerability and resilience to the stressors of aging and subsequent age-related cognitive decline. Cellular senescence occurs as a response to damaging or stress-inducing stimuli. The response includes a state of irreversible growth arrest, the development of a senescence-associated secretory phenotype, and the release of pro-inflammatory cytokines associated with aging and age-related diseases. Senolytics are compounds designed to eliminate senescent cells. Our recent work indicates that senolytic treatment preserves cognitive function in aging male F344 rats. The current study examined the effect of senolytic treatment on cognitive function in aging female rats. Female F344 rats (12 months) were treated with dasatinib (1.2 mg/kg) + quercetin (12 mg/kg) or ABT-263 (12 mg/kg) or vehicle for 7 months. Examination of the estrus cycle indicated that females had undergone estropause during treatment. Senolytic treatment may have increased sex differences in behavioral stress responsivity, particularly for the initial training on the cued version of the watermaze. However, pre-training on the cue task reduced stress responsivity for subsequent spatial training and all groups learned the spatial discrimination. In contrast to preserved memory observed in senolytic-treated males, all older females exhibited impaired episodic memory relative to young (6-month) females. We suggest that the senolytic treatment may not have been able to compensate for the loss of estradiol, which can act on aging mechanisms for anxiety and memory independent of cellular senescence.

The mitigation potential of synergistic quorum quenching and antibacterial properties for biofilm proliferation and membrane biofouling

Biofouling has been a persistent problem hindering the application of membranes in water treatment, and quorum quenching has been identified as an effective method for mitigating biofouling, but surface accumulation of live bacteria still induces biofilm secretion, which poses a significant challenge for sustained prevention of membrane biofouling. In this study, we utilized quercetin, a typical flavonoid with the dual functions of quorum quenching and bacterial inactivation, to evaluate its role in preventing biofilm proliferation and against biofouling. Quercetin exhibited excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and the decreased bioactivity was positively correlated with the quercetin concentration, with inhibition rates of 53.1 % and 57.4 %, respectively, at the experimental concentrations. The RT-qPCR results demonstrated that quercetin inhibited AI-2 of E. coli and AGR of S. aureus mediated quorum sensing system, and reduced the expression of genes such as adhesion, virulence, biofilm secretion, and key regulatory proteases. As a result, the bacterial growth cycle was retarded and the biomass and biofilm maturation cycles were alleviated with the synergistic effect of quorum quenching and antibacterial activity. In addition, membrane biofouling was significantly declined in the dynamic operation experiments, dead cells in the biofilm overwhelmingly dominated, and the final normalized water fluxes were increased by more than 49.9 % and 34.5 % for E. coli and S. aureus, respectively. This work demonstrates the potential for mitigating biofouling using protocols that quorum quenching and inactivate bacteria, also provides a unique and long-lasting strategy to alleviate membrane fouling.

Selenomethionine preconditioned mesenchymal stem cells derived extracellular vesicles exert enhanced therapeutic efficacy in intervertebral disc degeneration

Extracellular vesicles (EVs) derived from Mesenchymal Stromal Cells (MSCs) have shown promising therapeutic potential for multiple diseases, including intervertebral disc degeneration (IDD). Nevertheless, the limited production and unstable quality of EVs hindered the clinical application of EVs in IDD. Selenomethionine (Se-Met), the major form of organic selenium present in the cereal diet, showed various beneficial effects, including antioxidant, immunomodulatory and anti-apoptotic effects. In the current study, Se-Met was employed to treat MSCs to investigate whether Se-Met can facilitate the secretion of EVs by MSCs and optimize their therapeutic effects on IDD. On the one hand, Se-Met promoted the production of EVs by enhancing the autophagy activity of MSCs. On the other hand, Se-Met pretreated MSC-derived EVs (Se-EVs) exhibited an enhanced protective effects on alleviating nucleus pulposus cells (NPCs) senescence and attenuating IDD compared with EVs isolated from control MSCs (C-EVs) in vitro and in vivo. Moreover, we performed a miRNA microarray sequencing analysis on EVs to explore the potential mechanism of the protective effects of EVs. The result indicated that miR-125a-5p is markedly enriched in Se-EVs compared to C-EVs. Further in vitro and in vivo experiments revealed that knockdown of miR-125a-5p in Se-EVs (miRKD-Se-EVs) impeded the protective effects of Se-EVs, while overexpression of miR-125a-5p (miROE-Se-EVs) boosted the protective effects. In conclusion, Se-Met facilitated the MSC-derived EVs production and increased miR-125a-5p delivery in Se-EVs, thereby improving the protective effects of MSC-derived EVs on alleviating NPCs senescence and attenuating IDD.

Compliant substrates mitigate the senescence associated phenotype of stress induced mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are a promising cell population for musculoskeletal cell-based therapies due to their multipotent differentiation capacity and complex secretome. Cells from younger donors are mechanosensitive, evidenced by changes in cell morphology, adhesivity, and differentiation as a function of substrate stiffness in both two- and three-dimensional culture. However, MSCs from older individuals exhibit reduced differentiation potential and increased senescence, limiting their potential for autologous use. While substrate stiffness is known to modulate cell phenotype, the influence of the mechanical environment on senescent MSCs is poorly described. To address this question, we cultured irradiation induced premature senescent MSCs on polyacrylamide hydrogels and assessed expression of senescent markers, cell morphology, and secretion of inflammatory cytokines. Compared to cells on tissue culture plastic, senescent MSCs exhibited decreased markers of the senescence associated secretory phenotype (SASP) when cultured on 50 kPa gels, yet common markers of senescence (e.g., p21, CDKN2A, CDKN1A) were unaffected. These effects were muted in a physiologically relevant heterotypic mix of healthy and senescent MSCs. Conditioned media from senescent MSCs on compliant substrates increased osteoblast mineralization compared to conditioned media from cells on TCP. Mixed populations of senescent and healthy cells induced similar levels of osteoblast mineralization compared to healthy MSCs, further indicating an attenuation of the senescent phenotype in heterotypic populations. These data indicate that senescent MSCs exhibit a decrease in senescent phenotype when cultured on compliant substrates, which may be leveraged to improve autologous cell therapies for older donors.

DNA-PKcs/AKT1 inhibits epithelial-mesenchymal transition during radiation-induced pulmonary fibrosis by inducing ubiquitination and degradation of Twist1

INTRODUCTION

Radiation-induced pulmonary fibrosis (RIPF) is a chronic, progressive, irreversible lung interstitial disease that develops after radiotherapy. Although several previous studies have focused on the mechanism of epithelial-mesenchymal transition (EMT) in lung epithelial cells, the essential factors involved in this process remain poorly understood. The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) exhibits strong repair capacity when cells undergo radiation-induced damage; whether DNA-PKcs regulates EMT during RIPF remains unclear.

OBJECTIVES

To investigate the role and molecular mechanism of DNA-PKcs in RIPF and provide an important theoretical basis for utilising DNA-PKcs-targeted drugs for preventing RIPF.

METHODS

DNA-PKcs knockout (DPK-/-) mice were generated via the Cas9/sgRNA technique and subjected to whole chest ionizing radiation (IR) at a 20 Gy dose. Before whole chest IR, the mice were intragastrically administered the DNA-PKcs-targeted drug VND3207. Lung tissues were collected at 1 and 5 months after IR.

RESULTS

The expression of DNA-PKcs is low in pulmonary fibrosis (PF) patients. DNA-PKcs deficiency significantly exacerbated RIPF by promoting EMT in lung epithelial cells. Mechanistically, DNA-PKcs deletion by shRNA or inhibitor NU7441 maintained the protein stability of Twist1. Furthermore, AKT1 mediated the interaction between DNA-PKcs and Twist1. High Twist1 expression and EMT-associated changes caused by DNA-PKcs deletion were blocked by insulin-like growth factor-1 (IGF-1), an AKT1 agonist. The radioprotective drug VND3207 prevented IR-induced EMT and alleviated RIPF in mice by stimulating the kinase activity of DNA-PKcs.

CONCLUSION

Our study clarified the critical role and mechanism of DNA-PKcs in RIPF and showed that it could be a potential target for preventing RIPF.

Downregulated SPESP1-driven fibroblast senescence decreases wound healing in aged mice

BACKGROUND

Human dermal fibroblasts (HDFs) are essential in the processes of skin ageing and wound healing. However, the underlying mechanism of HDFs in skin healing of the elderly has not been well defined. This study aims to elucidate the mechanisms of HDFs senescence and how senescent HDFs affect wound healing in aged skin.

METHODS

The expression and function of sperm equatorial segment protein 1 (SPESP1) in skin ageing were evaluated via in vivo and in vitro experiments. To delve into the potential molecular mechanisms by which SPESP1 influences skin ageing, a combination of techniques was employed, including proteomics, RNA sequencing, immunoprecipitation, chromatin immunoprecipitation and liquid chromatography-mass spectrometry analyses. Clearance of senescent cells by dasatinib plus quercetin (D+Q) was investigated to explore the role of SPESP1-induced senescent HDFs in wound healing.

RESULTS

Here, we define the critical role of SPESP1 in ameliorating HDFs senescence and retarding the skin ageing process. Mechanistic studies demonstrate that SPESP1 directly binds to methyl-binding protein, leading to Decorin demethylation and subsequently upregulation of its expression. Moreover, SPESP1 knockdown delays wound healing in young mice and SPESP1 overexpression induces wound healing in old mice. Notably, pharmacogenetic clearance of senescent cells by D+Q improved wound healing in SPESP1 knockdown skin.

CONCLUSIONS

Taken together, these findings reveal the critical role of SPESP1 in skin ageing and wound healing, expecting to facilitate the development of anti-ageing strategies and improve wound healing in the elderly.

SOD2 orchestrates redox homeostasis in intervertebral discs: A novel insight into oxidative stress-mediated degeneration and therapeutic potential

Low back pain (LBP) is a pervasive global health concern, primarily associated with intervertebral disc (IVD) degeneration. Although oxidative stress has been shown to contribute to IVD degeneration, the underlying mechanisms remain undetermined. This study aimed to unravel the role of superoxide dismutase 2 (SOD2) in IVD pathogenesis and target oxidative stress to limit IVD degeneration. SOD2 demonstrated a dynamic regulation in surgically excised human IVD tissues, with initial upregulation in moderate degeneration and downregulation in severely degenerated IVDs. Through a comprehensive set of in vitro and in vivo experiments, we found a suggestive association between excessive mitochondrial superoxide, cellular senescence, and matrix degradation in human and mouse IVD cells. We confirmed that aging and mechanical stress, established triggers for IVD degeneration, escalated mitochondrial superoxide levels in mouse models. Critically, chondrocyte-specific Sod2 deficiency accelerated age-related and mechanical stress-induced disc degeneration in mice, and could be attenuated by β-nicotinamide mononucleotide treatment. These revelations underscore the central role of SOD2 in IVD redox balance and unveil potential therapeutic avenues, making SOD2 and mitochondrial superoxide promising targets for effective LBP interventions.

The p21+ perinecrotic hepatocytes produce the chemokine CXCL14 after a severe acetaminophen overdose promoting hepatocyte injury and delaying regeneration

Fifty percent of all acute liver failure (ALF) cases in the United States are due to acetaminophen (APAP) overdose. Assessment of canonical features of liver injury, such as plasma alanine aminotransferase activities are poor predictors of acute liver failure (ALF), suggesting the involvement of additional mechanisms independent of hepatocyte death. Previous work demonstrated a severe overdose of APAP results in impaired regeneration, the induction of senescence by p21, and increased mortality. We hypothesized that a discrete population of p21+ hepatocytes acquired a secretory phenotype that directly impedes liver recovery after a severe APAP overdose. Leveraging in-house human APAP explant liver and publicly available single-nuclei RNAseq data, we identified a subpopulation of p21+ hepatocytes enriched in a unique secretome of factors, such as CXCL14. Spatial transcriptomics in the mouse model of APAP overdose confirmed the presence of a p21+ hepatocyte population that directly surrounded the necrotic areas. In both male and female mice, we found a dose-dependent induction of p21 and persistent circulating levels of the p21-specific constituent, CXCL14, in the plasma after a severe APAP overdose. In parallel experiments, we targeted either the putative senescent hepatocytes with the senolytic drugs, dasatinib and quercetin, or CXCL14 with a neutralizing antibody. We found that targeting CXCL14 greatly enhanced liver recovery after APAP-induced liver injury, while targeting senescent hepatocytes had no effect. These data support the conclusion that the sustained induction of p21 in hepatocytes with persistent CXCL14 secretion are critical mechanistic events leading to ALF in mice and human patients.

Exploration of New Therapies for Heart Failure Targeting Age-Related Mechanisms

Evidence indicates a role of cellular senescence and systemic insulin resistance (hyperinsulinemia) in the pathogenesis of age-related cardiovascular-metabolic disorders, including heart failure, atherosclerotic diseases, obesity, and diabetes. "Metabolic remodeling" is one of the keywords for aging research, and studies with brown adipose tissue have shown that maintaining the homeostasis of this organ is crucial to suppressing the progression of pathologies in obesity and heart failure. The mechanisms contributing to the synchronization of aging (sync-aging) are mysterious and interesting. "Senometabolite" or "senoprotein" are defined as circulating molecules that have causal roles in sync-aging, which requires the establishment of new concepts: age-related fibrotic disorders (A-FiDs), and senometabolite-related disorders (SRDs). Globally, researchers are active in comprehensive and conclusive studies targeting age-related circulating molecules. Recently, the senolytic approach opened a new avenue for aging research. Senolysis, mediated through a genetic/pharmacologic/vaccination approach, reversed aging and pathologies in age-related diseases. Suppression of prosenescent molecules (senocules) and senolysis, the specific depletion of senescent cells, will become next-generation therapies for cardiovascular diseases.