Sirt3-mediated mitophagy regulates AGEs-induced BMSCs senescence and senile osteoporosis

An "inside-out"-guided genetically engineered hydrogel for augmenting aged bone regeneration

Senescent bone repair faces significant obstacles due to reduced cellular activity and an unfavorable microenvironment, both of which hinder the osteogenic differentiation of bone marrow-derived stem cells (BMSCs) into osteoblasts (OBs) and subsequent bone formation. Current approaches primarily target senescent cell clearance (senolytics) or suppression of the senescence-associated secretory phenotype (senomorphics), neglecting the complex interactions between BMSCs and the osteogenic microenvironment. In this study, a genetically engineered hydrogel incorporating NAD-dependent deacetylase sirtuins 3 (SIRT3)-loaded nano-vectors and poly (glycerol sebacate)-co-poly (ethylene glycol)/polyacrylic acid (PEGS/PAA) was developed as an "inside-out" strategy for bone regeneration. At the intracellular level, BMSC function is restored, and osteogenesis is promoted through genetically enhanced SIRT3 expression. At the extracellular level, carboxyl functional groups chelate iron ions, simulating a hypoxic environment and promoting synergistic interactions between angiogenesis and osteogenesis. The therapeutic effects of the genetically engineered hydrogel in alleviating senescent damage and enhancing osteogenic differentiation were confirmed in both chemically and naturally induced senescence models in vitro. Local delivery of the hydrogel significantly increased newly formed bone in rat cranial defects. Mechanistically, the central role of SIRT3 in balancing senescence and osteogenesis, as well as its involvement in bone immune signaling pathways, was elucidated through CRISPR/Cas9-mediated editing in mice and transcriptome sequencing. This work presents a novel paradigm that integrates cellular and microenvironmental factors to enhance bone regeneration, offering new hope for treating age-related bone injuries.

SENP3 alleviates osteoporosis via promoting SIRT3 transcription through the increase of DLX2 stability via SUMO2/3

BACKGROUND

Recent studies have indicated a close relationship between SENP3 and osteoporosis. However, the detailed molecular mechanism of SENP3 mediating osteoporosis has not been well studied. The goal of this work was to study the specific mechanism by which SENP3 regulates downstream genes through deSUMOylation and thus affects the progression of osteoporosis.

METHODS

Osteogenic differentiation was evaluated through osteogenic marker genes, mineralization, and ALP activity, which were detected by qPCR, western blot, and ALP staining assays. Osteoporosis was assessed in OVX mice assessed using qPCR, Micro-CT, and H&E staining assays. The levels of SENP3, DLX2, and SIRT3 were monitored using qPCR and western blot assays. The SUMOylated modification of DLX2 was evaluated using Co-IP and IP assays. The binding of DLX2 to the SIRT3 promoter was confirmed with ChIP, qPCR, dual-luciferase reporter and western blot assays.

RESULTS

SENP3, DLX2, and SIRT3 expressions were decreased in tissues of OVX mice. Mechanically, SENP3 inhibited SUMOylated modification of DLX2 and augmented DLX2 stability. Addition of SENP3 accelerated osteogenic differentiation via regulating DLX2. Moreover, DLX2 bound to SIRT3 promoter and accelerated SIRT3 transcription. DLX2 depletion-induced impeditive effects on osteogenic differentiation were reversed by SIRT3 overexpression. Moreover, DLX2 addition counteracted sh-SENP3-induced inhibitory effect on osteogenic differentiation, which was partially reversed by SIRT3 knockdown. Furthermore, SENP3 alleviated osteoporosis in OVX mice by regulating DLX2/SIRT3 axis.

CONCLUSION

Addition of SENP3 accelerated osteogenic differentiation and relieved osteoporosis via increasing SIRT3 transcription by the enhance of DLX2 stability via SUMO2/3.

A Novel Molecular Regulatory Network in Bone Marrow Mesenchymal Stem Cells for Age-Related Osteoporosis

BACKGROUND

This study evaluates the miRNA-mRNA regulatory networks that potentially influence the senescence mechanisms of bone marrow mesenchymal stem cells (BMSCs) in age-related osteoporosis (ARO). By identifying these networks, the study aims to offer new molecular markers and therapeutic targets for ARO.

METHODS

Five mRNA datasets were analyzed to identify common differentially expressed genes associated with senescence and osteoporosis. Seven hub genes were found to be enriched in the PI3K-Akt signaling pathway, and 22 hub miRNAs potentially regulating these genes. Primary BMSCs were harvested and cultured from seven younger, non-osteoporotic individuals and six older adults with osteoporosis. Expression levels of the hub genes and miRNAs were validated using quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Expression analysis showed that integrin subunit beta 3 (ITGB3), receptor tyrosine kinase ligand (KITLG), platelet-derived growth factor (PDGFB), and their associated regulatory miRNAs, exhibited significant differences between the two BMSC groups.

CONCLUSION

A newly identified miRNA-mRNA regulatory network may mediate ARO via the PI3K-Akt signaling pathway in BMSCs. These molecular insights provide a foundation for potential therapeutic interventions targeting age-related osteoporosis.

The Association Between Two Different Non-invasive Advanced Glycation End Products and Osteoporosis in the Non-diabetic Population: A Cross-Sectional Study

Advanced glycation end products (AGEs) are associated with osteoporosis (OP) in the diabetic population. However, their relationship with OP in the non-diabetic population remains unclear. This study aimed to investigate cross-sectional associations of AGEs levels in the skin and lens with OP in the non-diabetic population. A retrospective analysis of clinical data of 652 participants was conducted. Bone mineral density (BMD) was quantified by dual-energy X-ray absorptiometry. Lens and skin AGEs were assessed by lens and skin autofluorescence (LAF and SAF). This study included 652 individuals, 280 males (42.9%) and 372 females (57.1%), with a mean age of (55.5 ± 6.9) years. The population with osteopenia exhibited significantly higher levels of SAF-AGEs than those with normal BMD, while the population with OP had significantly higher levels of both SAF- and LAF-AGEs. After adjusting for age and body mass index, LAF-AGEs were negatively correlated with BMD at the femoral neck and total hip. In contrast, SAF-AGEs were negatively correlated with BMD at the lumbar1-4 spine. Furthermore, multiple linear stepwise regression analysis demonstrated that LAF-AGEs were negatively associated with BMD at both the femoral neck and total hip. However, SAF-AGEs showed no association with BMD at any of the three measured sites. Additionally, after adjusting for other covariates, the logistic regression analysis emphasized that LAF-AGEs were associated with OP in the non-diabetic population, but SAF-AGEs do not. The results revealed a significant correlation between LAF-AGEs and OP in the non-diabetic population and their potential clinical utility warrants further validation. Therefore, we urge for larger longitudinal analyses and experimental research to validate and extend these cross-sectional findings.

The MYC/TXNIP axis mediates NCL-Suppressed CD8+T cell immune response in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma is a deadly malignancy with immune evasion playing a key role in tumor progression. Glucose metabolism is crucial for T cell function, and the nucleolar protein NCL may influence T cell glucose metabolism. This study aims to investigate NCL's role in T cell glucose metabolism and immune evasion by lung adenocarcinoma cells.

METHODS

Utilizing single-cell RNA sequencing (scRNA-seq) data from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA), we analyzed cell clustering, annotation, and prognosis. In vitro experiments involved manipulating NCL expression in CD8+ T cells to study immune function and glucose metabolism. In vivo studies using an orthotopic transplant mouse model monitored NCL's impact on CD8+ T cell glucose metabolism and anti-tumor immune function.

RESULTS

NCL was associated with T cell dysfunction and glucose metabolism. NCL silencing enhanced CD8+ T cell glucose metabolism, cytotoxicity, and infiltration, while NCL overexpression had the opposite effect. NCL overexpression relieved MYC-mediated transcriptional repression of TXNIP, reducing CD8+ T cell glucose metabolism. In vivo, NCL inhibited CD8+ T cell glucose metabolism through the MYC/TXNIP axis, hindering anti-tumor immune function.

CONCLUSIONS

NCL overexpression suppresses CD8+ T cell glucose metabolism and anti-tumor immune function, promoting lung adenocarcinoma progression via the MYC/TXNIP axis.

Efficacy and safety of acupuncture as an adjuvant therapy for osteoporosis: a systematic review and meta-analysis of randomized controlled trials

Objective

To systematically evaluate the efficacy and safety of acupuncture as an adjuvant therapy for osteoporosis (OP) through a comprehensive synthesis of recent randomized controlled trial (RCT) evidence.

Methods

A systematic literature search was conducted across PubMed, Web of Science, CNKI, and Wanfang databases (2014 - 2024) to identify RCTs investigating acupuncture combined with conventional therapy for OP. Study quality was appraised using the Cochrane Risk of Bias tool, and meta-analyses were performed using RevMan 5.4 and Stata 15.0, with subgroup analyses stratified by intervention type, population characteristics, and treatment duration.

Results

28 RCTs (n=2,758) were included. Meta-analysis revealed acupuncture significantly enhanced bone mineral density (BMD) versus controls: total (SMD = 0.47, p = 0.03), femoral neck (MD = 0.05, p = 0.01), lumbar spine (SMD = 0.40, p < 0.001), Ward's triangle (MD = 0.07, p = 0.02), and hip (SMD = 0.55, p < 0.001), with particularly marked improvements in the postmenopausal osteoporosis subgroup. Acupuncture demonstrated significant improvements in treatment efficacy, biochemical markers, pain scores, and symptom assessments, while reducing adverse events. Warm needle moxibustion outperformed controls in femoral neck (MD = 0.07, p = 0.002) and hip BMD (SMD = 0.87, p < 0.001), while electroacupuncture significantly elevated serum calcium (MD = 0.18, p = 0.02). Short-term interventions (≤ 3 months) demonstrated optimal efficacy.

Conclusion

Acupuncture demonstrates efficacy and safety as an OP adjuvant therapy. Current evidence is limited by regional bias and methodological heterogeneity. Multicenter, large-sample RCTs are needed to standardize protocols and validate long-term therapeutic efficacy.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024499354.

Mitochondria at the crossroads: Quality control mechanisms in neuronal senescence and neurodegeneration

Mitochondria play a central role in essential cellular processes, including energy metabolism, biosynthesis of metabolic substances, calcium ion storage, and regulation of cell death. Maintaining mitochondrial quality control is critical for preserving mitochondrial health and ensuring cellular function. Given their high energy demands, neurons depend on effective mitochondrial quality control to sustain their health and functionality. Neuronal senescence, characterized by a progressive decline in structural integrity and function, is a hallmark of neurodegenerative diseases. In senescent neurons, abnormal mitochondrial morphology, functional impairments, increased reactive oxygen species production and disrupted quality control mechanisms are frequently observed. Understanding the pathological changes in neuronal structure, exploring the intricate relationship between mitochondrial quality control and neuronal health, and leveraging mitochondrial quality control interventions provide a promising foundation for addressing age-related neurodegenerative diseases. This review highlights key mitochondrial quality control, including biogenesis, dynamics, the ubiquitin-proteasome system, autophagy pathways, mitochondria-derived vesicles, and inter-organelle communication, while discussing their roles in neuronal senescence and potential therapeutic strategies. These insights may pave the way for innovative treatments to mitigate neurodegenerative disorders.

Regulation of protein arginine methyltransferase in osteoporosis: a narrative review

Osteoporosis (OP), a systemic bone disease characterised by increased bone fragility and susceptibility to fracture, is mainly caused by a decline in bone mineral density (BMD) and quality caused by an imbalance between bone formation and resorption. Protein arginine methyltransferases (PRMTs) are epigenetic factors and post-translational modification (PTM) enzymes participating in various biological processes, including mRNA splicing, DNA damage repair, transcriptional regulation, and cell signalling. They act by catalysing the transfer and modification of arginine residues and, thus, have become therapeutic targets for OP. In-depth studies have found that these enzymes also play key roles in bone matrix protein metabolism, skeletal cell proliferation and differentiation, and signal pathway regulation to regulate bone formation, bone resorption balance, or both and jointly maintain bone health and stability. However, the expression changes and mechanisms of action of multiple members of the PRMT family differ in OP. Therefore, this paper discusses the biological functions, mechanisms of action, and influencing factors of PRMTs in OP, which is expected to provide a new understanding of the pathogenesis of OP. Furthermore, we present theoretical support for the development of more precise and effective treatment strategies as well as for further study of the molecular mechanisms of PRMTs.

OGA promotes human dental pulp stem cell senescence and inhibits mitophagy by inhibition of O-GlcNAcylation of KLF2

BACKGROUND

Dental pulp stem cells (DPSCs) aging impedes its application in tooth regeneration techniques, involving abnormal mitophagy. O-GlcNAcylation is a post-translational modification that regulates various cellular processes. Here, we aimed to investigate the role of O-GlcNAcylation in mitophagy and senescence.

METHODS

DPSCs were cultured and passaged in vitro, and the 7th (p7) and 15th (p15) generation cells were collected. OGA and KLF2 were knocked down in p15 cells. Cell senescence was evaluated using senescence associated β-galactosidase staining, enzyme-linked immunosorbent assay, and western blotting; mitophagy was evaluated using western blotting. The regulation of OGA on the O-GlcNAcylation of KLF2 was analyzed using immunoprecipitation and western blotting.

RESULTS

The results showed that p15 cells were more senescent than p7 cells and had poor mitophagy, with the higher expression of OGA. Knockdown of OGA inhibited senescence and promoted mitophagy in DPSCs. Moreover, silencing of KLF2 reversed the effects on senescence and mitophagy mediated by OGA knockdown. Additionally, OGA suppressed the O-GlcNAcylation of KLF2 at S177 site and thus reduced its stability.

CONCLUSION

Silencing of OGA promotes mitophagy and inhibits DPSC senescence by promoting the O-GlcNAcylation of KLF2, suggesting a novel mechanism underlying DPSC senescence.

Engineered Extracellular Vesicles Derived from Juvenile Mice Enhance Mitochondrial Function in the Aging Bone Microenvironment and Achieve Rejuvenation

Aging-related bone degeneration and impaired healing capacity remain significant challenges in regenerative medicine, necessitating innovative, efficient, and targeted strategies to restore bone health. Here, we engineered extracellular vesicles (EVs) derived from the serum of pretreated juvenile mice, with the goals of reversing aging, enhancing osteogenic potential, and increasing bioavailability to rejuvenate the aging bone environment. First, we established bone healing models representing different phases of healing to identify the EV type with the highest potential for improving the bone microenvironment in older individuals. Second, we employed DSS6 for bone targeting to enhance the biological effects of the selected EVs in vivo. The engineered EVs effectively targeted bone repair sites and promoted fracture healing more effectively than unmodified EVs in older mice. RNA sequencing revealed that the translocase of outer mitochondrial membrane 7 (Tomm7) is crucial for the underlying mechanism. Silencing Tomm7 significantly diminished the positive regulatory effects of the EVs. Specifically, the engineered EVs may enhance mitochondrial function in aging cells by activating the Tomm7-mediated Pink1/Parkin mitophagy pathway, promoting stemness recovery in aging bone marrow stromal cells (BMSCs) and reversing the adverse conditions of the aging bone microenvironment. Overall, the developed engineered EVs derived from serum from juvenile mice offer an alternative approach for treating aging bones. The identified underlying biological mechanisms provide a valuable reference for precision treatment of aging bones in the future.

Posttranslational Modification in Bone Homeostasis and Osteoporosis

Bone is responsible for providing mechanical protection, attachment sites for muscles, hematopoiesis micssroenvironment, and maintaining balance between calcium and phosphorate. As a highly active and dynamically regulated organ, the balance between formation and resorption of bone is crucial in bone development, damaged bone repair, and mineral homeostasis, while dysregulation in bone remodeling impairs bone structure and strength, leading to deficiency in bone function and skeletal disorder, such as osteoporosis. Osteoporosis refers to compromised bone mass and higher susceptibility of fracture, resulting from several risk factors deteriorating the balanced system between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. This balanced system is strictly regulated by translational modification, such as phosphorylation, methylation, acetylation, ubiquitination, sumoylation, glycosylation, ADP-ribosylation, S-palmitoylation, citrullination, and so on. This review specifically describes the updating researches concerning bone formation and bone resorption mediated by posttranslational modification. We highlight dysregulated posttranslational modification in osteoblast and osteoclast differentiation. We also emphasize involvement of posttranslational modification in osteoporosis development, so as to elucidate the underlying molecular basis of osteoporosis. Then, we point out translational potential of PTMs as therapeutic targets. This review will deepen our understanding between posttranslational modification and osteoporosis, and identify novel targets for clinical treatment and identify future directions.

FKBP5 Induces Senescence in BMSCs and Inhibits Osteogenic Differentiation Through the Canonical WNT/β-Catenin Signalling Pathway in Senile Osteoporosis

Senile osteoporosis and its associated fractures significantly contribute to increased morbidity, mortality, and healthcare costs among older adults. Further research is needed to elucidate the molecular mechanisms underlying senile osteoporosis. This study found that FKBP5 expression in bone marrow mesenchymal stem cells (BMSCs) increases with age and is inversely correlated with patients' bone mineral density and CT values. Functional analyses revealed that FKBP5 plays a crucial regulatory role in BMSC osteogenic differentiation, acting through the canonical WNT/β-catenin signalling pathway. FKBP5 binds to β-catenin, promoting its ubiquitination and degradation. Importantly, administration of SAFit2, a selective FKBP5 inhibitor, enhanced bone mineral density in an animal model of senile osteoporosis. These findings suggest that FKBP5 may represent a novel therapeutic target and provide new insights into the treatment of senile osteoporosis.

Crocin facilitates osteogenesis and angiogenesis by moderating oxidative stress and ferroptosis via Nrf2/GPX4 pathway

Bone formation is a complex multi-factor process of bone defect healing. Oxidative stress (OS) is predisposed to induce regulatory cell death (RCD), such as ferroptosis. At present, the antioxidant effects of Crocin on erastin induced oxidative damage were studied. The activity of bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) was detected by CCK-8 and EdU staining. The production of reactive oxygen species (ROS), MDA, SOD and GSH were evaluated. Western blotting assay was used to detect ferroptosis-related proteins. The osteogenic function of BMSCs was determined by alkaline phosphatase (ALP) activity, ALP staining and alizarin red S (ARS) staining. Western blotting and RT-PCR assays were used to detect the expression of osteogenic proteins and genes. Angiogenesis of HUVECs was evaluated by tube formation, RT-PCR, scratch test and Transwell assay. The results showed that Crocin can promote the osteogenic function of BMSCs and angiogenesis of HUVECs. In addition, Crocin protects cells from erastin-induced oxidative injury and inhibits ferroptosis via the Nrf2/GPX4 pathway. These findings suggest that Crocin can promote bone defect healing by regulating OS and inhibiting ferroptosis through the Nrf2/GPX4 pathway.

Lactylation: A Novel Epigenetic Regulator of Cellular Senescence

Cellular senescence is the basic unit of organismal aging, a complicated biological process involving several cell types and tissues. It is also an important mechanism by which the body responds to damage and potential carcinogenesis. However, excessive or abnormal cellular senescence can lead to tissue functional degradation and the occurrence of diseases. In recent years, the role of epigenetic modifications in cellular senescence has received extensive attention. Lactylation, a novel post-translational modification derived from lactate, has recently gained significant attention as a key factor in cellular metabolism and epigenetic regulation, gradually demonstrating its importance in the regulation of cellular senescence. This review emphasizes the bidirectional causal relationship between lactylation and cellular senescence, highlighting its potential as a therapeutic target for aging-related diseases.

Exploring the impact of gut microbiota-mediated regulation of exosomal miRNAs from bone marrow mesenchymal stem cells on the regulation of bone metabolism

BACKGROUND

Osteoporosis, which is a prevalent metabolic bone disease, is closely associated with imbalances in the gut microbiota.

METHODS

The ovaries of female 6-month-old Sprague-Dawley rats were surgically removed to induce osteoporosis. Subsequently, 16S rRNA sequencing was employed to characterize the gut microbiota in the osteoporotic rats. Bone marrow mesenchymal stem cells (BMSCs) were isolated from osteoporotic rats and cultured separately, and their osteogenic and adipogenic differentiation was observed. Furthermore, exosomes were extracted from these cells, and miRNA sequencing was performed on the exosomes to identify key miRNAs. Osteoporotic rats were then treated with a member of the gut microbiota, and changes in the osteogenic and adipogenic differentiation of BMSCs were observed.

RESULTS

In our investigation, we observed altered proportions of Firmicutes and Bacteroidetes in the guts of ovariectomized rats, which contributed to dysbiosis and subsequent changes in intestinal permeability. The BMSCs exhibited disrupted osteogenic/adipogenic differentiation, which was associated with structural damage to bones. Through the isolation of exosomes from BMSCs and subsequent miRNA analysis, we identified miR-151-3p and miR-23b-3p as potential pivotal regulators of bone metabolism. Furthermore, through 16S rRNA sequencing, we identified g_Ruminococcus and its marked capacity to ameliorate the imbalance in BMSC osteogenic/adipogenic differentiation. Intervention with g_Ruminococcus demonstrated promising outcomes, mitigating bone loss and structural damage to the tibia and femur in ovariectomized rats.

CONCLUSIONS

These findings highlight the significant role of g_Ruminococcus in alleviating osteoporosis induced by estrogen deficiency, suggesting its therapeutic potential for addressing postmenopausal osteoporosis through the targeted modulation of BMSC-derived exosomal miR-151-3p and miR-23b-3p.

Specnuezhenide Alleviates Senile Osteoporosis by Activating TGR5/FXR Signaling in Bone Marrow Mesenchymal Stem Cells and RANKL-Induced Osteoclasts

Background

Specnuezhenide (SPN) is an iridoid glycoside isolated from Fructus Ligustri Lucidi, an herb prescribed for the treatment of senile osteoporosis. However, the direct role of SPN on bone metabolism remains unclear. In this study, the effects of SPN on d-galactose (d-gal)-induced mice, bone marrow mesenchymal stem cells (BMSCs), and nuclear factor-κB ligand-induced osteoclasts were examined.

Methods

Micro-computed tomography was used to observe the bone microstructure. Osteogenesis was examined using Western blotting and alkaline phosphatase staining. Osteoclastogenesis was examined using Western blotting and F-actin ring staining. Senescence-associated β-galactosidase was used to detect cell senescence. In addition, the expression of Takeda G protein-coupled receptor 5 (TGR5)/farnesoid X receptor (FXR) signaling pathway-related genes and proteins was determined through quantitative real-time polymerase chain reaction and immunofluorescence.

Results

Oral administration of SPN improved the bone microstructure in d-gal-induced mice and increased bone mineral density, bone volume, trabecular thickness, and trabecular number. SPN also upregulated the expression of the osteogenesis markers osteocalcin, bone morphogenetic protein 2, and runt-related transcription factor 2 and downregulated the expression of the osteoclasis markers tartrate-resistant acid phosphatase, nuclear factor-κB, and nuclear factor of activated T-cells in the d-gal-induced bone. Furthermore, SPN increased alkaline phosphatase staining, inhibited F-actin ring formation, and reduced the activity of senescence-associated β-galactosidase in vitro. Mechanistically, SPN activated the TGR5/FXR pathway in d-gal-induced BMSCs and osteoclasts. The protective effects of SPN were abolished after addition of the TGR5 inhibitor SBI-115 or FXR inhibitor DY268. Moreover, SPN could elevate the protein and mRNA levels of TGR5, FXR, and the downstream small heterodimer partner in d-gal-induced bone.

Conclusion

SPN alleviated senile osteoporosis and cell senescence by activating the TGR5/FXR pathway.

Luteolin Inhibits Dexamethasone-Induced Osteoporosis by Autophagy Activation Through miR-125b-5p/SIRT3/AMPK/mTOR Axis, an In Vitro and In Vivo Study

Luteolin (LUT) has been suggested as an inhibitor of osteoporosis (OP). This investigation examines the pivotal role of the miR-125b-5p/SIRT3/AMPK/mTOR pathway in mediating luteolin-induced effects on OP. Mesenchymal stem cells derived from bone marrow (BMSCs) were exposed to dexamethasone (DEX) to create an in vitro model of OP. Following treatment with luteolin, the levels of miR-125b-5p and SIRT3 were quantified using reverse transcription polymerase chain reaction. Moreover, SIRT3, AMPK, mTOR protein levels, and osteogenesis (OPN, Runx2, OSX, and OCN), and autophagy (p62, ATG5, LC3, and BECN1) were evaluated using ELISA. Additionally, specific mimics and siRNA were constructed to overexpress miR-125b-5p or downregulate SIRT3. Furthermore, animal models of DEX-induced OP were constructed to assess the effects of LUT at doses of 50 and 100 mg/kg/day on bone histology, stereology, biochemistry, and the expression of the miR-125b-5p, SIRT3/AMPK/mTOR axis, and markers of osteogenesis and autophagy. The findings revealed that LUT suppressed miR-125b-5p expression, overexpressed SIRT3 and AMPK, and downregulated mTOR in BMSCs compared to DEX (p-value < 0.01). Interestingly, LUT restored the levels of markers for osteogenesis and autophagy (p-value < 0.001). The overexpression of SIRT3 or miR-125b-5p downregulation inhibited LUT therapeutic properties. In animals, LUT improved bone histology (p-value < 0.05) and inhibited miR-125b-5p and mTOR expression while overexpressing SIRT3 and AMPK (p-value < 0.001). RUNX2, OSX, OPN, and OCN levels were improved, and autophagy was enhanced in LUT-treated rats. The current findings revealed that LUT could promote osteogenesis and improve OP via autophagy activation through the miR-125b-5p/SIRT3/AMPK/mTOR pathway.

Aloe-Emodin Improves Mitophagy in Alzheimer's Disease via Activating the AMPK/PGC-1α/SIRT3 Signaling Pathway

BACKGROUND

Impaired mitophagy results in the accumulation of defective mitochondria that are unable to be cleared effectively in Alzheimer's disease (AD). Aloe-emodin (AE), a key component of the traditional Chinese medicine Rhubarb, exhibits neuroprotective effects against Alzheimer's disease, though the underlying mechanism remains unclear. Studying aloe-emodin's role in enhancing mitophagy is vital for improving cognitive function and reducing neuronal damage in Alzheimer's disease.

METHODS

The APP/PS1 double transgenic mice were adopted as models for AD to assess the effects of aloe-emodin upon cognitive function and its neuroprotective impact on hippocampal neurons. Additionally, we investigated the regulatory mechanisms of proteins within the aforementioned pathway, and the morphological characteristics of mitophagy-related proteins. An AD hippocampal neuron model was developed using Aβ25-35 to evaluate the mitochondrial function, the protein expression of such a pathway and the mitophagy. This approach aims to elucidate the effects and underlying mechanisms of aloe-emodin in relation to AD.

RESULTS

AE activates mitophagy in neurons, improves cognitive dysfunction, reduces hippocampal damage, and alleviates AD symptoms in model mice. AE activates the expression of AMPK, PGC-1α and SIRT3. Increased expression of SIRT3 in mitochondria promotes mitophagy and regulates the function of mitochondrial proteins. When mitochondrial autophagy is enhanced, the expression of Beclin1, LC3, P62, Parkin, and PINK1-related proteins changes. Further in vitro experiments showed that AE can enhance mitochondrial function in Alzheimer's disease cell models. The mitochondrial membrane potential, GSH, ROS and Ca2+ levels gradually recover, alleviating the pathological manifestations of AD. Knocking down SIRT3 leads to increased mitochondrial damage and a reduction in mitophagy in HT22 cells.

CONCLUSION

Experimental results show that AE can activate mitophagy through AMPK/PGC-1α/SIRT3 pathway, alleviate cognitive dysfunction in AD, and reduce damage to hippocampal neurons.

Molecular mechanism of mitochondrial autophagy mediating impaired energy metabolism leading to osteoporosis

Osteoporosis (OP) is a bone metabolic disease caused by decreased bone mass leading to destruction of bone microstructure. Treatment of OP is characterized by a lifelong nature, causing extreme financial and psychological burdens to patients. Hormonal abnormalities, cellular autophagy, Ferroptosis, and oxidative stress are all part of the intricate and varied pathophysiology of OP. Recent research has revealed that mitochondrial dysfunction is a significant factor in the onset and progression of OP. By regulating bone marrow mesenchymal stem cell differentiation through various signaling pathways and cytokines, abnormal mitochondrial energy metabolism brought on by oxidative stress processes impacts osteoblast and osteoclast proliferation and differentiation, causing an imbalance in bone metabolism that ultimately results in OP. Therefore, one possible method to prevent and manage OP may be to use mitochondria as a carrier to trigger osteogenic differentiation of bone marrow mesenchymal stem cells from mitochondrial energy consumption, oxidative stress, autophagy, and osteoclast death. In order to offer some theoretical references and therapeutic approaches for the clinical prevention and treatment of OP, we will examine the pathophysiology of OP from mitochondrial dysfunction in this work.

A Functionalized 3D-Printed Ti6Al4V "Cell Climbing Frame" Inspired by Marine Sponges to Recruit and Rejuvenate Autologous BMSCs in Osteoporotic Bone Repair

Osteoporosis, characterized by low bone mass and high fracture risk, challenges orthopedic implant design. Conventional 3D-printed Ti6Al4V scaffolds are mechanically robust but suffer from poor bone regeneration in osteoporotic patients due to stress shielding and cellular senescence. In this study, a functionalized 3D-printed Ti6Al4V "Cell Climbing Frame" is developed, aiming to adapt to the mechanical microenvironment of osteoporosis, effectively recruit and support the adhesion and growth of autologous bone marrow mesenchymal stem cells (BMSCs), while rejuvenating senescent cells for improved bone regeneration. Inspired by marine sponges, the processing accuracy limitations of selective laser melting (SLM) technology is broke through innovatively constructing a hierarchical porous structure with macropores and micropores nested within each other. Results demonstrate that the unique hierarchical porous scaffold reduces the elastic modulus, facilitates blood penetration, and enhances cell adhesion and growth. Further surface functionalization with E7 peptides and exosomes promotes the attraction and rejuvenation of BMSCs and boosts migration, proliferation, and osteogenic differentiation in vitro. In vivo, the functionalized "Cell Climbing Frame" accelerates bone repair in osteoporotic rats, while delaying surrounding bone loss, enabling robust multi-stage osseointegration. This innovation advances 3D-printed regenerative implants for osteoporotic bone repair.

m7G-modified mt-tRF3b-LeuTAA regulates mitophagy and metabolic reprogramming via SUMOylation of SIRT3 in chondrocytes

N7-methylguanosine (m7G) modification is one of the most prevalent RNA modifications, and methyltransferase-like protein-1 (METTL1) is a key component of the m7G methyltransferase complex. METTL1-catalyzed m7G as a new RNA modification pathway that regulates RNA structure, biogenesis, and cell migration. Increasing evidence indicates that m7G modification has been implicated in the pathophysiological process of osteoarthritis (OA). However, the underlying molecular mechanisms of m7G modification remains incompletely elucidated during the progression of OA. Here we found that METTL1 and m7G levels were markedly increased in OA chondrocytes. In addition, METTL1-mediated m7G modification upregulated mt-tRF3b-LeuTAA expression to exacerbate chondrocyte degeneration. Mechanistically, mt-tRF3b-LeuTAA decreased the SUMO-specific protease 1 (SENP1) protein expression and upregulated the level of sirtuin 3 (SIRT3) SUMOylation to inhibit PTEN induced kinase 1 (PINK1)/Parkin-mediated mitochondrial mitophagy. Intra-articular injection of PMC-tRF3b-LeuTAA inhibitor (Polyamidoamine-polyethylene glycol surface-modified with Minimal self-peptides and Chondrocyte-affinity peptides, PMC) attenuated destabilization of the medial meniscus (DMM) mouse cartilage degeneration in vivo. Our study demonstrates that METTL1/m7G/mt-tRF3b-LeuTAA axis accelerate cartilage degradation by inhibiting mitophagy and promoting mitochondrial dysfunction through SIRT3 SUMOylation, and suggest that targeting METTL1 and its downstream signaling axis could be a promising therapeutic target for OA treatment.

Targeting NAMPT-OPA1 for treatment of senile osteoporosis

Senescence of bone marrow mesenchymal stem cells (BMSCs) impairs their stemness and osteogenic differentiation, which is the principal cause of senile osteoporosis (SOP). Imbalances in nicotinamide phosphoribosyltransferase (NAMPT) homeostasis have been linked to aging and various diseases. Herein, reduction of NAMPT and impaired osteogenesis were observed in BMSCs from aged human and mouse. Knockdown of Nampt in BMSCs promotes lipogenic differentiation and increases age-related bone loss. Overexpression of Nampt ameliorates the senescence-associated (SA) phenotypes in BMSCs derived from aged mice, as well as promoting osteogenic potential. Mechanistically, NAMPT inhibits BMSCs senescence by facilitating OPA1 expression, which is essential for mitochondrial dynamics. The defect of NAMPT reduced mitochondrial membrane potential, interfered with mitochondrial fusion，and increased SA protein and phenotypes. More importantly, we have confirmed that P7C3, the NAMPT activator, is a novel strategy for reducing SOP bone loss. P7C3 treatment significantly prevents BMSCs senescence by improving mitochondrial function through the NAMPT-OPA1 signaling axis. Taken together, these results reveal that NAMPT is a regulator of BMSCs senescence and osteogenic differentiation. P7C3 is a novel molecule drug to prevent the pathological progression of SOP.

A galactose-tethered tetraphenylethene prodrug mediated apoptosis of senescent cells for osteoporosis treatment

Osteoporosis and bone injury healing in elderly patients are major medical challenges, often exacerbated by the accumulation of senescent cells. Herein, we show that TPE-Gal, which contains a tetraphenylethene unit and a galactose moiety, offers a promising molecular therapy designed to light up and eliminate senescent cells through a hydrolysis reaction catalyzed by β-galactosidase, an enzyme overexpressed in senescent cells. The reaction produces TPE-OH, which, in turn, increases reactive oxygen species levels within the senescent cells, leading to noninflammatory apoptosis of senescent cells. This targeted clearance mechanism helps to alleviate osteoporosis symptoms and promotes bone injury healing. Moreover, apoptotic vesicles, which are generated during the process, are partly phagocytosed by macrophages, mimicking physiological metabolic processes. This study opens new avenues for addressing bone health issues through the designed bioclearance of senescent cells, aligning with the body's natural pathways for maintaining homeostasis.

Cordycepin ameliorates spaceflight-induced osteoporosis by preventing BMSCs oxidative stress and senescence via interacting with PI3K p110α and regulating PI3K/Akt/FOXO3 signalling

Spaceflight-induced osteoporosis (SFOP) is a detrimental healthcare consequence during spaceflight. Weightlessness and ionizing radiation were main environmental factors that contribute to SFOP, especially in the manned deep space voyages. However, currently there is scarce effective method to treat SFOP. This study aims at discovering the role and mechanism of cordycepin (COR) in treating SFOP. A combined ionizing radiation and tail suspension (IR/IS) model is constructed in mice to simulate SFOP. COR injection exhibits certain dose-dependent therapeutic effects including better imageological bone index and improved histological bone regeneration in treating SFOP, which is most prominent at a dose of 20 mg/kg. A combined radiation and microgravity (R/M) model is established to treat BMSCs in vitro. 10 μM COR alleviates oxidative stress and cellular senescence of BMSCs. Through high-throughput sequencing, molecular docking and microscale thermophoresis (MST), we reveal a novel mechanism that COR interacts with p110α subunit in PI3K isoform α (PI3Kα) and inhibits PI3K kinase activity, which then regulates the PI3K/Akt/FOXO3 signalling. To elevate the bioavailability of COR in the SFOP treatment, a BMSCs-targeted delivery system that uses exosomes (Exos) modified with BMSC-affinity peptide E7 (E7-Exos) is constructed and loaded with COR. E7-Exos loaded COR reduces the dosage of COR to 5 mg/kg while enhancing the therapeutic effect than using 20 mg/kg COR alone in treating SFOP. In conclusion, COR shows promise as a potential agent in SFOP therapy.

Rejuvenation of Bone Marrow Mesenchymal Stem Cells: Mechanisms and Their Application in Senile Osteoporosis Treatment

Bone marrow mesenchymal stromal cells (BM-MSCs) are multipotent cells present in bone marrow; they play a crucial role in the process of bone formation. Cellular senescence is defined as a stable state of cell cycle arrest that impairs the functioning of cells. Research has shown that aging triggers a state of senescence in BM-MSCs, leading to a reduced capacity for osteogenic differentiation and the accumulation of senescent cells, which can accelerate the onset of various diseases. Therefore, it is essential to explore mechanisms and strategies for the rejuvenation of senescent BM-MSCs. Senile osteoporosis (SOP) is a metabolic bone disease characterized by reduced bone formation. The senescence of BM-MSCs is considered one of the most important factors in the occurrence and development of SOP. Therefore, the rejuvenation of BM-MSCs for the treatment of SOP represents a promising strategy. This work provides a summary of the functional alterations observed in senescent BM-MSCs and a systematic review of the mechanisms that facilitate the rejuvenation of senescent BM-MSCs. Additionally, we analyze the progress in and the limitations associated with the application of rejuvenated senescent BM-MSCs to treat SOP, with the aim of providing new insights for the prevention and treatment of SOP.

Wen-Shen-Tong-Luo-Zhi-Tong-Decoction inhibits bone loss in senile osteoporosis model mice by promoting testosterone production

ETHNOPHARMACOLOGICAL RELEVANCE

Wen-Shen-Tong-Luo-Zhi-Tong-Decoction (WSTLZTD) is a traditional Chinese medicine formula, and its effectiveness in the treatment of senile osteoporosis(SOP) has been confirmed by clinical studies. However, the underlying mechanism of WSTLZTD in SOP is unclear.

AIM OF THE STUDY

This study aimed to clarify the unique effects of Wen-Shen-Tong-Luo-Zhi-Tong-Decoction(WSTLZTD) on senile osteoporosis(SOP) and its underlying mechanisms.

MATERIALS AND METHODS

SAMP6 mice were treated with varying doses of WSTLZTD as the SOP model. Bone loss was evaluated by micro-CT, HE, OCN immunohistochemistry staining, and serum Trap level. Metabolomics studies serum metabolites. ELISA, qPCR, and immunofluorescence were utilized to measure testosterone levels in mouse testis. The effect of testosterone on the mitochondrial energy metabolism of BMSCs was investigated using ROS generation, NAD+/NADH ratio, and WB. Cell senescence was examined by β-galactosidase staining and WB. The effect of TM3 cell conditioned media (CM) on mitochondrial energy metabolism and BMSCs osteogenesis were studied using ALP, ARS, ROS staining, the NAD+/NADH, and WB.

RESULTS

WSTLZTD effectively reversed bone loss in SOP model mice, resulting in better bone microstructure, increased BMD, BV/TV, Tb.n, Tb.Th and, and decreased Tb.Sp. WSTLZTD can increase OCN expression and decrease Trap levels. Network pharmacology data suggest that WSTLZTD regulates steroid hormone production, cellular senescence, inflammation. Metabolomic data indicate that WSTLZTD increases testosterone production or metabolism-related metabolites. WSTLZTD enhanced testosterone production and the mRNA expression of genes involved in testosterone synthesis. Testosterone inhibited the decline in osteogenic differentiation and mitochondrial energy metabolism of senescent BMSCs. The decreased testosterone production in senescent TM3 is reversed by WSTLZTD. CM derived from WSTLZTD-treated TM3 cells promoted osteogenic differentiation and mitochondrial energy metabolism of BMSCs.

CONCLUSIONS

By increasing testosterone production, WSTLZTD may promote mitochondrial energy metabolism and osteogenic differentiation of senescent BMSCs, thereby exerting its anti-SOP effect.

CircSPG21 ameliorates oxidative stress-induced senescence in nucleus pulposus-derived mesenchymal stem cells and mitigates intervertebral disc degeneration through the miR-217/SIRT1 axis and mitophagy

BACKGROUND

The microenvironment of intervertebral disc degeneration (IVDD) is characterized by oxidative stress, leading to the senescence of nucleus pulposus-derived mesenchymal stem cells (NPMSCs). The purpose of this study was to investigate the competitive endogenous RNA mechanism involved in the senescence of NPMSCs induced by tert-butyl hydroperoxide (TBHP).

METHODS

Bioinformatic analysis identified differentially expressed circRNAs. Interactions among circSPG21, miR-217, and the NAD-dependent protein deacetylase sirtuin-1 (SIRT1) were validated through dual-luciferase assays, RNA fluorescence in situ hybridization and RNA immune precipitation. β-Gal staining, EdU staining, Western blotting, JC-1 assays, cell cycle analysis, and quantitative reverse transcription PCR (RT‒qPCR) were used to examine the functions of these molecules in TBHP-induced senescent NPMSCs. The therapeutic effects of circSPG21 were evaluated in a rat IVDD model.

RESULTS

CircSPG21 expression was significantly decreased in both human and rat IVDD tissues, whereas miR-217 was upregulated and SIRT1 was downregulated. Overexpression of circSPG21 alleviated NPMSC senescence by reducing P21 and P53 levels and restoring mitophagy through Parkin. The protective effects of circSPG21 were mediated through the miR-217/SIRT1 axis, as SIRT1 knockdown attenuated these benefits. CircSPG21 also ameliorated disc degeneration in the IVDD rat model, highlighting its potential as a therapeutic target.

CONCLUSION

CircSPG21 reduces oxidative stress-induced NPMSC senescence through the miR-217/SIRT1 axis and mitophagy, providing new insights into IVDD and identifying circSPG21 as a potential therapeutic target for disc degeneration.

SIRT3 mitigates high glucose-induced damage in retinal microvascular endothelial cells via OPA1-mediated mitochondrial dynamics

Oxidative stress in endothelial cells is pivotal in diabetic retinopathy (DR), with mitochondrial homeostasis being crucial to mitigate this stress. This study explored the roles of mitochondrial sirtuins (SIRTs) in high glucose (HG)-induced oxidative stress, related endothelial impairment, and mitochondrial homeostasis damage in rat retinal microvascular endothelial cells (RMECs). RMECs were cultured under HG or equivalent osmotic conditions. Cell viability was assessed using the Cell Counting Kit-8 assay, whereas cell death and survival were determined via calcein-AM/propidium iodide double staining. Reactive oxygen species (ROS) levels were measured using 2',7'-dichlorofluorescein fluorescence. Expression of mitochondrial SIRTs3-5 and key mitochondrial homeostasis molecules was quantified by the quantitative real-time polymerase chain reaction and confirmed by western blotting. Mitochondrial morphology was evaluated using electron microscopy and the MitoTracker fluorescent probe. A SIRT3-overexpressing RMEC line was constructed to assess the role of SIRT3 in oxidative stress and mitochondrial dynamics. After 48 h of HG exposure, cell viability was significantly reduced, with a concomitant increase in cell death and ROS levels, alongside a marked decrease in SIRT3 expression and molecules associated with mitochondrial dynamics. SIRT3 overexpression reversed these effects, particularly increasing the mitochondrial fusion-related molecule, optic atrophy 1 (OPA1). However, the OPA1 inhibitor, MYLS22, blocked the protective effect of SIRT3, leading to more dead cells, a higher ROS level, and intensified mitochondrial fragmentation. These results suggest that SIRT3 is involved in HG-induced imbalanced mitochondrial dynamics of endothelial cells in DR, potentially through the OPA1 pathway.

The Role of mRNA Modifications in Bone Diseases

As a type of epigenetic modifications, mRNA modifications regulate the metabolism of mRNAs, thereby influencing gene expression. Previous studies have indicated that dysregulation of mRNA modifications is closely associated with the occurrence and progression of bone diseases (BDs). In this study, we first introduced the dynamic regulatory processes of five major mRNA modifications and their effects on the nucleus export, stability, and translation of mRNAs. We then summarized the mechanisms of mRNA modifications involved in the development of osteoporosis, osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, fractures, osteomyelitis, and osteosarcoma. Finally, we reviewed therapeutic strategies for BDs based on the above mechanisms, focusing on regulating osteoblast and osteoclast differentiation, inhibiting cellular senescence and injury, and alleviating inflammation. This review identified mRNA modifications as potential targets for treating BDs and proposes perspectives on the diversity, targetability, and safety of mRNA-modifying therapies.

17β-estradiol promotes osteogenic differentiation of BMSCs by regulating mitophagy through ARC

The study aims to elucidate the mechanism through which 17β-estradiol facilitates osteogenic differentiation in bone marrow mesenchymal stem cells (BMSCs). In our study, lentiviral transfection was employed to establish apoptosis repressor with caspase recruitment domain (ARC) knockdown or overexpression in BMSCs. The impact of 17β-estradiol on ARC expression was assessed using western blot, RT-PCR and immunofluorescence. Techniques such as ALP staining, ALP activity assay, western blot, RT-PCR and immunofluorescence staining were utilized to examine the influence of ARC expression levels on the osteogenic differentiation of BMSCs and the osteoclastic differentiation of Raw264.7 cell lines. Mitophagy flux levels in BMSCs were detected using the mitophagy detection kit. RNA sequencing and bioinformatics analyses were conducted to explore potential mechanisms of ARC regulation in BMSCs osteogenic differentiation. To sum up, 17β-estradiol can modulate bone homeostasis by adjusting ARC expression. ARC stimulates mitophagy in BMSCs via MAPK/Akt pathway, identifying ARC as a promising therapeutic target for postmenopausal osteoporosis (PMOP) treatment.

Chronic exposure to polystyrene microplastics triggers osteoporosis by breaking the balance of osteoblast and osteoclast differentiation

Plastic pollution is becoming more and more serious, and microplastics (MPs) formed by degradation from plastics significantly threaten the health of animals and humans. However, it remains unknown how MPs interfere with bone homeostasis by regulating the function of bone marrow mesenchymal stem cells (BMSCs). In order to simulate the toxic impacts of long-term low-dose MPs on the skeletal system, we constructed a 6-month drinking water model of mice exposed to MPs. We found that the bone microstructure in the femur of mice exposed to MPs was destroyed, the quantity of bone trabeculae decreased sharply and the bone mass decreased significantly, accompanied by the decrease of bone formation and the activation of osteoclasts. In addition, RNA sequencing showed NF-κB pathway was activated in MPs-treated BMSCs, manifested as significantly up-regulated inflammatory factors, accelerated the senescence of BMSCs, and inhibited their osteogenic differentiation and extracellular mineralization. Senescent BMSCs induced by MPs led to the overproduction of RANKL, which contributed to the production of more osteoclasts. Importantly, the administration of NF-κB inhibitors in vivo markedly diminished MPs-induced BMSCs senescence and impaired osteogenic differentiation. Meanwhile, the secretion of RANKL caused by MPs was reversed, and osteoclast formation was significantly reduced. In summary, our data innovatively reveal the core mechanism of MPs in bone balance. By promoting the NF-κB signaling pathway, it significantly accelerates the aging of BMSCs, causes a decrease in bone formation, and promotes osteoclast formation through RANKL.

SIRT3 Deficiency Promotes Lung Endothelial Pyroptosis Through Impairing Mitophagy to Activate NLRP3 Inflammasome During Sepsis-Induced Acute Lung Injury

Acute lung injury (ALI) is a major cause of death in bacterial sepsis due to endothelial inflammation and endothelial permeability defects. Mitochondrial dysfunction is recognized as a key mediator in the pathogenesis of sepsis-induced ALI. Sirtuin 3 (SIRT3) is a histone protein deacetylase involved in preservation of mitochondrial function, which has been demonstrated in our previous study. Here, we investigated the effects of SIRT3 deficiency on impaired mitophagy to promote lung endothelial cells (ECs) pyroptosis during sepsis-induced ALI. We found that 3-TYP aggravated sepsis-induced ALI with increased lung ECs pyroptosis and enhanced NLRP3 activation. Mitochondrial reactive oxygen species (mtROS) and extracellular mitochondrial DNA (mtDNA) released from damaged mitochondria could be exacerbated in SIRT3 deficiency, which further elicit NLRP3 inflammasome activation in lung ECs during sepsis-induced ALI. Furthermore, Knockdown of SIRT3 contributed to impaired mitophagy via downregulating Parkin, which resulted in mitochondrial dysfunction. Moreover, pharmacological inhibition NLRP3 or restoration of SIRT3 attenuates sepsis-induced ALI and sepsis severity in vivo. Taken together, our results demonstrated SIRT3 deficiency facilitated mtROS production and cytosolic release of mtDNA by impaired Parkin-dependent mitophagy, promoting to lung ECs pyroptosis through the NLRP3 inflammasome activation, which providing potential therapeutic targets for sepsis-induced ALI.

Enhancing Fracture Healing with 3D Bioprinted Hif1a-Overexpressing BMSCs Hydrogel: A Novel Approach to Accelerated Bone Repair

Addressing the urgent need for effective fracture treatments, this study investigates the efficacy of a 3D bioprinted biomimetic hydrogel, enriched with bone marrow mesenchymal stem cells (BMSCs) and targeted hypoxia-inducible factor 1 alpha (Hif1a) gene activation, in enhancing fracture healing. A photocross-linkable bioink, gelatin methacryloyl bone matrix anhydride (GBMA) is developed, and selected its 5% concentration for bioink formulation. Rat BMSCs are isolated and combined with GBMA to create the GBMA@BMSCs bioink. This bioink is then used in 3D bioprinting to fabricate a hydrogel for application in a rat femoral fracture model. Through transcriptome sequencing, WGCNA, and Venn analysis, the hypoxia-inducible factor Hif1a is identified as a critical gene in the fracture healing process. In vitro studies showed that Hif1a promoted BMSC proliferation, chondrogenic differentiation, and cartilage matrix stability. The in vivo application of the GBMA@BMSCs hydrogel with Hif1a overexpression significantly accelerated fracture healing, evidenced by early and enhanced cartilage callus formation. The study demonstrates that 3D bioprinting of GBMA@BMSCs hydrogel, particularly with Hif1a-enhanced BMSCs, offers a promising approach for rapid and effective fracture repair.

LEP O-GlcNAcylation inactivates NF-κB pathway by suppressing LEP protein level and thus mediates cellular senescence and osteogenic differentiation in mouse mesenchymal stem cells

BACKGROUND

Cellular senescence is a key driver of decreased bone formation and osteoporosis. Leptin (LEP) has been implicated in cellular senescence and osteogenic differentiation. The aim of this study was to investigate the mechanisms by which LEP mediates cellular senescence and osteogenic differentiation.

METHODS

C3H10T1/2 cells were treated with etoposide to induce cellular senescence, which was assessed by β-galactosidase staining. Quantitative real-time PCR and western blotting were used to measure the levels of senescence markers p21 and p16, as well as osteogenic differentiation-related genes ALP, COL1A1, and RUNX2. Alkaline phosphatase (ALP) staining and alizarin red S staining were performed to evaluate osteogenic differentiation. The NF-κB pathway and O-GlcNAcylation were assessed by western blotting.

RESULTS

Etoposide treatment increased the number of senescent cells and the levels of p21 and p16, along with elevated LEP expression. These effects were reversed by LEP knockdown. Additionally, LEP knockdown increased ALP staining density and osteoblast mineralization nodules, as well as the mRNA and protein levels of ALP, COL1A1, and RUNX2, indicating that LEP knockdown promoted osteogenic differentiation in C3H10T1/2 cells. Mechanistically, LEP knockdown inactivated the NF-κB pathway by inhibiting the nuclear translocation of p65. Furthermore, OGT was found to promote O-GlcNAcylation of LEP at the S50 site.

CONCLUSION

Our findings demonstrated that O-GlcNAcylation of LEP inactivated the NF-κB pathway by reducing LEP protein levels, thereby inhibiting cellular senescence and promoting osteogenic differentiation in C3H10T1/2 cells. This study may provide a novel therapeutic target for the treatment of osteoporosis.

The role of CYP-sEH derived lipid mediators in regulating mitochondrial biology and cellular senescence: implications for the aging heart

Cellular senescence is a condition characterized by stable, irreversible cell cycle arrest linked to the aging process. The accumulation of senescent cells in the cardiac muscle can contribute to various cardiovascular diseases (CVD). Telomere shortening, epigenetic modifications, DNA damage, mitochondrial dysfunction, and oxidative stress are known contributors to the onset of cellular senescence in the heart. The link between mitochondrial processes and cellular senescence contributed to the age-related decline in cardiac function. These include changes in mitochondrial functions and behaviours that arise from various factors, including impaired dynamics, dysregulated biogenesis, mitophagy, mitochondrial DNA (mtDNA), reduced respiratory capacity, and mitochondrial structural changes. Thus, regulation of mitochondrial biology has a role in cellular senescence and cardiac function in aging hearts. Targeting senescent cells may provide a novel therapeutic approach for treating and preventing CVD associated with aging. CYP epoxygenases metabolize N-3 and N-6 polyunsaturated fatty acids (PUFA) into epoxylipids that are readily hydrolyzed to diol products by soluble epoxide hydrolase (sEH). Increasing epoxylipids levels or inhibition of sEH has demonstrated protective effects in the aging heart. Evidence suggests they may play a role in cellular senescence by regulating mitochondria, thus reducing adverse effects of aging in the heart. In this review, we discuss how mitochondria induce cellular senescence and how epoxylipids affect the senescence process in the aged heart.

Exploration of Key Regulatory Factors in Mesenchymal Stem Cell Continuous Osteogenic Differentiation via Transcriptomic Analysis

BACKGROUND/OBJECTIVES

Mesenchymal stem cells (MSCs) possess the remarkable ability to differentiate into various cell types, including osteoblasts. Understanding the molecular mechanisms governing MSC osteogenic differentiation is crucial for advancing clinical applications and our comprehension of complex disease processes. However, the key biological molecules regulating this process remain incompletely understood.

METHODS

In this study, we conducted systematic re-analyses of published high-throughput transcriptomic datasets to identify and validate key biological molecules that dynamically regulate MSC osteogenic differentiation. Our approach involved a comprehensive analysis of gene expression patterns across human tissues, followed by the rigorous experimental validation of the identified candidates.

RESULTS

Through integrated analytical and experimental approaches, we utilized high-throughput transcriptomics to identify four critical regulators of MSC osteogenic differentiation: PTBP1, H2AFZ, BCL6, and TTPAL (C20ORF121). Among these, PTBP1 and H2AFZ functioned as positive regulators, while BCL6 and TTPAL acted as negative regulators in osteogenesis. The regulatory roles of these genes in osteogenesis were further validated via overexpression experiments.

CONCLUSIONS

Our findings advance our understanding of MSC differentiation fate determination and open new therapeutic possibilities for bone-related disorders. The identification of these regulators provides a foundation for developing targeted interventions in regenerative medicine.

Identification and experimental validation of PYCARD as a crucial PANoptosis-related gene for immune response and inflammation in COPD

Chronic inflammatory and immune responses play key roles in the development and progression of chronic obstructive pulmonary disease (COPD). PANoptosis, as a unique inflammatory cell death modality, is involved in the pathogenesis of many inflammatory diseases. We aim to identify critical PANoptosis-related biomarkers and explore their potential effects on respiratory tract diseases and immune infiltration landscapes in COPD. Total microarray data consisting of peripheral blood and lung tissue datasets associated with COPD were obtained from the GEO database. PANoptosis-associated genes in COPD were identified by intersecting differentially expressed genes (DEGs) with genes involved in pyroptosis, apoptosis, and necroptosis after normalizing and removing the batch effect. Furthermore, GO, KEGG, PPI network, WGCNA, LASSO-COX, and ROC curves analysis were conducted to screen and verify hub genes, and the correlation between PYCARD and infiltrated immune cells was analyzed. The effect of PYCARD on respiratory tract diseases and the potential small-molecule agents for the treatment of COPD were identified. PYCARD expression was verified in the lung tissue of CS/LPS-induced COPD mice. PYCARD was a critical PANoptosis-related gene in all COPD patients. PYCARD was positively related to NOD-like receptor signaling pathway and promoted immune cell infiltration. Moreover, PYCARD was significantly activated in COPD mice mainly by targeting PANoptosis. PANoptosis-related gene PYCARD is a potential biomarker for COPD diagnosis and treatment.

Enriched H3K27Me3 on BMP4 suppresses the osteoblastic differentiation potential of BMSCs in diabetes mellitus

Diabetes mellitus has been widely acknowledged to have a negative effect on the osteoblastic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). However, the underlying epigenetic mechanisms associated with this process remain to be elucidated. The goal of the present study was to investigate the effect of diabetes mellitus on the osteoblastic differentiation of BMSCs and assess the role of histone methylation in the observed phenomena. The osteoblastic differentiation ability of BMSCs was shown to be decreased in diabetes mellitus, as indicated by alkaline phosphatase activity and the mRNA levels of osteoblast-related genes. Furthermore, diabetes mellitus caused an increased expression of the histone methylase EZH2 and the levels of H3K27Me3 and decreased the expression of the histone demethylase KDM6B, as demonstrated by qRT-PCR and western blotting. Furthermore, immunofluorescence staining suggested that both EZH2 and H3K27Me3 were primarily localized in the nucleus. In addition, chromatin immunoprecipitation assays indicated an increased presence of H3K27Me3 on the promoter region of the BMP4 gene. In summary, in the present study, we demonstrated that the osteoblastic differentiation of BMSCs is dramatically reduced in diabetes mellitus. In addition, upregulation of EZH2 expression and downregulation of KDM6B expression may not be enough to eliminate transcriptional repression mediated by H3K27Me3 on the promoter region of the BMP4 gene during the osteoblastic differentiation of BMSCs in diabetes mellitus.

STING regulates aging-related osteoporosis by mediating the Hk2-Vdac1 mitochondrial axis

Metabolic abnormalities and mild inflammation are hallmarks of aging and major driving factors for aging-related damage and bone metabolic diseases. Mitochondria are crucial links in energy metabolism and immune homeostasis regulation. Mitochondrial dysfunction is considered one of the pathogenic factors of aging-related osteoporosis, but its mechanism of action needs further research. Here, we demonstrated that the interaction between stimulator of interferon genes (STING)-mediated regulation of hexokinase 2 (Hk2)-voltage-dependent anion channel-1 (Vdac1) is a critical factor contributing to mitochondrial dysfunction and osteogenic abnormalities during aging. As the aging process progresses, factors related to aging cause an increase in STING expression, which disrupts the interaction between Hk2 and Vdac1. Dissociation of Hk2 from Vadc1 triggered the opening of the mitochondrial inner mitochondrial permeability transition pore (mPTP), leading to mitochondrial dysfunction and abnormal osteogenic differentiation, thereby disrupting bone homeostasis. In brief, this study demonstrates that STING acts as an intracellular metabolic Checkpoint, influencing mitochondrial function to promote the development of osteoporosis. These findings significantly enhance the development of STING-targeted treatments for aging-related osteoporosis.

BMSC-derived exosomes promote osteoporosis alleviation via M2 macrophage polarization

Osteoporosis is characterized by reduced bone mass due to imbalanced bone metabolism. Exosomes derived from bone mesenchymal stem cells (BMSCs) have been shown to play roles in various diseases. This study aimed to clarify the regulatory function and molecular mechanism of BMSCs-derived exosomes in osteogenic differentiation and their potential therapeutic effects on osteoporosis. Exosomes were extracted from BMSCs. Bone marrow-derived macrophages (BMDMs) were cultured and internalized with BMSCs-derived exosomes. Real-time quantitative PCR was used to detect the expression of macrophage surface markers and tripartite motif (TRIM) family genes. BMDMs were co-cultured with human osteoblasts to assess osteogenic differentiation. Western blot was performed to analyze the ubiquitination of triggering receptor expressed on myeloid cell 1 (TREM1) mediated by TRIM25. An ovariectomized mice model was established to evaluate the role of TRIM25 and exosomes in osteoporosis. Exosomes were successfully isolated from BMSCs. BMSCs-derived exosomes upregulated TRIM25 expression, promoting M2 macrophage polarization and osteogenic differentiation. TRIM25 facilitated the ubiquitination and degradation of TREM1. Overexpression of TREM1 reversed the enhanced M2 macrophage polarization and osteogenic differentiation caused by TRIM25 overexpression. TRIM25 enhanced the protective effect of BMSCs-derived exosomes against bone loss in mice. These findings suggested that BMSCs-derived exosomes promoted osteogenic differentiation by regulating M2 macrophage polarization through TRIM25-mediated ubiquitination and degradation of TREM1. This mechanism might provide a novel approach for treating osteoporosis.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Knocking down EGR1 inhibits nucleus pulposus cell senescence and mitochondrial damage through activation of PINK1-Parkin dependent mitophagy, thereby delaying intervertebral disc degeneration

Mitophagy plays a crucial role in maintaining the homeostasis of intervertebral disc (IVD). Early Growth Response 1 (EGR1), a conservative transcription factor, is commonly upregulated under oxidative stress conditions and participates in regulating cellular senescence, apoptosis, and inflammatory responses. However, the specific role of EGR1 in nucleus pulposus (NP) cell senescence and mitophagy remains unclear. In this study, through bioinformatics analysis and validation using human tissue specimens, we found that EGR1 is significantly upregulated in IVD degeneration (IDD). Further experimental results demonstrate that knockdown of EGR1 inhibits TBHP-induced NP cell senescence and mitochondrial dysfunction while promoting the activation of mitophagy. The protective effect of EGR1 knockdown on NP cell senescence and mitochondrion disappears upon inhibition of mitophagy with mdivi1. Mechanistic studies reveal that EGR1 suppresses NP cell senescence and mitochondrial dysfunction by modulating the PINK1-Parkin dependent mitophagy pathway. Additionally, EGR1 knockdown delays acupuncture-induced IDD in rats. In conclusion, our study demonstrates that under TBHP-induced oxidative stress, EGR1 knockdown mitigates NP cell senescence and mitochondrial dysfunction through the PINK1-Parkin dependent mitophagy pathway, thereby alleviating IDD.

Bilobalide ameliorates osteoporosis by influencing the SIRT3/NF-κB axis in osteoclasts and promoting M2 polarization in macrophages

Osteoporosis is a systemic disease with complex etiology and high prevalence, resulting in a huge economic burden. For a long time, the search for new therapeutic pharmaceuticals has never stopped. Bone loss is related to the imbalance between bone resorption by osteoclasts and bone formation by osteoblasts. In recent years, the role of immunity and inflammation in the development of osteoporosis has studied well. For example, various cytokines, chemokines and endocrine factors regulate osteoclastogenesis via activating different macrophage subtypes, including pro-inflammatory M1 and anti-inflammatory M2. Bilobalide (Bil), an active Ginkgo biloba ingredient, has garnered great interest because of its anti-oxidant and anti-inflammatory activities. In this study, we found that Bil can attenuate osteoclast generation induced by receptor activator of nuclear factor- kappa B ligand (RANKL) through upregulating the sirtuin 3 (SIRT3) and negatively regulating NF-κB signaling. Furthermore, Bil promotes M2 polarization of macrophages in a dose-dependent manner. In vivo studies provided evidence that Bil improves bone density in osteoporosis mice models. Based on the above results, we have reason to believe that Bil has potential therapeutic value in osteoclast-mediated bone loss and offers an effective option for long-term osteoporosis management.

Sirtuin 3-activated superoxide dismutase 2 mediates fluoride-induced osteoblastic differentiation in vitro and in vivo by down-regulating reactive oxygen species

Skeletal fluorosis is a chronic metabolic bone disease caused by long-term excessive fluoride intake. Abnormal differentiation of osteoblasts plays an important role in disease progression. Research on the mechanism of fluoride-mediated bone differentiation is necessary for the prevention and treatment of skeletal fluorosis. In the present study, a rat model of fluorosis was established by exposing it to drinking water containing 50 mg/L F-. We found that fluoride promoted Runt-related transcription factor 2 (RUNX2) as well as superoxide dismutase 2 (SOD2) and sirtuin 3 (SIRT3) expression in osteoblasts of rat bone tissue. In vitro, we also found that 4 mg/L sodium fluoride promoted osteogenesis-related indicators as well as SOD2 and SIRT3 expression in MG-63 and Saos-2 cells. In addition, we unexpectedly discovered that fluoride suppressed the levels of reactive oxygen species (ROS) and mitochondrial reactive oxygen species (mtROS) in osteoblasts. When SOD2 or SIRT3 was inhibited in MG-63 cells, fluoride-decreased ROS and mtROS were alleviated, which in turn inhibited fluoride-promoted osteogenic differentiation. In conclusion, our results suggest that SIRT3/SOD2 mediates fluoride-promoted osteoblastic differentiation by down-regulating reactive oxygen species.

Mitochondrial protein deacetylation by SIRT3 in osteoclasts promotes bone resorption with aging in female mice

OBJECTIVES

The mitochondrial deacetylase sirtuin-3 (SIRT3) is necessary for the increased bone resorption and enhanced function of mitochondria in osteoclasts that occur with advancing age; how SIRT3 drives bone resorption remains elusive.

METHODS

To determine the role of SIRT3 in osteoclast mitochondria, we used mice with conditional loss of Sirt3 in osteoclast lineage and mice with germline deletion of either Sirt3 or its known target Pink1.

RESULTS

SIRT3 stimulates mitochondrial quality in osteoclasts in a PINK1-independent manner, promoting mitochondrial activity and osteoclast maturation and function, thereby contributing to bone loss in female but not male mice. Quantitative analyses of global proteomes and acetylomes revealed that deletion of Sirt3 dramatically increased acetylation of osteoclast mitochondrial proteins, particularly ATPase inhibitory factor 1 (ATPIF1), an essential protein for mitophagy. Inhibition of mitophagy via mdivi-1 recapitulated the effect of deletion of Sirt3 or Atpif1 in osteoclast formation and mitochondrial function.

CONCLUSIONS

Decreasing mitophagic flux in osteoclasts may be a promising pharmacotherapeutic approach to treat osteoporosis in older adults.

Radial extracorporeal shockwave promotes osteogenesis-angiogenesis coupling of bone marrow stromal cells from senile osteoporosis via activating the Piezo1/CaMKII/CREB axis

Radial extracorporeal shockwave (r-ESW) and bone marrow stromal cells (BMSCs) have been reported to alleviate senile osteoporosis (SOP), but its regulatory mechanism remains unclear. In this study, we firstly isolated human BMSCs from bone marrow samples and treated with varying r-ESW doses. And we found that r-ESW could enhance the proliferation of SOP-BMSCs in a dose-dependent manner by EdU assay. Subsequently, the impact of r-ESW on the proliferation, apoptosis and multipotency of BMSCs was assessed. And the outcomes of flow cytometry, Alizarin red S (ARS), and tube formation test demonstrated that the optimal shockwave obviously boosted SOP-BMSCs osteogenesis and angiogenesis but exhibited no significant impact on cell apoptosis. Additionally, the signaling of Piezo1 and CaMKII/CREB was examined by Western blotting, qPCR and immunofluorescence. And the results showed that r-ESW promoted the expression of Piezo1, increased intracellular Ca2+ and activated the CaMKII/CREB signaling pathway. Then, the application of Piezo1 siRNA hindered the r-ESW-induced enhancement ability of osteogenesis coupling with angiogenesis of SOP-BMSCs. The use of the CaMKII/CREB signaling pathway inhibitor KN93 suppressed the Piezo1-induced increase in osteogenesis and angiogenesis in SOP-BMSCs. Finally, we also found that r-ESW might alleviate SOP in the senescence-accelerated mouse prone 6 (SAMP6) model by activating Piezo1. In conclusion, our research offers experimental evidence and an elucidated underlying molecular mechanism to support the use of r-ESW as a credible rehabilitative treatment for senile osteoporosis.

Senescence of skeletal stem cells and their contribution to age-related bone loss

Human aging is linked to bone loss, resulting in bone fragility and an increased risk of fractures. This is primarily due to an age-related decline in the function of bone-forming osteoblastic cells and accelerated cellular senescence within the bone microenvironment. Here, we provide a detailed discussion of the hypothesis that age-related defective bone formation is caused by senescence of skeletal stem cells, as they are the main source of bone forming osteoblastic cells and influence the composition of bone microenvironment. Furthermore, this review discusses potential strategies to target cellular senescence as an emerging approach to treat age-related bone loss.

Enhanced osteogenic differentiation in 3D hydrogel scaffold via macrophage mitochondrial transfer

To assess the efficacy of a novel 3D biomimetic hydrogel scaffold with immunomodulatory properties in promoting fracture healing. Immunomodulatory scaffolds were used in cell experiments, osteotomy mice treatment, and single-cell transcriptomic sequencing. In vitro, fluorescence tracing examined macrophage mitochondrial transfer and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Scaffold efficacy was assessed through alkaline phosphatase (ALP), Alizarin Red S (ARS) staining, and in vivo experiments. The scaffold demonstrated excellent biocompatibility and antioxidant-immune regulation. Single-cell sequencing revealed a shift in macrophage distribution towards the M2 phenotype. In vitro experiments showed that macrophage mitochondria promoted BMSCs' osteogenic differentiation. In vivo experiments confirmed accelerated fracture healing. The GAD/Ag-pIO scaffold enhances osteogenic differentiation and fracture healing through immunomodulation and promotion of macrophage mitochondrial transfer.

Revealing the key role of cuproptosis in osteoporosis via the bioinformatic analysis and experimental validation of cuproptosis-related genes

The incidence of osteoporosis has rapidly increased owing to the ageing population. Cuproptosis, a novel mechanism that regulates cell death, may be a new therapeutic approach. However, the relevance of cuproptosis in the immune microenvironment and osteoporosis immunotherapy is still unknown. We intersected the differentially expressed genes from osteoporotic samples with 75 cuproptosis-related genes to identify 16 significantly expressed cuproptosis genes. We further explored the connection between the cuproptosis pattern, immune microenvironment, and immunotherapy. The weighted gene co-expression network analysis algorithm was used to identify cuproptosis phenotype-associated genes, and we used quantitative real-time PCR and immunohistochemistry in mouse femur tissues to verify hub gene (MAP2K2, FDX1, COX19, VEGFA, CDKN2A, and NFE2L2) expression. Six hub genes and 59 cuproptosis phenotype-associated genes involved in immunisation were identified among the osteoporosis and control groups, and the majority of these 59 genes were enriched in the inflammatory response, as well as in signal transducers, Janus kinase, and transcription pathway activators. In addition, two different clusters of cuproptosis were found, and immune infiltration analysis showed that gene Cluster 1 had a greater immune score and immune infiltration level. Further analysis revealed that three key genes (COX19, MAP2K2, and FDX1) were highly correlated with immune cell infiltration, and external experiments validated the association of these three genes with the prognosis of osteoporosis. We used the three key mRNAs COX19, MAP2K2, and FDX1 as a classification model that may systematically elucidate the complex connection between cuproptosis and the immune microenvironment of osteoporosis. New insights into osteoporosis pathogenesis and immunotherapy prospects may be gained from this study.