SIRT1, a promising regulator of bone homeostasis

Anti-osteoporosis effect of bioactives in edible medicinal plants: a comprehensive review

Current treatments for osteoporosis include a calcium-rich diet, adequate exercise, and medication. Many synthetic drugs, although fast-acting, can cause a range of side effects for patients when taken over a long period, such as irritation of the digestive tract and a burden on the kidneys. As the world's population ages, the prevalence of osteoporosis is increasing, and the development of safe and effective treatments is urgently needed. Active compounds in edible and medicinal homologous plants have been used for centuries to improve bone quality. It is possible to employ them as dietary supplements to prevent osteoporosis. In this review, we analyze the influencing factors of osteoporosis and systematically summarize the research progress on the anti-osteoporosis effects of active compounds in edible and medicinal homologous plants. The literature suggests that some naturally occurring active compounds in edible and medicinal homologous plants can inhibit bone loss, prevent the degeneration of bone cell microstructure, and reduce bone fragility through alleviating oxidative stress, regulating autophagy, anti-inflammation, improving gut flora, and regulating estrogen level with little side effects. Our review provides useful guidance for the use of edible and medicinal homologous plants and the development of safer novel anti-osteoporosis dietary supplements.

SIRT1 activation promotes bone repair by enhancing the coupling of type H vessel formation and osteogenesis

Bone repair is intricately correlated with vascular regeneration, especially of type H vessels. Sirtuin 1 (SIRT1) expression is closely associated with endothelial function and vascular regeneration; however, the role of SIRT1 in enhancing the coupling of type H vessel formation with osteogenesis to promote bone repair needs to be investigated. A co-culture system combining human umbilical vein endothelial cells and osteoblasts was constructed, and a SIRT1 agonist was used to evaluate the effects of SIRT1 activity. The angiogenic and osteogenic capacities of the co-culture system were examined using short interfering RNA. Mouse models with bone defects in the femur or mandible were established to explore changes in type H vessel formation and bone repair following modulated SIRT1 activity. SIRT1 activation augmented the angiogenic and osteogenic capacities of the co-culture system by activating the PI3K/AKT/FOXO1 signalling pathway and did not significantly regulate osteoblast differentiation. Inhibition of the PI3K/AKT/FOXO1 pathway attenuated SIRT1-mediated effects. The SIRT1 activity in bone defects was positively correlated with the formation of type H vessels and bone repair in vivo, whereas SIRT1 inhibition substantially weakened vascular and bone formation. Thus, SIRT1 is crucial to the coupling of type H vessels with osteogenesis during bone repair.

Excess glucose alone depress young mesenchymal stromal/stem cell osteogenesis and mitochondria activity within hours/days via NAD+/SIRT1 axis

BACKGROUND

The impact of global overconsumption of simple sugars on bone health, which peaks in adolescence/early adulthood and correlates with osteoporosis (OP) and fracture risk decades, is unclear. Mesenchymal stromal/stem cells (MSCs) are the progenitors of osteoblasts/bone-forming cells, and known to decrease their osteogenic differentiation capacity with age. Alarmingly, while there is correlative evidence that adolescents consuming greatest amounts of simple sugars have the lowest bone mass, there is no mechanistic understanding on the causality of this correlation.

METHODS

Bioinformatics analyses for energetics pathways involved during MSC differentiation using human cell information was performed. In vitro dissection of normal versus high glucose (HG) conditions on osteo-/adipo-lineage commitment and mitochondrial function was assessed using multi-sources of non-senescent human and murine MSCs; for in vivo validation, young mice was fed normal or HG-added water with subsequent analyses of bone marrow CD45- MSCs.

RESULTS

Bioinformatics analyses revealed mitochondrial and glucose-related metabolic pathways as integral to MSC osteo-/adipo-lineage commitment. Functionally, in vitro HG alone without differentiation induction decreased both MSC mitochondrial activity and osteogenesis while enhancing adipogenesis by 8 h' time due to depletion of nicotinamide adenine dinucleotide (NAD+), a vital mitochondrial co-enzyme and co-factor to Sirtuin (SIRT) 1, a longevity gene also involved in osteogenesis. In vivo, HG intake in young mice depleted MSC NAD+, with oral NAD+ precursor supplementation rapidly reversing both mitochondrial decline and osteo-/adipo-commitment in a SIRT1-dependent fashion within 1 ~ 5 days.

CONCLUSIONS

We found a surprisingly rapid impact of excessive glucose, a single dietary factor, on MSC SIRT1 function and osteogenesis in youthful settings, and the crucial role of NAD+-a single molecule-on both MSC mitochondrial function and lineage commitment. These findings have strong implications on future global OP and disability risks in light of current worldwide overconsumption of simple sugars.

SIRT5 promote malignant advancement of chordoma by regulating the desuccinylation of c-myc

Chordoma is a relatively rare and locally aggressive malignant tumor. Sirtuin (SIRT)5 plays pivotal roles in various tumors, but the role of SIRT5 in chordoma has not been found. This study was performed to investigate the regulatory effects of SIRT5 on cell proliferation, migration, and invasion and the underlying mechanism in chordoma. A xenograft tumor mouse model was established to assess tumor growth. Reverse transcription-quantitative polymerase chain reaction was used to analyze the mRNA levels of SIRT5 and c-myc. The effects of SIRT5 and c-myc on cell proliferation, migration, and invasion of chordoma cells were detected by cell counting kit-8, colony formation, and Transwell assays. The interaction between SIRT5 and c-myc was evaluated by co-immunoprecipitation (IP) assay. The succinylation of c-myc was analyzed by IP and Western blot. The results showed that SIRT5 expression was upregulated in chordoma tissues and cells. SIRT5 interacted with c-myc to inhibit the succinylation of c-myc at K369 site in human embryonic kidney (HEK)-293T cells. Silencing of SIRT5 suppressed the cell proliferation, migration, and invasion of chordoma cells, while the results were reversed after c-myc overexpression. Moreover, silencing SIRT5 suppressed tumor growth in mice. These findings suggested that SIRT5 promoted the malignant advancement of chordoma by regulating the desuccinylation of c-myc.

Analysis of SIRT1 Gene SNPs and Clinical Characteristics in Medication-Related Osteonecrosis of the Jaw

Certain genetic factors, including single-nucleotide polymorphisms (SNPs) in the SIRT1 gene, have been linked to medication-related osteonecrosis of the jaw (MRONJ). This study examined four SNPs in the SIRT1 gene and implemented multivariate statistical analysis to analyze genetic and clinical factors in MRONJ patients. Genomic DNA was isolated from peripheral blood samples of 63 patients of European origin treated for MRONJ, and four SNP genotypes in the gene encoding the SIRT-1 protein were determined by Sanger sequencing. The allele frequencies measured in the MRONJ population were compared with allele frequencies measured in the European population in the National Center for Biotechnology Information Allele Frequency Aggregator (NCBI ALFA) database. Genetic and clinical factors were examined with multivariate statistical analysis. A C:A allele distribution ratio of 77.8:22.2 was measured in the rs932658 SNP. In the ALFA project, a C:A allele distribution ratio of 59.9:40.1 was detected in the European population, which was found to be a significant difference (p = 4.5 × 10-5). Multivariate statistical analysis revealed a positive correlation (0.275) between the genotype of SNP rs932658 and the number of stages improved during appropriate MRONJ therapy. It is concluded that allele A in SNP rs932658 in the SIRT1 gene acts as a protective factor in MRONJ.

Emerging roles of SIRT1 activator, SRT2104, in disease treatment

Silent information regulator 1 (SIRT1) is a NAD+-dependent class III deacetylase that plays important roles in the pathogenesis of numerous diseases, positioning it as a prime candidate for therapeutic intervention. Among its modulators, SRT2104 emerges as the most specific small molecule activator of SIRT1, currently advancing into the clinical translation phase. The primary objective of this review is to evaluate the emerging roles of SRT2104, and to explore its potential as a therapeutic agent in various diseases. In the present review, we systematically summarized the findings from an extensive array of literature sources including the progress of its application in disease treatment and its potential molecular mechanisms by reviewing the literature published in databases such as PubMed, Web of Science, and the World Health Organization International Clinical Trials Registry Platform. We focuses on the strides made in employing SRT2104 for disease treatment, elucidating its potential molecular underpinnings based on preclinical and clinical research data. The findings reveal that SRT2104, as a potent SIRT1 activator, holds considerable therapeutic potential, particularly in modulating metabolic and longevity-related pathways. This review establishes SRT2104 as a leading SIRT1 activator with significant therapeutic promise.

Prevention and Co-Management of Breast Cancer-Related Osteoporosis Using Resveratrol

Breast cancer (BC) is currently one of the most common cancers in women worldwide with a rising tendency. Epigenetics, generally inherited variations in gene expression that occur independently of changes in DNA sequence, and their disruption could be one of the main causes of BC due to inflammatory processes often associated with different lifestyle habits. In particular, hormone therapies are often indicated for hormone-positive BC, which accounts for more than 50-80% of all BC subtypes. Although the cure rate in the early stage is more than 70%, serious negative side effects such as secondary osteoporosis (OP) due to induced estrogen deficiency and chemotherapy are increasingly reported. Approaches to the management of secondary OP in BC patients comprise adjunctive therapy with bisphosphonates, non-steroidal anti-inflammatory drugs (NSAIDs), and cortisone, which partially reduce bone resorption and musculoskeletal pain but which are not capable of stimulating the necessary intrinsic bone regeneration. Therefore, there is a great therapeutic need for novel multitarget treatment strategies for BC which hold back the risk of secondary OP. In this review, resveratrol, a multitargeting polyphenol that has been discussed as a phytoestrogen with anti-inflammatory and anti-tumor effects at the epigenetic level, is presented as a potential adjunct to both support BC therapy and prevent osteoporotic risks by positively promoting intrinsic regeneration. In this context, resveratrol is also known for its unique role as an epigenetic modifier in the regulation of essential signaling processes-both due to its catabolic effect on BC and its anabolic effect on bone tissue.

Mitochondrial dysfunction and therapeutic perspectives in osteoporosis

Osteoporosis (OP) is a systemic skeletal disorder characterized by reduced bone mass and structural deterioration of bone tissue, resulting in heightened vulnerability to fractures due to increased bone fragility. This condition primarily arises from an imbalance between the processes of bone resorption and formation. Mitochondrial dysfunction has been reported to potentially constitute one of the most crucial mechanisms influencing the pathogenesis of osteoporosis. In essence, mitochondria play a crucial role in maintaining the delicate equilibrium between bone formation and resorption, thereby ensuring optimal skeletal health. Nevertheless, disruption of this delicate balance can arise as a consequence of mitochondrial dysfunction. In dysfunctional mitochondria, the mitochondrial electron transport chain (ETC) becomes uncoupled, resulting in reduced ATP synthesis and increased generation of reactive oxygen species (ROS). Reinforcement of mitochondrial dysfunction is further exacerbated by the accumulation of aberrant mitochondria. In this review, we investigated and analyzed the correlation between mitochondrial dysfunction, encompassing mitochondrial DNA (mtDNA) alterations, oxidative phosphorylation (OXPHOS) impairment, mitophagy dysregulation, defects in mitochondrial biogenesis and dynamics, as well as excessive ROS accumulation, with regards to OP (Figure 1). Furthermore, we explore prospective strategies currently available for modulating mitochondria to ameliorate osteoporosis. Undoubtedly, certain therapeutic strategies still require further investigation to ensure their safety and efficacy as clinical treatments. However, from a mitochondrial perspective, the potential for establishing effective and safe therapeutic approaches for osteoporosis appears promising.

Icariin promotes osteogenic differentiation of human bone marrow mesenchymal stem cells by regulating USP47/SIRT1/Wnt/β-catenin

Icariin has been shown to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). However, the underlying molecular mechanism by which Icariin regulates osteogenic differentiation needs to be further revealed. The viability of BMSCs was assessed by cell counting kit 8 assay. BMSC osteogenic differentiation ability was evaluated by detecting alkaline phosphatase activity and performing alizarin red S staining. The protein levels of osteogenic differentiation-related markers, sirtuin 1 (SIRT1), ubiquitin-specific protease 47 (USP47), and Wnt/β-catenin-related markers were determined using western blot. SIRT1 mRNA level was measured using quantitative real-time PCR. The regulation of USP47 on SIRT1 was confirmed by ubiquitination detection and co-immunoprecipitation analysis. Icariin could promote BMSC osteogenic differentiation. SIRT1 expression was enhanced by Icariin, and its knockdown suppressed Icariin-induced BMSC osteogenic differentiation. Moreover, deubiquitinating enzyme USP47 could stabilize SIRT1 protein expression. Besides, SIRT1 overexpression reversed the inhibiting effect of USP47 knockdown on BMSC osteogenic differentiation, and USP47 knockdown also restrained Icariin-induced BMSC osteogenic differentiation. Additionally, Icariin enhanced the activity of the Wnt/β-catenin pathway by upregulating SIRT1. Icariin facilitated BMSC osteogenic differentiation via the USP47/SIRT1/Wnt/β-catenin pathway.

Identifying potential ferroptosis key genes for diagnosis and treatment of postmenopausal osteoporosis through competitive endogenous RNA network analysis

Objective

Postmenopausal osteoporosis (PMOP) is a common systemic metabolic bone disorder that is owing to the reduced estrogen secretion and imbalance of bone absorption and bone formation in postmenopausal women. Ferroptosis has been identified as a novel modulatory mechanism of osteoporosis. Nevertheless, the particular modulatory mechanism between ferroptosis and PMOP is still unclear. The objective of the current investigation was to detect potential biomarkers connected to ferroptosis in PMOP and discover its probable mechanism through bioinformatics.

Methods

We downloaded PMOP-related microarray datasets from the database of Gene Expression Omnibus (GEO) and obtained the differentially expressed genes (DEGs). Utilizing bioinformatics analysis, the DEGs were intersected with the ferroptosis dataset to obtain ferroptosis-connected mRNAs. Enrichment analysis employing KOBAS 3.0 was conducted to comprehend the biological functions and enrichment pathways of the DEGs. The generation of the protein-protein interaction (PPI) network was conducted with the aim of identifying central genes. Lastly, the coexpression and competitive endogenous RNA (ceRNA) networks were built using Cytoscape. With the help of external datasets GSE56815 to verify the reliability of the hub genes by plotting ROC curves.

Results

We identified 178 DE microRNAs (miRNAs), 138 DE circular RNAs (circRNAs), and 86 ferroptosis-related mRNAs. Enrichment analysis exhibited that mRNAs were primarily connected with the signaling pathways of PI3K/Akt, metabolism, mTOR, FoxO, HIF-1, AMPK, MAPK, ferroptosis, VEGF, and NOD-like receptors. Generation of the PPI network detected eight hub genes. The circRNA/miR-23b-3p/PTEN axis may relieve PMOP by inhibiting ferroptosis through targeting the pathway of PI3K/Akt signaling, which is a vital modulatory pathway for PMOP progression. Moreover, the ROC curves ultimately indicates that the four hub genes have greater diagnostic importance in PMOP samples in contrast to the normal group samples, which may be possible markers for PMOP diagnosis.

Conclusions

Bioinformatics analysis identified four hub genes, namely, PTEN, SIRT1, VEGFA, and KRAS, as potential biomarkers for PMOP diagnosis and management. Moreover, the circRNA/miR-23b-3p/PTEN axis may relieve PMOP by suppressing ferroptosis through targeting the pathway of PI3K/Akt signaling, providing a new avenue to explore the pathogenesis of PMOP.

Potential Roles for B cells and Autoantibodies in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease that predominantly affects young males. AS is a condition in which the spine and sacroiliac joints become inflamed. More specifically, most AS patients experience spine malformations over time, resulting in functional incapability. The etiopathogenesis of AS is a complex combination of genetic predisposition and environmental factors. Extensive studies on AS have revealed the central role of genetics and immune reactions in its etiology. However, an utmost agreement has yet to be created. The available evidence suggests that both autoinflammation and T-cell-mediated autoimmune processes have significant roles in the disease process of AS. So far, B cells have obtained moderately little attention in AS pathogenesis, primarily because of the absence of disease-defining autoantibodies. However, against general dogma, evidence is mounting showing B cell involvement. Disruptions depict this in circulating B cell populations, the increased expression of immunoglobulin (Ig)G, IgA, and IgM, and B cell infiltration within the axial skeleton of AS patients. Meanwhile, compared to many other inflammatory autoimmune disorders, AS has no disease-specific autoantibodies that help disease diagnosis. This study has provided an overview of the B lymphocytes and antibodies' role in AS pathogenesis. It also introduces autoantibodies that can be the prognosis and diagnosis biomarkers of AS.

5-(3',4'-dihydroxyphenyl)-γ-valerolactone, a microbiota metabolite of flavan-3-ols, activates SIRT1-mediated autophagy to attenuate H₂O₂-induced inhibition of osteoblast differentiation in MC3T3-E1 cells

Phenolic compounds are promising agents for the prevention of osteoporosis. 5-(3',4'-dihydroxyphenyl)-γ-valerolactone (DHPV) is the major microbiota metabolite of the flavan-3-ols phenolic compound. Herein, we aimed to investigate the potential mechanisms underlying the effects of DHPV on an osteoblast cell model with H2O2-induced oxidative injury. The MC3T3-E1 cell cultured with H2O2 was used as an oxidative injury model after pretreating with DHPV. Pretreatment with DHPV significantly attenuated cell viability decline, enhanced the activity of alkaline phosphatase and mineralization capacity in MC3T3-E1 cells. Reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels as well as increased in mitochondrial membrane potential and superoxide dismutase (SOD) activities indicated that DHPV affected both the oxidative and antioxidative processes in the cells. DHPV administration increased the LC3-II/I ratio and Beclin-1 protein levels, thereby promoting autophagy, which perhaps contributes to ROS elimination. However, the inhibition of Sirtuin 1 (SIRT1) by SIRT1 small interfering RNA reduced the protective effect of DHPV or SRT1720, as revealed by the increased ROS and MDA levels and decreased SOD, LC3-II/I ratio and Beclin-1 levels. DHPV may promote autophagy and reduce oxidative stress through the SIRT1-mediated pathway, thereby protecting MC3T3-E1 cells from H2O2-induced oxidative damage.

The role of non-coding RNAs in diabetes-induced osteoporosis

Diabetes mellitus (DM) and osteoporosis are two major health care problems worldwide. Emerging evidence suggests that DM poses a risk for osteoporosis and can contribute to the development of diabetes-induced osteoporosis (DOP). Interestingly, some epidemiological studies suggest that DOP may be at least partially distinct from those skeletal abnormalities associated with old age or postmenopausal osteoporosis. The increasing number of DM patients who also have DOP calls for a discussion of the pathogenesis of DOP and the investigation of drugs to treat DOP. Recently, non-coding RNAs (ncRNAs) have received more attention due to their significant role in cellular functions and bone formation. It is worth noting that ncRNAs have also been demonstrated to participate in the progression of DOP. Meanwhile, nano-delivery systems are considered a promising strategy to treat DOP because of their cellular targeting, sustained release, and controlled release characteristics. Additionally, the utilization of novel technologies such as the CRISPR system has expanded the scope of available options for treating DOP. Hence, this paper explores the functions and regulatory mechanisms of ncRNAs in DOP and highlights the advantages of employing nanoparticle-based drug delivery techniques to treat DOP. Finally, this paper also explores the potential of ncRNAs as diagnostic DOP biomarkers.

Biodegradable Implants for Internal Fixation of Fractures and Accelerated Bone Regeneration

Bone fractures have always been a burden to patients due to their common occurrence and severe complications. Traditionally, operative treatments have been widely used in the clinic for implanting, despite the fact that they can only achieve bone fixation with limited stability and pose no effect on promoting tissue growth. In addition, the nondegradable implants usually need a secondary surgery for implant removal, otherwise they may block the regeneration of bones resulting in bone nonunion. To overcome the low degradability of implants and avoid multiple surgeries, tissue engineers have investigated various biodegradable materials for bone regeneration, whereas the significance of stability of long-term bone fixation tends to be neglected during this process. Combining the traditional orthopedic implantation surgeries and emerging tissue engineering, we believe that both bone fixation and bone regeneration are indispensable factors for a successful bone repair. Herein, we define such a novel idea as bone regenerative fixation (BRF), which should be the main future development trend of biodegradable materials.

Safranal inhibits estrogen-deficiency osteoporosis by targeting Sirt1 to interfere with NF-κB acetylation

BACKGROUND

Osteoporosis is a prevalent bone metabolic disease in menopause, and long-term medication is accompanied by serious side effects. Estrogen deficiency-mediated hyperactivated osteoclasts is the initiating factor for bone loss, which is regulated by nuclear factor-κB (NF-κB) signaling. Safranal (Saf) is a monoterpene aldehyde produced from Saffron (Crocus sativus L.) and possesses multiple biological properties, particularly the anti-inflammatory property. However, Saf's role in osteoporosis remains unknown.

PURPOSE

This study aims to validate the role of Saf in osteoporosis and explore the potential mechanism.

STUDY DESIGN

The RANKL-exposed mouse BMM (bone marrow monocytes) and the castration-mediated osteoporosis model were applied to explore the effect and mechanism of Saf in vitro and in vivo.

METHOD

The effect of Saf on osteoclast formation and function were assessed by TRAcP staining, bone-resorptive experiment, qPCR, immunoblotting and immunofluorescence, etc. Micro-CT, HE, TRAcP and immunohistochemical staining were performed to estimate the effects of Saf administration on OVX-mediated osteoporosis in mice at imaging and histological levels.

RESULTS

Saf concentration-dependently inhibited RANKL-mediated osteoclast differentiation without affecting cellular viability. Meanwhile, Saf-mediated anti-osteolytic capacity and Sirt1 upregulation were also found in ovariectomized mice. Mechanistically, Saf interfered with NF-κB signaling by activating Sirt1 to increase p65 deacetylation and inactivating IKK to decrease IκBα degradation.

CONCLUSION

Our results support the potential application of Saf as a therapeutic agent for osteoporosis.

Revisiting Resveratrol as an Osteoprotective Agent: Molecular Evidence from In Vivo and In Vitro Studies

Resveratrol (RSV) (3,5,4'-trihydroxystilbene) is a stilbene found in abundance in berry fruits, peanuts, and some medicinal plants. It has a diverse range of pharmacological activities, underlining the significance of illness prevention and health promotion. The purpose of this review was to delve deeper into RSV's bone-protective properties as well as its molecular mechanisms. Several in vivo studies have found the bone-protective effects of RSV in postmenopausal, senile, and disuse osteoporosis rat models. RSV has been shown to inhibit NF-κB and RANKL-mediated osteoclastogenesis, oxidative stress, and inflammation while increasing osteogenesis and boosting differentiation of mesenchymal stem cells to osteoblasts. Wnt/β-catenin, MAPKs/JNK/ERK, PI3K/AKT, FoxOs, microRNAs, and BMP2 are among the possible kinases and proteins involved in the underlying mechanisms. RSV has also been shown to be the most potent SIRT1 activator to cause stimulatory effects on osteoblasts and inhibitory effects on osteoclasts. RSV may, thus, represent a novel therapeutic strategy for increasing bone growth and reducing bone loss in the elderly and postmenopausal population.

C-reactive protein predicts endocortical expansion but not fracture in older men: the prospective STRAMBO study

In older men, higher high-sensitivity C-reactive protein (hsCRP) concentrations were associated with faster prospectively assessed endocortical expansion (distal radius, distal tibia) and slightly higher cortical bone loss at distal tibia, but not with the fracture risk. High hsCRP level has a limited impact on bone decline in older men.

PURPOSE

Data on the link of the high-sensitivity C-reactive protein (hsCRP) with bone loss and fracture risk are discordant. We studied the association of the hsCRP with the prospectively assessed decrease in areal bone mineral density (aBMD), bone microarchitecture decline, and fracture risk in older men.

METHODS

At baseline, hsCRP was measured in 823 men aged 60-88. Areal BMD and bone microarchitecture (distal radius, distal tibia) were assessed by dual-energy X-ray absorptiometry and high-resolution peripheral QCT, respectively, at baseline and after 4 and 8 years. Data on incident fractures were collected for 8 years.

RESULTS

Higher hsCRP concentration was associated with faster increase in aBMD at the whole body and lumbar spine, but not other sites. Higher hsCRP levels were associated with faster decrease in cortical area and more rapid increase in trabecular area at the distal radius (0.048 mm²/year/SD, p < 0.05) and distal tibia (0.123 mm²/year/SD, p < 0.001). At the distal tibia, high hsCRP level was associated with greater decrease in total and cortical volumetric BMD (vBMD) and in failure load. The hsCRP levels were not associated with the fracture risk, even after accounting for competing risk of death.

CONCLUSION

Higher hsCRP levels were associated with greater endocortical expansion at the distal radius and tibia. Higher hsCRP was associated with slightly faster decrease in total and cortical vBMD and failure load at distal tibia, but not with the fracture risk. Thus, high hsCRP levels are associated with faster cortical bone loss, but not with fracture risk in older men.

SIRT1 as a Potential Therapeutic Target for Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable disease characterized by irreversible airflow obstruction and lung function decline. It is well established that COPD represents a major cause of morbidity and mortality globally. Due to the substantial economic and social burdens associated with COPD, it is necessary to discover new targets and develop novel beneficial therapies. Although the pathogenesis of COPD is complex and remains to be robustly elucidated, numerous studies have shown that oxidative stress, inflammatory responses, cell apoptosis, autophagy, and aging are involved in the pathogenesis of COPD. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase belonging to the silent information regulator 2 (Sir2) family. Multiple studies have indicated that SIRT1 plays an important role in oxidative stress, apoptosis, inflammation, autophagy, and cellular senescence, which contributes to the pathogenesis and development of COPD. This review aimed to discuss the functions and mechanisms of SIRT1 in the progression of COPD and concluded that SIRT1 activation might be a potential therapeutic strategy for COPD.

How Has Molecular Biology Enhanced Our Undertaking of axSpA and Its Management

PURPOSE

This review aims at investigating pathophysiological mechanisms in spondyloarthritis (SpA). Analysis of genetic factors, immunological pathways, and abnormalities of bone metabolism lay the foundations for a better understanding of development of the axial clinical manifestations in patients, allowing physician to choose the most appropriate therapeutic strategy in a more targeted manner.

RECENT FINDINGS

In addition to the contribution of MHC system, findings emerged about the role of non-HLA genes (as ERAP1 and 2, whose inhibition could represent a new therapeutic approach) and of epigenetic mechanisms that regulate the expression of genes involved in SpA pathogenesis. Increasing evidence of bone metabolism abnormalities secondary to the activation of immunological pathways suggests the development of various bone anomalies that are present in axSpA patients. SpA are a group of inflammatory diseases with a multifactorial origin, whose pathogenesis is linked to the genetic predisposition, the action of environmental risk factors, and the activation of immune response. It is now well known how bone metabolism leads to long-term structural damage via increased bone turnover, bone loss and osteoporosis, osteitis, erosions, osteosclerosis, and osteoproliferation. These effects can exist in the same patient over time or even simultaneously. Evidence suggests a cross relationship among innate immunity, autoimmunity, and bone remodeling in SpA, making treatment approach a challenge for rheumatologists. Specifically, treatment targets are consistently increasing as new drugs are upcoming. Both biological and targeted synthetic drugs are promising in terms of their efficacy and safety profile in patients affected by SpA.

Reversing the imbalance in bone homeostasis via sustained release of SIRT-1 agonist to promote bone healing under osteoporotic condition

The imbalance of bone homeostasis is the root cause of osteoporosis. However current therapeutic approaches mainly focus on either anabolic or catabolic pathways, which often fail to turn the imbalanced bone metabolism around. Herein we reported that a SIRT-1 agonist mediated molecular therapeutic strategy to reverse the imbalance in bone homeostasis by simultaneously regulating osteogenesis and osteoclastogenesis via locally sustained release of SRT2104 from mineral coated acellular matrix microparticles. Immobilization of SRT2104 on mineral coating (MAM/SRT) harnessing their electrostatic interactions resulted in sustained release of SIRT-1 agonist for over 30 days. MAM/SRT not only enhanced osteogenic differentiation and mineralization, but also attenuated the formation and function of excessive osteoclasts via integrating multiple vital upstream signals (β-catenin, FoxOs, Runx2, NFATc1, etc.) in vitro. Osteoporosis animal model also validated that it accelerated osteoporotic bone healing and improved osseointegration of the surrounding bone. Overall, our work proposes a promising strategy to treat osteoporotic bone defects by reversing the imbalance in bone homeostasis using designated small molecule drug delivery systems.

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A mineral coated acellular matrix microcarriers sustainably release SIRT2104 more than 30 days.

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This drug delivery system regulates osteogenesis and osteoclastogenesis.

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It can accelerate osteoporotic bone healing by reversing the imbalance in bone homeostasis.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

SIRT1/Notch1 signal axis involves in the promoting effect of Segetalin B on bone formation

Phytoestrogens are a class of potential natural medicines for treating postmenopausal osteoporosis (PMOP). Segetalin B (SB) is a cyclic peptide compound showing estrogenic activity. This study reports the effect of SB on bone formation among ovariectomized (OVX) rats. The bone marrow mesenchymal stem cells (BMSCs) from OVX rats were cultured in vitro. Alizarin Red staining was utilized to observe the effect of SB on the mineralization of BMSCs. The levels of alkaline phosphatase (ALP), osteocalcin, bone morphogenetic protein (BMP-2), and Sirtuin 1 (SIRT1) activities were detected. The OVX rats were treated with SB in vivo. Micro-CT was utilized for imaging analysis. Urine calcium and phosphorus, and ALP activity in bone marrow were assayed. Western blot analysis and immunofluorescence were incorporated to detect protein expressions in vitro and in vivo. The results showed that SB dose-dependently promoted mineralization of OVX rat-derived BMSCs in vitro increased the level of Osteocalcin, BMP-2, ALP, and SIRT1 activity. Moreover, it upregulated expressions of Runx2, Osterix, and SIRT1, downregulated expressions of Notch intracellular domain (NICD), acetyl-NICD, and hairy and enhancer of split 1 (Hes1). In addition, SB treatment significantly decreased bone loss, inhibited calcium and phosphorus loss, elevated ALP activity, upregulated Runx2, Osterix, and SIRT1, and downregulated NICD and Hes1 in OVX rats in vivo. However, EX527, a SIRT1-selective inhibitor, could reverse the above effects of SB in vitro or in vivo. These results indicate that SB is a potential natural medicine to improve PMOP. Thus, its mechanism of promoting bone formation involves the SIRT1/Notch1 signaling axis.

L-arginine protects cementoblasts against hypoxia-induced apoptosis through Sirt1-enhanced autophagy

BACKGROUND

L-arginine (L-arg) can reduce apoptosis in a variety of cells. Cementoblast apoptosis is related to root resorption during orthodontic treatment. In the present study, we aimed to study the regulatory effect and potential mechanism of L-arg on cementoblast apoptosis and root resorption.

METHODS

The apoptosis-related mRNA and protein expression of murine cementoblast (OCCM-30) was assessed after L-arg treatment. To investigate the role of Sirtuin 1 (Sirt1) and autophagy in L-arg resistance to cementoblast apoptosis and root absorption, resveratrol, and EX527 were used to activate or inhibit Sirt1, and chloroquine (CQ) was used to inhibit autophagy.

RESULTS

In vitro, L-arg inhibited hypoxia-induced apoptosis in OCCM-30. Further, L-arg increased Sirt1 expression whereas Sirt1 suppression by EX527 reversed the inhibitory effect of L-arg on cell apoptosis. Sirt1 activator resveratrol increased the ratio of microtubule-associated protein light chain 3 (LC3) II/I and decreased the expression of SQSTM1/p62 (p62), suggesting autophagy activation. Autophagy enhancement could reduce apoptosis. Caspase-3 and Bax expression was decreased, and Bcl-2 expression was increased. When autophagy was inhibited by CQ, the positive effects of Sirt1 were attenuated. In vivo, L-arg application reduced root resorption in rats, as demonstrated by decreased root absorption volume. Similarly, L-arg upregulated Sirt1, which activated autophagy in the root resorption model, and less root resorption was observed in the Sirt1 activation group.

CONCLUSION

L-arg reduced cementoblast apoptosis in hypoxia and reduced root resorption induced by loading force in rats, which may be partly mediated by Sirt1-enhanced autophagy.

The SIRT1 activator SRT2104 promotes BMP9-induced osteogenic and angiogenic differentiation in mesenchymal stem cells

Bone defects resulting from trauma, bone tumors, infections and skeletal abnormalities are a common osteoporotic condition with respect to clinical treatment. Of the known bone morphogenetic proteins (BMPs), BMP9 has the strongest osteogenic differentiation potential, which could be beneficial in the construction of tissue-engineered bone. Silent mating type information regulator 2 homolog-1 (SIRT1) is a highly conserved nicotinamide adenine dinucleotide-dependent deacetylase that deacetylates and modulates histone or non-histone substrates. However, the role of SIRT1 in BMP9-induced osteogenic differentiation of stem cells has not been studied. Furthermore, it is unclear whether SIRT1 interacts with the BMP/Smad and BMP/MAPK pathways in stem cells. We found that SIRT1 expression decreased gradually in a time-dependent manner during BMP9-induced osteogenic differentiation of MSCs. Interactions between SIRT1 and Smad7 promoted degradation of Smad7 and increased Smad1/5/8 phosphorylation. SRT2104, an activator of SIRT, enhanced the expression of osteogenic- and angiogenic-related proteins in BMP9-induced MSCs. In addition, we found that activation of the BMP/MAPK pathway led to osteogenic and angiogenic differentiation of MSCs. Our study demonstrated that SIRT1 expression decreased during BMP9-induced differentiation. The SIRT1 activator SRT2104 promoted BMP9-induced osteogenic and angiogenic differentiation of MSCs through the BMP/Smad and BMP/MAPK signaling pathways.

Safranal Treatment Induces Sirt1 Expression and Inhibits Endoplasmic Reticulum Stress in Mouse Chondrocytes and Alleviates Osteoarthritis Progression in a Mouse Model

Osteoarthritis (OA) is an age-related degenerative disease. Oxidative stress (OS) modulates OA pathogenesis by enhancing chondrocyte apoptosis and extracellular matrix (ECM) degeneration via activation of the endoplasmic reticulum (ER) stress. Prior studies revealed that safranal plays a critical role in multiple diseases treatments, but there are no reports on its effect on OA. Therefore, investigating the effect of safranal on OA is needed. As a compound that can lead excessive reactive oxygen species (ROS) accumulation, tert-butyl hydroperoxide (TBHP) was used to induce OS and OS-mediated endoplasmic reticulum (ER) stress for imitating OA in vitro. Besides, the bilateral medial meniscus was removed to induce joint instability and excessive friction of the joint surface to establish destabilization of medial meniscus for imitating the initiation and progression of OA in vivo. We, next, conducted Western blot and RT-PCR analyses to identify biomarkers of the underlying signaling pathway. Our results demonstrated that 30 μM safranal strongly upregulated Sirt1 expression, suppressed TBHP-mediated ER stress, and, in turn, prevented chondrocyte apoptosis and ECM degeneration. Furthermore, compared with the other two classic signaling pathways of ER stress, safranal can inhibit the PERK-eIF2α-CHOP axis at the lower concentration (5 and 15 μM). In vivo, using Safranin O staining, X-ray, immunofluorescence (IF), and immunohistochemical (IHC) staining, we demonstrated that OA progression can be postponed with intraperitoneal injection of 90 and 180 mg/kg safranal in an OA mouse model. Taken together, our analyses revealed that safranal can potentially prevent OA development.

DDIT3/CHOP mediates the inhibitory effect of ER stress on chondrocyte differentiation by AMPKα-SIRT1 pathway

Endoplasmic reticulum (ER) stress is an evolutionarily conserved cellular stress response related to multiple diseases, including temporomandibular joint (TMJ) cartilage-related diseases. Recent studies have indicated that DDIT3/CHOP (a downstream transcription factor of ER stress) is an important effector in mediating ER stress to inhibit chondrogenesis. However, the underlying mechanism by which DDIT3 regulates chondrogenesis remains unclear. In this study, tunicamycin (an ER stress agonist)-induced ER stress inhibited chondrocyte differentiation and matrix synthesis in vitro and led to an osteoarthritis-like phenotype in mouse TMJ cartilage. Meanwhile, DDIT3 expression in chondrocytes was robustly upregulated. Loss-of-function experiments validated the inhibiting effect of DDIT3 on chondrocyte differentiation and matrix synthesis. Mechanistically, the inhibiting effect was attributed to the direct and indirect regulatory effect of DDIT3 on SIRT1 (sirtuin1, silent mating type information regulation protein type 1, a member of NAD+ dependent class III histone deacetylases). On one hand, DDIT3 directly promoted the transcription of SIRT1. On the other hand, DDIT3 indirectly increased the expression of SIRT1 by promoting AMPKα phosphorylation and activation. Furthermore, activation of AMPKα or SIRT1 with the corresponding agonist AICAR or resveratrol in the DDIT3-knockdown cells partially restored the inhibiting effect of DDIT3 on chondrocyte differentiation and matrix synthesis. Collectively, these novel findings indicate that DDIT3 regulates the inhibitory effect of ER stress on chondrocyte differentiation and matrix synthesis partially via the AMPKα-SIRT1 pathway. A thorough understanding of ER stress in regulating chondrocyte homeostasis and its role in the onset of osteoarthritis may be promising to develop therapeutic targets and prevent condyle cartilage destruction.

The Epigenetic Regulation of Nonhistone Proteins by SETD7: New Targets in Cancer

Epigenetic modifications are essential mechanism by which to ensure cell homeostasis. One such modification is lysine methylation of nonhistone proteins by SETD7, a mono-methyltransferase containing SET domains. SETD7 methylates over 30 proteins and is thus involved in various classical pathways. As such, SETD7 has been implicated in both the basic functions of normal tissues but also in several pathologies, such as cancers. In this review, we summarize the current knowledge of SETD7 substrates, especially transcriptional-related proteins and enzymes, and their putative roles upon SETD7-mediated methylation. We focus on the role of SETD7 in cancers, and speculate on the possible points of intervention and areas for future research.

Isoquercitrin Attenuates Osteogenic Injury in MC3T3 Osteoblastic Cells and the Zebrafish Model via the Keap1-Nrf2-ARE Pathway

Isoquercitrin (IQ) widely exists in natural products, with a variety of pharmacological activities. In this study, the anti-apoptotic and antioxidative activities of IQ were evaluated. IQ showed protective activity against 2, 2′-azobis [2-methylpropionamidine] dihydrochloride (AAPH)-induced cell damage, as well as a marked reduction in reactive oxygen species (ROS). The evidence of IQ regulating Keap1-Nrf2-ARE and the mitochondrial-mediated Caspase 3 pathway were found in the MC3T3 osteoblastic cell line. Furthermore, IQ significantly decreased ROS production, apoptosis, and lipid peroxidation in AAPH-treated 72 h post-fertilization (hpf) zebrafish, as observed via DCFH-DA, acridine orange (AO), and a 1,3-bis(diphenylphosphino) propane (DPPP) probe, respectively. In AAPH-treated 9 day post-fertilization (dpf) zebrafish, IQ strongly promoted osteogenic development, with increased concentrations by calcein staining, compared with the untreated group. In a molecular docking assay, among all signal proteins, Keap1 showed the strongest affinity with IQ at −8.6 kcal/mol, which might be the reason why IQ regulated the Keap1-Nrf2-ARE pathway in vitro and in vivo. These results indicated that IQ promotes bone development and repairs bone injury, which is valuable for the prevention and treatment of bone diseases.

Fatty acids derived from apoptotic chondrocytes fuel macrophages FAO through MSR1 for facilitating BMSCs osteogenic differentiation

The nonunion following a fracture is associated with severe patient morbidity and economic consequences. Currently, accumulating studies are focusing on the importance of macrophages during fracture repair. However, details regarding the process by which macrophages facilitate endochondral ossification (EO) are largely unknown. In this study, we present evidence that apoptotic chondrocytes (ACs) are not inert corpses awaiting removal, but positively modulate the osteoinductive ability of macrophages. In vivo experiments revealed that fatty acid (FA) metabolic processes up-regulated following EO. In vitro studies further uncovered that FAs derived from ACs are taken up by macrophages mainly through macrophage scavenger receptor 1 (MSR1). Then, our functional experiments confirmed that these exogenous FAs subsequently activate peroxisome proliferator-activated receptor α (PPARα), which further facilitates lipid droplets generation and fatty acid oxidation (FAO). Mechanistically, elevated FAO is involved in up-regulating the osteoinductive effect by generating BMP7 and NAD⁺/SIRT1/EZH2 axis epigenetically controls BMP7 expression in macrophages cultured with ACs culture medium. Our findings advanced the concept that ACs could promote bone regeneration by regulating metabolic and function reprogram in macrophages and identified macrophage MSR1 represents a valuable target for fracture treatments.

Circulating SIRT1 and Sclerostin Correlates with Bone Status in Young Women with Different Degrees of Adiposity

Sirtuin1 (SIRT1) and sclerostin play important roles in adipose tissue and bone metabolism. We evaluated the circulating SIRT1 and sclerostin relationship with mass and quality of bone while considering the degree of adiposity. Sixty-six premenopausal women (16 underweight, 25 normal weight and 25 with obesity), aged <50 years, were enrolled. Plasma SIRT1, sclerostin and DXA body composition (total fat mass (FM), abdominal visceral adipose tissue, lean mass, trabecular bone score (TBS) and lumbar spine and femoral neck (FN) bone mineral density (BMD)) were assessed. The patients with obesity showed the lowest SIRT1 and TBS values and the highest sclerostin concentrations; BMD increased with FM and BMI and had an inverse association with SIRT1. Sclerostin was negatively correlated with SIRT1 (ρ = −0.37, p = 0.002). When spine BMD, FN BMD and TBS were standardized for BMI, a positive correlation with SIRT1 and a negative correlation with sclerostin were seen (p < 0.005). In the regression analysis, sclerostin was the best independent, negative predictor for BMD and TBS, while SIRT1 directly predicted TBS (p < 0.05). In conclusion, blood measurement of SIRT1 and sclerostin could represent a snapshot of the bone status that, taking into account the degree of adiposity, may reduce the interference of confounding factors in the interpretation of bone health parameters.

Vitamin D3 Stimulates Proliferation Capacity, Expression of Pluripotency Markers, and Osteogenesis of Human Bone Marrow Mesenchymal Stromal/Stem Cells, Partly through SIRT1 Signaling

The biology of vitamin D3 is well defined, as are the effects of its active metabolites on various cells, including mesenchymal stromal/stem cells (MSCs). However, the biological potential of its precursor, cholecalciferol (VD3), has not been sufficiently investigated, although its significance in regenerative medicine—mainly in combination with various biomaterial matrices—has been recognized. Given that VD3 preconditioning might also contribute to the improvement of cellular regenerative potential, the aim of this study was to investigate its effects on bone marrow (BM) MSC functions and the signaling pathways involved. For that purpose, the influence of VD3 on BM-MSCs obtained from young human donors was determined via MTT test, flow cytometric analysis, immunocytochemistry, and qRT-PCR. Our results revealed that VD3, following a 5-day treatment, stimulated proliferation, expression of pluripotency markers (NANOG, SOX2, and Oct4), and osteogenic differentiation potential in BM-MSCs, while it reduced their senescence. Moreover, increased sirtuin 1 (SIRT1) expression was detected upon treatment with VD3, which mediated VD3-promoted osteogenesis and, partially, the stemness features through NANOG and SOX2 upregulation. In contrast, the effects of VD3 on proliferation, Oct4 expression, and senescence were SIRT1-independent. Altogether, these data indicate that VD3 has strong potential to modulate BM-MSCs’ features, partially through SIRT1 signaling, although the precise mechanisms merit further investigation.

Diversity of Vascular Niches in Bones and Joints During Homeostasis, Ageing, and Diseases

The bones and joints in the skeletal system are composed of diverse cell types, including vascular niches, bone cells, connective tissue cells and mineral deposits and regulate whole-body homeostasis. The capacity of maintaining strength and generation of blood lineages lies within the skeletal system. Bone harbours blood and immune cells and their progenitors, and vascular cells provide several immune cell type niches. Blood vessels in bone are phenotypically and functionally diverse, with distinct capillary subtypes exhibiting striking changes with age. The bone vasculature has a special impact on osteogenesis and haematopoiesis, and dysregulation of the vasculature is associated with diverse blood and bone diseases. Ageing is associated with perturbed haematopoiesis, loss of osteogenesis, increased adipogenesis and diminished immune response and immune cell production. Endothelial and perivascular cells impact immune cell production and play a crucial role during inflammation. Here, we discuss normal and maladapted vascular niches in bone during development, homeostasis, ageing and bone diseases such as rheumatoid arthritis and osteoarthritis. Further, we discuss the role of vascular niches during bone malignancy.

B Cell Involvement in the Pathogenesis of Ankylosing Spondylitis

Extensive research into ankylosing spondylitis (AS) has suggested the major role of genetics, immune reactions, and the joint-gut axis in its etiology, although an ultimate consensus does not yet exist. The available evidence indicates that both autoinflammation and T-cell-mediated autoimmune processes are actively involved in the disease process of AS. So far, B cells have received relatively little attention in AS pathogenesis; this is largely due to a lack of conventional disease-defining autoantibodies. However, against prevailing dogma, there is a growing body of evidence suggestive of B cell involvement. This is illustrated by disturbances in circulating B cell populations and the formation of auto-reactive and non-autoreactive antibodies, along with B cell infiltrates within the axial skeleton of AS patients. Furthermore, the depletion of B cells, using rituximab, displayed beneficial results in a subgroup of patients with AS. This review provides an overview of our current knowledge of B cells in AS, and discusses their potential role in its pathogenesis. An overarching picture portrays increased B cell activation in AS, although it is unclear whether B cells directly affect pathogenesis, or are merely bystanders in the disease process.

Roles and mechanisms of exosomal non-coding RNAs in human health and diseases

Exosomes play a role as mediators of cell-to-cell communication, thus exhibiting pleiotropic activities to homeostasis regulation. Exosomal non-coding RNAs (ncRNAs), mainly microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), are closely related to a variety of biological and functional aspects of human health. When the exosomal ncRNAs undergo tissue-specific changes due to diverse internal or external disorders, they can cause tissue dysfunction, aging, and diseases. In this review, we comprehensively discuss the underlying regulatory mechanisms of exosomes in human diseases. In addition, we explore the current knowledge on the roles of exosomal miRNAs, lncRNAs, and circRNAs in human health and diseases, including cancers, metabolic diseases, neurodegenerative diseases, cardiovascular diseases, autoimmune diseases, and infectious diseases, to determine their potential implication in biomarker identification and therapeutic exploration.

Allogeneic vs. autologous mesenchymal stem/stromal cells in their medication practice

Mesenchymal stem/stromal cell (MSC)-based therapeutics is already available for treatment of a range of diseases or medical conditions. Autologous or allogeneic MSCs obtained from self or donors have their own advantages and disadvantages in their medical practice. Therapeutic benefits of using autologous vs. allogeneic MSCs are inconclusive. Transplanted MSCs within the body interact with their physical microenvironment or niche, physiologically or pathologically, and such cells in a newly established tissue microenvironment may be impacted by the pathological harmful environmental factors to alter their unique biological behaviors. Meanwhile, a temporary microenvironment/niche may be also altered by the resident or niche-surrounding MSCs. Therefore, the functional plasticity and heterogeneity of MSCs caused by different donors and subpopulations of MSCs may result in potential uncertainty in their safe and efficacious medical practice. Acknowledging a connection between MSCs' biology and their existing microenvironment, donor-controlled clinical practice for the long-term therapeutic benefit is suggested to further consider minimizing MSCs potential harm for MSC-based individual therapies. In this review, we summarize the advantages and disadvantages of autologous vs. allogeneic MSCs in their therapeutic applications. Among other issues, we highlight the importance of better understanding of the various microenvironments that may affect the properties of niche-surrounding MSCs and discuss the clinical applications of MSCs within different contexts for treatment of different diseases including cardiomyopathy, lupus and lupus nephritis, diabetes and diabetic complications, bone and cartilage repair, cancer and tissue fibrosis.

Up-regulation of SIRT1 induced by 17beta-estradiol promotes autophagy and inhibits apoptosis in osteoblasts

Osteoporosis is a common systemic skeletal metabolism disorder resulting in bone fragility and increased fracture risk. Silent information regulator factor 2 homolog 1 (SIRT1) is crucial in the regulation of several biological processes, including bone metabolism, autophagy, apoptosis, and aging. This study aimed to assess whether the up-regulation of SIRT1 induced by 17beta-estradiol (17β-E2) could promote autophagy and inhibit apoptosis in osteoblasts via the AMPK-mTOR and FOXO3a pathways, respectively. The study found that 17β-E2 (10^-6 M) administration induced the up-regulation of SIRT1 in osteoblasts. Up-regulation of SIRT1 induced by 17β-E2 increased the expression level of LC3, Beclin-1, Bcl-2, p-AMPK, FOXO3a but decreased caspase-3 and p-mTOR expression, and then promoted autophagy and inhibited apoptosis. More autophagosomes were observed under a transmission electron microscope (TEM) in 17β-E2 and SRT1720 (a selective SIRT1 activator) co-treated group. When Ex527 (a SIRT1-specific inhibitor) was pretreated, the reversed changes were observed. Taken together, our findings demonstrated that the up-regulation of SIRT1 induced by 17β-E2 could promote autophagy via the AMPK-mTOR pathway and inhibit apoptosis via the FOXO3a activation in osteoblasts, and SIRT1 might become a more significant target in osteoporosis treatment.

miR-3146 induces neutrophil extracellular traps to aggravate gout flare

Background

Gout is an inflammatory arthritis and is characterized by the accumulation of deposited monosodium urate (MSU) crystals in the joints. miRNAs may act as key regulators of gout pathogenesis. The aim of our study was to explore the underlying role and molecular mechanism of miR‐3146 in the formation of neutrophil extracellular traps (NETs) during the pathogenesis of gout.

Methods

The expression of miR‐3146 and sirtuin 1 (SIRT1) was determined by real‐time reverse transcription‐polymerase chain reaction and Western blot, respectively. The luciferase reporter assay was performed to identify the targeting relationship between miR‐3146 and SIRT1. Reactive oxygen species (ROS) production was detected by fluorescent staining. NETs formation was demonstrated via immunofluorescence staining and ELISA method. Gout model was induced in rats to verify the effects of miR‐3146 inhibition on histopathological changes and NETs.

Results

Here, we found miR‐3146 expression was dramatically increased in neutrophils of patients with gout, which was accompanied with the higher levels of NETs. MSU crystals significantly increased miR‐3146 expression and ROS production in neutrophils. The NETs process was also triggered by MSU crystals. Furthermore, we verified the interaction between miR‐3146 and SIRT1. Additionally, antagomir‐3146‐based therapy effectively inhibited the formation of NETs in rats with gout.

Conclusion

Our findings indicated that miR‐3146‐mediated NETs formation may play a potential role in the pathogenesis of gout. These results suggested that miR‐3146 could be used as a potential therapeutic target for the treatment of gout.

Uncarboxylated osteocalcin promotes osteogenesis and inhibits adipogenesis of mouse bone marrow-derived mesenchymal stem cells via the PKA-AMPK-SIRT1 axis

Osteoporosis is a bone disease characterized by reduced bone density, thin cortical bone and large gaps in the bone's honeycomb structure, which increases the risk of bone fragility. Uncarboxylated osteocalcin (unOC), a vitamin K-dependent bone protein, is known to regulate carbohydrate and energy metabolism. A previous study demonstrated that unOC promotes the differentiation of mouse bone marrow-derived mesenchymal stem cells (BMSCs) into osteoblasts, but inhibits their differentiation into adipocytes. However, the underlying mechanism remains unknown. The present study showed that unOC regulated the differentiation potential of BMSCs via protein kinase A (PKA)/AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) signaling. SIRT1, a member of the sirtuin family with deacetylation functions, was upregulated by unOC in BMSCs. Transfection analyses with SIRT1 small interfering RNA indicated that the unOC-induced differentiation shift in BMSCs required SIRT1. Examination of SIRT1 downstream targets revealed that unOC regulated the acetylation levels of runt-related transcription factor (RUNX) 2 and peroxisome proliferator-activated receptor γ (PPARγ). Therefore, unOC inhibited adipogenic differentiation by PPARγ acetylation and promoted osteogenic differentiation by RUNX2 deacetylation. Moreover, phosphorylated PKA and AMPK protein levels increased after unOC treatment, which led to the upregulation of SIRT1. Western blot analysis with PKA and AMPK inhibitors indicated that the PKA-AMPK signaling pathway functioned upstream of SIRT1 and positively regulated SIRT1 expression. These findings led us to propose a model in which unOC regulated BMSC osteogenic differentiation through the PKA-AMPK-SIRT1 axis, giving evidence towards the therapeutic potential of unOC in osteoporosis treatment.

SIRT2 and SIRT3 expression correlates with redox imbalance and advanced clinical stage in patients with multiple myeloma

OBJECTIVES

Sirtuins comprise seven family elements (SIRT1-7) involved in various cell signalling pathways comprising cancer inhibition and tumorigenesis. The present study aims to evaluate SIRT2 and SIRT3 gene expression and potential redox reactions in patients with multiple myeloma (MM) at onset and its correlation with disease status, extent and presence of organ damage secondary to myeloma.

DESIGN & METHODS

Total RNA was extracted from 17 MM patients and 10 controls to assess gene expression using real-time PCR. The NAD+/NADH ratio as well as the levels of glutathione peroxidase (GPx) and hydrogen peroxide (HP) in peripheral blood mononuclear cells (PBMCs) were determined using established biochemical assays.

RESULTS

SIRT2 and SIRT3 expression is reduced in MM patients compared to healthy controls. Correlational analysis demonstrated that SIRT2 reduction is associated with advanced clinical stage and with more advanced bone lesions than in the remaining patients. SIRT3 expression is correlated with lytic bone lesions. Biochemical analysis indicated an imbalance of oxidative stress biomarkers with low concentrations of the antioxidant enzyme GPx, low amounts of NAD + and higher concentrations of pro-oxidant enzyme HP in PBMCs of MM patients compared to controls. Moreover, MM patients with bone lesions had lower concentrations of NAD + and GPx in PBMCs than patients without signs of bone disease. In addition, MM patients had higher quantities of intracellular HP than controls.

CONCLUSIONS

Our results demonstrate that SIRT2 and SIRT3 are downregulated in MM and that lower concentrations correlate with an advanced stage of disease and redox imbalance. We conclude that SIRT2 and SIRT3 together with oxidative stress biomarkers, may be useful for improved risk stratification of MM patients.

Quantitative Proteomics Revealed the Pharmacodynamic Network of Bugu Shengsui Decoction Promoting Osteoblast Proliferation

BACKGROUND AND OBJECTIVE

With high morbidity and disability, osteoporosis is a worldwide bone metabolism disease, regulated by complex pathological processes. Insufficient osteogenesis is greatly essential to osteoporosis. Traditional Chinese Medicine, a complex natural herbal medicine system, has increasingly attracted attention all over the world. Bugu Shengsui Decoction, a compound formula for osteoporosis, has significant clinical effects in the treatment of osteoporosis. Yet the detailed mechanisms are unclear. Thus, we investigated the effects and mechanism of Bugu Shengsui Decoction on osteoporotic rats and osteoblasts in vitro.

METHODS

In this study, we evaluated the effect of Bugu Shengsui Decoction in an animal model of orchiectomy. Multi-pharmacology indexes revealed that Bugu Shengsui Decoction obviously improved bone metabolism, bone mineral density, bone morphology, and biomechanics in the castrated rats. Then, serum pharmacology was employed to unveil that Bugu Shengsui Decoction promoted the proliferation and differentiation of osteoblasts. Moreover, quantitative proteomics combined with RNA interference assay was used to analyze and verify the pathway and key targets in pro-proliferation of MC3T3-E1 cells.

RESULTS

Bugu Shengsui Decoction obviously improved the worse parameters of bone metabolism, bone mineral density, bone morphology, and biomechanics in a castrated rat model. In vitro, Bugu Shengsui Decoction exerted proliferation- and differentiation-promoting effects of osteoblasts induced by serum starvation. Moreover, quantitative proteomics analysis combined with RNA interfere assay illustrated that Bugu Shengsui Decoction promoted osteogenesis via the PI3K-AKT pathway.

CONCLUSION

Summarily, our discoveries certify that Bugu Shengsui Decoction is an effective treatment for osteoporosis via PI3K-AKT. This study is not only a beneficial attempt to explore the detailed mechanism of Traditional Chinese formula but also will provide inspiration for the treatment strategy of osteoporosis.