Melatonin enhances osteoblastogenesis of senescent bone marrow stromal cells through NSD2-mediated chromatin remodelling

HRP2 regulating MICU1-mediated Ca2+ overload to dictate chemoresistance of multiple myeloma

Despite the efficacy of bortezomib (BTZ)-based chemotherapy in treating multiple myeloma (MM) patients, chemoresistance occurs frequently over time, particularly in individuals exhibiting an initial positive response to BTZ therapy. In this study, we established BTZ-resistant MM cells and identified that suppressed expression of the hepatoma-derived growth factor (HDGF)-related protein-2 (HRP2) was a key determinant of chemoresistance in MM cells. Manipulating HRP2 expression remodeled the chemosensitivity of MM cells in vitro and in vivo. Clinically, lower expression of HRP2 predicted a shorter survival rate in MM patients receiving BTZ-based regimens. Mechanistically, HRP2 depletion resulted in elevated acetylation modifications of histone 3 at lysine 27 (H3K27Ac), and enhanced chromatin accessibility as well as transcriptional elongation of mitochondrial calcium uptake 1(MICU1) gene, thus promoting the expression of MICU1 gene and alleviating calcium (Ca2+) overload and excessive reactive oxygen species (ROS) induced mitochondria damage and apoptosis in MM cells. Thereby, MICU1 suppression improved BTZ sensitivity in vitro and relieved tumor burden in a mouse model of MM. Similarly, elevated MICU1 expression was observed in the B220+CD19+ B cells from HRP2-knockout mice and significantly correlated with poor prognosis in the clinic. Thus, our study elucidates the previously unrecognized epigenetic role of HRP2 in regulating calcium homeostasis of MM cells, providing new theoretical insights into the mechanisms underlying the development of drug resistance in multiple myeloma.

Metabolism-epigenetic interaction-based bone and dental regeneration: From impacts and mechanisms to treatment potential

Metabolic pathways exhibit fluctuating activities during bone and dental loss and defects, suggesting a regulated metabolic plasticity. Skeletal remodeling is an energy-demanding process related to altered metabolic activities. These metabolic changes are frequently associated with epigenetic modifications, including variations in the expression or activity of enzymes modified through epigenetic mechanisms, which directly or indirectly impact cellular metabolism. Metabolic reprogramming driven by bone and dental conditions alters the epigenetic landscape by modulating the activities of DNA and histone modification enzymes at the metabolite level. Epigenetic mechanisms modulate the expression of metabolic genes, consequently influencing the metabolome. The interplay between epigenetics and metabolomics is crucial in maintaining bone and dental homeostasis by preserving cell proliferation and pluripotency. This review, therefore, aims to examine the effects of metabolic reprogramming in bone and dental-related cells on the regulation of epigenetic modifications, particularly acetylation, methylation, and lactylation. We also discuss the effects of chromatin-modifying enzymes on metabolism and the potential therapeutic benefits of dietary compounds as epigenetic modulators. In this review, we highlight the inconsistencies in current research findings and suggest potential approaches to translate fundamental insights into clinical treatments for bone and tooth diseases.

4-Octyl Itaconate Attenuates Postmenopausal Osteoporosis by Inhibiting Ferroptosis and Enhancing Osteogenesis via the Nrf2 Pathway

Bone marrow mesenchymal stem cells (BMSCs) play an important role in bone metabolism and tissue repair, and their ability to differentiate into osteoblasts is crucial in the treatment of bone diseases such as postmenopausal osteoporosis (PMOP). However, the function of BMSCs may be affected by ferroptosis. Ferroptosis is a cell death mode characterized by excess Fe2+ and lipid peroxidation, which significantly affects the survival rate and differentiation ability of BMSCs. This study investigated the effect of exogenous itaconate derivative 4-octyl itaconate (4-OI) on Erastin-induced BMSCs ferroptosis. The results showed that 4-OI significantly inhibited Erastin-induced BMSCs ferroptosis by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, reduced reactive oxygen species levels and oxidative damage, and restored antioxidant capacity. At the same time, 4-OI promoted the osteogenic differentiation of BMSCs. Further experiments showed that Nrf2-IN-1, an inhibitor of the Nrf2 pathway, could reverse the protective effect of 4-OI. In vivo, 4-OI was shown to reduce bone loss in ovariectomized (OVX) mice, as assessed by Micro-CT analysis. Immunofluorescence staining further revealed increased GPX4 and Nrf2 expression in vertebral tissues following 4-OI treatment. These results indicate that 4-OI improves ferroptosis of BMSCs and enhances osteogenic differentiation ability by activating the Nrf2 pathway, providing new research ideas and potential targets for the treatment of PMOP.

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.

GRAMMAR-Lambda Delivers Efficient Understanding of the Genetic Basis for Head Size in Catfish

The shape of the skull plays a crucial role in the evolution and adaptation of species to their environments. In the case of aquaculture fish, the size of the head is also an important economic trait, as it is linked to fillet yield and ornamental value. This study applies our GRAMMAR-Lambda method to perform a genome-wide association study analysis on loci related to head size in catfish. Compared with traditional GWAS methods, the GRAMMAR-Lambda method offers higher computational efficiency, statistical power, and stability, especially in complex population structures. This research identifies many candidate genes closely related to cranial morphology in terms of head length, width, and depth in catfish, including bmpr1bb, fgfrl1b, nipbl, foxp2, and pax5, etc. Based on the results of gene-gene interaction analysis, we speculate that there may be frequent genetic interactions between chromosome 19 and chromosome 29 in bone development. Additionally, many candidate genes, gene families, and mechanisms (such as SOCE mechanisms) affecting skeletal development and morphology have been identified. These findings contribute to our understanding of the genetic architecture of head size and will support marker-assisted breeding in aquaculture, also reflecting the potential application of the GRAMMAR-Lambda method in genetic studies of complex traits.

Metabolomic characterization of MC3T3-E1pre-osteoblast differentiation induced by ipriflavone-loaded mesoporous nanospheres

This study reports on the metabolic changes accompanying the differentiation of MC3T3-E1 osteoprogenitor cells induced by mesoporous bioactive glass nanospheres (nMBG) loaded with ipriflavone (nMBG-IP). Ipriflavone (IP) is a synthetic isoflavone known for inhibiting bone resorption, maintaining bone density, and preventing osteoporosis. Delivering IP intracellularly is a promising strategy to modulate bone remodeling at significantly lower doses compared to free drug administration. Our results demonstrate that nMBG are efficiently internalized by pre-osteoblasts and, when loaded with IP, induce their differentiation. This differentiation process is accompanied by pronounced metabolic alterations, as monitored by NMR analysis of medium supernatants and cell extracts (exo- and endo-metabolomics, respectively). The main effects include an early-stage intensification of glycolysis and changes in several metabolic pathways, such as nucleobase metabolism, osmoregulatory and antioxidant pathways, and lipid metabolism. Notably, the metabolic impacts of nMBG-IP and free IP were very similar, whereas nMBG alone induced only mild changes in the intracellular metabolic profile without affecting the cells' consumption/secretion patterns or lipid composition. This finding indicates that the observed effects are primarily related to IP-induced differentiation and that nMBG nanospheres serve as convenient carriers with both efficient internalization and minimal metabolic impact. Furthermore, the observed link between pre-osteoblast differentiation and metabolism underscores the potential of utilizing metabolites and metabolic reprogramming as strategies to modulate the osteogenic process, for instance, in the context of osteoporosis and other bone diseases.

Quercetin ameliorates senescence and promotes osteogenesis of BMSCs by suppressing the repetitive element‑triggered RNA sensing pathway

Cell senescence impedes the self‑renewal and osteogenic capacity of bone marrow mesenchymal stem cells (BMSCs), thus limiting their application in tissue regeneration. The present study aimed to elucidate the role and mechanism of repetitive element (RE) activation in BMSC senescence and osteogenesis, as well as the intervention effect of quercetin. In an H2O2‑induced BMSC senescence model, quercetin treatment alleviated senescence as shown by a decrease in senescence‑associated β‑galactosidase (SA‑β‑gal)‑positive cell ratio, increased colony formation ability and decreased mRNA expression of p21 and senescence‑associated secretory phenotype genes. DNA damage response marker γ‑H2AX increased in senescent BMSCs, while expression of epigenetic markers methylation histone H3 Lys9, heterochromatin protein 1α and heterochromatin‑related nuclear membrane protein lamina‑associated polypeptide 2 decreased. Quercetin rescued these alterations, indicating its ability to ameliorate senescence by stabilizing heterochromatin structure where REs are primarily suppressed. Transcriptional activation of REs accompanied by accumulation of cytoplasmic double‑stranded (ds)RNA, as well as triggering of the RNA sensor retinoic acid‑inducible gene I (RIG‑I) receptor pathway in H2O2‑induced senescent BMSCs were shown. Similarly, quercetin treatment inhibited these responses. Additionally, RIG‑I knockdown led to a decreased number of SA‑β‑gal‑positive cells, confirming its functional impact on senescence. Induction of senescence or administration of dsRNA analogue significantly hindered the osteogenic capacity of BMSCs, while quercetin treatment or RIG‑I knockdown reversed the decline in osteogenic function. The findings of the current study demonstrated that quercetin inhibited the activation of REs and the RIG‑I RNA sensing pathway via epigenetic regulation, thereby alleviating the senescence of BMSCs and promoting osteogenesis.

Melatonin-loaded bioactive microspheres accelerate aged bone regeneration by formation of tunneling nanotubes to enhance mitochondrial transfer

The repair of bone defects in the elderly individuals is significantly delayed due to cellular senescence and dysfunction, which presents a challenge in clinical settings. Furthermore, there are limited effective methods available to promote bone repair in older individuals. Herein, melatonin-loaded mesoporous bioactive glasses microspheres (MTBG) were successfully prepared based on their mesoporous properties. The repair of bone defects in aged rats was significantly accelerated by enhancing mitochondrial function through the sustained release of melatonin and bioactive ions. MTBG effectively rejuvenated senescent bone marrow mesenchymal stem cells (BMSCs) by scavenging excessive reactive oxygen species (ROS), stabilizing the mitochondrial membrane potential (ΔΨm), and increasing ATP synthesis. Analysis of the underlying mechanism revealed that the formation of tunneling nanotubes (TNTs) facilitated the intercellular transfer of mitochondria, thereby resulting in the recovery of mitochondrial function. This study provides critical insights into the design of new biomaterials for the elderly individuals and the biological mechanism involved in aged bone regeneration.

One-carbon metabolism supports S-adenosylmethionine and m6A methylation to control the osteogenesis of bone marrow stem cells and bone formation

The skeleton is a metabolically active organ undergoing continuous remodeling initiated by bone marrow stem cells (BMSCs). Recent research has demonstrated that BMSCs adapt the metabolic pathways to drive the osteogenic differentiation and bone formation, but the mechanism involved remains largely elusive. Here, using a comprehensive targeted metabolome and transcriptome profiling, we revealed that one-carbon metabolism was promoted following osteogenic induction of BMSCs. Methotrexate (MTX), an inhibitor of one-carbon metabolism that blocks S-adenosylmethionine (SAM) generation, led to decreased N6-methyladenosine (m6A) methylation level and inhibited osteogenic capacity. Increasing intracellular SAM generation through betaine addition rescued the suppressed m6A content and osteogenesis in MTX-treated cells. Using S-adenosylhomocysteine (SAH) to inhibit the m6A level, the osteogenic activity of BMSCs was consequently impeded. We also demonstrated that the pro-osteogenic effect of m6A methylation mediated by one-carbon metabolism could be attributed to HIF-1α and glycolysis pathway. This was supported by the findings that dimethyloxalyl glycine rescued the osteogenic potential in MTX-treated and SAH-treated cells by upregulating HIF-1α and key glycolytic enzymes expression. Importantly, betaine supplementation attenuated MTX-induced m6A methylation decrease and bone loss via promoting the abundance of SAM in rat. Collectively, these results revealed that one-carbon metabolite SAM was a potential promoter in BMSC osteogenesis via the augmentation of m6A methylation, and the cross talk between metabolic reprogramming, epigenetic modification, and transcriptional regulation of BMSCs might provide strategies for bone regeneration.

Epigenetic regulations of cellular senescence in osteoporosis

Osteoporosis (OP) is a prevalent age-related disease that is characterized by a decrease in bone mineral density (BMD) and systemic bone microarchitectural disorders. With age, senescent cells accumulate and exhibit the senescence-associated secretory phenotype (SASP) in bone tissue, leading to the imbalance of bone homeostasis, osteopenia, changes in trabecular bone structure, and increased bone fragility. Cellular senescence in the bone microenvironment involves osteoblasts, osteoclasts, and bone marrow mesenchymal stem cells (BMSCs), whose effects on bone homeostasis are regulated by epigenetics. Therefore, the epigenetic regulatory mechanisms of cellular senescence have received considerable attention as potential targets for preventing and treating osteoporosis. In this paper, we systematically review the mechanisms of aging-associated epigenetic regulation in osteoporosis, emphasizing the impact of epigenetics on cellular senescence, and summarize three current methods of targeting cellular senescence, which is helpful better to understand the pathogenic mechanisms of cellular senescence in osteoporosis and provides strategies for the development of epigenetic drugs for the treatment of osteoporosis.

Age-related alveolar bone maladaptation in adult orthodontics: finding new ways out

Compared with teenage patients, adult patients generally show a slower rate of tooth movement and more pronounced alveolar bone loss during orthodontic treatment, indicating the maladaptation of alveolar bone homeostasis under orthodontic force. However, this phenomenon is not well-elucidated to date, leading to increased treatment difficulties and unsatisfactory treatment outcomes in adult orthodontics. Aiming to provide a comprehensive knowledge and further inspire insightful understanding towards this issue, this review summarizes the current evidence and underlying mechanisms. The age-related abatements in mechanosensing and mechanotransduction in adult cells and periodontal tissue may contribute to retarded and unbalanced bone metabolism, thus hindering alveolar bone reconstruction during orthodontic treatment. To this end, periodontal surgery, physical and chemical cues are being developed to reactivate or rejuvenate the aging periodontium and restore the dynamic equilibrium of orthodontic-mediated alveolar bone metabolism. We anticipate that this review will present a general overview of the role that aging plays in orthodontic alveolar bone metabolism and shed new light on the prospective ways out of the impasse.

Melatonin attenuates dental pulp stem cells senescence due to vitro expansion via inhibiting MMP3

OBJECTIVE

We aimed to identify the crucial genes involved in dental pulp stem cell (DPSC) senescence and evaluate the impact of melatonin on DPSC senescence.

METHODS

Western blotting, SA-β-Gal staining and ALP staining were used to evaluate the senescence and differentiation potential of DPSCs. The optimal concentration of melatonin was determined using the CCK-8 assay. Differentially expressed genes (DEGs) involved in DPSC senescence were obtained via bioinformatics analysis, followed by RT-qPCR. Gain- and loss-of-function studies were conducted to explore the role of MMP3 in DPSC in vitro expansion and in response to melatonin. GSEA was employed to analyse MMP3-related pathways in cellular senescence.

RESULTS

Treatment with 0.1 μM melatonin attenuated cellular senescence and differentiation potential suppression in DPSCs due to long-term in vitro expansion. MMP3 was a crucial gene in senescence, as confirmed by bioinformatics analysis, RT-qPCR and Western blotting. Furthermore, gain- and loss-of-function studies revealed that MMP3 played a regulatory role in cellular senescence. Rescue assays showed that overexpression of MMP3 reversed the effect of melatonin on senescence. GSEA revealed that the MMP3-dependent anti-senescence effect of melatonin was associated with the IL6-JAK-STAT3, TNF-α-Signalling-VIA-NF-κB, COMPLEMENT, NOTCH Signalling and PI3K-AKT-mTOR pathways.

CONCLUSION

Melatonin attenuated DPSC senescence caused by long-term expansion by inhibiting MMP3.

Epigenetic regulators controlling osteogenic lineage commitment and bone formation

Bone formation and homeostasis are controlled by environmental factors and endocrine regulatory cues that initiate intracellular signaling pathways capable of modulating gene expression in the nucleus. Bone-related gene expression is controlled by nucleosome-based chromatin architecture that limits the accessibility of lineage-specific gene regulatory DNA sequences and sequence-specific transcription factors. From a developmental perspective, bone-specific gene expression must be suppressed during the early stages of embryogenesis to prevent the premature mineralization of skeletal elements during fetal growth in utero. Hence, bone formation is initially inhibited by gene suppressive epigenetic regulators, while other epigenetic regulators actively support osteoblast differentiation. Prominent epigenetic regulators that stimulate or attenuate osteogenesis include lysine methyl transferases (e.g., EZH2, SMYD2, SUV420H2), lysine deacetylases (e.g., HDAC1, HDAC3, HDAC4, HDAC7, SIRT1, SIRT3), arginine methyl transferases (e.g., PRMT1, PRMT4/CARM1, PRMT5), dioxygenases (e.g., TET2), bromodomain proteins (e.g., BRD2, BRD4) and chromodomain proteins (e.g., CBX1, CBX2, CBX5). This narrative review provides a broad overview of the covalent modifications of DNA and histone proteins that involve hundreds of enzymes that add, read, or delete these epigenetic modifications that are relevant for self-renewal and differentiation of mesenchymal stem cells, skeletal stem cells and osteoblasts during osteogenesis.

Phytic acid improves osteogenesis and inhibits the senescence of human bone marrow mesenchymal stem cells under high-glucose conditions via the ERK pathway

Hyperglycaemia causes impairment of osteogenic differentiation and accelerates stem cell senescence, resulting in weakened osteogenesis and disordered bone metabolism. Phytic acid (PA) is an antioxidant that is reportedly beneficial to bone homeostasis. The present study aims to clarify how PA affects the osteogenic capacity and cellular senescence of bone marrow mesenchymal stem cells (BMSCs) exposed to high-glucose environments, as well as the potential molecular mechanisms. Our results indicate that osteogenic differentiation in BMSCs cultivated in high-glucose conditions is enhanced by PA, as evidenced by increased alkaline phosphatase activity and staining, Alizarin Red S staining, osteogenic marker in in vitro studies, and increased osteogenesis in animal experiments. PA also prevented high-glucose-induced senescence of BMSCs, as evidenced by the repression of reactive oxygen species production, senescence-associated β-galactosidase staining, and P21 and P53 expression. Furthermore, it was found that PA rescued the high-glucose-inhibited expression of phosphorylated extracellular regulated protein kinases (p-ERK). The inhibition of ERK pathway by the specific inhibitor PD98059 blocked the PA-enhanced osteogenesis of BMSCs and promoted cell senescence. Our results revealed that PA enhances osteogenic differentiation and inhibits BMSC senescence in a high-glucose environment. In addition, the activation of the ERK pathway seems to mediate the beneficial effects of PA. The findings provide novel insights that could facilitate bone regeneration in patients with diabetes.

Codonopsis pilosula polysaccharides promote osteogenic differentiation and inhibit lipogenic differentiation of rat bone marrow stem cells by activating β-catenin

Aberrant bone marrow mesenchymal stem cell (BMSC) lineage differentiation leads to osteoporosis. Codonopsis pilosula polysaccharides (CPPs) have been widely used in traditional Chinese medicines, due to their multiple pharmacological actions. However, little is known regarding their effects on BMSC differentiation. This study aimed to identify the effects and mechanisms of CPPs on osteogenic and adipogenic differentiation in rat BMSCs. An osteoporosis model was established in Sprague-Dawley (SD) rats through bilateral ovariectomy (OVX), and be applied to observe the effect of CPPs on osteoporosis in vivo. The ability of CPPs to affect rBMSC proliferation was determined using the CCK-8 assay, and the osteogenic differentiation of rBMSCs measured by ALP and Alizarin Red S staining. The adipogenic differentiation of rBMSCs was measured by Oil Red O staining. The mRNA and protein levels related to osteogenesis and adipogenic differentiation of rBMSCs were measured using qRT-PCR and western blotting, respectively. Cellular immunofluorescence was used to detect cytokine expression and localisation in rBMSCs. We observed that CPPs ameliorated bone loss in OVX rats. CPPs considerably enhanced osteogenic differentiation by increasing ALP activity and the prevalence of mineralised nodules and promoting the mRNA and protein expression of osteogenic differentiation markers (RUNX2, COL I, ALP, and OPN). Furthermore, it inhibited the accumulation of lipid vesicles in the cytoplasm and the mRNA and protein expression levels of adipogenic differentiation markers (PPARγ and C/EBPα) in a concentration-dependent manner. Meanwhile, CPPs notably increased the mRNA and protein expression of β-catenin, the core protein of the Wnt/β-catenin signaling pathway, in a concentration-dependent manner. Adding DKK1, a mature inhibitor of the Wnt/β-catenin signaling pathway, partially suppressed CPP-stimulated β-catenin activation, and reversed the acceleration of osteogenic differentiation and the inhibition of lipogenic differentiation. Our observations demonstrated CPPs ameliorate bone loss in OVX rats in vivo, and favour osteogenic differentiation while inhibit adipogenic differentiation of rBMSCs in vitro. The findings suggested that CPPs could serve as functional foods for bone health, and have great potential for the prevention and treatment of osteoporosis.

Melatonin and bone-related diseases: an updated mechanistic overview of current evidence and future prospects

PURPOSE

Bone diseases account for an enormous cost burden on health systems. Bone disorders are considered as age-dependent diseases. The aging of world population has encouraged scientists to further explore the most effective preventive modalities and therapeutic strategies to overcome and reduce the high cost of bone disorders. Herein, we review the current evidence of melatonin's therapeutic effects on bone-related diseases.

METHODS

This review summarized evidences from in vitro, in vivo, and clinical studies regarding the effects of melatonin on bone-related diseases, with a focus on the molecular mechanisms. Electronically, Scopus and MEDLINE®/PubMed databases were searched for articles published on melatonin and bone-related diseases from inception to June 2023.

RESULTS

The findings demonstrated that melatonin has beneficial effect in bone- and cartilage-related disorders such as osteoporosis, bone fracture healing, osteoarthritis, and rheumatoid arthritis, in addition to the control of sleep and circadian rhythms.

CONCLUSION

A number of animal and clinical studies have indicated that various biological effects of melatonin may suggest this molecule as an effective therapeutic agent for controlling, diminishing, or suppressing bone-related disorders. Therefore, further clinical studies are required to clarify whether melatonin can be effective in patients with bone-related diseases.

Dysregulation of histone modifications in bone marrow mesenchymal stem cells during skeletal ageing: roles and therapeutic prospects

Age-associated bone diseases such as osteoporosis (OP) are common in the elderly due to skeletal ageing. The process of skeletal ageing can be accelerated by reduced proliferation and osteogenesis of bone marrow mesenchymal stem cells (BM-MSCs). Senescence of BM-MSCs is a main driver of age-associated bone diseases, and the fate of BM-MSCs is tightly regulated by histone modifications, such as methylation and acetylation. Dysregulation of histone modifications in BM-MSCs may activate the genes related to the pathogenesis of skeletal ageing and age-associated bone diseases. Here we summarize the histone methylation and acetylation marks and their regulatory enzymes that affect BM-MSC self-renewal, differentiation and senescence. This review not only describes the critical roles of histone marks in modulating BM-MSC functions, but also underlines the potential of epigenetic enzymes as targets for treating age-associated bone diseases. In the future, more effective therapeutic approaches based on these epigenetic targets will be developed and will benefit elderly individuals with bone diseases, such as OP.

Rejuvenation of Mesenchymal Stem Cells to Ameliorate Skeletal Aging

Advanced age is a shared risk factor for many chronic and debilitating skeletal diseases including osteoporosis and periodontitis. Mesenchymal stem cells develop various aging phenotypes including the onset of senescence, intrinsic loss of regenerative potential and exacerbation of inflammatory microenvironment via secretory factors. This review elaborates on the emerging concepts on the molecular and epigenetic mechanisms of MSC senescence, such as the accumulation of oxidative stress, DNA damage and mitochondrial dysfunction. Senescent MSCs aggravate local inflammation, disrupt bone remodeling and bone-fat balance, thereby contributing to the progression of age-related bone diseases. Various rejuvenation strategies to target senescent MSCs could present a promising paradigm to restore skeletal aging.

Epigenetic regulation in metabolic diseases: mechanisms and advances in clinical study

Epigenetics regulates gene expression and has been confirmed to play a critical role in a variety of metabolic diseases, such as diabetes, obesity, non-alcoholic fatty liver disease (NAFLD), osteoporosis, gout, hyperthyroidism, hypothyroidism and others. The term 'epigenetics' was firstly proposed in 1942 and with the development of technologies, the exploration of epigenetics has made great progresses. There are four main epigenetic mechanisms, including DNA methylation, histone modification, chromatin remodelling, and noncoding RNA (ncRNA), which exert different effects on metabolic diseases. Genetic and non-genetic factors, including ageing, diet, and exercise, interact with epigenetics and jointly affect the formation of a phenotype. Understanding epigenetics could be applied to diagnosing and treating metabolic diseases in the clinic, including epigenetic biomarkers, epigenetic drugs, and epigenetic editing. In this review, we introduce the brief history of epigenetics as well as the milestone events since the proposal of the term 'epigenetics'. Moreover, we summarise the research methods of epigenetics and introduce four main general mechanisms of epigenetic modulation. Furthermore, we summarise epigenetic mechanisms in metabolic diseases and introduce the interaction between epigenetics and genetic or non-genetic factors. Finally, we introduce the clinical trials and applications of epigenetics in metabolic diseases.

Melatonin activates mitochondrial unfolded protein response to preserve osteogenic potential of senescent BMSCs via upregulating PDI-6

Bone marrow stromal cells (BMSCs) possess the capability to differentiate into osteogenic or adipogenic lineages. With aging, BMSCs suffer from mitochondrial dysfunction and undergo senescence, favoring adipogenesis at the expense of osteoblastogenesis. It leads to decreased bone formation and contributes to senile osteoporosis (SOP). In the current study, RNA-seq analysis unveiled that senescent BMSCs from mice exhibited a significant suppression in the expression of the protein disulfide isomerase PDI-6, an important regulator of mitochondrial unfolded protein response (UPR^mt) as well as maintenance of mitochondrial homeostasis. Overexpression of PDI-6 in senescent BMSCs partially rescued mitochondrial function and enhanced osteogenic differentiation. In contrast, osteoblastogenesis of BMSCs remarkably deteriorated under the condition of PDI-6 silencing. Furthermore, melatonin, an endocrine hormone, effectively enhanced PDI-6 expression and repaired injured mitochondria, and the effect of melatonin on PDI-6 expression was melatonin receptor dependent. We further identified that PDI-6 was a downstream effector of Wnt/β-catenin pathway, as the inhibitor of Wnt3A/TCF signaling, Wnt-C59, inhibited PDI-6 expression. Potential β-catenin-TCF/LEF binding sites on the promoter of PDI-6 gene were also validated by chromatin immunoprecipitation (ChIP) assay. Thus, our study suggests that PDI-6 is a pharmacological target of melatonin for the intervention of age-related osteoporosis via mitigating mitochondrial dysfunction in senescent BMSCs.

Human PARP1 substrates and regulators of its catalytic activity: An updated overview

Poly (ADP-ribose) polymerase 1 (PARP1) is a key DNA damage sensor that is recruited to damaged sites after DNA strand breaks to initiate DNA repair. This is achieved by catalyzing attachment of ADP-ribose moieties, which are donated from NAD⁺, on the amino acid residues of itself or other acceptor proteins. PARP inhibitors (PARPi) that inhibit PARP catalytic activity and induce PARP trapping are commonly used for treating BRCA1/2-deficient breast and ovarian cancers through synergistic lethality. Unfortunately, resistance to PARPi frequently occurs. In this review, we present the novel substrates and regulators of the PARP1-catalyzed poly (ADP-ribosyl)ation (PARylatison) that have been identified in the last 3 years. The overall aim is the presentation of protein interactions of potential therapeutic intervention for overcoming the resistance to PARPi.

Research progress of therapeutic drugs for doxorubicin-induced cardiomyopathy

Doxorubicin (DOX), as a kind of chemotherapy agent with remarkable therapeutic effect, can be used to treat diverse malignant tumors clinically. Dose-dependent cardiotoxicity is the most serious adverse reaction after DOX treatment, which eventually leads to cardiomyopathy and greatly limits the clinical application of DOX. DOX-induced cardiomyopathy is not a result of a single mechanistic action, and multiple mechanisms have been discovered and demonstrated experimentally, such as oxidative stress, inflammation, mitochondrial damage, calcium homeostasis disorder, ferroptosis, autophagy and apoptosis. Dexrazoxane (DEX) is the only protective agent approved by FDA for the treatment of DOX cardiomyopathy, but its clinical treatment still has some limitations. Therefore, we need to find other effective therapeutic drugs as soon as possible. In this paper, the drugs that effectively improve cardiomyopathy in recent years are mainly described from the aspects of natural drugs, endogenous substances, new dosage forms, herbal medicines, chemical modification and marketed drugs. The aim of the present study is to evaluate the effects of these drugs on DOX-induced anticancer and cardiomyopathy curative effects, so as to provide some reference value for clinical treatment of DOX-induced cardiomyopathy in the future.

The role of melatonin in bone regeneration: A review of involved signaling pathways

Increasing bone resorption followed by decreasing bone mineralization are hallmarks of bone degeneration, which mostly occurs in the elderly population and post-menopausal women. The use of mesenchymal stem cells (MSCs) has raised many promises in the field of bone regeneration due to their high osteoblastic differentiation capacity and easy availability from abundant sources. A variety of compounds, including growth factors, cytokines, and other internal factors, have been combined with MSCs to increase their osteoblastic differentiation capacity. One of these factors is melatonin, whose possible regulatory role in bone metabolism and formation has recently been suggested by many studies. Melatonin also is a potential signaling molecule and can affect many of the signaling pathways involved in MSCs osteoblastic differentiation, such as activation of PI3K/AKT, BMP/Smad, MAPK, NFkB, Nrf2/HO-1, Wnt, SIRT/SOD, PERK/ATF4. Furthermore, melatonin in combination with other components such as strontium, vitamin D3, and vitamin K2 has a synergistic effect on bone microstructure and improves bone mineral density (BMD). In this review article, we aim to summarize the regulatory mechanisms of melatonin in osteoblastic differentiation of MSCs and underling involved signaling pathways as well as the clinical potential of using melatonin in bone degenerative disorders.

The Zebrafish, an Outstanding Model for Biomedical Research in the Field of Melatonin and Human Diseases

The zebrafish has become an excellent model for the study of human diseases because it offers many advantages over other vertebrate animal models. The pineal gland, as well as the biological clock and circadian rhythms, are highly conserved in zebrafish, and melatonin is produced in the pineal gland and in most organs and tissues of the body. Zebrafish have several copies of the clock genes and of aanat and asmt genes, the latter involved in melatonin synthesis. As in mammals, melatonin can act through its membrane receptors, as with zebrafish, and through mechanisms that are independent of receptors. Pineal melatonin regulates peripheral clocks and the circadian rhythms of the body, such as the sleep/wake rhythm, among others. Extrapineal melatonin functions include antioxidant activity, inducing the endogenous antioxidants enzymes, scavenging activity, removing free radicals, anti-inflammatory activity through the regulation of the NF-κB/NLRP3 inflammasome pathway, and a homeostatic role in mitochondria. In this review, we introduce the utility of zebrafish to analyze the mechanisms of action of melatonin. The data here presented showed that the zebrafish is a useful model to study human diseases and that melatonin exerts beneficial effects on many pathophysiological processes involved in these diseases.

Mechanisms during Osteogenic Differentiation in Human Dental Follicle Cells

Human dental follicle cells (DFCs) as periodontal progenitor cells are used for studies and research in regenerative medicine and not only in dentistry. Even if innovative regenerative therapies in medicine are often considered the main research area for dental stem cells, these cells are also very useful in basic research and here, for example, for the elucidation of molecular processes in the differentiation into mineralizing cells. This article summarizes the molecular mechanisms driving osteogenic differentiation of DFCs. The positive feedback loop of bone morphogenetic protein (BMP) 2 and homeobox protein DLX3 and a signaling pathway associated with protein kinase B (AKT) and protein kinase C (PKC) are presented and further insights related to other signaling pathways such as the WNT signaling pathway are explained. Subsequently, some works are presented that have investigated epigenetic modifications and non-coding ncRNAs and their connection with the osteogenic differentiation of DFCs. In addition, studies are presented that have shown the influence of extracellular matrix molecules or fundamental biological processes such as cellular senescence on osteogenic differentiation. The putative role of factors associated with inflammatory processes, such as interleukin 8, in osteogenic differentiation is also briefly discussed. This article summarizes the most important insights into the mechanisms of osteogenic differentiation in DFCs and is intended to be a small help in the direction of new research projects in this area.

The "Three in One" Bone Repair Strategy for Osteoporotic Fractures

In aging society, osteoporotic fractures have become one major social problem threatening the health of the elderly population in China. Compared with conventional fractures, low bone mass, bone defect and retarded healing issues of osteoporotic fractures lead to great difficulties in treatment and rehabilitation. Addressing major concerns in clinical settings, we proposed the "three in one" bone repair strategy focusing on anti-osteoporosis therapies, appropriate bone grafting and fracture healing accelerating. We summarize misconceptions and repair strategies for osteoporotic fracture management, expecting improvement of prognosis and clinical outcomes for osteoporotic fractures, to further improve therapeutic effect and living quality of patients.