A novel phosphorylation by AMP-activated kinase regulates RUNX2 from ubiquitination in osteogenesis over adipogenesis. Cell Death Dis. 2018;9:754. [PMID: 29988028 PMCID: PMC6037667 DOI: 10.1038/s41419-018-0791-7]

AMP-activated protein kinase (AMPK) is essential for tendon homeostasis and prevents premature senescence and ectopic calcification

Tendinopathy is a debilitating tendon disorder affecting millions of people, characterized by pain, swelling, and diminished biomechanical properties. While the precise mechanisms underlying tendon homeostasis remain unclear, metabolic regulation plays a critical role. In this study, we combine transcriptomic analysis of human tendinopathic samples with a conditional mouse model in which Prkaa1 (encoding AMPKα1) is selectively deleted in tendon progenitors to elucidate the role of AMPK signaling in tendon homeostasis. RNA sequencing of diseased human tendons revealed downregulation of key metabolic genes, including several involved in the mitochondrial electron transport chain and AMPK signaling pathways, alongside an increase in markers associated with senescence and a secretory inflammatory profile. In parallel, mice with loss of Prkaa1 function exhibited normal postnatal development; however, by one month of age, tendons demonstrated widespread transcriptional alterations related to cell cycle regulation and ECM organization. By three months, AMPKα1-deficient tendons showed significant reductions in mechanical strength and increased expression of senescence markers p21 and p16, progressing to prominent ectopic calcification with age. In vitro studies further confirmed that tendon fibroblasts lacking AMPKα1 have altered ECM substrate adhesion profiles. Importantly, voluntary exercise partially rescued these deficits by enhancing ECM organization and reducing senescence marker expression. Collectively, our findings demonstrate that AMPKα1 is critical for maintaining energy balance, regulating ECM remodeling, and preventing premature cellular senescence in tendon. These insights highlight AMPK signaling as a promising therapeutic target and underscore the beneficial role of exercise in mitigating tendinopathic changes.

Osteoprotegerin mediates adipogenesis in obesity

INTRODUCTION

Adipogenesis, the process of white adipose tissue expansion, plays a critical role in the development of obesity. Osteoprotegerin (OPG), known for its role in bone metabolism regulation, emerges as a potential regulator in mediating adipogenesis during obesity onset.

OBJECTIVES

This study aims to elucidate the involvement of OPG in adipogenesis during the early phases of diet-induced obesity and explore its therapeutic potential in obesity management.

METHODS

Using a diet-induced obesity model, we investigated OPG expression patterns in adipocytes and explored the mechanisms underlying its involvement in adipogenesis. We also assessed the effects of targeted silencing of OPG and recombinant OPG administration on obesity progression and insulin resistance. Additionally, the impact of electroacupuncture treatment on OPG levels and obesity management was evaluated in both animal models and human participants.

RESULTS

OPG expression was prominently activated in adipocytes of white adipose tissues during the early phase of diet-induced obesity. Hyperlipidemia induced Cbfa1-dependent OPG transcription, initiating and promoting adipogenesis, leading to cell-size expansion and lipid storage. Intracellular OPG physically bound to RAR and released the PPARɤ/RXR complex, activating adipogenesis-associated gene expression. Targeted silencing of OPG suppressed obesity development, while recombinant OPG administration promoted disease progression and insulin resistance in obese mice. Electroacupuncture treatment suppressed obesity development in an OPG-dependent manner and improved obesity parameters in obese human participants.

CONCLUSION

OPG emerges as a key regulator in mediating adipogenesis during obesity development. Targeting OPG holds promise for the prevention and treatment of obesity, as evidenced by the efficacy of electroacupuncture treatment in modulating OPG levels and managing obesity-related outcomes.

Cell signaling and transcriptional regulation of osteoblast lineage commitment, differentiation, bone formation, and homeostasis

The initiation of osteogenesis primarily occurs as mesenchymal stem cells undergo differentiation into osteoblasts. This differentiation process plays a crucial role in bone formation and homeostasis and is regulated by two intricate processes: cell signal transduction and transcriptional gene expression. Various essential cell signaling pathways, including Wnt, BMP, TGF-β, Hedgehog, PTH, FGF, Ephrin, Notch, Hippo, and Piezo1/2, play a critical role in facilitating osteoblast differentiation, bone formation, and bone homeostasis. Key transcriptional factors in this differentiation process include Runx2, Cbfβ, Runx1, Osterix, ATF4, SATB2, and TAZ/YAP. Furthermore, a diverse array of epigenetic factors also plays critical roles in osteoblast differentiation, bone formation, and homeostasis at the transcriptional level. This review provides an overview of the latest developments and current comprehension concerning the pathways of cell signaling, regulation of hormones, and transcriptional regulation of genes involved in the commitment and differentiation of osteoblast lineage, as well as in bone formation and maintenance of homeostasis. The paper also reviews epigenetic regulation of osteoblast differentiation via mechanisms, such as histone and DNA modifications. Additionally, we summarize the latest developments in osteoblast biology spurred by recent advancements in various modern technologies and bioinformatics. By synthesizing these insights into a comprehensive understanding of osteoblast differentiation, this review provides further clarification of the mechanisms underlying osteoblast lineage commitment, differentiation, and bone formation, and highlights potential new therapeutic applications for the treatment of bone diseases.

Association of Body Mass Index and Chronology of Tooth Eruption in Children visiting a Dental Hospital in UAE: A Cross-sectional Study

The objective of this research was to investigate the relationship between body mass index (BMI) and the mean age at which permanent teeth erupt in school-going children. Materials and Method: This cross-sectional study at RAK College of Dental Sciences, UAE, involved 89 children aged 6-14 years. Erupted teeth in the mouth were included. Statistical analysis, including t-tests, ANOVA, and Kruskal-Wallis, was conducted using SPSS version 29, with a significance threshold set at p < 0.05. Results: Out of 89 children (41 girls and 48 boys) in the study, 56.17 % had normal weight, 20.22 % were overweight, 17.97 % were underweight, and 5.6 % were obese. Female children generally experienced earlier permanent tooth eruption than males. Additionally, there was an observed trend of earlier tooth eruption with increasing weight or BMI. Underweight children notably displayed a delayed mean age of tooth eruption. Conclusion: This study demonstrates a notable correlation between BMI and the mean age at which permanent teeth erupt in school-going children aged 6 to 14 years who visited our dental hospital. To establish a more precise understanding of the connection between BMI and dental development, we recommend conducting further longitudinal studies involving multiple centers. Clinical Significance: Monitoring a child's BMI is crucial for assessing dental health and planning tailored treatment for those aged 6 to 14. Understanding the BMI's connection to permanent tooth eruption timing allows dental professionals to identify trends in early or delayed development. This enables them to customize treatment strategies, promoting a precise and personalized approach for better oral health outcomes in this age group.

3D Molybdenum Disulfide Nanospheres Loaded with Metformin to Enhance SCPP Scaffolds for Bone Regeneration

Conventional strontium-doped calcium polyphosphate (SCPP) ceramics have attracted a lot of attention due to good cytocompatibility and controlled degradation. However, their poor mechanical strength, brittleness, and difficulty in eliminating unavoidable postoperative inflammation and bacterial infections in practical applications limit their further clinical application. In this study, carboxylated molybdenum disulfide nanospheres (MoS2-COOH) were first prepared via a one-step hydrothermal method. The optimal doping concentration of MoS2-COOH was then incorporated into SCPP to overcome its poor mechanical strength. To further enhance the anti-inflammatory properties of scaffolds, metformin (MET) was loaded onto MoS2-COOH through covalent bond cross-linking (MoS2-MET). Then MoS2-MET was doped into SCPP (SCPP/MoS2-MET) according to the previously obtained concentration, resulting in the controlled and sustained release of MET from the SCPP/MoS2-MET scaffolds for 21 days in vitro. The SCPP/MoS2-MET scaffolds were shown to have good biological activity in vitro to promote stem cell proliferation and the potential to promote mineralization in vitro. It also showed good osteoimmunomodulatory activity could reduce the expression of proinflammatory factors and effectively induce the differentiation of BMSCs under inflammatory conditions, upregulating the expression of relevant osteoblastic cytokines. In addition, SCPP/MoS2-MET scaffolds could effectively inhibit Staphylococcus aureus and Escherichia coli. In vivo experiments also demonstrated better osteogenic potential of SCPP/MoS2-MET scaffolds compared with the other scaffold-samples. Thus, the introduction of carboxylated molybdenum disulfide nanospheres is a promising approach to improve the properties of SCPP and may provide a new modification strategy for inert ceramic scaffolds and the construction of multifunctional composite scaffolds for bone tissue engineering.

WWP1 E3 ligase at the crossroads of health and disease

The E3 ubiquitin ligase WWP1 (WW Domain-containing E3 Ubiquitin Protein Ligase 1) is a member of the HECT (Homologous to the E6-associated protein Carboxyl Terminus) E3 ligase family. It is conserved across several species and plays crucial roles in various physiological processes, including development, cell growth and proliferation, apoptosis, and differentiation. It exerts its functions through ubiquitination or protein-protein interaction with PPXY-containing proteins. WWP1 plays a role in several human diseases, including cardiac conditions, neurodevelopmental, age-associated osteogenic disorders, infectious diseases, and cancers. In solid tumors, WWP1 plays a dual role as both an oncogene and a tumor suppressor, whereas in hematological malignancies such as AML, it is identified as a dedicated oncogene. Importantly, WWP1 inhibition using small molecule inhibitors such as Indole-3-Carbinol (I3C) and Bortezomib or siRNAs leads to significant suppression of cancer growth and healing of bone fractures, suggesting that WWP1 might serve as a potential therapeutic target for several diseases. In this review, we discuss the evolutionary perspective, structure, and functions of WWP1 and its multilevel regulation by various regulators. We also examine its emerging roles in cancer progression and its therapeutic potential. Finally, we highlight WWP1's role in normal physiology, contribution to pathological conditions, and therapeutic potential for cancer and other diseases.

AMPK-induced novel phosphorylation of RUNX1 inhibits STAT3 activation and overcome imatinib resistance in chronic myelogenous leukemia (CML) subjects

Imatinib resistance remains an unresolved problem in CML disease. Activation of JAK2/STAT3 pathway and increased expression of RUNX1 have become one reason for development of imatinib resistance in CML subjects. Metformin has gained attention as an antileukemic drug in recent times. However, the molecular mechanism remains elusive. The present study shows that RUNX1 is a novel substrate of AMP-activated kinase (AMPK), where AMPK phosphorylates RUNX1 at Ser 94 position. Activation of AMPK by metformin could lead to increased cytoplasmic retention of RUNX1 due to Ser 94 phosphorylation. RUNX1 Ser 94 phosphorylation resulted in increased interaction with STAT3, which was reflected in reduced transcriptional activity of both RUNX1 and STAT3 due to their cytoplasmic retention. The reduced transcriptional activity of STAT3 and RUNX1 resulted in the down-regulation of their signaling targets involved in proliferation and anti-apoptosis. Our cell proliferation assays using in vitro resistant cell line models and PBMCs isolated from CML clinical patients and normal subjects demonstrate that metformin treatment resulted in reduced growth and improved imatinib sensitivity of resistant subjects.

Clinical potentials of metformin in cancer therapy

Diabetes is a prevalent metabolic disorder that results in several comorbidities including cancer. Cancer becomes the most severe complication of diabetes patients. Growing evidence proved that impaired glucose homeostasis is an independent risk factor for the occurrence of various types of cancers including liver, pancreatic, gastric (stomach), colorectal, kidney, and breast cancers, and influences cancer prognosis. Diabetes mellitus and cancer have a bidirectional relationship, thus there is a need to look for drugs that can be beneficial in treating both diseases. Therefore, more research is focusing on evaluating the role of antihyperglycemic agents in the treatment of various types of cancers. Metformin, an FDA-approved first-line antihyperglycemic agent can be used as a monotherapy or as an adjuvant to chemotherapeutic agents in the treatment of various types of cancer. However, the exact mechanism of metformin as an anticancer agent is still unknown, the majority of the described putative mechanisms focus on promoting the activity of the AMP-activated protein kinase (AMPK) pathway. This review article thus gives insights into the prognosis of cancer in diabetes patients and aims to explore the possible mechanism of action of metformin in the prevention and treatment of cancer.

Phosphorylated MAPK11 promotes the progression of clear cell renal cell carcinoma by maintaining RUNX2 protein abundance

Previous studies have demonstrated that mitogen-activated protein kinase 11 (MAPK11) functions as an important point of integration in signalling transduction pathways and controlling endocellular processes, including viability of cells, differentiation, proliferation and apoptosis, through the sequence phosphorylation of the substrate protein Ser/Thr kinase protein cascade. Though MAPK 11 plays an important role in various tumours, especially in the invasive and metastatic processes, its expression and molecular mechanism in clear cell renal cell carcinoma (ccRCC) remain unclear. Runt-associated transcription factor 2 (RUNX2), a main transcription factor for osteoblast differentiation and chondrocyte maturation, has high expression in a number of tumours. In this study, the mRNA and protein levels of targeted genes in ccRCC tissues and adjacent tissues are analysed using the Cancer Genome Atlas (TCGA) database and western blotting. The ccRCC cell proliferation was measured with colony formation and EdU assay, and cell migration was examined through transwell assay. The interactive behaviour between proteins was detected with immunoprecipitation. Half-life period of RUNX2 protein was measured with cycloheximide chase assay. The results of the study indicated overexpression of MAPK11 and RUNX2 in ccRCC tissues and cell lines. MAPK11 and RUNX2 promoted the ccRCC cell proliferation and migration. Additionally, physical interaction took place between RUNX2 and P-MAPK11, which functioned to sustain the stability of RUNX2 protein. The high expression of RUNX2 could neutralize the functional degradation in MAPK11. And the outcomes of the study suggest that the P-MAPK11/RUNX2 axis may be used as a potential therapeutic target of ccRCC.

Small-molecule amines: a big role in the regulation of bone homeostasis

Numerous small-molecule amines (SMAs) play critical roles in maintaining bone homeostasis and promoting bone regeneration regardless of whether they are applied as drugs or biomaterials. On the one hand, SMAs promote bone formation or inhibit bone resorption through the regulation of key molecular signaling pathways in osteoblasts/osteoclasts; on the other hand, owing to their alkaline properties as well as their antioxidant and anti-inflammatory features, most SMAs create a favorable microenvironment for bone homeostasis. However, due to a lack of information on their structure/bioactivity and underlying mechanisms of action, certain SMAs cannot be developed into drugs or biomaterials for bone disease treatment. In this review, we thoroughly summarize the current understanding of SMA effects on bone homeostasis, including descriptions of their classifications, biochemical features, recent research advances in bone biology and related regulatory mechanisms in bone regeneration. In addition, we discuss the challenges and prospects of SMA translational research.

Small-Molecule Loaded Biomimetic Biphasic Scaffold for Osteochondral Regeneration: An In Vitro and In Vivo Study

Osteoarthritis is a prevalent musculoskeletal disorder in the elderly, which leads to high rates of morbidity. Mesenchymal stem cells (MSCs) are a promising approach to promote tissue regeneration in the absence of effective long-term treatments. Small molecules are relatively inexpensive and can selectively alter stem cell behavior during their differentiation, making them an attractive option for clinical applications. In this study, we developed an extracellular matrix (ECM)-based biphasic scaffold (BPS) loaded with two small-molecule drugs, kartogenin (KGN) and metformin (MET). This cell-free biomimetic biphasic scaffold consists of a bone (gelatin/hydroxyapatite scaffold embedded with metformin [GHSM]) and cartilage (nano-gelatin fiber embedded with kartogenin [NGFK]) layer designed to stimulate osteochondral regeneration. Extracellular matrix (ECM)-based biomimetic scaffolds can promote native cell recruitment, infiltration, and differentiation even in the absence of additional growth factors. The biphasic scaffold (BPS) showed excellent biocompatibility in vitro, with mesenchymal stem cells (MSCs) adhering, proliferating, and differentiated on the biomimetic biphasic scaffolds (GHSM and NGFK layers). The biphasic scaffolds upregulated both osteogenic and chondrogenic gene expression, sulfated glycosaminoglycan (sGAG), osteo- and chondrogenic biomarker, and relative mRNA gene expression. In an in vivo rat model, histo-morphological staining showed effective regeneration of osteochondral defects. This novel BPS has the potential to enhance both subchondral bone repair and cartilage regeneration, demonstrating excellent effects on cell homing and the recruitment of endogenous stem cells.

Policosanol Stimulates Osteoblast Differentiation via Adenosine Monophosphate-Activated Protein Kinase-Mediated Expression of Insulin-Induced Genes 1 and 2

Policosanol is known as a hypocholesterolemic compound and is derived from plants such as sugar cane and corn. Policosanol can lower blood pressure or inhibit adipogenesis, but its effect on osteogenic differentiation and the molecular mechanism is unclear. This study aims to investigate the effect of policosanol on osteogenic differentiation in MC3T3-E1 cells and zebrafish models. Administration of policosanol into MC3T3-E1 induced the expression of the osteogenic genes such as distal-less homeobox 5 (Dlx5) and runt-related transcription factor 2 (Runx2). Alkaline phosphatase activity and extracellular mineralization also increased. Policosanol promoted activation of adenosine monophosphate-activated protein kinase (AMPK) and insulin-induced genes (INSIGs) expression and regulation of INSIGs modulated osteoblast differentiation. AMPK activation through transfection of the constitutively active form of AMPK (CA-AMPK) increased INSIGs expression, whereas policosanol-induced INSIGs expression was suppressed by inhibitor of AMPK (Com. C). Furthermore, the osteogenic effects of policosanol were verified in zebrafish. Amputated caudal fin rays were regenerated by policosanol treatment. Taken together, these results show that policosanol increases osteogenic differentiation and contributes to fin regeneration in zebrafish via AMPK-mediated INSIGs expression, suggesting that policosanol has potential as an osteogenic agent.

Essential amino acid starvation induces cell cycle arrest, autophagy, and inhibits osteogenic differentiation in murine osteoblast

This study investigates the effects of essential amino acid (EAA) starvation on murine osteoblasts cells and the underlying mechanisms. We performed and observed the cell proliferation, autophagy, and osteogenic differentiation under deprivation of EAA in vitro. The results showed that EAA starvation resulted in cell cycle arrest via phosphorylation of the MAPK signaling pathway, leading to inhibition of cell proliferation and osteogenic differentiation. Additionally, the LKB1-AMPK signaling pathway was also found to be phosphorylated, inducing autophagy. These findings highlight the significant role of EAA in regulating cellular processes. Furthermore, this study contributes to our understanding of the effects of nutrient deprivation on cellular physiology and may aid in the development of novel therapeutic strategies for diseases associated with amino acid metabolism.

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.

Intracellular glucose starvation inhibits osteogenic differentiation in human periodontal ligament cells

BACKGROUND

Periodontal ligament cells (PDLCs), as mesenchymal cells in the oral cavity, are closely linked to periodontal tissue regeneration. However, the effect of local glucose deficiency on periodontal tissue regeneration, such as immediately post-surgery, remains unknown.

OBJECTIVE

In the present study, we investigated the effect of a low-glucose environment on the proliferation and osteogenic differentiation of PDLCs.

MATERIALS AND METHODS

We used media with five glucose concentrations (100, 75, 50, 25, and 0 mg/dL) and focused on the effects of a low-glucose environment on the proliferation, osteogenic differentiation, and autophagy of PDLCs. Additionally, we focused on changes in lactate production in a low-glucose environment and investigated the involvement of lactate with AZD3965, a monocarboxylate transporter-1 (MCT-1) inhibitor.

RESULTS

The low-glucose environment inhibited PDLCs proliferation, migration, and osteogenic differentiation, and induced the expression of the autophagy-related factors LC3 and p62. Lactate and ATP production were decreased under low-glucose conditions. The addition of AZD3965 (MCT-1 inhibitor) in normal glucose conditions caused a similar trend as in low-glucose conditions on PDLCs.

CONCLUSION

Our results suggest lactate production through glucose metabolism in the osteogenic differentiation of PDLCs. A low-glucose environment decreased lactate production, inhibiting cell proliferation, migration, and osteogenic differentiation and inducing autophagy in PDLCs.

Bioinspired drug-delivery system emulating the natural bone healing cascade for diabetic periodontal bone regeneration

Diabetes mellitus (DM) aggravates periodontitis, resulting in accelerated periodontal bone resorption. Disordered glucose metabolism in DM causes reactive oxygen species (ROS) overproduction resulting in compromised bone healing, which makes diabetic periodontal bone regeneration a major challenge. Inspired by the natural bone healing cascade, a mesoporous silica nanoparticle (MSN)-incorporated PDLLA (poly(dl-lactide))-PEG-PDLLA (PPP) thermosensitive hydrogel with stepwise cargo release is designed to emulate the mesenchymal stem cell "recruitment-osteogenesis" cascade for diabetic periodontal bone regeneration. During therapy, SDF-1 quickly escapes from the hydrogel due to diffusion for early rat bone marrow stem cell (rBMSC) recruitment. Simultaneously, slow degradation of the hydrogel starts to gradually expose the MSNs for sustained release of metformin, which can scavenge the overproduced ROS under high glucose conditions to reverse the inhibited osteogenesis of rBMSCs by reactivating the AMPK/β-catenin pathway, resulting in regulation of the diabetic microenvironment and facilitation of osteogenesis. In vitro experiments indicate that the hydrogel markedly restores the inhibited migration and osteogenic capacities of rBMSCs under high glucose conditions. In vivo results suggest that it can effectively recruit rBMSCs to the periodontal defect and significantly promote periodontal bone regeneration under type 2 DM. In conclusion, our work provides a novel therapeutic strategy of a bioinspired drug-delivery system emulating the natural bone healing cascade for diabetic periodontal bone regeneration.

Metformin increases bone marrow adipose tissue by promoting mesenchymal stromal cells apoptosis

Bone marrow adipose tissue (MAT) has the potential to exert both local and systemic effects on metabolic homeostasis. As a first-line drug used to treat type 2 diabetes mellitus, metformin has conflicting effects on MAT and bone marrow mesenchymal stem cell (BM-MSC) differentiation. Through a series of experiments in vivo and in vitro, we found that except improving the glucose and lipid metabolism disorder in ob/ob mice, 200 mg/kg metformin increased MAT in mice tibia, and prompted osteogenic genes (RunX2, OPN, OCN) and lipogenic genes (Ppar-γ, Cebpα, Scd1) expression in mice bone marrow. However, metformin promoted osteogenesis and inhibited lipogenesis of MSC in vitro, which is inconsistent with the results in vivo. Given MAT being considered the "filler" of the space after the apoptosis of bone marrow stroma, the effect of metformin on MSC apoptosis was examined. We discovered that metformin induces MSC apoptosis in vivo and in vitro. Therefore, we speculated that the increased MAT in mice tibia may be attributed to the filling of adipose tissue after apoptosis of bone marrow stromal cells induced by metformin. The increased MAT may be involved in the regulation of metformin on glucose, lipid, and bone metabolism in diabetic mice, providing a new way to understand the metabolic regulation of metformin. While increased MAT-associated insulin resistance and metabolic disorders may account for the poorer clinical benefits in patients with intensive glucose control.

Canagliflozin promotes osteoblastic MC3T3-E1 differentiation via AMPK/RUNX2 and improves bone microarchitecture in type 2 diabetic mice

Individuals with type 2 diabetes mellitus (T2DM) have an increased risk of bone metabolic disorders and bone fracture due to disease progression and clinical treatment. The effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors, now greatly prescribed for the treatment of T2DM, on bone metabolism is not clear. This study aimed to explore the possible influence of bone metabolic disorder and the underlying mechanism through a comparison of three different SGLT2 inhibitors (canagliflozin, dapagliflozin, and empagliflozin) in the treatment of type 2 diabetic mice. For the in vivo experiments, four groups (DM, DM+Cana, DM+Dapa, and DM+Empa) were established using micro-CT to detect the bone microarchitecture and bone-related parameters. The study results indicated that canagliflozin, but not dapagliflozin or empagliflozin, increased bone mineral density (p<0.05) and improved bone microarchitecture in type 2 diabetic mice. Furthermore, canagliflozin promoted osteoblast differentiation at a concentration of 5 μM under high glucose concentration (HG). Phosphorylated adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) α (Thr172) has been confirmed to activate run-related transcription factor-2 (RUNX2) to perform this function. This effect can be partially reversed by the AMPK inhibitor dorsomorphin (compound C) and strengthened by the AMPK activator acadesine (AICAR) in vitro. The level trend of RUNX2 and p-AMPK in vivo were consistent with those in vitro. This study suggested that canagliflozin played a beneficial role in bone metabolism in type 2 diabetic mice compared with dapagliflozin and empagliflozin. It provides some theoretical support for the chosen drugs, especially for patients with osteoporosis or a high risk of fracture.

Regulatory network of metformin on adipogenesis determined by combining high-throughput sequencing and GEO database

Adipose differentiation and excessive lipid accumulation are the important characteristics of obesity. Metformin, as a classic hypoglycaemic drug, has been proved to reduce body weight in type 2 diabetes, the specific mechanism has not been completely clear. A few studies have explored its effect on adipogenesis in vitro, but the existing experimental results are ambiguous. 3T3-L1 preadipocytes were used to explore the effects of metformin on the morphological and physiological changes of lipid droplets during adipogenesis. A high throughput sequencing was used to examine the effects of metformin on the transcriptome of adipogenesis. Considering the inevitable errors among independent experiments, we performed integrated bioinformatics analysis to identify important genes involved in adipogenesis and reveal potential molecular mechanisms. During the process of adipogenesis, metformin visibly relieved the morphological and functional changes. In addition, metformin reverses the expression pattern of genes related to adipogenesis at the transcriptome level. Combining with integrated bioinformatics analyses to further identify the potential targeted genes regulated by metformin during adipogenesis. The present study identified novel changes in the transcriptome of metformin in the process of adipogenesis that might shed light on the underlying mechanism by which metformin impedes the progression of obesity.

Regulatory Effects and Mechanism of Action of Green Tea Polyphenols on Osteogenesis and Adipogenesis in Human Adipose Tissue-Derived Stem Cells

We previously showed that green tea polyphenols (GTPs) exert antiadipogenic effects on preadipocyte proliferation. Here, we investigated the regulatory effects of GTPs on osteogenesis and adipogenesis during early differentiation of human adipose tissue-derived stem cells (hADSC). Adipogenesis of hADSCs was determined by oil-red-O staining and triglycerides synthesis measurement. Osteoporosis of hADSC was measured using alkaline phosphatase assays and intracellular calcium levels. Immunofluorescence staining and qRT-PCR were used to detect PPARγ-CEBPA regulated adipogenic pathway regulated by PPAR-CEBPA and the osteogenic pathway mediated by RUNX2-BMP2. We found that GTPs treatment significantly decreased lipid accumulation and cellular triglyceride synthesis in mature adipocytes and attenuated pioglitazone-induced adipogenesis in a dose-dependent manner. GTPs downregulated protein and mRNA expression of Pparγ and attenuated pioglitazone-stimulated-Cebpa expression. GTPs treatment significantly enhanced hADSCs differentiation into osteoblasts compared to control and pioglitazone-treated cells. GTPs upregulated RunX2 and Bmp2 proteins and mRNA expression compared to control and significantly attenuated decreased RunX2 and Bmp2 mRNA expression by pioglitazone. In conclusion, our data demonstrates GTPs possesses great ability to facilitate osteogenesis and simultaneously inhibits hADSC differentiation into adipogenic lineage by upregulating the RUNX2-BMP2 mediated osteogenic pathway and suppressing PPARγ-induced signaling of adipogenesis. These findings highlight GTPs' potential to combat osteoporosis associated with obesity.

Recent advances on small molecules in osteogenic differentiation of stem cells and the underlying signaling pathways

Bone-related diseases are major contributors to morbidity and mortality in elderly people and the current treatments result in insufficient healing and several complications. One of the promising areas of research for healing bone fractures and skeletal defects is regenerative medicine using stem cells. Differentiating stem cells using agents that shift cell development towards the preferred lineage requires activation of certain intracellular signaling pathways, many of which are known to induce osteogenesis during embryological stages. Imitating embryological bone formation through activation of these signaling pathways has been the focus of many osteogenic studies. Activation of osteogenic signaling can be done by using small molecules. Several of these agents, e.g., statins, metformin, adenosine, and dexamethasone have other clinical uses but have also shown osteogenic capacities. On the other hand, some other molecules such as T63 and tetrahydroquinolines are not as well recognized in the clinic. Osteogenic small molecules exert their effects through the activation of signaling pathways known to be related to osteogenesis. These pathways include more well-known pathways including BMP/Smad, Wnt, and Hedgehog as well as ancillary pathways including estrogen signaling and neuropeptide signaling. In this paper, we review the recent data on small molecule-mediated osteogenic differentiation, possible adjunctive agents with these molecules, and the signaling pathways through which each small molecule exerts its effects.

Association between Molecular Mechanisms and Tooth Eruption in Children with Obesity

Different works have reported earlier permanent teething in obese/overweight children compared to control ones. In contrast, others have reported a delayed permanent teething in undernutrition/underweight children compared to control one. It has been reported that becoming overweight or suffering from obesity can increase gingival pro-inflammatory drive and can affect orthodontic treatment (among other complications). In this sense, little is known about the molecular mechanisms affecting dental eruption timing. Leptin and adiponectin are adipocytokines signaling molecules released in overweight and underweight conditions, respectively. These adipocytokines can modulate osteocyte, odontoblast, and cementoblast activity, even regulating dental lamina initiation. The present review focuses on the molecular approach wherein leptin and adiponectin act as modulators of Runt-related transcription factor 2 (Runx 2) gene regulating dental eruption timing.

High glutamine suppresses osteogenesis through mTORC1-mediated inhibition of the mTORC2/AKT-473/RUNX2 axis

Activation of the key nutrient cellular sensors mTORC1 and mTORC2 directs the fate of mesenchymal stromal cells (MSCs). Here, we report that glutamine regulates crosstalk between mTOR complexes and lineage commitment of MSCs independent of glucose concentration. High glutamine-induced mTORC1 hyperactivation resulted in the suppression of mTORC2, which otherwise stabilizes RUNX2 via GSK3β inhibition through pAKT-473. Activation of GSK3β resulted in the ubiquitination of RUNX2, a key transcription factor for the osteogenic commitment of MSCs. However, low glutamine conditions inhibit mTORC1 hyperactivation followed by increased mTORC2 activation and RUNX2 stabilization. Under diabetic/high-glucose conditions, glutamine-triggered hyperactivation of mTORC1 resulted in mTORC2 suppression, and active GSK3β led to suppression of RUNX2. Activation of p-AMPK by metformin inhibits high glutamine-induced mTORC1 hyperactivation and rescues RUNX2 through the mTORC2/AKT-473 axis. Collectively, our study indicates the role of glutamine in modulating MSC fate through cross-talk between mTOR complexes by identifying a critical switch in signaling. It also shows the importance of glutamine in modulating molecular cues (mTORC1/p-70S6K/mTORC2/RUNX2) that are involved in driving diabetes-induced bone adipogenesis and other secondary complications.

Targeting Sirt1, AMPK, Nrf2, CK2, and Soluble Guanylate Cyclase with Nutraceuticals: A Practical Strategy for Preserving Bone Mass

There is a vast pre-clinical literature suggesting that certain nutraceuticals have the potential to aid the preservation of bone mass in the context of estrogen withdrawal, glucocorticoid treatment, chronic inflammation, or aging. In an effort to bring some logical clarity to these findings, the signaling pathways regulating osteoblast, osteocyte, and osteoclast induction, activity, and survival are briefly reviewed in the present study. The focus is placed on the following factors: the mechanisms that induce and activate the RUNX2 transcription factor, a key driver of osteoblast differentiation and function; the promotion of autophagy and prevention of apoptosis in osteoblasts/osteoclasts; and the induction and activation of NFATc1, which promotes the expression of many proteins required for osteoclast-mediated osteolysis. This analysis suggests that the activation of sirtuin 1 (Sirt1), AMP-activated protein kinase (AMPK), the Nrf2 transcription factor, and soluble guanylate cyclase (sGC) can be expected to aid the maintenance of bone mass, whereas the inhibition of the serine kinase CK2 should also be protective in this regard. Fortuitously, nutraceuticals are available to address each of these targets. Sirt1 activation can be promoted with ferulic acid, N1-methylnicotinamide, melatonin, nicotinamide riboside, glucosamine, and thymoquinone. Berberine, such as the drug metformin, is a clinically useful activator of AMPK. Many agents, including lipoic acid, melatonin, thymoquinone, astaxanthin, and crucifera-derived sulforaphane, can promote Nrf2 activity. Pharmacological doses of biotin can directly stimulate sGC. Additionally, certain flavonols, notably quercetin, can inhibit CK2 in high nanomolar concentrations that may be clinically relevant. Many, though not all, of these agents have shown favorable effects on bone density and structure in rodent models of bone loss. Complex nutraceutical regimens providing a selection of these nutraceuticals in clinically meaningful doses may have an important potential for preserving bone health. Concurrent supplementation with taurine, N-acetylcysteine, vitamins D and K2, and minerals, including magnesium, zinc, and manganese, plus a diet naturally high in potassium, may also be helpful in this regard.

A-769662 stimulates the differentiation of bone marrow-derived mesenchymal stem cells into osteoblasts via AMP-activated protein kinase-dependent mechanism

AMP-activated protein kinase (AMPK) signaling shows an important role in energy metabolism and has recently been involved in osteogenic and adipogenic differentiation. In this study we aimed to investigate the role of AMPK activator, A-769662, in regulating the differentiation of mesenchymal stem cells derived from bone marrow (BMSCs) into osteoblastic and adipocytic cell lineage. The effect of A-769662 on osteogenesis was assessed by quantitative alkaline phosphatase (ALP) activity, matrix mineralization stained with Alizarin red, and gene expression analysis by quantitative polymerase chain reaction (qPCR). Adipogenesis was determined by Oil Red O staining for fat droplets and qPCR analysis of adipogenic markers. A-769662 activated the phosphorylation of AMPKα1 during the osteogenesis of mBMSCs as revealed by western blot analysis. A-769662 promoted the early stage of the commitment of mouse (m) BMSCs differentiation into osteoblasts, while inhibiting their differentiation into adipocytes in a dose-dependent manner. The effects of A-769662 on stimulating osteogenesis and inhibiting adipogenesis of mBMSCs were significantly eliminated in the presence of either AMPKα1 siRNA or Compound C, an inhibitor of AMPK pathway. In conclusion, we identified A-769662 as a new compound that promotes the commitment of BMSCs into osteoblasts versus adipocytes via AMPK-dependent mechanism. Thus our data show A-769662 as a potential osteo-anabolic drug for treatment of osteoporosis.

Metformin enhances the osteogenesis and angiogenesis of human umbilical cord mesenchymal stem cells for tissue regeneration engineering

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are a potential clinical material in regenerative medicine applications. Metformin has shown safety and effectiveness as a clinical drug. However, the effect of metformin as a treatment on hUC-MSCs is unclear. Our research aimed to explore the effects of metformin on the osteogenesis, adipogenesis and angiogenesis of hUC-MSCs, and attempted to explain the molecular fluctuations of metformin through the mapping of protein profiles. Proliferation assay, osteogenic and adipogenic differentiation induction, cell cycle, flow cytometry, quantitative proteomics techniques and bioinformatics analysis were used to detect the influences of metformin treatment on hUC-MSCs. Our results demonstrated that low concentrations of metformin promoted the proliferation of hUC-MSCs, but high concentrations of metformin inhibited it. Metformin exhibited promotion of osteogenesis but inhibition of adipogenesis. Metformin treated hUC-MSCs up-regulated the expression of osteogenic marker ALP, OCN and RUNX2, but down-regulated the expression of adipogenic markers PPARγ and LPL. Proteomics analysis found that up-regulation of differentially expressed proteins in metformin treatment group involved the biological process of cell migration in Gene Ontology analysis. Metformin enhanced cell migration of HUVEC in a co-culture system, and hUC-MSCs treated with metformin exhibited stronger angiogenesis in vitro and in vivo compared to the hUC-MSCs group. The results of RT-qPCR revealed that the SCF and VEGFR2 were raised in metformin treatment. This study can promote the application of hUC-MSCs treated with metformin to tissue engineering for vascular reconstruction and angiogenesis.

Tissue-Nonspecific Alkaline Phosphatase, a Possible Mediator of Cell Maturation: Towards a New Paradigm

Alkaline phosphatase (ALP) is a ubiquitous membrane-bound glycoprotein capable of providing inorganic phosphate by catalyzing the hydrolysis of organic phosphate esters, or removing inorganic pyrophosphate that inhibits calcification. In humans, four forms of ALP cDNA have been cloned, among which tissue-nonspecific ALP (TNSALP) (TNSALP) is widely distributed in the liver, bone, and kidney, making it an important marker in clinical and basic research. Interestingly, TNSALP is highly expressed in juvenile cells, such as pluripotent stem cells (i.e., embryonic stem cells and induced pluripotent stem cells (iPSCs)) and somatic stem cells (i.e., neuronal stem cells and bone marrow mesenchymal stem cells). Hypophosphatasia is a genetic disorder causing defects in bone and tooth development as well as neurogenesis. Mutations in the gene coding for TNSALP are thought to be responsible for the abnormalities, suggesting the essential role of TNSALP in these events. Moreover, a reverse-genetics-based study using mice revealed that TNSALP is important in bone and tooth development as well as neurogenesis. However, little is known about the role of TNSALP in the maintenance and differentiation of juvenile cells. Recently, it was reported that cells enriched with TNSALP are more easily reprogrammed into iPSCs than those with less TNSALP. Furthermore, in bone marrow stem cells, ALP could function as a "signal regulator" deciding the fate of these cells. In this review, we summarize the properties of ALP and the background of ALP gene analysis and its manipulation, with a special focus on the potential role of TNSALP in the generation (and possibly maintenance) of juvenile cells.

Ultrathin 2D Titanium Carbide MXene (Ti3 C2 Tx ) Nanoflakes Activate WNT/HIF-1α-Mediated Metabolism Reprogramming for Periodontal Regeneration

Periodontal defect regeneration in severe periodontitis relies on the differentiation and proliferation of periodontal ligament cells (PDLCs). Recently, an emerging 2D nanomaterial, MXene (Ti3 C2 Tx ), has gained more and more attention due to the extensive antibacterial and anticancer activity, while its potential biomedical application on tissue regeneration remains unclear. Through a combination of experimental and multiscale simulation schemes, Ti3 C2 Tx has exhibited satisfactory biocompatibility and induced distinguish osteogenic differentiation of human PDLCs (hPDLCs), with upregulated osteogenesis-related genes. Ti3 C2 Tx manages to activate the Wnt/β-catenin signaling pathway by enhancing the Wnt-Frizzled complex binding, thus stabilizing HIF-1α and altering metabolic reprogramming into glycolysis. In vivo, hPDLCs pretreated by Ti3 C2 Tx display excellent performance in new bone formation and osteoclast inhibition with enhanced RUNX2, HIF-1α, and β-catenin in an experimental rat model of periodontal fenestration defects, indicating that this material has high efficiency of periodontal regeneration promotion. It is demonstrated in this work that Ti3 C2 Tx has highly efficient therapeutic effects in osteogenic differentiation and periodontal defect repairment.

Inhibiting PHD2 in human periodontal ligament cells via lentiviral vector-mediated RNA interference facilitates cell osteogenic differentiation and periodontal repair

Periodontal defect regeneration in severe periodontitis remains a challenging task in clinic owing to poor survival of seed cells caused by the remaining oxidative stress microenvironment. Recently, the reduction of prolyl hydroxylase domain-containing protein 2 (PHD2), a primary cellular oxygen sensor, has shown an incredible extensive effect on skeletal muscle tissue regeneration by improving cell resistance to reactive oxygen species, whereas its role in periodontal defect repair is unclear. Here, through lentivirus vector-mediated RNA interference, the PHD2 gene in human periodontal ligament cells (hPDLCs) is silenced, leading to hypoxia-inducible factor-1α stabilization in normoxia. In vitro, PHD2 silencing not only exhibited a satisfactory effect on cell proliferation, but also induced distinguished osteogenic differentiation of hPDLCs. Real-time polymerase chain reaction and Western blotting revealed significant up-regulation of osteocalcin, alkaline phosphatase (ALP), runt-related transcription factor 2, and collagen type I (COL I). Under oxidative stress conditions, COL I and ALP expression levels, suppressed by 100 μM H₂ O₂ , were elevated by PHD2-gene-silencing in hPDLCs. In vivo, periodontal fenestration defects were established in 18 female Sprague-Dawley rats aged 6 wk old, followed by implantation of PHD2 silencing hPDLCs in situ for 21 d. Persistent and stable silencing of PHD2 in hPDLCs promoted better new bone formation according to microcomputed tomography 3D reconstruction and related bone parameter analysis. This work demonstrates the therapeutic efficiency of PHD2 gene interference in osteogenic differentiation and periodontal defect repair for highly efficient periodontal regeneration.

AMP-activated protein kinase and the down-stream activated process of autophagy regulate the osteogenic differentiation of human dental follicle cells

OBJECTIVE

Dental follicle cells (DFCs) are progenitors of alveolar osteoblasts. AMP-activated protein kinase (AMPK) and the down-stream activated autophagy process play a key role in cellular energy and metabolic homeostasis and are involved in many biological processes including differentiation. Previous studies showed ambiguous results about the role of AMPK and autophagy in osteogenic differentiation of various osteogenic progenitors, but the role of AMPK and autophagy in DFCs is unknown. This study examined the role of AMPK and autophagy in the osteogenic differentiation of DFCs.

MATERIALS AND METHODS

We evaluated the expression of AMPK isoforms and autophagy markers during osteogenic differentiation via Western Blot analyses and the impact of AMPK / autophagy activators and inhibitors and siRNAs on osteogenic differentiation via ALP activity assay, Alizarin Red staining and Real-Time Reverse-Transcription PCR.

RESULTS

We have shown that expression of AMPK and autophagy markers are regulated during osteogenic differentiation and that activation of AMPK inhibits the ALP activity and other osteogenic markers after induction of osteogenic differentiation, while inhibition of AMPK and autophagy increased the expression of some osteogenic markers. In long-term cultures with osteogenic differentiation medium, however, both the activation and the inhibition of AMPK significantly inhibited biomineralization of DFCs. In contrast, activation or inhibition of autophagy barely affected early differentiation markers, while autophagy inhibition enhanced biomineralization and autophagy activation diminished mineralization capability of DFCs.

CONCLUSIONS

AMPK regulates the osteogenic differentiation in earlier stages while indirectly affecting biomineralization at least partly via autophagy. The osteogenic differentiation of DFCs is sensitive to changes in AMPK and autophagic activity.

Effect of metformin on stem cells: Molecular mechanism and clinical prospect

Metformin is a first-line medication for type II diabetes. Numerous studies have shown that metformin not only has hypoglycemic effects, but also modulates many physiological and pathological processes ranging from aging and cancer to fracture healing. During these different physiological activities and pathological changes, stem cells usually play a core role. Thus, many studies have investigated the effects of metformin on stem cells. Metformin affects cell differentiation and has promising applications in stem cell medicine. It exerts anti-aging effects and can be applied to gerontology and regenerative medicine. The potential anti-cancer stem cell effect of metformin indicates that it can be an adjuvant therapy for cancers. Furthermore, metformin has beneficial effects against many other diseases including cardiovascular and autoimmune diseases. In this review, we summarize the effects of metformin on stem cells and provide an overview of its molecular mechanisms and clinical prospects.

Effect of Age and Lipoperoxidation in Rat and Human Adipose Tissue-Derived Stem Cells

A wide range of clinical applications in regenerative medicine were opened decades ago with the discovery of adult stem cells. Highly promising adult stem cells are mesenchymal stem/stromal cells derived from adipose tissue (ADSCs), primarily because of their abundance and accessibility. These cells have multipotent properties and have been used extensively to carry out autologous transplants. However, the biology of these cells is not entirely understood. Among other factors, the regeneration capacity of these cells will depend on both their capacity of proliferation/differentiation and the robustness of the biochemical pathways that allow them to survive under adverse conditions like those found in damaged tissues. The transcription factors, such as Nanog and Sox2, have been described as playing an important role in stem cell proliferation and differentiation. Also, the so-called longevity pathways, in which AMPK and SIRT1 proteins play a crucial role, are essential for cell homeostasis under stressful situations. These pathways act by inhibiting the translation through downregulation of elongation factor-2 (eEF2). In order to deepen knowledge of mesenchymal stem cell biology and which factors are determinant in the final therapeutic output, we evaluate in the present study the levels of all of these proteins in the ADSCs from humans and rats and how these levels are affected by aging and the oxidative environment. Due to the effect of aging and oxidative stress, our results suggest that before performing a cell therapy with ADSCs, several aspects reported in this study such as oxidative stress status and proliferation and differentiation capacity should be assessed on these cells. This would allow us to know the robustness of the transplanted cells and to predict the therapeutic result, especially in elder patients, where probably ADSCs do not carry out their biological functions in an optimal way.

Phosphorylated MAPK14 Promotes the Proliferation and Migration of Bladder Cancer Cells by Maintaining RUNX2 Protein Abundance

Background

Mitogen-activated protein kinase 14 (MAPK14) acts as an integration point for multiple biochemical signal pathways. High expressions of MAPK14 have been found in a variety of tumors. Runt‑related transcription factor 2 (RUNX2) is related to many tumors, especially in tumor invasion and metastasis. However, the mechanism of these two genes in bladder cancer remains unclear.

Methods

TCGA database and Western blot were used to analyze the mRNA and protein levels of the target gene in bladder cancer tissues and adjacent tissues. The proliferation ability of bladder cancer cells was tested by colony forming and EdU assay. The migration ability of cells was detected by transwell assay. Immunoprecipitation was utilized to detect protein-protein interaction. Cycloheximide chase assay was used to measure the half-life of RUNX2 protein.

Results

Phosphorylated mitogen-activated protein kinase 14 (P-MAPK14, Thr180/Tyr182) was highly expressed in bladder cancer tissues and bladder cancer cell lines. Accordingly, P-MAPK14 could be combined with RUNX2 and maintain its protein stability and promote the proliferation and migration of bladder cancer cells. In addition, the functional degradation caused by the downregulation of MAPK14 and P-MAPK14 could be partially compensated by the overexpression of RUNX2.

Conclusion

These results suggest that P-MAPK14 might play an important role in the development of bladder cancer and in the regulation of RUNX2 protein expression. P-MAPK14 might become a potential target for the treatment of bladder cancer.

Metformin enhances osteogenic differentiation of stem cells from human exfoliated deciduous teeth through AMPK pathway

Stem cells from human exfoliated deciduous teeth (SHEDs) are ideal seed cells in bone tissue engineering. As a first-line antidiabetic drug, metformin has recently been found to promote bone formation. The purpose of this study was to investigate the effect of metformin on the osteogenic differentiation of SHEDs and its underlying mechanism. SHEDs were isolated from the dental pulp of deciduous teeth from healthy children aged 6 to 12, and their surface antigen markers of stem cells were detected by flow cytometry. The effect of metformin (10-200 μM) treatment on SHEDs cell viability, proliferation, and osteogenic differentiation was analyzed. The activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation Thr172 (p-AMPK) was determined by western blot assay. SHEDs were confirmed as mesenchymal stem cells (MSCs) on the basis of the expression of characteristic surface antigens. Metformin (10-200 μM) did not affect the viability and proliferation of SHEDs but significantly increased the expression of osteogenic genes, alkaline phosphatase activity, matrix mineralization, and p-AMPK level expression in SHEDs. Compound C, a specific inhibitor of the AMPK pathway, abolished metformin-induced osteogenic differentiation of SHEDs. Moreover, metformin treatment enhanced the expression of proangiogenic/osteogenic growth factors BMP2 and VEGF but reduced the osteoclastogenic factor RANKL/OPG expression in SHEDs. In conclusion, metformin could induce the osteogenic differentiation of SHEDs by activating the AMPK pathway and regulates the expression of proangiogenic/osteogenic growth factors and osteoclastogenic factors in SHEDs. Therefore, metformin-pretreated SHEDs could be a potential source of seed cells during stem cell-based bone tissue engineering.

Crocin promotes osteogenesis differentiation of bone marrow mesenchymal stem cells

Crocin has plentiful pharmacological effects, but its role in osteogenesis differentiation of bone marrow mesenchymal stem cells (BMSCs) is unexplored. This study explored the effect of crocin on osteogenesis differentiation, in order to provide evidence for its clinical application. In cell experiments, human BMSCs (hBMSCs) were induced by osteogenesis differentiation medium or crocin. In animal experiments, steroid-induced osteonecrosis of the femoral head (SANFH) rat models was established using lipopolysaccharide (LPS) plus methylprednisolone (MPS), and then treated with crocin. The osteogenesis differentiation capacity of hBMSCs was analyzed by alkaline phosphatase (ALP) and alizarin red S staining. Histopathological changes in rat femoral head tissues were observed by hematoxylin and eosin (H&E) staining. The expression levels of RUNX2, COL1A1, OCN, and GSK-3β in hBMSCs and rat femoral head tissues were measured by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot (WB) analysis. ALP and alizarin red S staining demonstrated that LAP activity and calcium nodules were increased in hBMSCs treated with crocin. From H&E staining results, femoral head tissues of SANFH models showed typical osteonecrosis, which could be ameliorated by crocin. WB and qRT-PCR assays detected that the expression levels of RUNX2, COL1A1, and OCN in hBMSCs and femoral head tissues of models were obviously increased after crocin treatment, while GSK-3β phosphorylation was reduced. In general, the action of crocin was concentration-dependent. Crocin might be beneficial to the recovery of SANFH through accelerating osteogenesis differentiation of BMSCs, which might be a novel therapy for related diseases.

Metformin promotes the osseointegration of titanium implants under osteoporotic conditions by regulating BMSCs autophagy, and osteogenic differentiation

Osteoporosis is a common bone disorder with adverse effects on oral osseointegration, and the effects of metformin on bone metabolism have received increasing attention. The aim of the present study was to test the hypothesis that metformin promoted osteogenesis of bone mesenchymal stem cells (BMSCs) and osseointegration of titanium implants. BMSCs were treated with metformin to assess autophagic capacity, reactive oxygen species (ROS) production, anti-aging ability, and osteogenic differentiation. To determine its potential application in peri-implant of the maxilla, metformin was injected around the implant each day, immediately after the implant was embedded into the tooth socket. The results showed that metformin increased the autophagic capacity and decreased ROS production of osteoporotic BMSCs under hypoxia and serum deprivation (H/SD) culturing conditions. Metformin treatment significantly enhanced stemness properties and mineralized nodule formation, and increased the expression of osteogenic markers, including runt related transcription factor 2 (Runx2), osteocalcin (OCN), and alkaline phosphatase (ALP). Moreover, metformin substantially accelerated the formation of new bone, ameliorated the bone microarchitecture and promoted osseointegration of the dental implant. Collectively, metformin induces an osteogenic effect around the implant. Considering the widespread use of metformin, the results of the present study might promote a novel understanding of the positive effects of local metformin delivery on alveolar ridge defect, and have potential clinical application for the acceleration of osseointegration.

Berberine and musculoskeletal disorders: The therapeutic potential and underlying molecular mechanisms

BACKGROUND

Musculoskeletal disorders are a group of disorders that affect the joints, bones, and muscles, causing long-term disability. Berberine, an isoquinoline alkaloid, has been previously established to exhibit beneficial properties in preventing various diseases, including musculoskeletal disorders.

PURPOSE

This review article aims to recapitulate the therapeutic potential of berberine and its mechanism of action in treating musculoskeletal disorders.

METHODS

A wide range of literature illustrating the effects of berberine in ameliorating musculoskeletal disorders was retrieved from online electronic databases (PubMed and Medline) and reviewed.

RESULTS

Berberine may potentially retard the progression of osteoporosis, osteoarthritis and rheumatoid arthritis. Limited studies reported the effects of berberine in suppressing the proliferation of osteosarcoma cells. These beneficial properties of berberine are mediated in part through its ability to target multiple signaling pathways, including PKA, p38 MAPK, Wnt/β-catenin, AMPK, RANK/RANKL/OPG, PI3K/Akt, NFAT, NF-κB, Hedgehog, and oxidative stress signaling. In addition, berberine exhibited anti-apoptotic, anti-inflammatory, and immunosuppressive properties.

CONCLUSION

The current evidence indicates that berberine may be effective in preventing musculoskeletal disorders. However, findings from in vitro and in vivo investigations await further validation from human clinical trial.

Static magnetic fields accelerate osteogenesis by regulating FLRT/BMP pathway

OBJECTIVES

Static magnetic fields (SMF) have been proved to enhance osteogenic differentiation in mesenchymal stem cells (MSCs). However, the effect of SMF on mandibular condylar chondrocytes (MCCs) are less investigated, which contributes to the vertical formation of mandible. The purpose of the present study was to identify whether SMF accelerate the osteogenesis on mature condylar cartilage and explore the potential regulatory mechanism.

METHODS

In this study, we presented a 280 mT SMF stimulation set-up to investigate the genomic effects of SMF exposure on MCCs differentiation and osteoblast-related factor secretion in vitro. Induced by Oricell™ for osteogenesis, MCCs from primary SD Rat were stimulated with or without SMF for cell culture. Cell proliferation was determined by CCK-8. The enhanced osteogenetic capacity of the SMF stimulated MCCs was identified by Alizarin red staining (ARS). Additionally, the effects of SMF on the expression of transmembrane protein marker (FLRT3), terminal differentiation markers (BMP2), and transcription factors (Smad1/5/8) were quantified by Western blot and immunofluorescence analysis.

RESULTS

Compared with the control group, SMF decreased the proliferation of MCCs (p < 0.05) after 14 days osteogenesis-specific induction. The mineral synthesis of MCCs was upregulated by SMF (p < 0.0001). The expression of BMP2, Smad1/5/8 showed decrease trends while the protein level of FLRT3 acted in contrary manner (p < 0.05).

CONCLUSIONS

Our findings emphasized the ability of osteogenesis positively respond to SMF stimulation by exhibiting enhanced differentiation via FLRT/BMP signaling.

AMP-activated protein kinase (AMPK) regulates autophagy, inflammation and immunity and contributes to osteoclast differentiation and functionabs

Osteoclasts are multinucleated giant cells, responsible for bone resorption. Osteoclast differentiation and function requires a series of cytokines to remove the old bone, which coordinates with the induction of bone remodelling by osteoblast-mediated bone formation. Studies have demonstrated that AMP-activated protein kinase (AMPK) play a negative regulatory role in osteoclast differentiation and function. Research involving AMPK, a nutrient and energy sensor, has primarily focused on osteoclast differentiation and function; thus, its role in autophagy, inflammation and immunity remains poorly understood. Autophagy is a conservative homoeostatic mechanism of eukaryotic cells, and response to osteoclast differentiation and function; however, how it interacts with inflammation remains unclear. Additionally, based on the regulatory function of different AMPK subunits for osteoclast differentiation and function, its activation is regulated by upstream factors to perform bone metabolism. This review summarises the critical role of AMPK-mediated autophagy, inflammation and immunity by upstream and downstream signalling during receptor activator of nuclear factor kappa-B ligand-induced osteoclast differentiation and function. This pathway may provide therapeutic targets for bone-related diseases, as well as function as a biomarker for bone homoeostasis.

Functional variations between Mesenchymal Stem Cells of different tissue origins: A comparative gene expression profiling

BACKGROUND

Mesenchymal Stem Cells (MSCs), regardless of the tissue sources, are considered as excellent candidates for cellular therapy as they are immune-privileged cells containing a multitude of therapeutic functions that aid in tissue regeneration and repair. For the effective application of these cells in cell therapy, it is important to understand and characterize their biological functions.

OBJECTIVES

The present study attempts to characterize the variations in multipotent function such as cell surface antigen levels, proliferation, differentiation and stemness (pluripotency) potential of MSCs isolated from foetal [wharton's jelly (WJ), foetal and maternal side of placenta (PF and PM)] and adult tissue sources [bone marrow (BM) and adipose tissue (AT)] using gene expression by real time PCR (qRT-PCR).

RESULTS

Amongst the different tissue sources, PM, PF and AT-MSCs exhibited significant increase (p < 0.001, p < 0.001 and p < 0.01 respectively) in CD 73 expression and therefore could have a role in immunomodulation. WJ-MSCs exhibited superior proliferation potential based on growth curve, PCNA and Wnt gene expression. BM-MSCs were superior in exhibiting trilineage differentiation. Enhanced stemness potential (Oct 4 and Nanog) was observed for both BM and WJ-MSCs. In addition, BM and WJ-MSCs expressed high levels of CD 90 making them suitable in bone repair and regeneration.

CONCLUSION

Thus to conclude, out of the five different sources tested, BM an adult source and WJ-MSCs a foetal source were superior in exhibiting most of the biological functions indicating that these sources may be suitable candidates for cell repair and regeneration studies.

Descending Expression of miR320 in Insulin-Resistant Adipocytes Treated with Ascending Concentrations of Metformin

Some miRNAs are supposed to play a role in insulin resistance and metabolic disorders. Such miRNAs can be differentially expressed in response to a pharmacologic intervention for insulin resistance as a biomarker/risk factor for insulin resistance. This study aimed at determining the effect of Metformin on miR320 expression in insulin-resistant (IR) adipocytes. The 3T3L1 cells were expanded in DMEM, differentiated into adipocytes by differentiating medium, became resistant to insulin, and then were treated with ascending concentrations of Metformin. Quantitative real-time PCR was performed to profile the miR320 expression in 3T3L1 adipocytes, IR adipocytes, and Metformin-treated IR adipocytes. Compared to the normal adipocytes, IR adipocytes exhibited a significantly higher level of miR320 expression, however, in response to Metformin graded concentrations, IR adipocytes down-regulated miR320 and were almost at normal level. The maximum effect of Metformin was at 10 mM. In IR adipocytes, miR320 expression is over-expressed which can be down-regulated by Metformin treatment. The findings provide some information on a potentially new marker to determine insulin resistance and to predict response to insulin resistance therapy.

MicroRNA-505 is involved in the regulation of osteogenic differentiation of MC3T3-E1 cells partially by targeting RUNX2

Objective

Evidence suggests that microRNAs (miRNAs) regulate the expression of genes involved in bone metabolism. This study aimed to investigate the role of miR-505 in the osteogenic differentiation of MC3T3-E1 cells.

Methods

We performed miRNA sequencing to identify differentially expressed miRNAs between MC3T3-E1 cells treated with osteogenic induction medium (OIM) and control cells. Bioinformatics analysis was performed by using the TargetScan and miRDB databases. The expression of miR-505 in MC3T3-E1 cells was detected during osteogenic differentiation. After transfection with miR-505 mimic or miR-505 inhibitor, MC3T3-E1 cells were induced to differentiate into osteoblasts, and the expression of osteogenic differentiation markers (Runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN), and osterix (OSX)) was detected.

Results

miR-505 was the most downregulated miRNA among the differentially expressed miRNAs. The RUNX2 gene was identified as a potential target of miR-505 using the target prediction program. miR-505 expression was downregulated during osteogenic differentiation of MC3T3-E1 cells. The expression of osteogenic marker genes was inhibited in MC3T3-E1 cells after transfection with miR-505. However, the expression of osteogenic marker genes was upregulated after transfection with miR-505 inhibitor.

Conclusion

This study is the first to report miR-505 could bind to the RUNX2 gene and thus regulate partly the dysfunction of osteoblasts differentiation, which is expected to be targets for the treatment of osteoporosis.

A Metformin-Responsive Metabolic Pathway Controls Distinct Steps in Gastric Progenitor Fate Decisions and Maturation

Cellular metabolism plays important functions in dictating stem cell behaviors, although its role in stomach epithelial homeostasis has not been evaluated in depth. Here, we show that the energy sensor AMP kinase (AMPK) governs gastric epithelial progenitor differentiation. Administering the AMPK activator metformin decreases epithelial progenitor proliferation and increases acid-secreting parietal cells (PCs) in mice and organoids. AMPK activation targets Krüppel-like factor 4 (KLF4), known to govern progenitor proliferation and PC fate choice, and PGC1α, which we show controls PC maturation after their specification. PC-specific deletion of AMPKα or PGC1α causes defective PC maturation, which could not be rescued by metformin. However, metformin treatment still increases KLF4 levels and suppresses progenitor proliferation. Thus, AMPK activates KLF4 in progenitors to reduce self-renewal and promote PC fate, whereas AMPK-PGC1α activation within the PC lineage promotes maturation, providing a potential suggestion for why metformin increases acid secretion and reduces gastric cancer risk in humans.

Dietary intake of bioactive ingredients impacts liver and adipose tissue transcriptomes in a porcine model of prepubertal early obesity

Global prevalence of obesity has increased to epidemic proportions over the past 40 years, with childhood obesity reaching alarming rates. In this study, we determined changes in liver and adipose tissue transcriptomes of a porcine model for prepubertal early obesity induced by a high-calorie diet and supplemented with bioactive ingredients. A total of 43 nine-weeks-old animals distributed in four pens were fed with four different dietary treatments for 10 weeks: a conventional diet; a western-type diet; and a western-type diet with Bifidobacterium breve and rice hydrolysate, either adding or not omega-3 fatty acids. Animals fed a western-type diet increased body weight and total fat content and exhibited elevated serum concentrations of cholesterol, whereas animals supplemented with bioactive ingredients showed lower body weight gain and tended to accumulate less fat. An RNA-seq experiment was performed with a total of 20 animals (five per group). Differential expression analyses revealed an increase in lipogenesis, cholesterogenesis and inflammatory processes in animals on the western-type diet while the supplementation with bioactive ingredients induced fatty acid oxidation and cholesterol catabolism, and decreased adipogenesis and inflammation. These results reveal molecular mechanisms underlying the beneficial effects of bioactive ingredient supplementation in an obese pig model.

Bone Regeneration, Reconstruction and Use of Osteogenic Cells; from Basic Knowledge, Animal Models to Clinical Trials

The deterioration of the human skeleton's capacity for self-renewal occurs naturally with age. Osteoporosis affects millions worldwide, with current treatments including pharmaceutical agents that target bone formation and/or resorption. Nevertheless, these clinical approaches often result in long-term side effects, with better alternatives being constantly researched. Mesenchymal stem cells (MSCs) derived from bone marrow and adipose tissue are known to hold therapeutic value for the treatment of a variety of bone diseases. The following review summarizes the latest studies and clinical trials related to the use of MSCs, both individually and combined with other methods, in the treatment of a variety of conditions related to skeletal health. For example, some of the most recent works noted the advantage of bone grafts based on biomimetic scaffolds combined with MSC and growth factor delivery, with a greatly increased regeneration rate and minimized side effects for patients. This review also highlights the continuing research into the mechanisms underlying bone homeostasis, including the key transcription factors and signalling pathways responsible for regulating the differentiation of osteoblast lineage. Paracrine factors and specific miRNAs are also believed to play a part in MSC differentiation. Furthering the understanding of the specific mechanisms of cellular signalling in skeletal remodelling is key to incorporating new and effective treatment methods for bone disease.

Melatonin promotes the BMP9-induced osteogenic differentiation of mesenchymal stem cells by activating the AMPK/β-catenin signalling pathway

Background

Mesenchymal stem cells (MSCs) play a crucial role in maintaining the dynamic balance of bone metabolism. Melatonin may have a regulatory effect on bone metabolism by regulating the lineage commitment and differentiation signalling pathways of MSCs. Among the BMP families, the osteogenesis of BMP9 is considered to be one of the strongest in MSCs. Here, we explored whether melatonin and BMP9 act synergistically on MSC osteogenic differentiation.

Methods

The C3H10T1/2 osteogenic differentiation function induced by melatonin synergizes with BMP9, as detected by the expression of osteogenic markers at different periods. The result was further confirmed by foetal limb explant culture and in vivo stem cell implantation experiments. The effects of the AMPK/β-catenin pathway on the osteogenic differentiation of C3H10T1/2 cells were evaluated by Western blotting.

Results

Melatonin combined with BMP9 significantly enhanced the expression of osteogenic markers at different periods in C3H10T1/2 cells, effectively enhancing BMP9-induced bone formation in cultured foetal explants and ectopic bone formation in vivo in stem cell transplantation experiments. Melatonin increases the expression of BMP9 in C3H10T1/2 cells and induces Smad1/5/8 translocation from the cytoplasm to the nucleus. In addition, melatonin and BMP9 synergistically promote AMPK and β-catenin phosphorylation, which can be largely eliminated by AMPK siRNA pretreatment.

Conclusions

Melatonin and BMP9 in C3H10T1/2 cells synergistically promote osteogenic differentiation at least in part by activating the AMPK/β-catenin signalling pathway.

Role of Metformin on Osteoblast Differentiation in Type 2 Diabetes

Metformin, an effective hypoglycemic, can modulate different points of malignant mass, polycystic ovary syndrome (PCOS), cardiovascular diseases, tuberculosis, and nerve regeneration. Recently, the effect of metformin on bone metabolism has been analyzed. Metformin relies on organic cation transporters (OCT1), a polyspecific cell membrane of the solute carrier 22A (SLC22A) gene family, to facilitate its intracellular uptake and action on complex I of the respiratory chain of mitochondria. These changes activate the cellular energy sensor AMP-activated protein kinase (AMPK). Thus, the increased cellular AMP/ATP ratio causes a dramatic and progressive activation of insulin and lysosomes, resulting in a decrease in intracellular glucose level, which promotes osteoblast proliferation and differentiation. AMPK also phosphorylates runt-related transcription factor 2 (Runx2) at S118, the lineage-specific transcriptional regulators, to promote osteogenesis. Metformin phosphorylates extracellular signal-regulated kinase (ERK), stimulates endothelial and inducible nitric oxide synthases (e/iNOS), inhibits the GSK3β/Wnt/β-catenin pathway, and promotes osteogenic differentiation of osteoblasts. The effect of metformin on hyperglycemia decreases intracellular reactive oxygen species (ROS) and advanced glycation end-products (AGEs) in collagen, and reduced serum levels of insulin-like growth factors (IGF-1) were beneficial for bone formation. Metformin has a certain effect on microangiopathy and anti-inflammation, which can induce osteoporosis, activate the activity of osteoclasts, and inhibit osteoblast activity, and has demonstrated extensive alteration in bone and mineral metabolism. The aim of this review was to elucidate the mechanisms of metformin on osteoblasts in insulin-deficient diabetes.

Mitochondrial Regulation of Stem Cells in Bone Homeostasis

Mitochondria have emerged as key contributors to the organismal homeostasis, in which mitochondrial regulation of stem cells is becoming increasingly important. Originated from mesenchymal stem cell (MSC) and hematopoietic stem cell (HSC) lineage commitments and interactions, bone is a representative organ where the mitochondrial essentiality to stem cell function has most recently been discovered, underlying skeletal health, aging, and diseases. Furthermore, mitochondrial medications based on modulating stem cell specification are emerging to provide promising therapies to counteract bone aging and pathologies. Here we review the cutting-edge knowledge regarding mitochondrial regulation of stem cells in bone homeostasis, highlighting mechanistic insights as well as mitochondrial strategies for augmented bone healing and tissue regeneration.