Runx2/Cbfa1 stimulates transdifferentiation of primary skeletal myoblasts into a mineralizing osteoblastic phenotype

NOTCH1, 2, and 3 receptors enhance osteoblastogenesis of mesenchymal C3H10T1/2 cells and inhibit this process in preosteoblastic MC3T3-E1 cells

Osteoblastogenesis is governed by complex interplays among signaling pathways, which modulate the expression of specific markers at each differentiation stage. This process enables osteoblast precursor cells to adopt the morphological and biochemical characteristics of mature bone cells. Our study investigates the role of NOTCH signaling in osteogenesis in MC3T3-E1 and C3H10T1/2 cell lines. MC3T3-E1 cells are preosteoblast precursors widely recognized as a model for bone biology research, offering a convenient and physiologically relevant system to study osteoblast transcriptional regulation. Conversely, the mesenchymal C3H10T1/2 cells are multipotent, capable of differentiating into osteoblasts, adipocytes, and chondrocytes under specific extracellular cues. The core of this in vitro study is the comparative analysis of the impact of overexpressing each mammalian NOTCH receptor on osteoblastogenesis in two cell lines reflecting different cell differentiation stages. We generated stable transfectant pools of both cell lines for each of the four NOTCH receptors and characterized their effect on osteoblastogenesis. We successfully obtained transfectant pools that overexpress Notch1, Notch2 and Notch3 at both mRNA and protein levels. However, we were unable to obtain cells overexpressing Notch4 at protein level. Our findings reveal that the overexpression of NOTCH1, NOTCH2, and NOTCH3 receptors promotes osteoblast differentiation in mesenchymal C3H10T1/2 cells, while inhibiting it in preosteoblastic MC3T3-E1 cells. These results provide novel insights into the distinct roles of NOTCH receptors in osteoblastogenesis across two different precursor cell types, potentially guiding the development of new therapeutic approaches for bone diseases.

GDF10 is a negative regulator of vascular calcification

Cardiovascular mortality is particularly high and increasing in patients with chronic kidney disease, with vascular calcification (VC) as a major pathophysiologic feature. VC is a highly regulated biological process similar to bone formation involving osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs). We have previously demonstrated that loss of T-cell death-associated gene 51 (TDAG51) expression leads to an attenuation of medial VC. We now show a significant induction of circulating levels of growth differentiation factor 10 (GDF10) in TDAG51-/- mice, which was of interest due to its established role as an inhibitor of osteoblast differentiation. The objective of this study was to examine the role of GDF10 in the osteogenic transdifferentiation of VSMCs. Using primary mouse and human VSMCs, as well as ex vivo aortic ring cultures, we demonstrated that treatment with recombinant human (rh) GDF10 mitigated phosphate-mediated hydroxyapatite (HA) mineral deposition. Furthermore, ex vivo aortic rings from GDF10-/- mice exhibited increased HA deposition compared to C57BL/6J controls. To explain our observations, we identified that rhGDF10 treatment reduced protein expression of runt-related transcription factor 2, a key driver of osteogenic transdifferentiation of VSMCs and VC. In support of these findings, in vivo treatment with rhGDF10 attenuated VD3-induced VC. Furthermore, we demonstrated an increase in circulating GDF10 in patients with chronic kidney disease with clinically defined severe VC, as assessed by coronary artery calcium score. Thus, our studies identify GDF10 as a novel inhibitor of mineral deposition and as such, may represent a potential novel biomarker and therapeutic target for the detection and management of VC.

Bioinspired oriented calcium phosphate nanocrystal arrays with bactericidal and osteogenic properties

The global diffusion of antibiotic resistance poses a severe threat to public health. Addressing antibiotic-resistant infections requires innovative approaches, such as antibacterial nanostructured surfaces (ANSs). These surfaces, featuring ordered arrays of nanostructures, exhibit the ability to kill bacteria upon contact. However, most currently developed ANSs utilize bioinert materials, lacking bioactivity crucial for promoting tissue regeneration, particularly in the context of bone infections. This study introduces ANSs composed of bioactive calcium phosphate nanocrystals. Two distinct ANSs were created through a biomineralization-inspired growth of amorphous calcium phosphate (ACP) precursors. The ANSs demonstrated efficient antibacterial properties against both Gram-negative (P. aeruginosa) and Gram-positive (S. aureus) antibiotic resistant bacteria, with up to 75 % mortality in adhered bacteria after only 4 h of contact. Notably, the ANS featuring thinner and less oriented nano-needles exhibited superior efficacy attributed to simultaneous membrane rupturing and oxidative stress induction. Moreover, the ANSs facilitate the proliferation of mammalian cells, enhancing adhesion, spreading, and reducing oxidative stress. The ANSs displayed also significant bioactivity towards human mesenchymal stem cells, promoting colonization and inducing osteogenic differentiation. Specifically, the ANS with thicker and more ordered nano-needles demonstrated heightened effects. In conclusion, ANSs introduced in this work have the potential to serve as foundation for developing bone graft materials capable of eradicate site infections while concurrently stimulating bone regeneration. STATEMENT OF SIGNIFICANCE: Nanostructured surfaces with antibacterial properties through a mechano-bactericidal mechanism have shown significant potential in fighting antibiotic resistance. However, these surfaces have not been fabricated with bioactive materials necessary for developing devices that are both antibacterial and able to stimulate tissue regeneration. This study demonstrates the feasibility of creating nanostructured surfaces of ordered calcium phosphate nano-needles through a biomineralization-inspired growth. These surfaces exhibit dual functionality, serving as effective bactericidal agents against Gram-negative and Gram-positive antibiotic-resistant bacteria while also promoting the proliferation of mammalian cells and inducing osteogenic differentiation of human mesenchymal stem cells. Consequently, this approach holds promise in the context of bone infections, introducing innovative nanostructured surfaces that could be utilized in the development of antimicrobial and osteogenic grafts.

Hypomethylation of the RUNX2 Gene Is a New Potential Biomarker of Primary Osteoporosis in Men and Women

The search for the molecular markers of osteoporosis (OP), based on the analysis of differential deoxyribonucleic acid (DNA) methylation in bone cells and peripheral blood cells, is promising for developments in the field of the early diagnosis and targeted therapy of the disease. The Runt-related transcription factor 2 (RUNX2) gene is one of the key genes of bone metabolism, which is of interest in the search for epigenetic signatures and aberrations associated with the risk of developing OP. Based on pyrosequencing, the analysis of the RUNX2 methylation profile from a pool of peripheral blood cells in men and women over 50 years of age of Russian ethnicity from the Volga-Ural region of Russia was carried out. The level of DNA methylation in three CpG sites of the RUNX2 gene was assessed and statistically significant hypomethylation was revealed in all three studied CpG sites in men (U = 746.5, p = 0.004; U = 784, p = 0.01; U = 788.5, p = 0.01, respectively) and in one CpG site in women (U = 537, p = 0.03) with primary OP compared with control. In the general sample, associations were preserved for the first CpG site (U = 2561, p = 0.0001766). The results were obtained for the first time and indicate the existence of potentially new epigenetic signatures of RUNX2 in individuals with OP.

Complex intrinsic abnormalities in osteoblast lineage cells of X-linked hypophosphatemia: Analysis of human iPS cell models generated by CRISPR/Cas9-mediated gene ablation

X-linked hypophosphatemia (XLH) is caused by inactivating variants of the phosphate regulating endopeptidase homolog X-linked (PHEX) gene. Although the overproduction of fibroblast growth factor 23 (FGF23) is responsible for hypophosphatemia and impaired vitamin D metabolism, the pathogenesis of XLH remains unclear. We herein generated PHEX-knockout (KO) human induced pluripotent stem (iPS) cells by applying CRISPR/Cas9-mediated gene ablation to an iPS clone derived from a healthy male, and analyzed PHEX-KO iPS cells with deletions extending from exons 1 to 3 and frameshifts by inducing them to differentiate into the osteoblast lineage. We confirmed the increased production of FGF23 in osteoblast lineage cells differentiated from PHEX-KO iPS cells. In vitro mineralization was enhanced in osteoblast lineage cells from PHEX-KO iPS cells than in those from isogenic control iPS cells, which reminded us of high bone mineral density and enthesopathy in patients with XLH. The extracellular level of pyrophosphate (PPi), an inhibitor of mineralization, was elevated, and this increase appeared to be partly due to the reduced activity of tissue non-specific alkaline phosphatase (TNSALP). Osteoblast lineage cells derived from PHEX-KO iPS cells also showed the increased expression of multiple molecules such as dentine matrix protein 1, osteopontin, RUNX2, FGF receptor 1 and early growth response 1. This gene dysregulation was similar to that in the osteoblasts/osteocytes of Phex-deficient Hyp mice, suggesting that common pathogenic mechanisms are shared between human XLH and Hyp mice. Moreover, we found that the phosphorylation of CREB was markedly enhanced in osteoblast lineage cells derived from PHEX-KO iPS cells, which appeared to be associated with the up-regulation of the parathyroid hormone related protein gene. PHEX deficiency also affected the response of the ALPL gene encoding TNSALP to extracellular Pi. Collectively, these results indicate that complex intrinsic abnormalities in osteoblasts/osteocytes underlie the pathogenesis of human XLH.

BushenHuoxue formula promotes osteogenic differentiation via affecting Hedgehog signaling pathway in bone marrow stem cells to improve osteoporosis symptoms

BACKGROUND

The BushenHuoxue formula (BSHX) has been previously demonstrated to ameliorate osteoporosis, but the mechanisms underlying this phenomenon are currently unclear. The present study aims at investigating the mechanisms that BSHX induces osteogenesis.

METHODS

We established an osteoporosis model in rats by bilateral ovariectomy and then treated the rats with an osteogenic inducer (dexamethasone, β-sodium glycerophosphate and Vitamin C) and BSHX. After that, bone marrow density and histopathological bone examination were evaluated by using HE staining and immunohistochemistry, respectively. We also assessed the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts by using immunofluorescence staining. ALP, BMP, and COL1A1 levels were determined by ELISA. We identified genes involved in pathogenesis of osteoporosis through Gene Expression Omnibus (GEO) database and subsequently selected Hedgehog signaling-related genes Shh, Ihh, Gli2, and Runx2 for assessment via qRT-PCR and ELISA, Western blotting. Network pharmacology analysis was performed to identify bioactive metabolites of BSHX.

RESULTS

BSHX treatment in osteoporosis model rats promoted tightening of the morphological structure of the trabecular bone and increased the bone mineral density (BMD). BSHX also increased levels of osteoblast makers ALP, BMP, and COL1A1. Additionally, bioinformatics analysis of the GEO dataset showed that Hedgehog signaling pathway was involved in pathogenesis of osteoporosis, especially related genes Shh, Ihh, Gli2, and Runx2. Remarkably, BHSX upregulated these genes indispensably involved in the osteogenesis-related Hedgehog signaling pathway in both bone tissue and BMSCs. Importantly, we identified that quercetin was the active compounds that involved in the mechanism of BSHX-improved OP via affecting Hedgehog-related genes.

CONCLUSION

Our results indicate that BSHX promotes osteogenesis by improving BMSC differentiation into osteoblasts via increased expression of Hedgehog signaling-related genes Shh, Ihh, Gli2, and Runx2, and quercetin was the bioactive compound of BSHX.

Inhibition of Osteoclast Differentiation and Promotion of Osteogenic Formation by Wolfiporia extensa Mycelium

Osteoporosis, Greek for "porous bone," is a bone disease characterized by a decrease in bone strength, microarchitectural changes in the bone tissues, and an increased risk of fracture. An imbalance of bone resorption and bone formation may lead to chronic metabolic diseases such as osteoporosis. Wolfiporia extensa, known as "Bokryung" in Korea, is a fungus belonging to the family Polyporaceae and has been used as a therapeutic food against various diseases. Medicinal mushrooms, mycelium and fungi, possess approximately 130 medicinal functions, including antitumor, immunomodulating, antibacterial, hepatoprotective, and antidiabetic effects, and are therefore used to improve human health. In this study, we used osteoclast and osteoblast cell cultures treated with Wolfiporia extensa mycelium water extract (WEMWE) and investigated the effect of the fungus on bone homeostasis. Subsequently, we assessed its capacity to modulate both osteoblast and osteoclast differentiation by performing osteogenic and anti-osteoclastogenic activity assays. We observed that WEMWE increased BMP-2-stimulated osteogenesis by inducing Smad-Runx2 signal pathway axis. In addition, we found that WEMWE decreased RANKL-induced osteoclastogenesis by blocking c-Fos/NFATc1 via the inhibition of ERK and JNK phosphorylation. Our results show that WEMWE can prevent and treat bone metabolic diseases, including osteoporosis, by a biphasic activity that sustains bone homeostasis. Therefore, we suggest that WEMWE can be used as a preventive and therapeutic drug.

Osteogenesis promotion by injectable methacryloylated gelatin containing psoralen and its bacteriostatic properties

The treatment of periodontitis focuses on controlling the progression of inflammation, reducing plaque accumulation, and promoting bone tissue reconstruction. Among them, the reconstruction of irregular bone resorption caused by periodontitis is a long-standing challenge. At present, the local drug treatment of periodontitis is mainly anti-inflammatory and antibacterial drugs. In this study, psoralen (Pso), a Chinese herbal medicine with anti-inflammatory, antibacterial, and osteogenic effects, was selected for the local treatment of periodontitis. Meanwhile, an injectable methacrylate gelatin (GelMA) platform loading with Pso was constructed. Pso-GelMA had the properties of fluidity, light cohesion, self-healing, and slow release, which could be better used in the deep and narrow structure of the periodontal pocket, and greatly increased the effectiveness of local drug delivery. The pore size of Gelma hydrogel did not change after loading Pso by SEM. In vitro, Pso-GelMA effectively upregulated the expression of osteogenic genes and proteins, increased alkaline phosphatase activity, promoted the mineralisation of rat bone marrow mesenchymal stem cells (BMSCs) extracellular matrix, and had significant antibacterial effects on Staphylococcus aureus and Fusobacterium nucleatum. Therefore, Pso-GelMA has immense promise in the adjuvant treatment of periodontitis.

Bone marrow mesenchymal stem cells paracrine TGF-β1 to mediate the biological activity of osteoblasts in bone repair

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) are an important source of seed cells for regenerative medicine and tissue engineering therapy. BMSCs have multiple differentiation potentials and can release paracrine factors to facilitate tissue repair. Although the role of the osteogenic differentiation of BMSCs has been fully confirmed, the function and mechanism of BMSC paracrine factors in bone repair are still largely unclear. This study aimed to determine the roles of transforming growth factor beta-1 (TGF-β1) produced by BMSCs in bone tissue repair.

METHODS

To confirm our hypothesis, we used a Transwell system to coculture hBMSCs and human osteoblast-like cells without contact, which could not only avoid the interference of the osteogenic differentiation of hBMSCs but also establish the cell-cell relationship between hBMSCs and human osteoblast-like cells and provide stable paracrine substances. In the transwell coculture system, alkaline phosphatase activity, mineralized nodule formation, cell migration and chemotaxis analysis assays were conducted.

RESULTS

Osteogenesis, migration and chemotaxis of osteoblast-like cells were regulated by BMSCs in a paracrine manner via the upregulation of osteogenic and migration-associated genes. A TGF-β receptor I inhibitor (LY3200882) significantly antagonized BMSC-induced biological activity and related gene expression in osteoblast-like cells. Interestingly, coculture with osteoblast-like cells significantly increased the production of TGF-β1 by BMSCs, and there was potential intercellular communication between BMSCs and osteoblast-like cells.

CONCLUSIONS

Our findings provide evidence that the biological mechanism of BMSC-produced TGF-β1 promotes bone regeneration and repair, providing a theoretical basis and new directions for the application of BMSC transplantation in the treatment of osteonecrosis and bone injury.

SMAD4 contributes to chondrocyte and osteocyte development

Different cellular and molecular mechanisms contribute to chondrocyte and osteocyte development. Although vital roles of the mothers against decapentaplegic homolog 4 (also called 'SMAD4') have been discussed in different cancers and stem cell-related studies, there are a few reviews summarizing the roles of this protein in the skeletal development and bone homeostasis. In order to fill this gap, we discuss the critical roles of SMAD4 in the skeletal development. To this end, we review the different signalling pathways and also how SMAD4 defines stem cell features. We also elaborate how the epigenetic factors-ie DNA methylation, histone modifications and noncoding RNAs-make a contribution to the chondrocyte and osteocyte development. To better grasp the important roles of SMAD4 in the cartilage and bone development, we also review the genotype-phenotype correlation in animal models. This review helps us to understand the importance of the SMAD4 in the chondrocyte and bone development and the potential applications for therapeutic goals.

Hydroxytyrosol prevents periodontitis-induced bone loss by regulating mitochondrial function and mitogen-activated protein kinase signaling of bone cells

Reactive oxygen species (ROS) overproduction promotes the alveolar bone loss during the development of periodontitis. Mitochondria are the principal source of ROS. Hydroxytyrosol (HT), a natural phenolic compound present in olive oil, is well known for its antioxidant and mitochondrial-protective prosperities. Nonetheless, the impact of HT on periodontitis and its related mechanisms underlying bone cell behavior remains unknown. Osteoclasts differentiated from RAW264.7 model and oxidative stress (OS) induced pre-osteoblast MC3T3-E1 cell injury model were treated with and without HT. Cell viability, apoptosis, differentiation, mitochondrial function along with mitogen-activated protein kinase (MAPK) signaling pathway were investigated. Meanwhile, the effect and related mechanisms of HT on bone loss in mice with periodontitis were also detected. HT inhibited osteoclast differentiation and prevented OS induced pre-osteoblast cells injury via regulating mitochondrial function as well as ERK and JNK signaling pathways. Moreover, HT attenuated the alveolar bone loss, increased bone forming activity, inhibited the osteoclasts differentiation and decreased the level of OS in mice with periodontitis. Our findings, for the first time, revealed a novel function of HT in bone remodeling of periodontitis, and highlighted its therapeutical potential for the prevention/treatment of periodontitis.

The Role of Extracellular Vesicles Secreted From Thermal Stress-Induced Adipose-Derived Stem Cells on Bone Regeneration

PURPOSE

Extracellular vesicles (EVs) are responsible for intercellular communication. Mesenchymal stem cell-derived vesicles have been shown to have similar properties as functional mesenchymal stem cells. The aim of this study was to compare the therapeutic benefit of EVs obtained from adipose tissue-derived stem cells (ADSC) on bone repair whereas using ß-tricalcium phosphate (ß-TCP) biomaterial as a carrier.

MATERIALS AND METHOD

A single critical size bone defect of 8 mm in diameter was created on the right side of rat calvarium using a custom-made punch needle. Animals were randomly divided into 5 groups: group 1 (no treatment), group 2 (bone graft), group 3 (ß-TCP + ADSC), group 4 (ß-TCP + EV), group 5 (ß-TCP). Eight weeks later, animals were sacrificed and histologic and radiologic evaluation was performed.

RESULTS

Semiquantitative histologic scoring demonstrated significantly higher bone regeneration scores for groups 2, 3, and 4 compared to group 1. Radiologic imaging showed significantly higher bone mineral density for groups 2, 3, and 5 compared to group 1. There were no significant differences between treatment groups in either histologic or radiologic scoring.

CONCLUSIONS

Our data showed that EVs provided from thermally induced ADSCs did not show any significant difference in bone regeneration when compared to ADSCs themselves. Future studies should focus on determining the optimum amount and content of EV application since these vary significantly depending on the microenvironment.

Transcriptional networks controlling stromal cell differentiation

Stromal progenitors are found in many different tissues, where they play an important role in the maintenance of tissue homeostasis owing to their ability to differentiate into parenchymal cells. These progenitor cells are differentially pre-programmed by their tissue microenvironment but, when cultured and stimulated in vitro, these cells - commonly referred to as mesenchymal stromal cells (MSCs) - exhibit a marked plasticity to differentiate into many different cell lineages. Loss-of-function studies in vitro and in vivo have uncovered the involvement of specific signalling pathways and key transcriptional regulators that work in a sequential and coordinated fashion to activate lineage-selective gene programmes. Recent advances in omics and single-cell technologies have made it possible to obtain system-wide insights into the gene regulatory networks that drive lineage determination and cell differentiation. These insights have important implications for the understanding of cell differentiation, the contribution of stromal cells to human disease and for the development of cell-based therapeutic applications.

Gold Nanoparticles Promote the Bone Regeneration of Periodontal Ligament Stem Cell Sheets Through Activation of Autophagy

OBJECTIVE

Cell sheet technology (CST) is advantageous for repairing alveolar bone defects in clinical situations, and osteogenic induction before implantation may result in enhanced bone regeneration. Herein, we observed the effect of gold nanoparticles (AuNPs) on osteogenic differentiation of periodontal ligament stem cell (PDLSC) sheets and explored their potential mechanism of action.

METHODS

PDLSCs were cultured in cell sheet induction medium to obtain cell sheets. PDLSC sheets were treated with or without AuNPs. Alkaline phosphatase, alizarin red S, von Kossa, and immunofluorescence staining were used to observe the effects of AuNPs on the osteogenic differentiation of PDLSC sheets. Western blotting was performed to evaluate the osteogenic effects and autophagy activity. The cell sheets were transplanted into the dorsa of nude mice, and bone regeneration was analyzed by micro-CT and histological staining.

RESULTS

AuNPs could promote the osteogenic differentiation of PDLSC sheets by upregulating bone-related protein expression and mineralization. The 45-nm AuNPs were more effective than 13-nm AuNPs. Additional analysis demonstrated that their ability to promote differentiation could depend on activation of the autophagy pathway through upregulation of microtubule-associated protein light chain 3 and downregulation of sequestosome 1/p62. Furthermore, AuNPs significantly promoted the bone regeneration of PDLSC sheets in ectopic models.

CONCLUSION

AuNPs enhance the osteogenesis of PDLSC sheets by activating autophagy, and 45-nm AuNPs were more effective than 13-nm AuNPs. This study may provide an AuNP-based pretreatment strategy for improving the application of CST in bone repair and regeneration.

Angelicin-A Furocoumarin Compound With Vast Biological Potential

Angelicin, a member of the furocoumarin group, is related to psoralen which is well known for its effectiveness in phototherapy. The furocoumarins as a group have been studied since the 1950s but only recently has angelicin begun to come into its own as the subject of several biological studies. Angelicin has demonstrated anti-cancer properties against multiple cell lines, exerting effects via both the intrinsic and extrinsic apoptotic pathways, and also demonstrated an ability to inhibit tubulin polymerization to a higher degree than psoralen. Besides that, angelicin too demonstrated anti-inflammatory activity in inflammatory-related respiratory and neurodegenerative ailments via the activation of NF-κB pathway. Angelicin also showed pro-osteogenesis and pro-chondrogenic effects on osteoblasts and pre-chondrocytes respectively. The elevated expression of pro-osteogenic and chondrogenic markers and activation of TGF-β/BMP, Wnt/β-catenin pathway confirms the positive effect of angelicin bone remodeling. Angelicin also increased the expression of estrogen receptor alpha (ERα) in osteogenesis. Other bioactivities, such as anti-viral and erythroid differentiating properties of angelicin, were also reported by several researchers with the latter even displaying an even greater aptitude as compared to the commonly prescribed drug, hydroxyurea, which is currently on the market. Apart from that, recently, a new application for angelicin against periodontitis had been studied, where reduction of bone loss was indirectly caused by its anti-microbial properties. All in all, angelicin appears to be a promising compound for further studies especially on its mechanism and application in therapies for a multitude of common and debilitating ailments such as sickle cell anaemia, osteoporosis, cancer, and neurodegeneration. Future research on the drug delivery of angelicin in cancer, inflammation and erythroid differentiation models would aid in improving the bioproperties of angelicin and efficacy of delivery to the targeted site. More in-depth studies of angelicin on bone remodeling, the pro-osteogenic effect of angelicin in various bone disease models and the anti-viral implications of angelicin in periodontitis should be researched. Finally, studies on the binding of angelicin toward regulatory genes, transcription factors, and receptors can be done through experimental research supplemented with molecular docking and molecular dynamics simulation.

Exendin‑4 promotes osteogenic differentiation of adipose‑derived stem cells and facilitates bone repair

Inflammation-related bone defects pose a heavy burden on patients and orthopedic surgeons. Although stem-cell-based bone repair has developed rapidly, it is of great significance to characterize bio-active molecules that facilitate bone regeneration. It is reported that a glucagon-like peptide 1 receptor agonist, exendin-4, promoted bone regeneration mediated by the transplantation of adipose-derived stem cells in a metaphyseal defect mouse model of femur injury. However, the underlying mechanism is unclear. Bone imaging, immunohistochemistry real-time PCR and western blot analysis were used in the present study, and the results revealed that exendin-4 increased the transcription of the osteogenic differentiation-related genes and induced osteogenic differentiation in situ. Furthermore, the present data obtained from sorted adipose-derived stem cells revealed that exendin-4 promoted osteogenic differentiation and inhibited adipogenic differentiation in vitro. These findings indicated that exendin-4 facilitates osteogenic differentiation of transplanted adipose-derived stem cells for bone repair and illuminated clinical prospects of both adipose-derived stem cells and exendin-4 in stem-cell-based bone defect repair.

TGF‑β1 promotes the osteoinduction of human osteoblasts via the PI3K/AKT/mTOR/S6K1 signalling pathway

Transforming growth factor β1 (TGF-β1) has been suggested to be a candidate cytokine in the field of bone tissue engineering. Cytokines serve important roles in tissue engineering, particularly in the repair of bone damage; however, the underlying molecular mechanisms remain unclear. In the present study, the effects of TGF-β1 on the osteogenesis and motility of hFOB1.19 human osteoblasts were demonstrated via the phenotype and gene expression of cells. Additionally, the role of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin/S6 kinase 1 (PI3K/AKT/mTOR/S6K1) signalling pathway in the effects of TGF-β1 on osteoblasts was investigated. It was demonstrated using Cell Counting Kit-8 and flow cytometry assays that the proliferation of human osteoblasts was promoted by 1 ng/ml TGF-β1. In addition, alkaline phosphatase activity, Alizarin red staining, scratch-wound and Transwell assays were conducted. It was revealed that osteogenesis and the migration of cells were regulated by TGF-β1 via the upregulation of osteogenic and migration-associated genes. Alterations in the expression of osteogenesis- and migration-associated genes were evaluated following pre-treatment with a PI3K/AKT inhibitor (LY294002) and an mTOR/S6K1 inhibitor (rapamycin), with or without TGF-β1. The results indicated that TGF-β1 affected the osteogenesis and mineralisation of osteoblasts via the PI3K/AKT signalling pathway. Furthermore, TGF-β1 exhibited effects on mTOR/S6K1 downstream of PI3K/AKT. The present study demonstrated that TGF-β1 promoted the proliferation, differentiation and migration of human hFOB1.19 osteoblasts, and revealed that TGF-β1 affected the biological activity of osteoblasts via the PI3K/AKT/mTOR/S6K1 signalling pathway. Our findings may provide novel insight to aid the development of bone tissue engineering methods for the treatment of bone injury.

Distal-less homeobox 3, a negative regulator of myogenesis, is downregulated by microRNA-133

Distal-less homeobox 3 (Dlx3), a member of the Dlx family of homeobox proteins, is a transcriptional activator of runt-related transcription factor 2 (Runx2) during osteogenic differentiation. It has been demonstrated that forced expression of Runx2 induces an osteogenic program and ectopic calcification in muscles. Therefore, it would be reasonable to predict that Dlx3 also affects myogenic differentiation. The relationship between Dlx3 and myogenesis, however, remains poorly understood. Therefore, in this study, the role and regulation of Dlx3 during myogenic differentiation were investigated. Expression level of Dlx3 was downregulated in human mesenchymal stem cells (MSCs), mouse MSCs, and C2C12 cells cultured in myogenic medium. Dlx3 level was inversely correlated with myogenic differentiation 1 and the muscle-specific microRNA, microRNA-133 (miR-133). The expression level of Runx2 was closely regulated by Dlx3 even under myogenic conditions. Overexpression of Dlx3 markedly downregulated expression levels of myogenic transcription factors and myotube formation in C2C12 cells, whereas Dlx3 knockdown enhanced myogenic differentiation. The Dlx3 3'-untranslated region (3'-UTR) has two potential binding sites for miR-133. Luciferase reporter assays demonstrated that Dlx3 is a direct target of miR-133a and miR-133b, and that the two target sites are redundantly active. Taken together, these results suggest that Dlx3 is a negative regulator of myogenic differentiation and that miR-133a and miR-133b enhance myogenic differentiation, partly through inhibition of Dlx3 expression via direct targeting of the Dlx3 3'-UTR.

Fabrication of sulphonated poly(ethylene glycol)-diacrylate hydrogel as a bone grafting scaffold

To improve the biological performance of poly(ethylene glycol)-diacrylate (PEGDA) hydrogel as an injectable bone grafting scaffold, sodium methallyl sulphonate (SMAS) was incorporated into PEGDA hydrogel. The physiochemical properties of the resultant polymers were assessed via Fourier transform infrared spectroscopy (FTIR), swelling ratio, zeta potential, surface morphology, and protein adsorption analysis. MC3T3-E1 cells were seeded on the hydrogel to evaluate the effect of the sulphonated modification on their attachment, proliferation, and differentiation. The results of FTIR and zeta potential evaluations revealed that SMAS was successfully incorporated into PEGDA. With increasing concentrations of SMAS, the swelling ratio of the hydrogels increased in deionized water but stayed constant in phosphate buffered saline. The protein adsorption also increased with increasing concentration of SMAS. Moreover, the sulphonated modification of PEGDA hydrogel not only enhanced the attachment and proliferation of osteoblast-like MC3T3-E1 cells but also up-regulated alkaline phosphatase activity as well as gene expression of osteogenic markers and related growth factors, including collagen type I, osteocalcin, runt related transcription factor 2, bone morphogenetic protein 2, and transforming growth factor beta 1. These findings indicate that the sulphonated modification could significantly improve the biological performance of PEGDA hydrogel. Thus, the sulphonated PEGDA is a promising scaffold candidate for bone grafting.

The Dual Role of Oat Bran Water Extract in Bone Homeostasis Through the Regulation of Osteoclastogenesis and Osteoblast Differentiation

The number of patients with bone metabolic disorders including osteoporosis is increasing worldwide. These disorders often facilitate bone fractures, which seriously impact the patient's quality of life and could lead to further health complications. Bone homeostasis is tightly regulated to balance bone resorption and formation. However, many anti-osteoporotic agents are broadly categorized as either bone forming or anti-resorptive, and their therapeutic use is often limited due to unwanted side effects. Therefore, safe and effective therapeutic agents are needed for osteoporosis. This study aims to clarify the bone protecting effects of oat bran water extract (OBWE) and its mode of action. OBWE inhibited RANKL (receptor activator of nuclear factor-κB ligand)-induced osteoclast differentiation by blocking c-Fos/NFATc1 through the alteration of I-κB. Furthermore, we found that OBWE enhanced BMP-2-stimulated osteoblast differentiation by the induction of Runx2 via Smad signaling molecules. In addition, the anti-osteoporotic activity of OBWE was also evaluated using an in vivo model. OBWE significantly restored ovariectomy-induced bone loss. These in vitro and in vivo results showed that OBWE has the potential to prevent and treat bone metabolic disorders including osteoporosis.

Development of a 3D Collagen Model for the In Vitro Evaluation of Magnetic-assisted Osteogenesis

Magnetic stimulation has been applied to bone regeneration, however, the cellular and molecular mechanisms of repair still require a better understanding. A three-dimensional (3D) collagen model was developed using plastic compression, which produces dense, cellular, mechanically strong native collagen structures. Osteoblast cells (MG-63) and magnetic iron oxide nanoparticles (IONPs) were incorporated into collagen gels to produce a range of cell-laden models. A magnetic bio-reactor to support cell growth under static magnetic fields (SMFs) was designed and fabricated by 3D printing. The influences of SMFs on cell proliferation, differentiation, extracellular matrix production, mineralisation and gene expression were evaluated. Polymerase chain reaction (PCR) further determined the effects of SMFs on the expression of runt-related transcription factor 2 (Runx2), osteonectin (ON), and bone morphogenic proteins 2 and 4 (BMP-2 and BMP-4). Results demonstrate that SMFs, IONPs and the collagen matrix can stimulate the proliferation, alkaline phosphatase production and mineralisation of MG-63 cells, by influencing matrix/cell interactions and encouraging the expression of Runx2, ON, BMP-2 and BMP-4. Therefore, the collagen model developed here not only offers a novel 3D bone model to better understand the effect of magnetic stimulation on osteogenesis, but also paves the way for further applications in tissue engineering and regenerative medicine.

Genetic Engineering of Mesenchymal Stem Cells for Differential Matrix Deposition on 3D Woven Scaffolds

Tissue engineering approaches for the repair of osteochondral defects using biomaterial scaffolds and stem cells have remained challenging due to the inherent complexities of inducing cartilage-like matrix and bone-like matrix within the same local environment. Members of the transforming growth factor β (TGFβ) family have been extensively utilized in the engineering of skeletal tissues, but have distinct effects on chondrogenic and osteogenic differentiation of progenitor cells. The goal of this study was to develop a method to direct human bone marrow-derived mesenchymal stem cells (MSCs) to deposit either mineralized matrix or a cartilaginous matrix rich in glycosaminoglycan and type II collagen within the same biochemical environment. This differential induction was performed by culturing cells on engineered three-dimensionally woven poly(ɛ-caprolactone) (PCL) scaffolds in a chondrogenic environment for cartilage-like matrix production while inhibiting TGFβ3 signaling through Mothers against DPP homolog 3 (SMAD3) knockdown, in combination with overexpressing RUNX2, to achieve mineralization. The highest levels of mineral deposition and alkaline phosphatase activity were observed on scaffolds with genetically engineered MSCs and exhibited a synergistic effect in response to SMAD3 knockdown and RUNX2 expression. Meanwhile, unmodified MSCs on PCL scaffolds exhibited accumulation of an extracellular matrix rich in glycosaminoglycan and type II collagen in the same biochemical environment. This ability to derive differential matrix deposition in a single culture condition opens new avenues for developing complex tissue replacements for chondral or osteochondral defects.

The art of building bone: emerging role of chondrocyte-to-osteoblast transdifferentiation in endochondral ossification

There is a worldwide epidemic of skeletal diseases causing not only a public health issue but also accounting for a sizable portion of healthcare expenditures. The vertebrate skeleton is known to be formed by mesenchymal cells condensing into tissue elements (patterning phase) followed by their differentiation into cartilage (chondrocytes) or bone (osteoblasts) cells within the condensations. During the growth and remodeling phase, bone is formed directly via intramembranous ossification or through a cartilage to bone conversion via endochondral ossification routes. The canonical pathway of the endochondral bone formation process involves apoptosis of hypertrophic chondrocytes followed by vascular invasion that brings in osteoclast precursors to remove cartilage and osteoblast precursors to form bone. However, there is now an emerging role for chondrocyte-to-osteoblast transdifferentiation in the endochondral ossification process. Although the concept of "transdifferentiation" per se is not recent, new data using a variety of techniques to follow the fate of chondrocytes in different bones during embryonic and post-natal growth as well as during fracture repair in adults have identified three different models for chondrocyte-to-osteoblast transdifferentiation (direct transdifferentiation, dedifferentiation to redifferentiation, and chondrocyte to osteogenic precursor). This review focuses on the emerging models of chondrocyte-to-osteoblast transdifferentiation and their implications for the treatment of skeletal diseases as well as the possible signaling pathways that contribute to chondrocyte-to-osteoblast transdifferentiation processes.

The art of building bone: emerging role of chondrocyte-to-osteoblast transdifferentiation in endochondral ossification

There is a worldwide epidemic of skeletal diseases causing not only a public health issue but also accounting for a sizable portion of healthcare expenditures. The vertebrate skeleton is known to be formed by mesenchymal cells condensing into tissue elements (patterning phase) followed by their differentiation into cartilage (chondrocytes) or bone (osteoblasts) cells within the condensations. During the growth and remodeling phase, bone is formed directly via intramembranous ossification or through a cartilage to bone conversion via endochondral ossification routes. The canonical pathway of the endochondral bone formation process involves apoptosis of hypertrophic chondrocytes followed by vascular invasion that brings in osteoclast precursors to remove cartilage and osteoblast precursors to form bone. However, there is now an emerging role for chondrocyte-to-osteoblast transdifferentiation in the endochondral ossification process. Although the concept of "transdifferentiation" per se is not recent, new data using a variety of techniques to follow the fate of chondrocytes in different bones during embryonic and post-natal growth as well as during fracture repair in adults have identified three different models for chondrocyte-to-osteoblast transdifferentiation (direct transdifferentiation, dedifferentiation to redifferentiation, and chondrocyte to osteogenic precursor). This review focuses on the emerging models of chondrocyte-to-osteoblast transdifferentiation and their implications for the treatment of skeletal diseases as well as the possible signaling pathways that contribute to chondrocyte-to-osteoblast transdifferentiation processes.

A Novel Diterpenoid Suppresses Osteoclastogenesis and Promotes Osteogenesis by Inhibiting Ifrd1-Mediated and IκBα-Mediated p65 Nuclear Translocation

Osteoporosis develops because of impaired bone formation and/or excessive bone resorption. Although the pharmacological treatment of osteoporosis has been extensively developed, alternative treatments are still needed. Here, we showed that oridonin (ORI), a diterpenoid isolated from Rabdosia rubescens, can suppress osteoclastogenesis and enhance osteogenesis. ORI inhibited the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation and bone resorption through the inhibition of p65 nuclear translocation. ORI-induced inhibition of this translocation led to an increase in osteoblast differentiation and mineralization through the promotion of Smad1/Smad5 phosphorylation. Further analyses demonstrated that the inhibition of p65 nuclear translocation is due to the suppression of IκBα phosphorylation and the induced proteasomal degradation of interferon-related development regulator 1 (Ifrd1), a transcriptional corepressor that is involved in the suppression of NF-κB nuclear translocation. Moreover, mice treated with ORI at catabolic and anabolic windows showed a considerable attenuation of ovariectomy (OVX)-induced osteoporosis. Taken together, our findings reveal that ORI protects against OVX-induced bone loss via inhibiting osteoclastic bone resorption but enhancing osteoblastic bone formation through abolishing both Ifrd1-mediating and IκBα-mediated p65 nuclear translocation. These results show the potential of ORI for treatment of osteoporosis and highlight Ifrd1 as a another novel promising target for anti-osteoporotic drugs. © 2017 American Society for Bone and Mineral Research.

Ion channel functional protein kinase TRPM7 regulates Mg ions to promote the osteoinduction of human osteoblast via PI3K pathway: In vitro simulation of the bone-repairing effect of Mg-based alloy implant

Mg-based alloys, as the potential orthopaedic implant, can self-degrade to avoid second operation for its remove, and enable to promote bone repair; however, the underlying molecular mechanisms remain unclear. In the present study, we examined the effect of Mg ions on osteogenesis, chemotaxis and anti-alkaline stress in hFOB1.19 human osteoblast cells to simulate bone-repairing effect of a biodegradable Mg-based alloy implant in vitro, and explored the regulatory role of the transient receptor potential melastatin 7 (TRPM7)/phosphoinositide 3-kinase (PI3K) signalling pathway in the process of Mg ion-induced bone repair by knockdown of TRPM7 and antagonizing PI3K activity. Results indicate that Mg ions up-regulated the expression of Runx2 and alkaline phosphatase (ALP) through TRPM7/PI3K signalling pathway, which could significantly enhance the osteogenic activity of human osteoblasts. Furthermore, the expression levels of MMP2, MMP9 and vascular endothelial growth factor (VEGF) were increased by TRPM7/PI3K signalling pathway, which recruits osteoblasts from low- to high-Mg ion environments by inducing cell migration. Although an alkaline environment has antibacterial effects, alkaline stress can cause cytotoxicity and induce cell death. Finally, we found that Mg ions could activate PI3K phosphorylation to promote cell growth and survival, protecting cells against the alkaline-stress-induced cytotoxicity caused by the degradation of Mg-based alloy implants. Our study not only revealed the molecular mechanism of Mg in promoting bone repair but also explained the protective effects of Mg ions on osteoblasts in an alkaline environment, which provides a theoretical basis and new directions for the application of Mg-based alloy implant material in orthopaedics fixations and osteosarcoma treatment.

STATEMENTS OF SIGNIFICANCE

As a potential biomaterial for orthopaedic implant, biodegradable magnesium has several advantages including self-degradation and bone repair promotion; however, the underlying mechanisms and effective concentration by which molecular regulates the bone repair remain unclear. The present study revealed that Mg ion and its effective concentration for activating PI3K phosphorylation via TRPM7, which causes three processes affecting bone repair, namely, osteoblast recruitment, osteogenesis and resistance to alkaline stress in human osteoblast. Therefore, our results have provided insight into the underlying molecular biological basis, and guidance for manipulating degradation rate, such as surface modification, of orthopaedic Mg-based implants.

Transdifferentiation of myoblasts into osteoblasts – possible use for bone therapy

Objectives

Transdifferentiation is defined as the conversion of one cell type to another and is an ever-expanding field with a growing number of cells found to be capable of such a process. To date, the fact remains that there are limited treatment options for fracture healing, osteoporosis and bone repair post-destruction by bone tumours. Hence, this review focuses on the transdifferentiation of myoblast to osteoblast as a means to further understand the transdifferentiation process and to investigate a potential therapeutic option if successful.

Key findings

The potent osteoinductive effects of the bone morphogenetic protein-2 are largely implicated in the transdifferentiation of myoblast to osteoblast. Bone morphogenetic protein-2-induced activation of the Smad1 protein ultimately results in JunB synthesis, the first transcriptional step in myoblast dedifferentiation. The upregulation of the activating protein-1 binding activity triggers the transcription of the runt-related transcription factor 2 gene, a transcription factor that plays a major role in osteoblast differentiation.

Summary

This potential transdifferentiation treatment may be utilised for dental implants, fracture healing, osteoporosis and bone repair post-destruction by bone tumours.

* Biomineralized Recombinant Collagen-Based Scaffold Mimicking Native Bone Enhances Mesenchymal Stem Cell Interaction and Differentiation

The need of synthetic bone grafts that recreate from macro- to nanoscale level the biochemical and biophysical cues of bone extracellular matrix has been a major driving force for the development of new generation of biomaterials. In this study, synthetic bone substitutes have been synthesized via biomimetic mineralization of a recombinant collagen type I-derived peptide (RCP), enriched in tri-amino acid sequence arginine-glycine-aspartate (RGD). Three-dimensional (3D) isotropic porous scaffolds of three different compositions are developed by freeze-drying: non-mineralized (RCP, as a control), mineralized (Ap/RCP), and mineralized scaffolds in the presence of magnesium (MgAp/RCP) that closely imitate bone composition. The effect of mineral phase on scaffold pore size, porosity, and permeability, as well as on their in vitro kinetic degradation, is evaluated. The ultimate goal is to investigate how chemical (i.e., surface chemistry and ion release from scaffold) together with physical signals (i.e., surface nanotopography) conferred via biomimetic mineralization can persuade and guide mesenchymal stem cell (MSC) interaction and fate. The three scaffold compositions showed optimum pore size and porosity for osteoconduction, without significant differences between them. The degradation tests confirmed that MgAp/RCP scaffolds presented higher reactivity under physiological condition compared to Ap/RCP ones. The in vitro study revealed an enhanced cell growth and proliferation on MgAp/RCP scaffolds at day 7, 14, and 21. Furthermore, MgAp/RCP scaffolds potentially promoted cell migration through the inner areas reaching the bottom of the scaffold after 14 days. MSCs cultured on MgAp/RCP scaffolds displayed higher gene and protein expressions of osteogenic markers when comparing them with the results of those MSCs grown on RCP or Ap/RCP scaffolds. This work highlights that mineralization of recombinant collagen mimicking bone mineral composition and morphology is a versatile approach to design smart scaffold interface in a 3D model guiding MSC fate.

A limb-girdle myopathy phenotype of RUNX2 mutation in a patient with cleidocranial dysplasia: a case study and literature review

Background

Cleidocranial dysplasia (CCD) is a rare hereditary disorder that arises from heterozygous loss of function mutations in the runt-related transcription factor 2 (RUNX2) gene. As RUNX2 is mainly expressed in osteoblasts, CCD typically affects the skeletal and dental systems. Few studies have investigated RUNX2 mutation effects on non-skeletal systems. Here, we describe limb-girdle myopathy, an uncommon phenotype of CCD, in a patient with a heterozygous missense mutation (p.R225Q) in the RUNX2 gene.

Case presentation

A 58 year-old man presented with progressive back pain and six months of weakness in the proximal parts of all four limbs. Physical examinations showed that he was short in stature (height, 164.4 cm; weight, 79.1 kg) with a dysmorphic face, including hypertelorism, midface hypoplasia, and chin protrusion. At a young age, he had received orthodontic surgery, due to dental abnormalities. Neurological examinations revealed sloping shoulders, weakness, and atrophy in the proximal areas of the arms, shoulder girdle muscles, and legs. The deep tendon reflex and sensory system were normal. Radiological examinations revealed mild scoliosis, shortened clavicles, and a depressed skull bone, which were consistent with a clinical diagnosis of CCD. Electromyography (EMG) studies showed myogenic polyphasic waves in the deltoid, biceps brachii, and rectus femoris muscles. Instead, the EMG findings were normal in the first dorsal interosseous, tibialis anterior and facial muscles. The EMG findings were compatible with a limb-girdle pattern with facial sparing. The patient’s family history showed his father and eldest daughter with similar dysmorphic faces, skeletal disorders and proximal upper extremity weakness. We sequenced the RUNX2 gene and discovered a heterozygous missense mutation (c.G674A, p.R225Q), which altered the C-terminal end of the RUNX2 protein. This mutation was predicted to inactivate the protein and might affect its interactions with other proteins. This mutation co-segregated with the disease phenotypes in the family.

Conclusions

We described limb-girdle myopathy in a patient with CCD that carried a heterozygous RUNX2 missense mutation. This uncommon phenotype expanded the phenotypic spectrum of the RUNX2 p.R225Q mutation. The role of RUNX2 in myogenic development merits future studies. Our findings remind clinicians that myopathic patients with myopathies combined with facial dysmorphism and shortened clavicles should consider the diagnosis of CCD.

Biological Approaches to Bone Regeneration by Gene Therapy

Safe, effective approaches for bone regeneration are needed to reverse bone loss caused by trauma, disease, and tumor resection. Unfortunately, the science of bone regeneration is still in its infancy, with all current or emerging therapies having serious limitations. Unlike current regenerative therapies that use single regenerative factors, the natural processes of bone formation and repair require the coordinated expression of many molecules, including growth factors, bone morphogenetic proteins, and specific transcription factors. As will be developed in this article, future advances in bone regeneration will likely incorporate therapies that mimic critical aspects of these natural biological processes, using the tools of gene therapy and tissue engineering. This review will summarize current knowledge related to normal bone development and fracture repair, and will describe how gene therapy, in combination with tissue engineering, may mimic critical aspects of these natural processes. Current gene therapy approaches for bone regeneration will then be summarized, including recent work where combinatorial gene therapy was used to express groups of molecules that synergistically interacted to stimulate bone regeneration. Last, proposed future directions for this field will be discussed, where regulated gene expression systems will be combined with cells seeded in precise three-dimensional configurations on synthetic scaffolds to control both temporal and spatial distribution of regenerative factors. It is the premise of this article that such approaches will eventually allow us to achieve the ultimate goal of bone tissue engineering: to reconstruct entire bones with associated joints, ligaments, or sutures. Abbreviations used: BMP, bone morphogenetic protein; FGF, fibroblast growth factor; AER, apical ectodermal ridge; ZPA, zone of polarizing activity; PZ, progress zone; SHH, sonic hedgehog; OSX, osterix transcription factor; FGFR, fibroblast growth factor receptor; PMN, polymorphonuclear neutrophil; PDGF, platelet-derived growth factor; IGF, insulin-like growth factor; TGF-β, tumor-derived growth factor β; CAR, coxsackievirus and adenovirus receptor; MLV, murine leukemia virus; HIV, human immunodeficiency virus; AAV, adeno-associated virus; CAT, computer-aided tomography; CMV, cytomegalovirus; GAM, gene-activated matrix; MSC, marrow stromal cell; MDSC, muscle-derived stem cell; VEGF, vascular endothelial growth factor.

Chemical stability and osteogenic activity of plasma-sprayed boron-modified calcium silicate-based coatings

In recent years, CaSiO₃ bio-ceramic coatings have attracted great attention because of their good bioactivity. However, their high degradation rates in physiological environment restrict their practical applications. In this work, boron-modified CaSiO₃ ceramic (Ca₁₁Si₄B₂O₂₂, B-CS) coating was developed on Ti substrates by plasma-spraying technique attempting to obtain enhanced chemical stability and osteogenic activity. The B-CS coating possessed significantly increased chemical stability due to the introduction of boron and consequently the modified crystal structure, while maintaining good bioactivity. Scanning electron microscope and immunofluorescence studies showed that better cellular adhesion and extinctive filopodia-like processes were observed on the B-CS coating. Compared with the pure CaSiO₃ (CS) coating, the B-CS coating promoted MC3T3-E1 cells attachment and proliferation. In addition, enhanced collagen I (COL-I) secretion, alkaline phosphatase activity, and extracellular matrix mineralization levels were detected from the B-CS coating. According to RT-PCR results, notable up-regulation expressions of mineralized tissue-related genes, such as runt-related transcription factor 2 (Runx2), bone sialoprotein and osteocalcin, and bone morphogenetic protein 7 (BMP-7) were observed on the B-CS coating compared with the CS coating. The above results suggested that Ca₁₁Si₄B₂O₂₂ coatings possess excellent osteogenic activity and might be a promising candidate for orthopedic applications.

Systematic Analysis of Known and Candidate Lysine Demethylases in the Regulation of Myoblast Differentiation

Histone methylation dynamics plays a critical role in cellular programming during development. For example, specific lysine methyltransferases (KMTs) and lysine demethylases (KDMs) have been implicated in the differentiation of mesenchymal stem cells into various cell lineages. However, a systematic and functional analysis for an entire family of KMT or KDM enzymes has not been performed. Here, we test the function of all the known and candidate KDMs in myoblast and osteoblast differentiation using the C2C12 cell differentiation model system. Our analysis identified that LSD1 is the only KDM required for myogenic differentiation and that KDM3B, KDM6A, and KDM8 are the candidate KDMs required for osteoblast differentiation. We find that LSD1, via H3K4me1 demethylation, represses the master regulator of osteoblast differentiation RUNX2 to promote myogenesis in the C2C12 model system. Finally, MLL4 is required for efficient osteoblast differentiation in part by countering LSD1 H3K4me1 demethylation at the RUNX2 enhancer. Together, our findings provide additional mechanisms by which lysine methylation signaling impacts on cell fate decisions.

Gene-Activated Titanium Surfaces Promote In Vitro Osteogenesis

PURPOSE

Commercially pure titanium (CpTi) and its alloys possess favorable mechanical and biologic properties for use as implants in orthopedics and dentistry. However, failures in osseointegration still exist and are common in select individuals with risk factors such as smoking. Therefore, in this study, a proposal was made to enhance the potential for osseointegration of CpTi discs by coating their surfaces with nanoplexes comprising polyethylenimine (PEI) and plasmid DNA (pDNA) encoding bone morphogenetic protein-2 (pBMP-2).

MATERIALS AND METHODS

The nanoplexes were characterized for size and surface charge with a range of N/P ratios (the molar ratio of amine groups of PEI to phosphate groups in pDNA backbone). CpTi discs were surface characterized for morphology and composition before and after nanoplex coating using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). The cytotoxicity and transfection ability of CpTi discs coated with nanoplexes of varying N/P ratios in human bone marrow-derived mesenchymal stem cells (BMSCs) was measured via MTS assays and flow cytometry, respectively.

RESULTS

The CpTi discs coated with nanoplexes prepared at an N/P ratio of 10 (N/P-10) were considered optimal, resulting in 75% cell viability and 14% transfection efficiency. Enzyme-linked immunosorbent assay results demonstrated a significant enhancement in BMP-2 protein secretion by BMSCs 7 days posttreatment with PEI/pBMP-2 nanoplexes (N/P-10) compared to the controls, and real-time PCR data demonstrated that the BMSCs treated with PEI/pBMP-2 nanoplex-coated CpTi discs resulted in an enhancement of Runx-2, alkaline phosphatase, and osteocalcin gene expressions on day 7 posttreatment. In addition, these BMSCs demonstrated enhanced calcium deposition on day 30 posttreatment as determined by qualitative (alizarin red staining) and quantitative (atomic absorption spectroscopy) assays.

CONCLUSION

It can be concluded that PEI/pBMP-2 nanoplex (N/P-10)-coated CpTi discs have the potential to induce osteogenesis and enhance osseointegration.

Porcine placenta hydrolysates enhance osteoblast differentiation through their antioxidant activity and effects on ER stress

BACKGROUND

Osteoporosis is a disease characterized by decreased bone strength, decreased bone mass, and bone deterioration. Oxidative damage is an important contributor to functional changes in the development of osteoporosis. Here we found that porcine placenta hydrolysates (PPHs) protect MC3T3-E1 osteoblastic cells against hydrogen peroxide (H2O2)-induced oxidative damage.

METHODS

In vitro cell viability was determined using trypan blue dye exclusion. ER stress and apoptosis were evaluated using immunoblotting and a commercially available caspase kit. ALP, osteocalcin, Runx2, and osterix expression levels were evaluated by RT-PCR using isolated RNA. ROS, NADPH oxidase, and SOD activity levels were also measured.

RESULTS

We investigated the mechanisms underlying PPH-mediated inhibition of H2O2-induced ER stress and ROS production. PPHs also regulated osteoblast differentiation via the upregulation of alkaline phosphatase (ALP) expression in MC3T3-E1 osteoblastic cells. Also, treatment with PPHs enhanced the transcription of osteocalcin, Runx2, and osterix. These effects were all associated with the antioxidant actions of PPHs. Moreover, PPHs reversed the decrease in SOD activity, decreased ROS release, and inhibited NADPH oxidase activity in H2O2-treated MC3T3-E1 osteoblastic cells.

CONCLUSIONS

PPHs protect cells against H2O2-induced cell damage when ER stress is involved. In addition, PPHs enhance osteoblast differentiation. This enhancement likely explains the regulatory effect of PPHs on bone metabolism disturbances, i.e. PPHs control ER stress and the related ROS production in osteoblasts.

Acredinone C and the Effect of Acredinones on Osteoclastogenic and Osteoblastogenic Activity

A new inhibitor, acredinone C (1), of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation was isolated from the culture broth of the fungus Acremonium sp. (F9A015) along with acredinones A (2) and B (3). The structure of acredinone C (1), which incorporates benzophenone and xanthone moieties, was established by the analyses of combined spectroscopic data including 1D and 2D NMR and MS. All of the acredinones studied efficiently inhibited the RANKL-induced formation of TRAP(+)-MNCs in a dose-dependent manner without any cytotoxicity up to 10 μM. Acredinone A showed dual activity in both osteoclast and osteoblast differentiation in vitro and good efficacy in an animal disease model of bone formation.

Different Sialoside Epitopes on Collagen Film Surfaces Direct Mesenchymal Stem Cell Fate

3'-Sialyllactose and 6'-sialyllactose have been covalently linked to collagen films. Preliminary in vitro study on the behavior of mesenchymal stem cells (MSCs) in terms of cell viability, proliferation and induction of osteogenic and chondrogenic related genes has been performed. Results indicate that sialoside epitopes on collagen surface represent a suitable support for MSCs adhesion and cell proliferation, moreover, the neoglycosylation provide MSCs with different and specific stimuli, saccharide-type depending, in term of expression of osteogenic and chondrogenic related genes. In particular, 3'-sialyllactose significantly upregulate the expression of RUNX2 and ALP, well-known markers of osteogenesis, whereas 6'-sialyllactose up-regulate the expression of chondrocyte marker ACAN. Because no osteogenic or chondrogenic supplements in culture media were added, the inductive effect in terms of increased gene expression has to be ascribed uniquely to collagen surface functionalization. These results support the promising role of sialosides in the regulation of stem cells fate and open brilliant perspective for the future use of the presented approach toward osteochondral tissue engineering applications.

Poly(L-Lactide)/Poly(ε-Caprolactone) and Collagen/β-Tricalcium Phosphate Scaffolds for the Treatment of Critical-Sized Rat Alveolar Defects: A Microtomographic, Molecular-Biological, and Histological Study

OBJECTIVE

To determine the efficacy of a newly developed scaffold (col/β-TCP) in a preclinical rat model as compared with the gold standard treatment (autograft) and control scaffolds (PLLA/PCL).

DESIGN

Fifty-six Sprague-Dawley rats were randomized into four experimental groups, and critical-sized alveolar defects (7 × 4 × 3 mm) were created in each animal. Group A was the blank defect group, group B received autograft, group C received col/β-TCP scaffolds, and group D received PLLA/PCL blend scaffolds to fill the bone defects. New bone formation was assessed radiomorphometrically, histomorphometrically, and molecular-biologically at 1 and 4 months following surgery.

RESULTS

Radiomorphometrically, the best new bone volume rate at 1 month (43.7%) and 4 months (45.4%) was observed in the autograft group, and the difference was significantly higher than in the other three groups (P < .005, P < .001, P < .001 for 1 month and P = .004, P < .001, P < .001 for 4 months). Even though the new bone volume rate in the col/β-TCP group (21.5%) was higher than that of the PLLA/PCL group (18.2%), the difference was not significant (P = .08). Molecular-genetic analysis revealed significantly higher BSP and ALP gene expression levels in the autograft and col/β-TCP groups than in the blank defect group (P = .002 and P = .004).

CONCLUSION

The engineered tissue scaffolds described herein have great potential as an alternative treatment option when cost, donor region morbidity, and duration of hospitalization are considered.

Dynamic Expression Profiles of Marker Genes in Osteogenic Differentiation of Human Bone Marrow-derived Mesenchymal Stem Cells

OBJECTIVE

To observe the expression profiles of osteoblast-related genes in human mesenchymal stem cells (MSCs) derived from bone marrow during osteogenic differentiation.

METHODS

MSCs were induced to differentiate with MSC osteogenic differentiation medium for 7, 14, 21 and 28 days respectively. Alizarin Red staining was used to detect matrix mineralization. Expression of osteoblast-related genes, including osteocalcin, osteopontin, Runt-related transcription factor 2 (Runx2), alkaline phosphatase and collagen type 1, was assessed with quantitative reverse transcription-polymerase chain reaction.

RESULTS

On day 14 after induction of differentiation, cells were stained positively with Alizarin Red. The expression levels of these genes exhibited an upward trend as induction time was prolonged. Exposure to osteogenic differentiation medium less than 21 days did not significantly induce osteocalcin expression; osteocalcin expression levels in the differentiated cells induced for 21 and 28 days were 1.63 and 2.46 times as high as the undifferentiated cells respectively (all P<0.05). Stimulation with MSC osteogenic differentiation medium over 14 days significantly enhanced bone marrow-derived MSCs to express osteopontin and Runx2 genes (all P<0.05). Osteogenic differentiation medium could significantly induce the expressions of alkaline phosphatase and collagen type1 genes (all P<0.05). Their expressions reached the peak levels on day 21, which were increased more than 4- and 3-fold respectively.

CONCLUSION

Human bone marrow-derived MSCs could exhibit the sequential expression pattern of osteoblast marker genes during osteogenic differentiation in vitro.

Cationic Nanogel-mediated Runx2 and Osterix siRNA Delivery Decreases Mineralization in MC3T3 Cells

BACKGROUND

Heterotopic ossification (HO) may occur after musculoskeletal trauma, traumatic brain injury, and total joint arthroplasty. As such, HO is a compelling clinical concern in both military and civilian medicine. A possible etiology of HO involves dysregulated signals in the bone morphogenetic protein osteogenic cascade. Contemporary treatment options for HO (ie, nonsteroidal antiinflammatory drugs and radiation therapy) have adverse effects associated with their use and are not biologically engineered to abrogate the molecular mechanisms that govern osteogenic differentiation.

QUESTIONS/PURPOSES

We hypothesized that (1) nanogel-mediated short interfering RNA (siRNA) delivery against Runt-related transcription factor 2 (Runx2) and osterix (Osx) genes will decrease messenger RNA expression; (2) inhibit activity of the osteogenic marker alkaline phosphatase (ALP); and (3) inhibit hydroxyapatite (HA) deposition in osteoblast cell cultures.

METHODS

Nanogel nanostructured polymers delivered siRNA in 48-hour treatment cycles against master osteogenic regulators, Runx2 and Osx, in murine calvarial preosteoblasts (MC3T3-E1.4) stimulated for osteogenic differentiation by recombinant human bone morphogenetic protein (rhBMP-2). The efficacy of RNA interference (RNAi) therapeutics was determined by quantitation of messenger RNA knockdown (by quantitative reverse transcription-polymerase chain reaction), downstream protein knockdown (determined ALP enzymatic activity assay), and HA deposition (determined by OsteoImage™ assay).

RESULTS

Gene expression assays demonstrated that nanogel-based RNAi treatments at 1:1 and 5:1 nanogel:short interfering RNA weight ratios reduced Runx2 expression by 48.59% ± 19.53% (p < 0.001) and 43.22% ± 18.01% (both p < 0.001). The same 1:1 and 5:1 treatments against both Runx2 and Osx reduced expression of Osx by 51.65% ± 10.85% and 47.65% ± 9.80% (both p < 0.001). Moreover, repeated 48-hour RNAi treatment cycles against Runx2 and Osx rhBMP-2 administration reduced ALP activity after 4 and 7 days. ALP reductions after 4 days in culture by nanogel 5:1 and 10:1 RNAi treatments were 32.4% ± 12.0% and 33.6% ± 13.8% (both p < 0.001). After 7 days in culture, nanogel 1:1 and 5:1 RNAi treatments produced 35.9% ± 14.0% and 47.7% ± 3.2% reductions in ALP activity. Osteoblast mineralization data after 21 days suggested that nanogel 1:1, 5:1, and 10:1 RNAi treatments decreased mineralization (ie, HA deposition) from cultures treated only with rhBMP-2 (p < 0.001). However, despite RNAi attack on Runx2 and Osx, HA deposition levels remained greater than non-rhBMP-2-treated cell cultures.

CONCLUSIONS

Although mRNA and protein knockdown were confirmed as a result of RNAi treatments against Runx2 and Osx, complete elimination of mineralization processes was not achieved. RNAi targeting mid- and late-stage osteoblast differentiation markers such as ALP, osteocalcin, osteopontin, and bone sialoprotein) may produce the desired RNAi-nanogel nanostructured polymer HO prophylaxis.

CLINICAL RELEVANCE

Successful HO prophylaxis should target and silence osteogenic markers critical for heterotopic bone formation processes. The identification of such markers, beyond RUNX2 and OSX, may enhance the effectiveness of RNAi prophylaxes for HO.

Histochemical examination of adipose derived stem cells combined with β-TCP for bone defects restoration under systemic administration of 1α,25(OH)2D3

The purpose of this study was to evaluate the effects of osteogenic differentiated adipose-derived stem cell (ADSC) loaded beta-tricalcium phosphate (β-TCP) in the restoration of bone defects under intraperitoneal administration of 1α,25-dihydroxyvitamin D3(1α,25(OH)2D3). ADSCs were isolated from the fat tissue of 8 week old Wister rats and co-cultured with β-TCP for 21 days under osteogenic induction. Then the ADSC-β-TCP complexes were implanted into bone defects in the femora of rats. 1α,25(OH)2D3 (VD) or normal saline (NS) was administrated intraperitoneally every other day after the surgery. Femora were harvested at day 7, day 14 and day 28 post-surgery. There were 4 groups for all specimens: β-TCP-NS group; β-TCP-ADSC-NS group; β-TCP-VD group and β-TCP-ADSC-VD group. Alkaline phosphatase (ALP) was up-regulated obviously in ADSC groups compared with non-ADSC groups at day 7, day 14 and day 28, although high expression of runt-related transcription factor 2 (RUNX2) was only seen at day 7. Furthermore, the number of TRAP-positive osteoclasts and the expression of cathepsin K (CK) were significantly decreased in VD groups compared with non-VD groups at day 7 and day 14. As a most significant finding, the β-TCP-ADSC-VD group showed the highest BV/TV ratio compared with the other three groups at day 28. Taken together, ADSC-loaded β-TCP under the administration of 1α,25(OH)2D3 made a promising therapy for bone defects restoration.

Emodin regulates bone remodeling by inhibiting osteoclastogenesis and stimulating osteoblast formation

Bone remodeling, a physiological process in which new bone is formed by osteoblasts and the preexisting bone matrix is resorbed by osteoclasts, is vital for the maintenance of healthy bone tissue in adult humans. Imbalances in this process can cause various pathological conditions, including osteoporosis. Emodin, a naturally occurring anthraquinone derivative found in Asian herbal medicines, has numerous beneficial pharmacologic effects, including anticancer and antidiabetic activities. However, the effect of emodin on the regulation of osteoblast and osteoclast activity has not yet been investigated. We show here that emodin is a potential target for osteoporosis therapeutics, as treatment with this agent enhances osteoblast differentiation and bone growth and suppresses osteoclast differentiation and bone resorption. In this study, emodin suppressed receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation of bone marrow macrophages (BMMs) and the bone-resorbing activity of mature osteoclasts by inhibiting RANKL-induced NF-κB, c-Fos, and NFATc1 expression. Emodin also increased ALP, Alizarin Red-mineralization activity, and the expression of osteoblastogenic gene markers, such as Runx2, osteocalcin (OCN), and ALP in mouse calvarial primary osteoblasts, as well as activated the p38-Runx2 pathway, which enhanced osteoblast differentiation. Moreover, mice treated with emodin showed marked attenuation of lipopolysaccharide (LPS)-induced bone erosion and increased bone-forming activity in a mouse calvarial bone formation model based on micro-computed tomography and histologic analysis of femurs. Our findings reveal a novel function for emodin in bone remodeling, and highlight its potential for use as a therapeutic agent in the treatment of osteoporosis that promotes bone anabolic activity and inhibits osteoclast differentiation.

Osteoactivin induces transdifferentiation of C2C12 myoblasts into osteoblasts

Osteoactivin (OA) is a novel osteogenic factor important for osteoblast differentiation and function. Previous studies showed that OA stimulates matrix mineralization and transcription of osteoblast specific genes required for differentiation. OA plays a role in wound healing and its expression was shown to increase in post fracture calluses. OA expression was reported in muscle as OA is upregulated in cases of denervation and unloading stress. The regulatory mechanisms of OA in muscle and bone have not yet been determined. In this study, we examined whether OA plays a role in transdifferentiation of C2C12 myoblast into osteoblasts. Infected C2C12 with a retroviral vector overexpressing OA under the CMV promoter were able to transdifferentiate from myoblasts into osteoblasts. Immunofluorescence analysis showed that skeletal muscle marker MF-20 was severely downregulated in cells overexpressing OA and contained significantly less myotubes compared to uninfected control. C2C12 myoblasts overexpressing OA showed an increase in expression of bone specific markers such as alkaline phosphatase and alizarin red staining, and also showed an increase in Runx2 protein expression. We also detected increased levels of phosphorylated focal adhesion kinase (FAK) in C2C12 myoblasts overexpressing OA compared to control. Taken together, our results suggest that OA is able to induce transdifferentiation of myoblasts into osteoblasts through increasing levels of phosphorylated FAK.

Genomic occupancy of Runx2 with global expression profiling identifies a novel dimension to control of osteoblastogenesis

BACKGROUND

Osteogenesis is a highly regulated developmental process and continues during the turnover and repair of mature bone. Runx2, the master regulator of osteoblastogenesis, directs a transcriptional program essential for bone formation through genetic and epigenetic mechanisms. While individual Runx2 gene targets have been identified, further insights into the broad spectrum of Runx2 functions required for osteogenesis are needed.

RESULTS

By performing genome-wide characterization of Runx2 binding at the three major stages of osteoblast differentiation--proliferation, matrix deposition and mineralization--we identify Runx2-dependent regulatory networks driving bone formation. Using chromatin immunoprecipitation followed by high-throughput sequencing over the course of these stages, we identify approximately 80,000 significantly enriched regions of Runx2 binding throughout the mouse genome. These binding events exhibit distinct patterns during osteogenesis, and are associated with proximal promoters and also non-promoter regions: upstream, introns, exons, transcription termination site regions, and intergenic regions. These peaks were partitioned into clusters that are associated with genes in complex biological processes that support bone formation. Using Affymetrix expression profiling of differentiating osteoblasts depleted of Runx2, we identify novel Runx2 targets including Ezh2, a critical epigenetic regulator; Crabp2, a retinoic acid signaling component; Adamts4 and Tnfrsf19, two remodelers of the extracellular matrix. We demonstrate by luciferase assays that these novel biological targets are regulated by Runx2 occupancy at non-promoter regions.

CONCLUSIONS

Our data establish that Runx2 interactions with chromatin across the genome reveal novel genes, pathways and transcriptional mechanisms that contribute to the regulation of osteoblastogenesis.

Histone deacetylase inhibitor sodium butyrate promotes the osteogenic differentiation of rat adipose-derived stem cells

Adult stem cells hold great promise for use in tissue repair and regeneration. Recently, adipose tissue-derived stem cells (ADSCs) were found to be an appealing alternative to bone marrow stem cells (BMSCs) for bone tissue engineering. The main benefit of ADSCs is that they can be easily and abundantly available from adipose tissue. However, our prior study discovered an important phenomenon that BMSCs have greater osteogenic potential than ADSCs in vitro and epigenetic regulation plays a critical role in runt-related transcription factor 2 (Runx2) expression and thus osteogenesis. In this study, we aimed to improve the osteogenic potential of ADSCs by histone deacetylase inhibitor sodium butyrate (NaBu). We found that NaBu promoted rat ADSC osteogenic differentiation by altering the epigenetic modifications on the Runx2 promoter.

Phosphoserine promotes osteogenic differentiation of human adipose stromal cells through bone morphogenetic protein signalling

Phosphoserine has potential effectiveness as a simple substrate in preparing bone replacement materials, which could enhance bone forming ability. However, there is a need to investigate the independent effect of phosphoserine on osteogenic differentiation of human adipose stem cells (hADSCs). hADSCs were cultured in an osteogenic medium with phosphoserine. Cell proliferation was analysed by CCK8 and osteogenic differentiation was measured by alkaline phosphatase (ALP) activity, von Kossa staining and real time-polymerase chain reaction (RT-PCR). No stimulatory effect of phosphoserine on cell proliferation was noted at Days 1, 4 and 7. Deposition of calcium increased after the addition of phosphoserine. mRNA expression of type I collagen (COL-I), alkaline phosphatase (ALP), osteocalcin (OCN), Osterix, bone morphogenetic protein-2 (BMP-2) and RUNX2 increased markedly with phosphoserine treatment. The BMP-2 antagonist, noggin, and its receptor kinase inhibitors, dorsomorphin and LDN-193189, attenuated phosphoserine-promoted ALP activity. BMP-responsive and Runx2-responsive reporters were activated by phosphoserine treatment. Thus phosphoserine can promote osteogenic differentiation of hADSCs, probably by activating BMP and Runx2 pathways, which could be a promising approach for enhancing osteogenic capacity of cell-based construction in bone tissue engineering.

Heparin-binding EGF-like growth factor and miR-1192 exert opposite effect on Runx2-induced osteogenic differentiation

Osteoblast differentiation is a pivotal event in bone formation. Runt-related transcription factor-2 (Runx2) is an essential factor required for osteoblast differentiation and bone formation. However, the underlying mechanism of Runx2-regulated osteogenic differentiation is still unclear. Here, we explored the corresponding mechanism using the C2C12/Runx2(Dox) subline, which expresses Runx2 in response to doxycycline (Dox). We found that Runx2-induced osteogenic differentiation of C2C12 cells results in a sustained decrease in the expression of heparin-binding EGF-like growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family. Forced expression of HB-EGF or treatment with HB-EGF is capable of reducing the expression of alkaline phosphatase (ALP), a defined marker of early osteoblast differentiation. HB-EGF-mediated inhibition of ALP depends upon activation of the EGFR and the downstream extracellular signal-regulated kinase, c-Jun N-terminal kinase mitogen-activated protein kinase pathways as well as phosphatidylinositol 3-kinase/Akt pathway. Runx2 specifically binds to the Hbegf promoter, suggesting that Hbegf transcription is directly inhibited by Runx2. Runx2 can upregulate miR-1192, which enhances Runx2-induced osteogenic differentiation. Moreover, miR-1192 directly targets Hbegf through translational inhibition, suggesting enhancement of Runx2-induced osteogenic differentiation by miR-1192 through the downregulation of HB-EGF. Taken together, our results suggest that Runx2 induces osteogenic differentiation of C2C12 cells by inactivating HB-EGF-EGFR signaling through the downregulation of HB-EGF via both transcriptional and post-transcriptional mechanisms.

The role of single-cell analyses in understanding cell lineage commitment

The study of cell lineage commitment is critical for improving our understanding of tissue development and regeneration, and for realizing stem cell-based therapies and engineered tissue replacements. Recently, the discovery of an unanticipated degree of variability in fundamental biological processes, including divergent responses of genetically identical cells to various stimuli, has provided mechanistic insight into cellular decision making and the collective behavior of cell populations. Therefore, the study of lineage commitment with single-cell resolution could provide greater knowledge of cellular differentiation mechanisms and the influence of noise on cellular processes. This will require the adoption of new technologies for single-cell analysis as traditional methods typically measure average values of bulk population behavior. This review discusses the recent developments in methods for analyzing the behavior of individual cells, and how these approaches are leading to a deeper understanding and better control of cellular decision making.

Histone deacetylase inhibitor trichostatin A promotes the osteogenic differentiation of rat adipose-derived stem cells by altering the epigenetic modifications on Runx2 promoter in a BMP signaling-dependent manner

Adult stem cells reside in many types of tissues and adult stem cell-based regenerative medicine holds great promise for repair of diseased tissues. Recently, adipose-derived stem cells (ADSCs) were found to be an appealing alternative to bone marrow stem cells (BMSCs) for tissue-engineered bone regeneration. Compared with BMSCs, ADSCs can be easily and abundantly available from adipose tissue. However, our previous study has discovered an important phenomenon that BMSCs have greater osteogenic potential than ADSCs in vitro. In this study, we aimed to explore its mechanism and improve the osteogenic potential of ADSCs for bone tissue regeneration. It has been reported that the epigenetic states could contribute to lineage-specific differentiation of adult stem cells. We observed that the epigenetic changes of BMSCs were much greater compared with ADSCs after a 3-day osteogenic induction. Runt-related transcription factor 2 (Runx2) is essential for osteoblast differentiation and bone formation. We found that BMSCs underwent more obvious epigenetic changes on the Runx2 promoter than ADSCs after osteogenic induction. These results suggest the epigenetic regulation involvement in Runx2 expression, and thus osteogenesis. We subsequently used a histone deacetylase inhibitor, trichostatin A (TSA), to promote the osteogenesis capacity of ADSCs. The results showed that TSA promoted rat ADSCs osteogenic differentiation by altering the epigenetic modifications on the Runx2 promoter in a bone morphogenetic protein signaling-dependent manner.