Runx2: of bone and stretch

Characterization of open chromatin sensitive to actin polymerization and identification of core-binding factor subunit beta as mechanosensitive nucleocytoplasmic shuttling protein

Mechanotransduction leads to a variety of biological responses including gene expression, changes in cell shape, migration, tissue development, and immune responses. Dysregulation of mechanotransduction is implicated in the progression of various diseases such as cardiovascular diseases and cancer. The actin cytoskeleton plays a crucial role in transmitting mechanical stimuli. Actin filaments, essential for cell motility and shape changes, respond to mechanical cues by remodeling, influencing gene expression via the linker of nucleoskeleton and cytoskeleton complex and mechanosensitive transcription factors. This study employs the dithiobis(succinimidyl propionate) (DSP)-micrococcal nuclease (MNase) proteogenomics method to explore the relationship between cellular mechanosensing, chromatin architecture, and the identification of proteins involved in mechanosensitive nucleocytoplasmic shuttling, revealing how actin polymerization affects chromatin and gene expression. We found that depolymerization of actin filaments by latrunculin B (Lat B) for 30 min is sufficient to alter open chromatin and identified core-binding factor subunit beta as mechanosensitive nucleocytoplasmic shuttling protein.

Perfluorooctanoic acid and perfluorooctane sulfonate inhibit in vitro osteogenesis: possible role of connexin 43-mediated gap-junctional intercellular communication

In the current study, we investigated the effects of two legacy per- and polyfluoroalkyl substances (PFASs) namely perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) on osteogenesis. The alterations of connexin 43 (Cx43)-mediated gap junctions (GJs) were further explored as a potential mechanism. The two cell models (C3H10T1/2 and MC3T3-E1 cells) differentiated into osteoblasts (OBs) were utilized, and treated with PFOA and PFOS at the doses of 0.25, 2.5, 25, and 75 μM. Real-time PCR and Western blot were applied to assess the mRNA and protein expression of osteogenic-specific markers and Cx43. ALP staining and ARS staining were used to evaluate the osteogenesis process. The scrape-loading dye transfer assay was performed to assess the GJ-mediated intercellular coupling. To investigate the role of gap-junctional intercellular communication (GJIC) in the PFAS-induced osteogenic inhibition, the Cx43-specific GJIC enhancer, rotigaptide (ZP123), was added into the differentiation medium of C3H10T1/2 cells. After the exposure of PFOA and PFOS, the osteogenic molecules were down-regulated and the calcium deposition was reduced in the two cell models, indicating the inhibitory effects of the legacy PFASs. The Cx43 expression and GJIC activity were significantly suppressed, and the usage of ZP123 rescued the adverse impact on osteogenesis, suggesting the remarkable role of GJIC herein.

Treatment with Lactobacillus paracasei L30 extract induces osteogenic differentiation of human bone marrow mesenchymal stem cells in vitro

Bone-related diseases such as osteoporosis pose a significant health economic burden to countries around the world and, because current treatments are insufficient, more effective therapies are desperately needed. This study explored the potential of Lactobacillus paracasei L30 extract to influence the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs). Our results showed that L30 extract significantly enhanced the expression of osteogenic markers in hBM-MSCs, including alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and collagen type I alpha 1 (COL1A1). Mechanistic studies revealed that L30 extract activated the p38 MAPK and AKT signaling pathways, leading to phosphorylation of Glycogen synthase kinase-3 beta (GSK3β) and subsequent nuclear translocation of β-catenin. Conversely, inhibition of p38 MAPK, AKT, or knockdown of β-catenin significantly attenuated the osteogenic effects of L30 extract on hBM-MSCs. Furthermore, we found that L30 extract promoted osteogenic differentiation in primary osteoblast precursors isolated from mouse calvaria and enhances bone formation in ex vivo calvarial organ cultures. Therefore, the application of Lactobacillus paracasei L30 extract in such contexts could serve as a therapeutic approach for promoting bone formation. Collectively, our findings suggest a novel approach for the clinical management of bone-related disorders, with possible applications for treating diseases such as osteoporosis.

In situ osteogenic activation of mesenchymal stem cells by the blood clot biomimetic mechanical microenvironment

Blood clots (BCs) play a crucial biomechanical role in promoting osteogenesis and regulating mesenchymal stem cell (MSC) function and fate. This study shows that BC formation enhances MSC osteogenesis by activating Itgb1/Fak-mediated focal adhesion and subsequent Runx2-mediated bone regeneration. Notably, BC viscoelasticity regulates this effect by modulating Runx2 nuclear translocation. To mimic this property, a viscoelastic peptide bionic hydrogel named BCgel was developed, featuring a nanofiber network, Itgb1 binding affinity, BC-like viscoelasticity, and biosafety. The anticipated efficacy of BCgel is demonstrated by its ability to induce nuclear translocation of Runx2 and promote bone regeneration in both in vitro experiments and in vivo bone defect models with blood clot defect, conducted on rats as well as beagles. This study offers insights into the mechano-transduction mechanisms of MSCs during osteogenesis and presents potential guidelines for the design of viscoelastic hydrogels in bone regenerative medicine.

The Regulatory Role of miRNAs in Zebrafish Fin Regeneration

Since Teleostei fins have a strong regenerative capacity, further research was conducted on the regulation of gene expression during fin regeneration. This research focuses on miRNA, which is a key post-transcriptional regulatory molecule. In this study, a miRNA library for the fin regeneration of zebrafish was constructed to reveal the differential expression of miRNA during fin regeneration and to explore the regulatory pathway for fin regeneration. Following the injection of miRNA agomir into zebrafish, the proliferation of blastema cells and the overall fin regeneration area were significantly reduced. It was observed that the miRNAs impaired blastocyte formation by affecting fin regeneration through the inhibition of the expressions of genes and proteins associated with blastocyte formation (including yap1 and Smad1/5/9), which is an effect associated with the Hippo pathway. Furthermore, it has been demonstrated that miRNAs can impair the patterns and mineralization of newly formed fin rays. The miRNAs influenced fin regeneration by inhibiting the expression of a range of bone-related genes and proteins in osteoblast lineages, including sp7, runx2a, and runx2b. This study provides a valuable reference for the further exploration of morphological bone reconstruction in aquatic vertebrates.

Runx2 and Polycystins in Bone Mechanotransduction: Challenges for Therapeutic Opportunities

Bone mechanotransduction is a critical process during skeletal development in embryogenesis and organogenesis. At the same time, the type and level of mechanical loading regulates bone remodeling throughout the adult life. The aberrant mechanosensing of bone cells has been implicated in the development and progression of bone loss disorders, but also in the bone-specific aspect of other clinical entities, such as the tumorigenesis of solid organs. Novel treatment options have come into sight that exploit the mechanosensitivity of osteoblasts, osteocytes, and chondrocytes to achieve efficient bone regeneration. In this regard, runt-related transcription factor 2 (Runx2) has emerged as a chief skeletal-specific molecule of differentiation, which is prominent to induction by mechanical stimuli. Polycystins represent a family of mechanosensitive proteins that interact with Runx2 in mechano-induced signaling cascades and foster the regulation of alternative effectors of mechanotransuction. In the present narrative review, we employed a PubMed search to extract the literature concerning Runx2, polycystins, and their association from 2000 to March 2024. The keywords stated below were used for the article search. We discuss recent advances regarding the implication of Runx2 and polycystins in bone remodeling and regeneration and elaborate on the targeting strategies that may potentially be applied for the treatment of patients with bone loss diseases.

Runt-related transcription factors in human carcinogenesis: a friend or foe?

PURPOSE

Cancer is one of the deadliest pathologies with more than 19 million new cases and 10 million cancer-related deaths across the globe. Despite development of advanced therapeutic interventions, cancer remains as a fatal pathology due to lack of early prognostic biomarkers, therapy resistance and requires identification of novel drug targets.

METHODS

Runt-related transcription factors (Runx) family controls several cellular and physiological functions including osteogenesis. Recent literatures from PubMed was mined and the review was written in comprehensive manner RESULTS: Recent literature suggests that aberrant expression of Runx contributes to tumorigenesis of many organs. Conversely, cell- and tissue-specific tumor suppressor roles of Runx are also reported. In this review, we have provided the structural/functional properties of Runx isoforms and its regulation in context of human cancer. Moreover, in an urgent need to discover novel therapeutic interventions against cancer, we comprehensively discussed the reported oncogenic and tumor suppressive roles of Runx isoforms in several tumor types and discussed the discrepancies that may have risen on Runx as a driver of malignant transformation.

CONCLUSION

Runx may be a novel therapeutic target against a battery of deadly human cancers.

In situ activation of flexible magnetoelectric membrane enhances bone defect repair

For bone defect repair under co-morbidity conditions, the use of biomaterials that can be non-invasively regulated is highly desirable to avoid further complications and to promote osteogenesis. However, it remains a formidable challenge in clinical applications to achieve efficient osteogenesis with stimuli-responsive materials. Here, we develop polarized CoFe₂O₄@BaTiO₃/poly(vinylidene fluoridetrifluoroethylene) [P(VDF-TrFE)] core-shell particle-incorporated composite membranes with high magnetoelectric conversion efficiency for activating bone regeneration. An external magnetic field force conduct on the CoFe₂O₄ core can increase charge density on the BaTiO₃ shell and strengthens the β-phase transition in the P(VDF-TrFE) matrix. This energy conversion increases the membrane surface potential, which hence activates osteogenesis. Skull defect experiments on male rats showed that repeated magnetic field applications on the membranes enhanced bone defect repair, even when osteogenesis repression is elicited by dexamethasone or lipopolysaccharide-induced inflammation. This study provides a strategy of utilizing stimuli-responsive magnetoelectric membranes to efficiently activate osteogenesis in situ.

The Role of the Piezo1 Mechanosensitive Channel in the Musculoskeletal System

Since the recent discovery of the mechanosensitive Piezo1 channels, many studies have addressed the role of the channel in various physiological or even pathological processes of different organs. Although the number of studies on their effects on the musculoskeletal system is constantly increasing, we are still far from a precise understanding. In this review, the knowledge available so far regarding the musculoskeletal system is summarized, reviewing the results achieved in the field of skeletal muscles, bones, joints and cartilage, tendons and ligaments, as well as intervertebral discs.

Calcium Phosphate Bone Cements Incorporated with Black Phosphorus Nanosheets Enhanced Osteogenesis

For decades, calcium phosphate bone cements (CPCs) showed impressive advantages for their good biocompatibility, injectability, and osteoconductivity in the bone repair field. However, it is still difficult to prepare CPCs with outstanding antibacterial and self-curing properties, sufficient phosphorus release, and osteoinductivity for clinical application. Herein, we used partially crystallized calcium phosphate and dicalcium phosphate anhydrate particles incorporated with black phosphorous nanosheets to prepare calcium phosphate bone cements (CPCs). The curing time, compressive strength, photothermal properties, and degradation performance of BP/CPC were investigated. In addition, the cytocompatibility and osteoinductivity of BP/CPC were evaluated by cell adhesion, cytotoxicity, alkaline phosphatase detection, alizarin red staining, and western blot assay. The results indicated that BP/CPC showed adjustable curing time, good cytocompatibility, outstanding photothermal properties, and osteoinductivity, suggesting their potential application for bone regeneration.

Odontogenesis-Associated Phosphoprotein (ODAPH) Overexpression in Ameloblasts Disrupts Enamel Formation via Inducing Abnormal Mineralization of Enamel in Secretory Stage

Odontogenesis-associated phosphoprotein (ODAPH) is a recently discovered enamel matrix protein. Our previous study demonstrated that knockouting out Odaph in mice resulted in enamel hypomineralization. To further investigate the effect of Odaph on enamel mineralization, we constructed an Odaph overexpression mouse model, controlled by an amelogenin promoter. Our histological analysis of OdaphTg mice revealed that the enamel layer was thinner than in WT mice. An uneven, thinner enamel layer was confirmed using micro-computed tomography (uCT). It was subsequently found that the Tomes' processes lost their normal morphology, resulting in the loss of the enamel prism structure. These results indicate that Odaph overexpression in ameloblasts led to enamel dysplasia. In conjunction with this, Odaph overexpression hindered Amelx secretion, and may result in endoplasmic reticulum stress. Interestingly, uCT revealed that enamel had higher mineral density at the secretory stage; due to this, we did the histological staining for the mineralization-related proteins Alkaline phosphatase (ALPL) and Runt-related transcription factor 2 (RUNX2). It was observed that these proteins were up-regulated in OdaphTg mice versus WT mice, indicating that Odaph overexpression led to abnormal enamel mineralization. To confirm this, we transfected ameloblast-like cell line (ALC) with Odaph overexpression lentivirus in vitro and identified that both Alpl and Runx2 were strikingly upregulated in OE-mus-Odaph versus OE-NC cells. We concluded that the ectopic overexpression of Odaph in ameloblasts led to abnormal enamel mineralization. In summary, Odaph profoundly influences amelogenesis by participating in enamel mineralization.

Craniomaxillofacial derived bone marrow mesenchymal stem/stromal cells (BMSCs) for craniomaxillofacial bone tissue engineering: A literature review

Craniomaxillofacial bone defects seriously affect the appearance, function, and psychological status of patients. Traditional autologous bone grafting is very challenging due to the limited sources of bone tissue, excessive surgical trauma, and high incidence of related complications. Craniomaxillofacial bone tissue engineering (BTE) strategies based on bone marrow mesenchymal stem cells (BMSCs) are emerging as an alternative. Craniomaxillofacial BMSCs (C-BMSCs) are homologous to craniomaxillofacial bones, which develop from the mesoderm and neural crest. This article aims to compare the differences in osteogenesis, angiogenesis, and immune regulation of C-BMSCs and other sources of BMSCs, and propose ideas and strategies such as 3D printing and mechanotherapy to completely harness the characteristics of C-BMSCs. In conclusion, C-BSMCs are a promising source of stem cells for the repair and reconstruction of craniomaxillofacial bone defects, and more attention should be paid to accelerating their basic research and clinical practices.

Effect of Puerarin on Osteogenic Differentiation in vitro and on New Bone Formation in vivo

Purpose

Puerarin (C₂₁H₂₀O₁₀) is a phytoestrogen that possesses various pharmacological effect, and several researches have revealed the relationship between puerarin and bone metabolism. This study was aimed to evaluate the potential influence of puerarin on the proliferation and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs) as well as on new bone formation following rapid maxillary expansion (RME) model in rats.

Methods

Rat BMSCs were adopted, and the cell proliferation was detected by cell-counting kit-8 (CCK-8) assay in vitro experiments. Alkaline phosphatase (ALP) activity and alizarin red staining were analyzed quantitatively to show extracellular matrix mineralization. The mRNA and protein expression levels were used to detect osteogenic differentiation of BMSCs. In vivo bone regeneration was analyzed in a rat RME model. Eighteen 6-week-old male Wistar rats were divided into 3 groups: group 1 without any treatment, group 2 received RME and saline solution (15mg/kg), group 3 received RME and puerarin solution (15mg/kg). After 2 weeks, micro-computed tomography (Micro-CT), hematoxylin and eosin (HE) staining, and Masson staining were used to detect the new bone formation and morphological changes. Besides, ALP and bone morphogenetic protein 2 (BMP2) expression levels in mid-palatal suture were evaluated by immunohistochemical staining.

Results

The results showed that puerarin upregulates cell proliferation dose-dependently. ALP activity and mineralized matrix generation were clearly enhanced at certain specific concentrations (10⁻⁵ and 10⁻⁶ mol/L); the expression levels of the osteoblast-related genes and proteins were increased. The measurement of micro-CT imaging revealed that puerarin significantly promoted new bone formation. Concomitantly, the histological examinations showed that puerarin solution enhanced osteogenesis in mid-palatal suture.

Conclusion

Those works indicated that puerarin regulates osteogenesis in vitro and exerts a beneficial impact on bone regeneration in vivo, revealing that puerarin treatment may become one of the potential keys for improving the stability and preventing relapse of RME.

Roles of mechanosensitive channel Piezo1/2 proteins in skeleton and other tissues

Mechanotransduction is a fundamental ability that allows living organisms to receive and respond to physical signals from both the external and internal environments. The mechanotransduction process requires a range of special proteins termed mechanotransducers to convert mechanical forces into biochemical signals in cells. The Piezo proteins are mechanically activated nonselective cation channels and the largest plasma membrane ion channels reported thus far. The regulation of two family members, Piezo1 and Piezo2, has been reported to have essential functions in mechanosensation and transduction in different organs and tissues. Recently, the predominant contributions of the Piezo family were reported to occur in the skeletal system, especially in bone development and mechano-stimulated bone homeostasis. Here we review current studies focused on the tissue-specific functions of Piezo1 and Piezo2 in various backgrounds with special highlights on their importance in regulating skeletal cell mechanotransduction. In this review, we emphasize the diverse functions of Piezo1 and Piezo2 and related signaling pathways in osteoblast lineage cells and chondrocytes. We also summarize our current understanding of Piezo channel structures and the key findings about PIEZO gene mutations in human diseases.

Modifications in Gene Expression in the Process of Osteoblastic Differentiation of Multipotent Bone Marrow-Derived Human Mesenchymal Stem Cells Induced by a Novel Osteoinductive Porous Medical-Grade 3D-Printed Poly(ε-caprolactone)/β-tricalcium Phosphate Composite

In this work, we evaluated the influence of a novel hybrid 3D-printed porous composite scaffold based on poly(ε-caprolactone) (PCL) and β-tricalcium phosphate (β-TCP) microparticles in the process of adhesion, proliferation, and osteoblastic differentiation of multipotent adult human bone marrow mesenchymal stem cells (ah-BM-MSCs) cultured under basal and osteogenic conditions. The in vitro biological response of ah-BM-MSCs seeded on the scaffolds was evaluated in terms of cytotoxicity, adhesion, and proliferation (AlamarBlue Assay®) after 1, 3, 7, and 14 days of culture. The osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity, mineralization (Alizarin Red Solution, ARS), expression of surface markers (CD73, CD90, and CD105), and reverse transcription-quantitative polymerase chain reaction (qRT-PCR) after 7 and 14 days of culture. The scaffolds tested were found to be bioactive and biocompatible, as demonstrated by their effects on cytotoxicity (viability) and extracellular matrix production. The mineralization and ALP assays revealed that osteogenic differentiation increased in the presence of PCL/β-TCP scaffolds. The latter was also confirmed by the gene expression levels of the proteins involved in the ossification process. Our results suggest that similar bio-inspired hybrid composite materials would be excellent candidates for osteoinductive and osteogenic medical-grade scaffolds to support cell proliferation and differentiation for tissue engineering, which warrants future in vivo research.

Effect of Tension on Human Periodontal Ligament Cells: Systematic Review and Network Analysis

Orthodontic tooth movement is based on the remodeling of tooth-surrounding tissues in response to mechanical stimuli. During this process, human periodontal ligament cells (hPDLCs) play a central role in mechanosensing and mechanotransduction. Various in vitro models have been introduced to investigate the effect of tension on hPDLCs. They provide a valuable body of knowledge on how tension influences relevant genes, proteins, and metabolites. However, no systematic review summarizing these findings has been conducted so far. Aim of this systematic review was to identify all related in vitro studies reporting tension application on hPDLCs and summarize their findings regarding force parameters, including magnitude, frequency and duration. Expression data of genes, proteins, and metabolites was extracted and summarized. Studies' risk of bias was assessed using tailored risk of bias tools. Signaling pathways were identified by protein-protein interaction (PPI) networks using STRING and GeneAnalytics. According to our results, Flexcell Strain Unit^® and other silicone-plate or elastic membrane-based apparatuses were mainly adopted. Frequencies of 0.1 and 0.5 Hz were predominantly applied for dynamic equibiaxial and uniaxial tension, respectively. Magnitudes of 10 and 12% were mostly employed for dynamic tension and 2.5% for static tension. The 10 most commonly investigated genes, proteins and metabolites identified, were mainly involved in osteogenesis, osteoclastogenesis or inflammation. Gene-set enrichment analysis and PPI networks gave deeper insight into the involved signaling pathways. This review represents a brief summary of the massive body of knowledge in this field, and will also provide suggestions for future researches on this topic.

Multiple versus solitary giant cell lesions of the jaw: Similar or distinct entities?

The majority of giant cell lesions of the jaw present as a solitary focus of disease in bones of the maxillofacial skeleton. Less frequently they occur as multifocal lesions. This raises the clinical dilemma if these should be considered distinct entities and therefore each need a specific therapeutic approach. Solitary giant cell lesions of the jaw present with a great diversity of symptoms. Recent molecular analysis revealed that these are associated with somatic gain-of-function mutations in KRAS, FGFR1 or TRPV4 in a large component of the mononuclear stromal cells which all act on the RAS/MAPK pathway. For multifocal lesions, a small group of neoplastic multifocal giant cell lesions of the jaw remain after ruling out hyperparathyroidism. Strikingly, most of these patients are diagnosed with jaw lesions before the age of 20 years, thus before the completion of dental and jaw development. These multifocal lesions are often accompanied by a diagnosis or strong clinical suspicion of a syndrome. Many of the frequently reported syndromes belong to the so-called RASopathies, with germline or mosaic mutations leading to downstream upregulation of the RAS/MAPK pathway. The other frequently reported syndrome is cherubism, with gain-of-function mutations in the SH3BP2 gene leading through assumed and unknown signaling to an autoinflammatory bone disorder with hyperactive osteoclasts and defective osteoblastogenesis. Based on this extensive literature review, a RAS/MAPK pathway activation is hypothesized in all giant cell lesions of the jaw. The different interaction between and contribution of deregulated signaling in individual cell lineages and crosstalk with other pathways among the different germline- and non-germline-based alterations causing giant cell lesions of the jaw can be explanatory for the characteristic clinical features. As such, this might also aid in the understanding of the age-dependent symptomatology of syndrome associated giant cell lesions of the jaw; hopefully guiding ideal timing when installing treatment strategies in the future.

Polycystin-1 modulates RUNX2 activation and osteocalcin gene expression via ERK signalling in a human craniosynostosis cell model

Craniosynostosis refers to the premature fusion of one or more cranial sutures leading to skull shape deformities and brain growth restriction. Among the many factors that contribute to abnormal suture fusion, mechanical forces seem to play a major role. Nevertheless, the underlying mechanobiology-related mechanisms of craniosynostosis still remain unknown. Understanding how aberrant mechanosensation and mechanotransduction drive premature suture fusion will offer important insights into the pathophysiology of craniosynostosis and result in the development of new therapies, which can be used to intervene at an early stage and prevent premature suture fusion. Herein, we provide evidence for the first time on the role of polycystin-1 (PC1), a key protein in cellular mechanosensitivity, in craniosynostosis, using primary cranial suture cells isolated from patients with trigonocephaly and dolichocephaly, two common types of craniosynostosis. Initially, we showed that PC1 is expressed at the mRNA and protein level in both trigonocephaly and dolichocephaly cranial suture cells. Followingly, by utilizing an antibody against the mechanosensing extracellular N-terminal domain of PC1, we demonstrated that PC1 regulates runt-related transcription factor 2 (RUNX2) activation and osteocalcin gene expression via extracellular signal-regulated kinase (ERK) signalling in our human craniosynostosis cell model. Altogether, our study reveals a novel mechanotransduction signalling axis, PC1-ERK-RUNX2, which affects osteoblastic differentiation in cranial suture cells from trigonocephaly and dolichocephaly patients.

miR300 intervenes Smad3/β-catenin/RunX2 crosstalk for therapy with an alternate function as indicative biomarker in osteoporosis

The study reports a theranostic nature of rno-miR-300 (miR300) in the osteoblast functioning, by influencing the signaling pathway(s), associated with osteoblast differentiation. Excessive expression of miR300 suppresses osteoblast functions. Smad3 served as a validated target for miR300, on homology-based computational analysis and experimental testimony, which activates β-catenin, and subsequently potentiates Runx2. The impact of miR300 on the Smad3/β-catenin/Runx2 signaling interactions in the induction of osteoblast differentiation was scrutinized by immunoblotting and in vivo miRNA antagonism. Overexpression of miR300 in the rat calvarial osteoblasts decreases the protein levels of Smad3, β-catenin and Runx2. Besides, in vivo silencing of miR300 in the neonatal pups and adult rats by AntimiR300 abolishes the suppressing action of miR300 on the osteoblast differentiation and expressions of Smad3/β-catenin/Runx2 axis. MicroCT studies showed improved trabecular microarchitecture in the AntimiR300 transfected ovariectomised rat model compared to sham and negative control. Furthermore, expression levels of miR300 were evaluated in serum samples from an independent set of 30 osteoporotic patients followed by a Receiver Operating Characteristic Curve (ROC) based analysis for the diagnostic efficiency of miR300. Interestingly, the results exhibited high levels of miR300 (p < 0.0001) in the serum samples from osteoporotic patients relative to non-osteoporotic subjects (AUC = 0.9689). Thus, miR300 negatively regulates the differentiation of osteoblasts by targeting crosstalk among Smad3, β-catenin and Runx2, unveiling an enormous ability to serve as a therapeutic target for bone-related disorder management strategies. Besides, miR300 may potentially function for the diagnosis of osteoporosis as a non-invasive biomarker.

The Polymorphism at PLCB4 Promoter (rs6086746) Changes the Binding Affinity of RUNX2 and Affects Osteoporosis Susceptibility: An Analysis of Bioinformatics-Based Case-Control Study and Functional Validation

PURPOSE

Genome-wide association studies have identified numerous genetic variants that are associated with osteoporosis risk; however, most of them are present in the non-coding regions of the genome and the functional mechanisms are unknown. In this study, we aimed to investigate the potential variation in runt domain transcription factor 2 (RUNX2), which is an osteoblast-specific transcription factor that normally stimulates bone formation and osteoblast differentiation, regarding variants within RUNX2 binding sites and risk of osteoporosis in postmenopausal osteoporosis (PMOP).

METHODS

We performed bioinformatics-based prediction by combining whole genome sequencing and chromatin immunoprecipitation sequencing to screen functional SNPs in the RUNX2 binding site using data from the database of Taiwan Biobank; Case-control studies with 651 postmenopausal women comprising 107 osteoporosis patients, 290 osteopenia patients, and 254 controls at Tri-Service General Hospital between 2015 and 2019 were included. The subjects were examined for bone mass density and classified into normal and those with osteopenia or osteoporosis by T-scoring with dual-energy X-ray absorptiometry. Furthermore, mRNA expression and luciferase reporter assay were used to provide additional evidence regarding the associations identified in the association analyses. Chi-square tests and logistic regression were mainly used for statistical assessment.

RESULTS

Through candidate gene approaches, 3 SNPs in the RUNX2 binding site were selected. A novel SNP rs6086746 in the PLCB4 promoter was identified to be associated with osteoporosis in Chinese populations. Patients with AA allele had higher risk of osteoporosis than those with GG+AG (adjusted OR = 6.89; 95% confidence intervals: 2.23-21.31, p = 0.001). Moreover, the AA genotype exhibited lower bone mass density (p < 0.05). Regarding mRNA expression, there were large differences in the correlation between PLCB4 and different RUNX2 alleles (Cohen's q = 0.91). Functionally, the rs6086746 A allele reduces the RUNX2 binding affinity, thus enhancing the suppression of PLCB4 expression (p < 0.05).

CONCLUSIONS

Our results provide further evidence to support the important role of the SNP rs6086746 in the etiology of osteopenia/osteoporosis, thereby enhancing the current understanding of the susceptibility to osteoporosis. We further studied the mechanism underlying osteoporosis regulation by PLCB4.

Identification of a novel RUNX2 gene mutation and early diagnosis of CCD in a cleidocranial dysplasia suspected Iranian family

This research resulted in the identification and submission of a novel RUNX2 gene mutation in the affected members of the studied pedigree. Mutation screening is an effective method for the early diagnosis of CCD in the affected individuals.

lncRNA TUG1 promotes proliferation and differentiation of osteoblasts by regulating the miR-545-3p/CNR2 axis

Osteoblast differentiation is an effective way to promote bone formation. Long non-coding RNA taurine upregulated 1 (TUG1) has been identified as a crucial modulator of multiple biological processes. This study was designed to investigate the function of TUG1 in the proliferation and differentiation of osteoblast precursor cells hFOB1.19. In this study, we found that TUG1 promoted hFOB1.19 cell proliferation, while TUG1 knockdown hindered cell proliferation. TUG1 and cannabinoid receptor 2 (CNR2) were upregulated, while miR-545-3p was down-regulated in hFOB1.19 cells undergoing osteoblastic differentiation. TUG1 induced osteoblast differentiation by increasing alkaline phosphatase (ALP) activity and the expression of osteoblastic differentiation markers. TUG1 was a sponge of miR-545-3p and regulated osteoblastic differentiation by modulating miR-545-3p. Moreover, miR-545-3p directly targeted CNR2 and restored the effect of CNR2 on osteoblastic differentiation. In conclusion, TUG1 accelerated the proliferation and differentiation of osteoblasts by sponging miR-545-3p and increasing CNR2 expression, which might provide a new biomarker for bone diseases.

MiR-155 inhibition alleviates suppression of osteoblastic differentiation by high glucose and free fatty acids in human bone marrow stromal cells by upregulating SIRT1

Diabetic osteoporosis is a severe and chronic complication of diabetes in the bone and joint system, and its pathogenesis is needed to be explored. In the present study, we examined the effect and underlying mechanism of miR-155 on osteogenic differentiation in human bone marrow-derived mesenchymal stem cells (hBMSCs) under high glucose and free fatty acids (HG-FFA) conditions. It was shown that miR-155 levels in hBMSCs increased corresponding to the time of exposure to HG-FFA treatment. MiR-155 expression was altered by transfecting miR-155 mimic or miR-155 inhibitor. HG-FFA exposure resulted in an obviously decrease in cell viability and alkaline phosphatase (ALP) activity, and downregulated the expressionof runt-related transcription factor 2 (Runx2) and osteocalcin (OCN) in hBMSCs. Transfection of miR-155 mimic further exacerbated HG-FFA-induced inhibitory effect on osteogenic differentiation, and miR-155 inhibitor neutralized this inhibitory effect. Luciferase assays confirmed that SIRT1 was a direct target of miR-155 and can be negatively modulated by miR-155. Furthermore, SIRT1 siRNA partially counteracted miR-155 inhibitor-induced upregulation of SIRT1in HG-FFA-treated hBMSCs. SIRT1 siRNA also reversed the promotional effect of the miR-155 inhibitor on ALP activity and expression of the Runx2 and OCN proteins under HG-FFA conditions. In conclusion, the results suggest that miR-155 suppression promoted osteogenic differentiation of hBMSCs under HG-FFA conditions by targeting SIRT1. Inhibition of MiR-155 may provide a new therapeutic method for the prevention and treatment of diabetic osteoporosis.

Post-Translational Regulations of Transcriptional Activity of RUNX2

Runt-related transcription factor 2 (RUNX2) is a key transcription factor for bone formation and osteoblast differentiation. Various signaling pathways and mechanisms that regulate the expression and transcriptional activity of RUNX2 have been thoroughly investigated since the involvement of RUNX2 was first reported in bone formation. As the regulation of Runx2 expression by extracellular signals has recently been reviewed, this review focuses on the regulation of post-translational RUNX2 activity. Transcriptional activity of RUNX2 is regulated at the post-translational level by various enzymes including kinases, acetyl transferases, deacetylases, ubiquitin E3 ligases, and prolyl isomerases. We describe a sequential and linear causality between post-translational modifications of RUNX2 by these enzymes. RUNX2 is one of the most important osteogenic transcription factors; however, it is not a suitable drug target. Here, we suggest enzymes that directly regulate the stability and/or transcriptional activity of RUNX2 at a post-translational level as effective drug targets for treating bone diseases.

Spatiotemporal characterization of microdamage accumulation and its targeted remodeling mechanisms in diabetic fatigued bone

The skeleton of type 1 diabetes mellitus (T1DM) has deteriorated mechanical integrity and increased fragility, whereas the mechanisms are not fully understood. Load-induced microdamage naturally occurs in bone matrix and can be removed by initiating endogenous targeted bone remodeling. However, the microdamage accumulation in diabetic skeleton and the corresponding bone remodeling mechanisms remain poorly understood. Herein, streptozotocin-induced T1DM rats and age-matched non-diabetic rats were subjected to daily uniaxial ulnar loading for 1, 4, 7, and 10 days, respectively. The SPECT/CT and basic fuchsin staining revealed significant higher-density spatial accumulation of linear and diffuse microdamage in diabetic ulnae than non-diabetic ulnae. Linear microcracks increased within 10-day loading in diabetic bone, whereas peaked at Day 7 in non-diabetic bone. Moreover, diabetic fatigued ulnae had more severe disruptions of osteocyte canaliculi around linear microcracks. Immunostaining results revealed that diabetes impaired targeted remodeling in fatigued bone at every key stage, including increased apoptosis of bystander osteocytes, decreased RANKL secretion, reduced osteoclast recruitment and bone resorption, and impaired osteoblast-mediated bone formation. This study characterizes microdamage accumulation and abnormal remodeling mechanisms in the diabetic skeleton, which advances our etiologic understanding of diabetic bone deterioration and increased fragility from the aspect of microdamage accumulation and bone remodeling.

Loss of Dkk-1 in Osteocytes Mitigates Alveolar Bone Loss in Mice With Periodontitis

Background: Periodontitis is a highly prevalent infection-triggered inflammatory disease that results in bone loss. Inflammation causes bone resorption by osteoclasts, and also by suppression of bone formation via increase of Dickkopf-1 (Dkk-1), an inhibitor of Wnt signaling. Here, we tested the hypothesis that osteocytic Dkk-1 is a key factor in the pathogenesis of periodontitis-induced alveolar bone loss (ABL).

Methods: Twelve-week-old female mice with a constitutive deletion of Dkk-1 specifically in osteocytes (Dkk-1^fl/fl;Dmp1:Cre) were subjected to experimental periodontitis (EP). Cre-negative littermates served as controls. EP was induced by placing a ligature around the upper 2nd left molar, the contralateral side was used as control. Mice were killed after 11 days and maxillae removed for micro-CT and histological analyses. The mRNA expression of Dkk-1, Runx2, Osteocalcin, OPG, RANKL, RANKL/OPG ratio, LEF-1, and TCF-7 were assessed in maxillae, while mRNA expressions of TNF and IL-1 were evaluated on gingiva using real-time PCR. Blood samples were collected for Dkk-1, CTX, and P1NP measurement by ELISA.

Results: The deletion of Dkk-1 in osteocytes prevented ABL in mice with EP, compared to Cre-negative control mice with EP. Micro-CT analysis showed a significant reduction of bone loss (−28.5%) in EP Dkk-1^fl/fl;Dmp1:Cre-positive mice compared to their littermate controls. These mice showed a greater alveolar bone volume, bone mineral density, trabecular number, and trabecular thickness after EP when compared to the Cre-negative controls. The local expression in maxillae as well as the serum levels of Dkk-1 were reduced in Dkk-1^fl/fl;Dmp1:Cre-positive mice with EP. The transgenic mice submitted to EP showed increase of P1NP and reduction of CTX-I serum levels, and increase of TCF-7 expression. Histological analysis displayed less inflammatory infiltrates, a reduction of TNF and IL-1 expressions in the gingiva and fewer osteoclasts in Cre-positive animals with EP. Moreover, in mice with EP, the osteocytic deletion of Dkk-1 enhanced bone formation due to increased expressions of Runx2 and Osteocalcin and decreased expression of RANKL in maxillae.

Conclusion: In summary, Dkk-1 derived from osteocytes plays a crucial role in ABL in periodontitis.

Chiari malformation type I: what information from the genetics?

PURPOSE

Chiari malformation type I (CMI), a rare disorder of the craniocerebral junction with an estimated incidence of 1 in 1280, is characterized by the downward herniation of the cerebellar tonsils of at least 5 mm through the foramen magnum, resulting in significant neurologic morbidity. Classical CMI is thought to be caused by an underdeveloped occipital bone, resulting in a posterior cranial fossa which is too small to accommodate the normal-sized cerebellum. In this review, we dissect the lines of evidence supporting a genetic contribution for this disorder.

METHODS

We present the results of two types of approaches: animal models and human studies encompassing different study designs such as whole genome linkage analysis, case-control association studies, and expression studies. The update of the literature also includes the most recent findings emerged by whole exome sequencing strategy.

RESULTS

Despite evidence for a genetic component, no major genes have been identified and the genetics of CMI is still very much unknown. One major challenge is the variability of clinical presentation within CMI patient population that reflects an underlying genetic heterogeneity.

CONCLUSIONS

The identification of the genes that contribute to the etiology of CMI will provide an important step to the understanding of the underlying pathology. The finding of a predisposing gene may lead to the development of simple and accurate diagnostic tests for better prognosis, counseling, and clinical management of patients and their relatives.

Orthosilicic Acid Accelerates Bone Formation in Human Osteoblast-Like Cells Through the PI3K-Akt-mTOR Pathway

Silicon is one of the essential trace elements in the human body; the deficiency of which may lead to bone diseases. Numerous animal experiments have shown that an appropriate increase in the intake of silicon is beneficial to enhancing bone density and toughness to prevent osteoporosis. However, the molecular mechanisms of the silicon-mediated osteogenesis process have not been sufficiently clarified. In this study, we determined the possible osteogenesis-related mechanisms of orthosilicic acid at a molecular level. We detected the relevant pathway and osteogenic indicators by immunofluorescence (IF), Western blot, alkaline phosphatase (ALP) staining (using 5-bromo-4-chloro-3-indolyl phosphate/nitro blue tetrazolium [BCIP/NBT]), ALP enzyme labeling method, osteocalcin (OCN), and N-terminal propeptide of type 1 procollagen (P1NP) enzyme-linked immunosorbent assay (ELISA). We found that orthosilicic acid is capable of enhancing the expression of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), phospho-protein kinase B (P-Akt), phospho-mammalian target of rapamycin (P-mTOR), and related osteogenic markers (runt-related transcription factor 2 [RUNX2], type I collagen [COL1], ALP, OCN, and P1NP). However, with the addition of PI3K-Akt-mTOR pathway-specific inhibitor LY294002, the expression of PI3K, P-Akt, P-mTOR, RUNX2, COL1, ALP, OCN, and P1NP decreased. The results indicated that the PI3K-Akt-mTOR pathway played a positive regulatory role in the process of orthosilicic acid-mediated osteogenesis in vitro.

Regulation of Runx2 by MicroRNAs in osteoblast differentiation

Bone is one of the most dynamic organs in the body that continuously undergoes remodeling through bone formation and resorption. A cascade of molecules and pathways results in the osteoblast differentiation that is attributed to osteogenesis, or bone formation. The process of osteogenesis is achieved through participation of the Wnt pathway, FGFs, BMPs/TGF-β, and transcription factors such as Runx2 and Osx. The activity and function of the master transcription factor, Runx2, is of utmost significance as it can induce the function of osteoblast differentiation markers. A number of microRNAs [miRNAs] have been recently identified in the regulation of Runx2 expression/activity, thus affecting the process of osteogenesis. miRNAs that target Runx2 corepressors favor osteogenesis, while miRNAs that target Runx2 coactivators inhibit osteogenesis. In this review, we focus on the regulation of Runx2 by miRNAs in osteoblast differentiation and their potential for treating bone and bone-related diseases.

Biological response of chemically treated surface of the ultrafine-grained Ti-6Al-7Nb alloy for biomedical applications

Background

Nanophase surface properties of titanium alloys must be obtained for a suitable biological performance, particularly to facilitate cell adhesion and bone tissue formation. Obtaining a bulk nanostructured material using severe plastic deformation is an ideal processing route to improve the mechanical performance of titanium alloys. By decreasing the grain size of a metallic material, a superior strength improvement can be obtained, while surface modification of a nanostructured surface can produce an attractive topography able to induce biological responses in osteoblastic cells.

Methods

Aiming to achieve such an excellent synergetic performance, a processing route, which included equal channel angular pressing (ECAP), hot and cold extrusion, and heat treatments, was used to produce a nanometric and ultrafine-grained (UFG) microstructure in the Ti-6Al-7Nb alloy (around of 200 nm). Additionally, UFG samples were surface-modified with acid etching (UFG-A) to produce a uniform micron and submicron porosity on the surface. Subsequently, alkaline treatment (UFG-AA) produced a sponge-like nanotopographic substrate able to modulate cellular interactions.

Results

After several kinds of biological tests for both treatment conditions (UFG-A and UFG-AA), the main results have shown that there was no cytotoxicity, expressed alkaline phosphatase activity and total protein amounts without statistical differences compared to control. However, the UFG-AA samples presented an attractive effect on the cell membranes, and cell adhesions were preferentially induced as compared with UFG-A. Both conditions demonstrated cell projections, but for UFG-AA, cells were more widely dispersed, and more quantities of filopodia formation could be observed.

Conclusion

Herein, the reasons for such behaviors are discussed, and further results are presented in addition to those mentioned above.

Complete digestion of edible bird's nest releases free N-acetylneuraminic acid and small peptides: an efficient method to improve functional properties

Edible bird's nest (EBN), an Asian health food, contains insoluble proteins and conjugated N-acetylneuraminic acid (NANA) that are difficult to be absorbed by humans. In order to increase the nutritional value of EBN, we developed methods to digest EBN targeting the release of proteins and NANA. By using simulated gastric fluid under acidic conditions, the complex proteins were fully digested into smaller peptides, and in parallel, NANA was fully released from the conjugated form. The completely digested EBN showed better nutraceutical properties. In a skin whitening test, the EBN digest showed stronger inhibition of melanogenesis of cultured B16 cells and enzymatic activity of tyrosinase, as compared to that of undigested EBN. In addition, the EBN digest exhibited stronger osteogenic activity in cultured osteoblasts. Thus, the complete digestion of EBN could be applied to the development of a new generation of EBN health food products, including EBN drinks and skincare products.

Evaluation of Proliferation and Osteogenic Differentiation of Human Umbilical Cord-Derived Mesenchymal Stem Cells in Porous Scaffolds

INTRODUCTION

Human umbilical cord-derived mesenchymal stem cells (UCMSCs) are multiple potential stem cells that can differentiate into various kinds of functional cells, including adipocytes, osteoblasts, and chondroblasts. Thus, UCMSCs have recently been used in both stem cell therapy and tissue engineering applications to produce various functional tissues. This study aimed to evaluate the proliferation and differentiation of UCMSCs on porous scaffolds.

METHODS

UCMSCs were established in a previous study and kept in liquid nitrogen. They were thawed and expanded in vitro to yield enough cells for further experiments. The cells were characterized as having MSC phenotype. They were seeded onto culture medium-treated porous scaffolds or on non-treated porous scaffolds at different densities of UCMSCs (10⁵, 2.1 × 10⁵, and 5 × 10⁵ cells/0.005 g scaffold). The existence of UCMSCs on the scaffold was evaluated by nucleic staining using Hoechst 33342 dye, while cell proliferation on the scaffold was determined by MTT assay. Osteogenic differentiation was evaluated by changes in cellular morphology, accumulation of extracellular calcium, and expression of osteoblast-specific genes (including runx2, osteopontin (OPN), and osteocalcin (OCN)).

RESULTS

The data showed that UCMSCs could attach, proliferate, and differentiate on both treated and non-treated scaffolds but were better on the treated scaffold. At a cell density of 10⁵ cells/0.005 g scaffold, the adherent and proliferative abilities of UCMSCs were higher than that of the other densities after 14 days of culture (p < 0.05). Adherent UCMSCs on the scaffold could be induced into osteoblasts in the osteogenic medium after 21 days of induction. These cells accumulated calcium in the extracellular matrix that was positive with Alizarin Red staining. They also expressed some genes related to osteoblasts, including runx2, OPN, and OCN.

CONCLUSION

UCMSCs could adhere, proliferate, and differentiate into osteoblasts on porous scaffolds. Therefore, porous scaffolds (such as Variotis) may be suitable scaffolds for producing bone tissue in combination with UCMSCs.

Expression of the ectodomain-releasing protease ADAM17 is directly regulated by the osteosarcoma and bone-related transcription factor RUNX2

Osteoblast differentiation is controlled by transcription factor RUNX2 which temporally activates or represses several bone-related genes, including those encoding extracellular matrix proteins or factors that control cell-cell, and cell-matrix interactions. Cell-cell communication in the many skeletal pericellular micro-niches is critical for bone development and involves paracrine secretion of growth factors and morphogens. This paracrine signaling is in part regulated by "A Disintegrin And Metalloproteinase" (ADAM) proteins. These cell membrane-associated metalloproteinases support proteolytic release ("shedding") of protein ectodomains residing at the cell surface. We analyzed microarray and RNA-sequencing data for Adam genes and show that Adam17, Adam10, and Adam9 are stimulated during BMP2 mediated induction of osteogenic differentiation and are robustly expressed in human osteoblastic cells. ADAM17, which was initially identified as a tumor necrosis factor alpha (TNFα) converting enzyme also called (TACE), regulates TNFα-signaling pathway, which inhibits osteoblast differentiation. We demonstrate that Adam17 expression is suppressed by RUNX2 during osteoblast differentiation through the proximal Adam17 promoter region (-0.4 kb) containing two functional RUNX2 binding motifs. Adam17 downregulation during osteoblast differentiation is paralleled by increased RUNX2 expression, cytoplasmic-nuclear translocation and enhanced binding to the Adam17 proximal promoter. Forced expression of Adam17 reduces Runx2 and Alpl expression, indicating that Adam17 may negatively modulate osteoblast differentiation. These findings suggest a novel regulatory mechanism involving a reciprocal Runx2-Adam17 negative feedback loop to regulate progression through osteoblast differentiation. Our results suggest that RUNX2 may control paracrine signaling through regulation of ectodomain shedding at the cell surface of osteoblasts by directly suppressing Adam17 expression.

Creating diversity in mammalian facial morphology: a review of potential developmental mechanisms

Mammals (class Mammalia) have evolved diverse craniofacial morphology to adapt to a wide range of ecological niches. However, the genetic and developmental mechanisms underlying the diversification of mammalian craniofacial morphology remain largely unknown. In this paper, we focus on the facial length and orofacial clefts of mammals and deduce potential mechanisms that produced diversity in mammalian facial morphology. Small-scale changes in facial morphology from the common ancestor, such as slight changes in facial length and the evolution of the midline cleft in some lineages of bats, could be attributed to heterochrony in facial bone ossification. In contrast, large-scale changes of facial morphology from the common ancestor, such as a truncated, widened face as well as the evolution of the bilateral cleft possessed by some bat species, could be brought about by changes in growth and patterning of the facial primordium (the facial processes) at the early stages of embryogenesis.

The role of transient receptor potential polycystin channels in bone diseases

Transient receptor potential (TRP) channels are cation channels which act as molecular sensors that enable cells to detect and respond to a plethora of mechanical and environmental cues. TRPs are involved in various physiological processes, such as mechanosensation, non-inception and thermosensation, while mutations in genes encoding them can lead to pathological conditions, called "channelopathies". The subfamily of transient receptor potential polycystins (TRPPs), Polycystin 1 (PC1, TRPP1) and Polycystin 2 (PC2, TRPP2), act as mechanoreceptors, sensing external mechanical forces, including strain, stretch and fluid shear stress, triggering a cascade of signaling pathways involved in osteoblastogenesis and ultimately bone formation. Both in vitro studies and research on animal models have already identified their implications in bone homeostasis. However, uncertainty veiling the role of polycystins (PCs) in bone disease urges studies to elucidate further their role in this field. Mutations in TRPPs have been related to autosomal polycystic kidney disease (ADKPD) and research groups try to identify their role beyond their well-established contribution in kidney disease. Such an elucidation would be beneficial for identifying signaling pathways where polycystins are involved in bone diseases related to exertion of mechanical forces such as osteoporosis, osteopenia and craniosynostosis. A better understanding of the implications of TRPPs in bone diseases would possibly lay the cornerstone for effective therapeutic schemes.

Contrasting patterns of RUNX2 repeat variations are associated with palate shape in phyllostomid bats and New World primates

Establishing the genetic basis that underlies craniofacial variability in natural populations is one of the main topics of evolutionary and developmental studies. One of the genes associated with mammal craniofacial variability is RUNX2, and in the present study we investigated the association between craniofacial length and width and RUNX2 across New World bats (Phyllostomidae) and primates (Catarrhini and Platyrrhini). Our results showed contrasting patterns of association between the glutamate/alanine ratios (Q/A ratio) and palate shape in these highly diverse groups. In phyllostomid bats, we found an association between shorter/broader faces and increase of the Q/A ratio. In New World monkeys (NWM) there was a positive correlation of increasing Q/A ratios to more elongated faces. Our findings reinforced the role of the Q/A ratio as a flexible genetic mechanism that would rapidly change the time of skull ossification throughout development. However, we propose a scenario in which the influence of this genetic adjustment system is indirect. The Q/A ratio would not lead to a specific phenotype, but throughout the history of a lineage, would act along with evolutionary constraints, as well as other genes, as a facilitator for adaptive morphological changes.

Fatigue resistance, electrochemical corrosion and biological response of Ti-15Mo with surface modified by amorphous TiO2 nanotubes layer

The objective of this work was a systemic evaluation of the anodizing treatment in a β-type Ti-15Mo alloy to grow a TiO₂ nanostructured layer for osseointegration improvement. The technical viability of the surface modification was assessed based on the resistance to mechanical fatigue, electrochemical corrosion, and biological response. By using an organic solution of NH₄ F in ethylene glycol, a well-organized array of 90 nm diameter nanotubes was obtained with a potential of 40 V for 6 h, while undefined nanotubes of 25 nm diameter were formed with a potential of 20 V for 1 h. Nevertheless, the production of the 90 nm diameter nanotubes was followed by micrometer pits that significantly reduced the fatigue performance. The undefined nanotubes of 25 nm diameter, besides the greater cell viability and improved osteoblastic cell differentiation in comparison to the as-polished surface, were not deleterious to the fatigue and corrosion properties. This result strengthens the necessity of an overall evaluation of the anodizing treatment, particularly the fatigue resistance, before suggesting it for the design of implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 86-96, 2019.

The biological basis of treating jaw discrepancies: An interplay of mechanical forces and skeletal configuration

Jaw discrepancies and malrelations affect a large proportion of the general population and their treatment is of utmost significance for individuals' health and quality of life. The aim of their therapy is the modification of aberrant jaw development mainly by targeting the growth potential of the mandibular condyle through its cartilage, and the architectural shape of alveolar bone through a suture type of structure, the periodontal ligament. This targeted treatment is achieved via external mechanical force application by using a wide variety of intraoral and extraoral appliances. Condylar cartilage and sutures exhibit a remarkable plasticity due to the mechano-responsiveness of the chondrocytes and the multipotent mesenchymal cells of the sutures. The tissues respond biologically and adapt to mechanical force application by a variety of signaling pathways and a final interplay between the proliferative activity and the differentiation status of the cells involved. These targeted therapeutic functional alterations within temporo-mandibular joint ultimately result in the enhancement or restriction of mandibular growth, while within the periodontal ligament lead to bone remodeling and change of its architectural structure. Depending on the form of the malrelation presented, the above treatment approaches, in conjunction or separately, lead to the total correction of jaw discrepancies and the achievement of facial harmony and function. Overall, the treatment of craniofacial and jaw anomalies can be seen as an interplay of mechanical forces and adaptations occurring within temporo-mandibular joint and alveolar bone. The aim of the present review is to present up-to-date knowledge on the mechano-biology behind jaw growth modification and alveolar bone remodeling. Furthermore, future molecular targeted therapeutic strategies are discussed aiming at the improvement of mechanically-driven chondrogenesis and osteogenesis.

Regulatory effect of microRNA-34a on osteogenesis and angiogenesis in glucocorticoid-induced osteonecrosis of the femoral head

Glucocorticoid-induced osteonecrosis of the femoral head (GIOFH) is a common and devastating orthopedic disease, and its underlying mechanism remains unclear. The aim of this study was to determine the role of microRNA-34a (mir-34a) in GIOFH. C57 mouse mesenchymal stem cells (mMSCs) and human umbilical vein endothelial cells (HUVECs) were cultured with dexamethasone (Dex). A total of 48 adult rats were treated with glucocorticoids, and after the onset of GIOFH, each femoral head was removed. Mir-34a mimics, an inhibitor and over-expressing lentivirus were used in vitro and in vivo, respectively. Real-time PCR, immunohistochemistry, ELISA, cell proliferation assays, osteoblastic differentiation, and endothelial activity assays were employed to evaluate the effect of mir-34a on mMSCs, osteoblasts, and vascular endothelial cells in glucocorticoid-treated mice. We found that Dex inhibited mMSC proliferation and osteoblastic differentiation, as well as the viability and activity of endothelial cells. Dex also caused osteonecrosis and decreased new vessel formation in vivo. Mir-34a alleviated the inhibitory effects of Dex on mMSCs and osteoblasts, while facilitating its inhibitory effects on endothelial cells. Mir-34a is an important regulator in osteogenesis and angiogenesis, and it might be useful as a therapeutic target for GIOFH. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:417-424, 2018.

Facing the facts: The Runx2 gene is associated with variation in facial morphology in primates

The phylogenetic and adaptive factors that cause variation in primate facial form-including differences among the major primate clades and variation related to feeding and/or social behavior-are relatively well understood. However, comparatively little is known about the genetic mechanisms that underlie diversity in facial form in primates. Because it is essential for osteoblastic differentiation and skeletal development, the runt-related transcription factor 2 (Runx2) is one gene that may play a role in these genetic mechanisms. Specifically, polymorphisms in the QA ratio (determined by the ratio of the number of polyglutamines to polyalanines in one functional domain of Runx2) have been shown to be correlated with variation in facial length and orientation in other mammal groups. However, to date, the relationship between variation in this gene and variation in facial form in primates has not been explicitly tested. To test the hypothesis that the QA ratio is correlated with facial form in primates, the current study quantified the QA ratio, facial length, and facial angle in a sample of 33 primate species and tested for correlation using phylogenetic generalized least squares. The results indicate that the QA ratio of the Runx2 gene is positively correlated with variation in relative facial length in anthropoid primates. However, no correlation was found in strepsirrhines, and there was no correlation between facial angle and the QA ratio in any groups. These results suggest that, in primates, the QA ratio of the Runx2 gene may play a role in modulating facial size, but not facial orientation. This study therefore provides important clues about the genetic and developmental mechanisms that may underlie variation in facial form in primates.

Enamel matrix derivative enhances the proliferation and osteogenic differentiation of human periodontal ligament stem cells on the titanium implant surface

Periodontal ligament stem cells (PDLSCs) have mesenchymal-stem-cells-like qualities, and are considered as one of the candidates of future clinical application in periodontal regeneration therapy. Enamel matrix derivative (EMD) is widely used in promoting periodontal regeneration. However, the effects of EMD on the proliferation and osteogenic differentiation of human PDLSCs grown on the Ti implant surface are still no clear. Therefore, this study examined the effects of EMD on human PDLSCs in vitro. Human PDLSCs were isolated from healthy participants, and seeded on the surface of Ti implant disks and stimulated with various concentrations of EMD. Cell proliferation was determined with Cell Counting Kit-8 (CCK-8). The osteogenic differentiation of PDLSCs was evaluated by the measurement of alkaline phosphatase (ALP) activity, Alizarin red staining, and real-time polymerase chain reaction (qRT-PCR) and Western blotting, respectively. The results indicated that EMD at concentrations (5-60 µg/ml) increased the viability and proliferation of PDLSCs. The treatment with 30 and 60 µg/ml of EMD significantly elevated ALP activity, augmented mineralized nodule formation and calcium deposition, and upregulated the mRNA and protein levels of Runx-2 and osteocalcin (OCN) in the PDLSCs grown on the Ti surface. Further investigation found that EMD treatment did not change the protein levels of phosphatidylinositol-3-kinase (PI3K), p-PI3K, Akt and mTOR, but significantly upregulated the phosphorylated levels of Akt and mTOR. Collectively, these results suggest that EMD stimulation can promote the proliferation and osteogenic differentiation of PDLSCs grown on Ti surface, which is possibly associated with the activation of Akt/mTOR signaling pathway.

RUNX2 repeat variation does not drive craniofacial diversity in marsupials

BACKGROUND

Runt-related transcription factor 2 (RUNX2) is a transcription factor essential for skeletal development. Variation within the RUNX2 polyglutamine / polyalanine (QA) repeat is correlated with facial length within orders of placental mammals and is suggested to be a major driver of craniofacial diversity. However, it is not known if this correlation exists outside of the placental mammals.

RESULTS

Here we examined the correlation between the RUNX2 QA repeat ratio and facial length in the naturally evolving sister group to the placental mammals, the marsupials. Marsupials have a diverse range of facial lengths similar to that seen in placental mammals. Despite their diversity there was almost no variation seen in the RUNX2 QA repeat across individuals spanning the entire marsupial infraclass. The extreme conservation of the marsupial RUNX2 QA repeat indicates it is under strong purifying selection. Despite this, we observed an unexpectedly high level of repeat purity.

CONCLUSIONS

Unlike within orders of placental mammals, RUNX2 repeat variation cannot drive craniofacial diversity in marsupials. We propose conservation of the marsupial RUNX2 QA repeat is driven by the constraint of accelerated ossification of the anterior skeleton to facilitate life in the pouch. Thus, marsupials must utilize alternate pathways to placental mammals to drive craniofacial evolution.

Caffeic acid phenethyl ester protects against glucocorticoid-induced osteoporosis in vivo: Impact on oxidative stress and RANKL/OPG signals

Glucocorticoid-induced osteoporosis (GIO) is one of the most common causes of secondary osteoporosis. Given that glucocorticoids are considered as a main component of the treatment protocols for a variety of inflammation and immune-mediated diseases besides its use as adjuvant to several chemotherapeutic agents, it is crucial to find ways to overcome this critical adverse effect. Caffeic acid phenethyl ester (CAPE), which is a natural compound derived from honeybee propolis displayed promising antiosteoporotic effects against mechanical bone injury in various studies. The current work aimed at investigating the potential protective effect of CAPE against GIO in vivo with emphasis on the modulation of oxidative status and receptor activator of NF-kB ligand (RANKL)/osteoprotegrin (OPG) signaling. The results showed that CAPE opposed dexamethasone (DEX)-mediated alterations in bone histology and tartarate-resistant acid phosphatase (TRAP) activity. In addition, CAPE restored oxidative balance, Runt-related transcription factor 2 (RunX2) expression and reduced caspase-3 activity in femur tissues. Co-administration of CAPE with DEX normalized RANKL/OPG ratio and Akt activation indicating a reduction in DEX-osteoclastogenesis. In conclusion, concurrent treatment of CAPE with DEX exhibited promising effects in the protection against DEX-induced osteoporosis through opposing osteoclastogenesis and protecting osteoblasts. The potent antioxidant activity of CAPE is, at least in part, involved in its anti-apoptotic effects and modulation of RunX2 and RANKL/OPG signals. The use of CAPE-enriched propolis formulas is strongly recommended for patients on chronic glucocorticoid therapy to help in the attenuation of GIO.

Mechanosensor polycystin-1 potentiates differentiation of human osteoblastic cells by upregulating Runx2 expression via induction of JAK2/STAT3 signaling axis

Polycystin-1 (PC1) has been proposed as a chief mechanosensing molecule implicated in skeletogenesis and bone remodeling. Mechanotransduction via PC1 involves proteolytic cleavage of its cytoplasmic tail (CT) and interaction with intracellular pathways and transcription factors to regulate cell function. Here we demonstrate the interaction of PC1-CT with JAK2/STAT3 signaling axis in mechanically stimulated human osteoblastic cells, leading to transcriptional induction of Runx2 gene, a master regulator of osteoblastic differentiation. Primary osteoblast-like PC1-expressing cells subjected to mechanical-stretching exhibited a PC1-dependent increase of the phosphorylated(p)/active form of JAK2. Specific interaction of PC1-CT with pJAK2 was observed after stretching while pre-treatment of cells with PC1 (anti-IgPKD1) and JAK2 inhibitors abolished JAK2 activation. Consistently, mechanostimulation triggered PC1-mediated phosphorylation and nuclear translocation of STAT3. The nuclear phosphorylated(p)/DNA-binding competent pSTAT3 levels were augmented after stretching followed by elevated DNA-binding activity. Pre-treatment with a STAT3 inhibitor either alone or in combination with anti-IgPKD1 abrogated this effect. Moreover, PC1-mediated mechanostimulation induced elevation of Runx2 mRNA levels. ChIP assays revealed direct regulation of Runx2 promoter activity by STAT3/Runx2 after mechanical-stretching that was PC1-dependent. Our findings show that mechanical load upregulates expression of Runx2 gene via potentiation of PC1-JAK2/STAT3 signaling axis, culminating to possibly control osteoblastic differentiation and ultimately bone formation.

Continuous hydrostatic pressure induces differentiation phenomena in chondrocytes mediated by changes in polycystins, SOX9, and RUNX2

PURPOSE

The present study aimed to investigate the long-term effects of hydrostatic pressure on chondrocyte differentiation, as indicated by protein levels of transcription factors SOX9 and RUNX2, on transcriptional activity of SOX9, as determined by pSOX9 levels, and on the expression of polycystin-encoding genes Pkd1 and Pkd2.

MATERIALS AND METHODS

ATDC5 cells were cultured in insulin-supplemented differentiation medium (ITS) and/or exposed to 14.7 kPa of hydrostatic pressure for 12, 24, 48, and 96 h. Cell extracts were assessed for SOX9, pSOX9, and RUNX2 using western immunoblotting. The Pkd1 and Pkd2 mRNA levels were detected by real-time PCR.

RESULTS

Hydrostatic pressure resulted in an early drop in SOX9 and pSOX9 protein levels at 12 h followed by an increase from 24 h onwards. A reverse pattern was followed by RUNX2, which reached peak levels at 24 h of hydrostatic pressure-treated chondrocytes in ITS culture. Pkd1 and Pkd2 mRNA levels increased at 24 h of combined hydrostatic pressure and ITS treatment, with the latter remaining elevated up to 96 h.

CONCLUSIONS

Our data indicate that long periods of continuous hydrostatic pressure stimulate chondrocyte differentiation through a series of molecular events involving SOX9, RUNX2, and polycystins-1, 2, providing a theoretical background for functional orthopedic mechanotherapies.