BMP signaling and skeletogenesis

Prospects and challenges for the application of tissue engineering technologies in the treatment of bone infections

Osteomyelitis is a devastating disease caused by microbial infection in deep bone tissue. Its high recurrence rate and impaired restoration of bone deficiencies are major challenges in treatment. Microbes have evolved numerous mechanisms to effectively evade host intrinsic and adaptive immune attacks to persistently localize in the host, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants (SCVs). Moreover, microbial-mediated dysregulation of the bone immune microenvironment impedes the bone regeneration process, leading to impaired bone defect repair. Despite advances in surgical strategies and drug applications for the treatment of bone infections within the last decade, challenges remain in clinical management. The development and application of tissue engineering materials have provided new strategies for the treatment of bone infections, but a comprehensive review of their research progress is lacking. This review discusses the critical pathogenic mechanisms of microbes in the skeletal system and their immunomodulatory effects on bone regeneration, and highlights the prospects and challenges for the application of tissue engineering technologies in the treatment of bone infections. It will inform the development and translation of antimicrobial and bone repair tissue engineering materials for the management of bone infections.

Application of dental pulp stem cells for bone regeneration

Bone defects resulting from severe trauma, tumors, inflammation, and other factors are increasingly prevalent. Stem cell-based therapies have emerged as a promising alternative. Dental pulp stem cells (DPSCs), sourced from dental pulp, have garnered significant attention owing to their ready accessibility and minimal collection-associated risks. Ongoing investigations into DPSCs have revealed their potential to undergo osteogenic differentiation and their capacity to secrete a diverse array of ontogenetic components, such as extracellular vesicles and cell lysates. This comprehensive review article aims to provide an in-depth analysis of DPSCs and their secretory components, emphasizing extraction techniques and utilization while elucidating the intricate mechanisms governing bone regeneration. Furthermore, we explore the merits and demerits of cell and cell-free therapeutic modalities, as well as discuss the potential prospects, opportunities, and inherent challenges associated with DPSC therapy and cell-free therapies in the context of bone regeneration.

Advancements in Genetic Marker Exploration for Livestock Vertebral Traits with a Focus on China

In livestock breeding, the number of vertebrae has gained significant attention due to its impact on carcass quality and quantity. Variations in vertebral traits have been observed across different animal species and breeds, with a strong correlation to growth and meat production. Furthermore, vertebral traits are classified as quantitative characteristics. Molecular marker techniques, such as marker-assisted selection (MAS), have emerged as efficient tools to identify genetic markers associated with vertebral traits. In the current review, we highlight some key potential genes and their polymorphisms that play pivotal roles in controlling vertebral traits (development, length, and number) in various livestock species, including pigs, donkeys, and sheep. Specific genetic variants within these genes have been linked to vertebral development, number, and length, offering valuable insights into the genetic mechanisms governing vertebral traits. This knowledge has significant implications for selective breeding strategies to enhance structural characteristics and meat quantity and quality in livestock, ultimately improving the efficiency and quality of the animal husbandry industry.

Biomimetic Collagen Membranes as Drug Carriers of Geranylgeraniol to Counteract the Effect of Zoledronate

To counteract the effect of zoledronate and decrease the risk of osteonecrosis of the jaw (BRONJ) development in patients undergoing guided bone regeneration surgery, the use of geranylgeraniol (GGOH) has been proposed. Collagen membranes may act as biomimetical drug carriers. The objective of this study was to determine the capacity of collagen-based membranes doped with GGOH to revert the negative impact of zoledronate on the growth and differentiation of human osteoblasts. MG-63 cells were cultured on collagen membranes. Two groups were established: (1) undoped membranes and (2) membranes doped with geranylgeraniol. Osteoblasts were cultured with or without zoledronate (50 μM). Cell proliferation was evaluated at 48 h using the MTT colorimetric method. Differentiation was tested by staining mineralization nodules with alizarin red and by gene expression analysis of bone morphogenetic proteins 2 and 7, alkaline phosphatase (ALP), bone morphogenetic proteins 2 and 7 (BMP-2 and BMP-7), type I collagen (Col-I), osterix (OSX), osteocalcin (OSC), osteoprotegerin (OPG), receptor for RANK (RANKL), runt-related transcription factor 2 (Runx-2), TGF-β1 and TGF-β receptors (TGF-βR1, TGF-βR2, and TGF-βR3), and vascular endothelial growth factor (VEGF) with real-time PCR. One-way ANOVA or Kruskal-Wallis and post hoc Bonferroni tests were applied (p < 0.05). Scanning electron microscopy (SEM) observations were also performed. Treatment of osteoblasts with 50 μM zoledronate produced a significant decrease in cell proliferation, mineralization capacity, and gene expression of several differentiation markers if compared to the control (p < 0.001). When osteoblasts were treated with zoledronate and cultured on GGOH-doped membranes, these variables were, in general, similar to the control group (p > 0.05). GGOH applied on collagen membranes is able to reverse the negative impact of zoledronate on the proliferation, differentiation, and gene expression of different osteoblasts' markers.

New insights into the properties, functions, and aging of skeletal stem cells

Bone-related diseases pose a major health burden for modern society. Bone is one of the organs that rely on stem cell function to maintain tissue homeostasis. Stem cell therapy has emerged as an effective new strategy to repair and replace damaged tissue. Although research on bone marrow mesenchymal stem cells has been conducted over the last few decades, the identity and definition of the true skeletal stem cell population remains controversial. Due to technological advances, some progress has been made in the prospective separation and function research of purified skeletal stem cells. Here, we reviewed the recent progress of highly purified skeletal stem cells, their function in bone development and repair, and the impact of aging on skeletal stem cells. Various studies on animal and human models distinguished and isolated skeletal stem cells using different surface markers based on flow-cytometry-activated cell sorting. The roles of different types of skeletal stem cells in bone growth, remodeling, and repair are gradually becoming clear. Thanks to technological advances, SSCs can be specifically identified and purified for functional testing and molecular analysis. The basic features of SSCs and their roles in bone development and repair and the effects of aging on SSCs are gradually being elucidated. Future mechanistic studies can help to develop new therapeutic interventions to improve various types of skeletal diseases and enhance the regenerative potential of SSCs.

Doxycycline-doped collagen membranes accelerate in vitro osteoblast proliferation and differentiation

OBJECTIVE

The aim of the study was to evaluate the effect of doxycycline- and dexamethasone-doped collagen membranes on the proliferation and differentiation of osteoblasts.

BACKGROUND

Collagen barrier membranes are frequently used to promote bone regeneration and to boost this biological activity their functionalization with antibacterial and immunomodulatory substances has been suggested.

METHODS

The design included commercially available collagen membranes doped with doxycycline (Dox-Col-M) or dexamethasone (Dex-Col-M), as well as undoped membranes (Col-M) as controls, which were placed in contact with cultured MG63 osteoblast-like cells (ATCC). Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay and differentiation by measuring the alkaline phosphatase (ALP) activity using spectrophotometry. Real-time quantitative polymerase chain reaction was used to study the expression of the genes: Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3. Scanning electron microscopy was used to study osteoblast morphology. Data were assessed using one-way analysis of variance or Kruskal-Wallis tests, once their distribution normality was assessed by Kolmogorov-Smirnov tests (p > .05). Bonferroni for multiple comparisons were carried out (p < .05).

RESULTS

Osteoblast proliferation was significantly enhanced in the functionalized membranes as follows: (Col-M < Dex-Col-M < Dox-Col-M). ALP activity was significantly higher on cultured osteoblasts on Dox-Col-M. Runx-2, OSX, ALP, OSC, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3 were overexpressed, and RANKL was down-regulated in osteoblasts cultured on Dox-Col-M. The osteoblasts cultured in contact with the functionalized membranes demonstrated an elongated spindle-shaped morphology.

CONCLUSION

The functionalization of collagen membranes with Dox promoted an increase in the proliferation and differentiation of osteoblasts.

Skeletal dysplasia-causing TRPV4 mutations suppress the hypertrophic differentiation of human iPSC-derived chondrocytes

Mutations in the TRPV4 ion channel can lead to a range of skeletal dysplasias. However, the mechanisms by which TRPV4 mutations lead to distinct disease severity remain unknown. Here, we use CRISPR-Cas9-edited human-induced pluripotent stem cells (hiPSCs) harboring either the mild V620I or lethal T89I mutations to elucidate the differential effects on channel function and chondrogenic differentiation. We found that hiPSC-derived chondrocytes with the V620I mutation exhibited increased basal currents through TRPV4. However, both mutations showed more rapid calcium signaling with a reduced overall magnitude in response to TRPV4 agonist GSK1016790A compared to wildtype (WT). There were no differences in overall cartilaginous matrix production, but the V620I mutation resulted in reduced mechanical properties of cartilage matrix later in chondrogenesis. mRNA sequencing revealed that both mutations up-regulated several anterior HOX genes and down-regulated antioxidant genes CAT and GSTA1 throughout chondrogenesis. BMP4 treatment up-regulated several essential hypertrophic genes in WT chondrocytes; however, this hypertrophic maturation response was inhibited in mutant chondrocytes. These results indicate that the TRPV4 mutations alter BMP signaling in chondrocytes and prevent proper chondrocyte hypertrophy, as a potential mechanism for dysfunctional skeletal development. Our findings provide potential therapeutic targets for developing treatments for TRPV4-mediated skeletal dysplasias.

Small-Molecule-Mediated Suppression of BMP Signaling by Selective Inhibition of BMP1-Dependent Chordin Cleavage

BMP signaling is critical for many biological processes. Therefore, small molecules that modulate BMP signaling are useful for elucidating the function of BMP signaling and treating BMP signaling-related diseases. Here, we performed a phenotypic screening in zebrafish to examine the in vivo effects of N-substituted-2-amino-benzoic acid analogs NPL1010 and NPL3008 and found that they affect BMP signaling-dependent dorsal-ventral (D-V) patterning and bone formation in zebrafish embryos. Furthermore, NPL1010 and NPL3008 suppressed BMP signaling upstream of BMP receptors. BMP1 cleaves Chordin, an antagonist of BMP, and negatively regulates BMP signaling. Docking simulations demonstrated that NPL1010 and NPL3008 bind BMP1. We found that NPL1010 and NPL3008 partially rescued the disruptions in the D-V phenotype caused by bmp1 overexpression and selectively inhibited BMP1-dependent Chordin cleavage. Therefore, NPL1010 and NPL3008 are potentially valuable inhibitors of BMP signaling that act through selective inhibition of Chordin cleavage.

Genetic Analyses of Enamel Hypoplasia in Multiethnic Cohorts

Enamel hypoplasia causes reduction in the thickness of affected enamel and is one of the most common dental anomalies. This defect is caused by environmental and/or genetic factors that interfere with tooth formation, emphasizing the importance of investigating enamel hypoplasia on an epidemiological and genetic level. A genome-wide association of enamel hypoplasia was performed in multiple cohorts, overall comprising 7,159 individuals ranging in age from 7-82 years. Mixed-models were used to test for genetic association while simultaneously accounting for relatedness and genetic population structure. Meta-analysis was then performed. More than 5 million single-nucleotide polymorphisms were tested in individual cohorts. Analyses of the individual cohorts and meta-analysis identified association signals close to genome-wide significance (P < 510-8), and many suggestive association signals (510-8 < P < 510-6) near genes with plausible roles in tooth/enamel development. The strongest association signal (P = 1.5710-9) was observed near BMP2K in one of the individual cohorts. Additional suggestive signals were observed near genes with plausible roles in tooth development in the meta-analysis, such as SLC4A4 which can influence enamel hypoplasia. Additional human genetic studies are needed to replicate these results and functional studies in model systems are needed to validate our findings.

BMPR1A maintains skeletal stem cell properties in craniofacial development and craniosynostosis

Skeletal stem cells from the suture mesenchyme, which are referred to as suture stem cells (SuSCs), exhibit long-term self-renewal, clonal expansion, and multipotency. These SuSCs reside in the suture midline and serve as the skeletal stem cell population responsible for calvarial development, homeostasis, injury repair, and regeneration. The ability of SuSCs to engraft in injury site to replace the damaged skeleton supports their potential use for stem cell-based therapy. Here, we identified BMPR1A as essential for SuSC self-renewal and SuSC-mediated bone formation. SuSC-specific disruption of Bmpr1a in mice caused precocious differentiation, leading to craniosynostosis initiated at the suture midline, which is the stem cell niche. We found that BMPR1A is a cell surface marker of human SuSCs. Using an ex vivo system, we showed that SuSCs maintained stemness properties for an extended period without losing the osteogenic ability. This study advances our knowledge base of congenital deformity and regenerative medicine mediated by skeletal stem cells.

A biomechanical switch regulates the transition towards homeostasis in oesophageal epithelium

Epithelial cells rapidly adapt their behaviour in response to increasing tissue demands. However, the processes that finely control these cell decisions remain largely unknown. The postnatal period covering the transition between early tissue expansion and the establishment of adult homeostasis provides a convenient model with which to explore this question. Here, we demonstrate that the onset of homeostasis in the epithelium of the mouse oesophagus is guided by the progressive build-up of mechanical strain at the organ level. Single-cell RNA sequencing and whole-organ stretching experiments revealed that the mechanical stress experienced by the growing oesophagus triggers the emergence of a bright Krüppel-like factor 4 (KLF4) committed basal population, which balances cell proliferation and marks the transition towards homeostasis in a yes-associated protein (YAP)-dependent manner. Our results point to a simple mechanism whereby mechanical changes experienced at the whole-tissue level are integrated with those sensed at the cellular level to control epithelial cell fate.

Doxycycline-doped membranes induced osteogenic gene expression on osteoblastic cells

OBJECTIVES

To analyze how novel developed silicon dioxide composite membranes, functionalized with zinc or doxycycline, can modulate the expression of genes related to the osteogenic functional capacity of osteoblastic cells.

METHODS

The composite nanofibers membranes were manufactured by using a novel polymeric blend and 20 nm silicon dioxide nanoparticles (SiO₂-NPs). To manufacture the membranes, 20 nm SiO₂-NPs were added to the polymer solution and the resulting suspension was processed by electrospinning. In a second step, the membranes were functionalized with zinc or doxycycline. Then, they were subjected to MG63 osteoblast-like cells culturing for 48 h. After this time, real-time quantitative polymerase chain reaction (RT-qPCR) was carried out to study the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF- βR2, and TGF-βR3. Mean comparisons were conducted by One-way ANOVA and Tukey tests (p < 0.05).

RESULTS

In general, the blending of SiO₂-NPs in the tested non-resorbable polymeric scaffold improves the expression of osteogenic genes over the control membranes. Doxycycline doping of experimental scaffolds attained the best results, encountering up-regulation of BMP-2, ALP, OPG, TGFβ-1 and TGFβ-R1. Membranes with zinc induced a significant increase in the expression of Col-I, ALP and TGF β1. Both, zinc and doxycycline functionalized membranes enormously down-regulated the expression of RANKL.

CONCLUSIONS

Zinc and doxycycline doped membranes are bioactive inducing overexpression of several osteogenic gene markers.

CLINICAL SIGNIFICANCE

Doxycycline doped membranes may be a potential candidate for use in GBR procedures in several challenging pathologies, including periodontal diseases.

The Marine Polysaccharide Ulvan Confers Potent Osteoinductive Capacity to PCL-Based Scaffolds for Bone Tissue Engineering Applications

Hybrid composites of synthetic and natural polymers represent materials of choice for bone tissue engineering. Ulvan, a biologically active marine sulfated polysaccharide, is attracting great interest in the development of novel biomedical scaffolds due to recent reports on its osteoinductive properties. Herein, a series of hybrid polycaprolactone scaffolds containing ulvan either alone or in blends with κ-carrageenan and chondroitin sulfate was prepared and characterized. The impact of the preparation methodology and the polysaccharide composition on their morphology, as well as on their mechanical, thermal, water uptake and porosity properties was determined, while their osteoinductive potential was investigated through the evaluation of cell adhesion, viability, and osteogenic differentiation of seeded human adipose-derived mesenchymal stem cells. The results verified the osteoinductive ability of ulvan, showing that its incorporation into the polycaprolactone matrix efficiently promoted cell attachment and viability, thus confirming its potential in the development of biomedical scaffolds for bone tissue regeneration applications.

Osteogenic differentiation system based on biopolymer nanoparticles for stem cells in simulated microgravity

An efficient long-term intracellular growth factor release system in simulated microgravity for osteogenic differentiation was prepared based on polylactic acid (PLA) and polyhydroxyalkanoate (PHA) nanoparticles for loading of bone morphogenetic protein 2 (BMP2) and bone morphogenetic protein 7 (BMP7) (defined as sB2-PLA-NP and sB7-PHA-NP), respectively, associated with osteogenic differentiation of human adipose derived stem cells (hADSCs). On account of soybean lecithin (SL) as biosurfactants, sB2-PLA-NPs and sB7-PHA-NPs had a high encapsulation efficiency (>80%) of BMPs and uniform small size (<100 nm), and showed different slow-release to provide BMP2 in early stage and BMP7 in late stages of osteogenic differentiation within 20 days, due to degradation rate of PLA and PHA in cells. After uptake into hADSCs, by comparison with single sB2-PLA-NP or sB7-PHA-NP, the Mixture NPs, compound of sB2-PLA-NP and sB7-PHA-NP with a mass ratio of 1:1, can well-promote ALP activity, expression of OPN and upregulated related osteo-genes. Directed osteo-differentiation of Mixture NPs was similar to result of sustained free-BMP2 and BMP7-supplying (sFree-B2&B7) in simulated microgravity, which demonstrated the reliability and stability of Mixture NPs as a long-term osteogenic differentiation system in space medicine and biology in future.

Altered BMP-Smad4 signaling causes complete cleft palate by disturbing osteogenesis in palatal mesenchyme

As the major receptor mediated BMP signaling in craniofacial development, Bmpr1a expression was detected in the anterior palatal shelves from E13.5 and the posterior palatal shelves from E14.5. However, inactivating BMP receptor in the mesenchyme only leads to anterior cleft palate or submucous cleft palate. The role of BMP signaling in posterior palatal mesenchyme and palatal osteogenesis is still unknown. In this study, a secreted BMP antagonist, Noggin was over-expressed by Osr2-cre^KI to suppress BMP signaling intensively in mouse palatal mesenchyme, which made the newborn mouse displaying complete cleft palate, a phenotype much severer than the anterior or submucous cleft palate. Immunohistochemical analysis indicated that in the anterior and posterior palatal mesenchyme, the canonical BMP-Smad4 signaling was dramatically down-regulated, while the non-canonical BMP signaling pathways were altered little. Although cell proliferation was reduced only in the anterior palatal mesenchyme, the osteogenic condensation and Osterix distribution were remarkably repressed in the posterior palatal mesenchyme by Noggin over-expression. These findings suggested that BMP-Smad4 signaling was essential for the cell proliferation in the anterior palatal mesenchyme, and for the osteogenesis in the posterior palatal mesenchyme. Interestingly, the constitutive activation of Bmpr1a in palatal mesenchyme also caused the complete cleft palate, in which the enhanced BMP-Smad4 signaling resulted in the premature osteogenic differentiation in palatal mesenchyme. Moreover, neither the Noggin over-expression nor Bmpr1a activation disrupted the elevation of palatal shelves. Our study not only suggested that BMP signaling played the differential roles in the anterior and posterior palatal mesenchyme, but also indicated that BMP-Smad4 signaling was required to be finely tuned for the osteogenesis of palatal mesenchyme.

BMP and TGFβ use and release in bone regeneration

A fracture that does not unite in nine months is defined as nonunion. Nonunion is common in fragmented fractures and large bone defects where vascularization is impaired. The distal third of the tibia, the scaphoid bone or the talus fractures are furthermore prone to nonunion. Open fractures and spinal fusion cases also need special monitoring for healing. Bone tissue regeneration can be attained by autografts, allografts, xenografts and synthetic materials, however their limited availability and the increased surgical time as well as the donor site morbidity of autograft use, and lower probability of success, increased costs and disease transmission and immunological reaction probability of allografts oblige us to find better solutions and new grafts to overcome the cons. A proper biomaterial for regeneration should be osteoinductive, osteoconductive, biocompatible and mechanically suitable. Cytokine therapy, where growth factors are introduced either exogenously or triggered endogenously, is one of the commonly used method in bone tissue engineering. Transforming growth factor β (TGFβ) superfamily, which can be divided structurally into two groups as bone morphogenetic proteins (BMPs), growth differentiation factors (GDFs) and TGFβ, activin, Nodal branch, Mullerian hormone, are known to be produced by osteoblasts and other bone cells and present already in bone matrix abundantly, to take roles in bone homeostasis. BMP family, as the biggest subfamily of TGFβ superfamily, is also reported to be the most effective growth factors in bone and development, which makes them one of the most popular cytokines used in bone regeneration. Complications depending on the excess use of growth factors, and pleiotropic functions of BMPs are however the main reasons of why they should be approached with care. In this review, the Smad dependent signaling pathways of TGFβ and BMP families and their relations and the applications in preclinical and clinical studies will be briefly summarized.

Comparing bone tissue engineering efficacy of HDPSCs, HBMSCs on 3D biomimetic ABM-P-15 scaffolds in vitro and in vivo

Human bone marrow mesenchymal stem cells (HBMSCs) has been the gold standard for bone regeneration. However, the low proliferation rate and long doubling time limited its clinical applications. This study aims to compare the bone tissue engineering efficacy of human dental pulp stem cells (HDPSCs) with HBMSCs in 2D, and 3D anorganic bone mineral (ABM) coated with a biomimetic collagen peptide (ABM-P-15) for improving bone-forming speed and efficacy in vitro and in vivo. The multipotential of both HDPSCs and HBMSCs have been compared in vitro. The bone formation of HDPSCs on ABM-P-15 was tested using in vivo model. The osteogenic potential of the cells was confirmed by alkaline phosphatase (ALP) and immunohistological staining for osteogenic markers. Enhanced ALP, collagen, lipid droplet, or glycosaminoglycans production were visible in HDPSCs and HBMSCs after osteogenic, adipogenic and chondrogenic induction. HDPSC showed stronger ALP staining compared to HBMSCs. Confocal images showed more viable HDPSCs on both ABM-P-15 and ABM scaffolds compared to HBMSCs on similar scaffolds. ABM-P-15 enhanced cell attachment/spreading/bridging formation on ABM-P-15 scaffolds and significantly increased quantitative ALP specific activities of the HDPSCs and HBMSCs. After 8 weeks in vivo implantation in diffusion chamber model, the HDPSCs on ABM-P-15 scaffolds showed extensive high organised collagenous matrix formation that was positive for COL-I and OCN compared to ABM alone. In conclusion, the HDPSCs have a higher proliferation rate and better osteogenic capacity, which indicated the potential of combining HDPSCs with ABM-P-15 scaffolds for improving bone regeneration speed and efficacy.

Results of advanced core decompression in patients with osteonecrosis of the femoral head depending on age and sex-a prospective cohort study

Background

Core decompression is a common surgical technique to treat osteonecrosis of the femoral head. The aim of this study is to evaluate the effect of the parameters “age” and “sex” on the outcome of this type of treatment.

Methods

A prospective cohort study was performed. Eighty-six osteonecrotic hips with a mean follow-up of 32.5 months (± 24.8) after advanced core decompression were analysed regarding age- and sex-dependent treatment failure. Additionally, the modified Harris Hip Score and Numeric Rating Scale were compared regarding the parameters age and sex.

Results

The mean hip survival of the male participants was 51.3 months (39.4% treatment failure), whereas females presented a longer, thus not significant, mean survival of 61.4 months (30% therapy failure; p = 0.48). The further evaluation revealed significantly better survival in the patients aged < 40 years (mean survival 66.09 months, 16% treatment failure) in comparison to those aged ≥ 40 years (mean survival 50.14 months, 46% therapy failure; p = 0.03). The modified Harris Hip Score and Numeric Rating Scale results of patients whose treatment did not fail during the study period were similar, irrespective of the patient’s sex or age.

Conclusions

The study shows that the number of therapy failures is significantly higher in older patients, with 40 years of age marking the borderline. Patients’ sex does not seem to affect the outcome of treatment, and postoperative clinical scores appear to be identical with individuals not affected by therapy failure. Since age and sex are unalterable parameters, the study helps to provide valuable predictions regarding the chances of long-term hip survival after treatment of osteonecrosis.

Cabozantinib Reverses Renal Cell Carcinoma-mediated Osteoblast Inhibition in Three-dimensional Coculture In Vitro and Reduces Bone Osteolysis In Vivo

Renal cell carcinoma bone metastases (RCCBM) are typically osteolytic. We previously showed that BIGH3 (beta Ig-h3/TGFBI), secreted by 786-O renal cell carcinoma, plays a role in osteolytic bone lesion in RCCBM through inhibition of osteoblast (OSB) differentiation. To study this interaction, we employed three-dimensional (3D) hydrogels to coculture bone-derived 786-O (Bo-786) renal cell carcinoma cells with MC3T3-E1 pre-OSBs. Culturing pre-OSBs in the 3D hydrogels preserved their ability to differentiate into mature OSB; however, this process was decreased when pre-OSBs were cocultured with Bo-786 cells. Knockdown of BIGH3 in Bo-786 cells recovered OSB differentiation. Furthermore, treatment with bone morphogenetic protein 4, which stimulates OSB differentiation, or cabozantinib (CBZ), which inhibits VEGFR1 and MET tyrosine kinase activities, also increased OSB differentiation in the coculture. CBZ also inhibited pre-osteoclast RAW264.7 cell differentiation. Using RCCBM mouse models, we showed that CBZ inhibited Bo-786 tumor growth in bone. CBZ treatment also increased bone volume and OSB number, and decreased osteoclast number and blood vessel density. When tested in SN12PM6 renal cell carcinoma cells that have been transduced to overexpress BIGH3, CBZ also inhibited SN12PM6 tumor growth in bone. These observations suggest that enhancing OSB differentiation could be one of the therapeutic strategies for treating RCCBM that exhibit OSB inhibition characteristics, and that this 3D coculture system is an effective tool for screening osteoanabolic agents for further in vivo studies.

Senile Osteoporosis: The Involvement of Differentiation and Senescence of Bone Marrow Stromal Cells

Senile osteoporosis has become a worldwide bone disease with the aging of the world population. It increases the risk of bone fracture and seriously affects human health. Unlike postmenopausal osteoporosis which is linked to menopause in women, senile osteoporosis is due to aging, hence, affecting both men and women. It is commonly found in people with more than their 70s. Evidence has shown that with age increase, bone marrow stromal cells (BMSCs) differentiate into more adipocytes rather than osteoblasts and undergo senescence, which leads to decreased bone formation and contributes to senile osteoporosis. Therefore, it is necessary to uncover the molecular mechanisms underlying the functional changes of BMSCs. It will benefit not only for understanding the senile osteoporosis development, but also for finding new therapies to treat senile osteoporosis. Here, we review the recent advances of the functional alterations of BMSCs and the related mechanisms during senile osteoporosis development. Moreover, the treatment of senile osteoporosis by aiming at BMSCs is introduced.

Disulfiram suppressed ethanol promoted RANKL-induced osteoclastogenesis in vitro and ethanol-induced osteoporosis in vivo via ALDH1A1-NFATc1 axis

Excessive alcohol consumption is positively related to osteoporosis, and its treatment strategies are poorly developed. Disulfiram inhibits receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastogenesis; however, whether it can be used for ethanol-induced osteoclastogenesis and its underlying mechanism are still unclear. In this study, we demonstrated that ethanol promoted RANKL-induced osteoclast formation and bone resorption, whereas, disulfiram suppressed ethanol-induced osteoclastogenesis by abrogating the expression of nuclear factor of activated T cell c1 (NFATc1) in vitro. Further analysis revealed that aldehyde dehydrogenase 1A1 (ALDH1A1) is important for the expression of NFATc1, the master regulator of osteoclast differentiation. Furthermore, we showed that disulfiram protected ethanol-induced osteoporosis in vivo. Overall, our study provides promising evidence that disulfiram can be used as a treatment strategy for alcohol-related osteoporosis via the ALDH1A1T–NFATc1 axis.

Inhibition of the negative effect of high glucose on osteogenic differentiation of bone marrow stromal cells by silicon ions from calcium silicate bioceramics

Human bone marrow stem cells (hBMSCs) are exploited for miscellaneous applications in bone tissue engineering where they are mainly used as seed cells. However, high glucose (HG) environment has negative impacts on the proliferation and osteogenic differentiation of hBMSCs, thus reducing the bone formation in diabetic patients. In our former research works, we discovered that silicon (Si) ions extracted from silicate-based bioceramics are able to stimulate the proliferation and osteogenic differentiation of hBMSCs under normal culture condition. This study aimed to investigate if Si ions could prevent HG-induced inhibition of proliferation and osteogenesis of hBMSCs. We found that 2.59 ppm concentration of Si ions promoted the proliferation of hBMSCs under HG condition. The results from alkaline phosphatase (ALP) activity assay, Alizarin red S staining and quantitative real-time PCR analysis of osteogenic genes (BMP2, RUNX2, ALP, COL1 and OCN) demonstrated that the 15.92 ppm concentration of Si ions prevented HG-induced inhibition of the osteogenic differentiation of hBMSCs. Moreover, application of Si ions reduced the level of reactive oxygen species in HG-treated hBMSCs. In HG-treated hBMSCs following 15.92 ppm Si ions treatment, activation of BMP2/SMAD signaling pathway was detected, as indicated by the increased expression of BMP2 receptors and its downstream genes such as SMAD1, SMAD4 and SMAD5. Taken together, we provide evidence that the specific concentration of Si ions compensated HG-induced inhibition of proliferation and osteogenic differentiation of hBMSCs through antioxidant effect and modulation of BMP2/SMAD pathway. The results suggest that silicate-based bioceramics might be good scaffold biomaterials for bone engineering applications in diabetes patients.

Conductive nanostructured Si biomaterials enhance osteogeneration through electrical stimulation

It is well known that the differentiation of stem cells is affected by the cell culture medium, the scaffold surface and electrochemical signals. However, stimulation of patterned biomaterials seeded with stem cell cultures has not been explored. Herein the effect of electrical stimulation on osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) cultured on solid and nanoporous micropyramid patterned Si surfaces was evaluated. It was found that both stimulation and scaffold patterning significantly enhanced osteo-differentiation. The stimulated nanoporous micropyramid scaffolds were more promising compared to the stimulated solid micropyramid surfaces, as they significantly promoted the osteogenic differentiation of rBMSCs via BMP/Smad signaling pathway. Particularly, as compared to the unstimulated patterned biomaterials, the stimulated patterned scaffolds allowed for a significant increase in core binding factor alpha l, alkaline phosphatase, the alpha l chain of type I Col, osteocalcin, and osteonectin, all of which are characteristic for osteo-differentiation. The proposed combination of electrical stimulation with scaffold patterning may provide novel promising strategies for bone tissue engineering and regenerative medicine.

PLGA-based control release of Noggin blocks the premature fusion of cranial sutures caused by retinoic acid

Craniosynostosis (CS), the premature and pathological fusion of cranial sutures, is a relatively common developmental disorder. Elucidation of the pathways involved and thus therapeutically targeting it would be promising for the prevention of CS. In the present study, we examined the role of BMP pathway in the all-trans retinoic acid (atRA)-induced CS model and tried to target the pathway in vivo via PLGA-based control release. As expected, the posterior frontal suture was found to fuse prematurely in the atRA subcutaneous injection mouse model. Further mechanism study revealed that atRA could repress the proliferation while promote the osteogenic differentiation of suture-derived mesenchymal cells (SMCs). Moreover, BMP signal pathway was found to be activated by atRA, as seen from increased expression of BMPR-2 and pSMAD1/5/9. Recombinant mouse Noggin blocked the atRA-induced enhancement of osteogenesis of SMCs in vitro. In vivo, PLGA microsphere encapsulated with Noggin significantly prevented the atRA-induced suture fusion. Collectively, these data support the hypothesis that BMP signaling is involved in retinoic acid-induced premature fusion of cranial sutures, while PLGA microsphere-based control release of Noggin emerges as a promising strategy for prevention of atRA-induced suture fusion.

Bisphosphonate Modulation of the Gene Expression of Different Markers Involved in Osteoblast Physiology: Possible Implications in Bisphosphonate-Related Osteonecrosis of the Jaw

The aim of the present study was to elucidate the role of osteoblasts in bisphosphonates-related osteonecrosis of the jaw (BRONJ). The specific objective was to evaluate the effect on osteoblasts of two nitrogen-containing BPs (zoledronate and alendronate) and one non-nitrogen-containing BP (clodronate) by analyzing modulations in their expression of genes essential for osteoblast physiology. Real-time polymerase chain reaction (RT-PCR) was used to study the effects of zoledronate, alendronate, and clodronate at doses of 10-5, 10-7, or 10-9 M on the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3 by primary human osteoblasts (HOBs) and MG-63 osteosarcoma cells. Expression of these markers was found to be dose-dependent, with no substantive differences between these cell lines. In general, results demonstrated a significant increase in TFG-β1, TGF-βR1, TGF-βR2, TGF-βR3, and VEGF expressions and a significant reduction in RUNX-2, Col-1, OSX, OSC, BMP-2, BMP-7, ALP, and RANKL expressions, while OPG expression varied according to the dose and cell line. The results of this in vitro study of HOBS and MG-63 cell lines indicate that low BP doses can significantly affect the expression of genes essential for osteoblast growth and differentiation and of genes involved in regulating osteoblast-osteoclast interaction, possibly by increasing TGF-β1 production. These findings suggest that osteoblasts may play an important role in BRONJ development, without ruling out other factors.

Neural EGF-like protein 1 (NELL-1): Signaling crosstalk in mesenchymal stem cells and applications in regenerative medicine

Bone tissue regeneration holds the potential to solve both osteoporosis and large skeletal defects, two problems associated with significant morbidity. The differentiation of mesenchymal stem cells into the osteogenic lineage requires a specific microenvironment and certain osteogenic growth factors. Neural EGF Like-Like molecule 1 (NELL-1) is a secreted glycoprotein that has proven, both in vitro and in vivo, to be a potent osteo-inductive factor. Furthermore, it has been shown to repress adipogenic differentiation and inflammation. NELL-1 can work synergistically with other osteogenic factors such as Bone Morphogenic Protein (BMP) -2 and -9, and has shown promise for use in tissue engineering and as a systemically administered drug for the treatment of osteoporosis. Here we provide a comprehensive up-to-date review on the molecular signaling cascade of NELL-1 in mesenchymal stem cells and potential applications in bone regenerative engineering.

Peripheral denervation participates in heterotopic ossification in a spinal cord injury model

We previously reported the development of a new acquired neurogenic HO (NHO) mouse model, combining spinal cord transection (SCI) and chemical muscle injury. Pathological mechanisms responsible for ectopic osteogenesis after central neurological damage are still to be elucidated. In this study, we first hypothesized that peripheral nervous system (PNS) might convey pathological signals from injured spinal cord to muscles in NHO mouse model. Secondly, we sought to determine whether SCI could lead to intramuscular modifications of BMP2 signaling pathways. Twenty one C57Bl6 mice were included in this protocol. Bilateral cardiotoxin (CTX) injection in hamstring muscles was associated with a two-stage surgical procedure, combining thoracic SCI with unilateral peripheral denervation. Volumes of HO (Bone Volume, BV) were measured 28 days after surgery using micro-computed tomography imaging techniques and histological analyses were made to confirm intramuscular osteogenesis. Volume comparisons were conducted between right and left hind limb of each animal, using a Wilcoxon signed rank test. Quantitative polymerase chain reaction (qPCR) was performed to explore intra muscular expression of BMP2, Alk3 and Id1. Nineteen mice survive the complete SCI and peripheral denervation procedure. When CTX injections were done right after surgery (n = 7), bilateral HO were detected in all animals after 28 days. Micro-CT measurements showed significantly increased BV in denervated paws (1.47 mm3 +/- 0.5) compared to contralateral sides (0.56 mm3 +/-0.4), p = 0.03. When peripheral denervation and CTX injections were performed after sham SCI surgery (n = 6), bilateral HO were present in three mice at day 28. Quantitative PCR analyses showed no changes in intra muscular BMP2 expression after SCI as compared to control mice (shamSCI). Peripheral denervation can be reliably added to spinal cord transection in NHO mouse model. This new experimental design confirms that neuro inflammatory mechanisms induced by central or peripheral nervous system injury plays a key role in triggering ectopic osteogenesis.

Epigenetic regulation of Runx2 transcription and osteoblast differentiation by nicotinamide phosphoribosyltransferase

BACKGROUND

Bone degenerative disorders like osteoporosis may be initiated by age-related shifts in anabolic and catabolic responses that control bone homeostasis. Although there are studies suggesting that metabolic changes occur with stem cell differentiation, the molecular mechanisms governing energy metabolism and epigenetic modification are not understood fully. Here we reported the key role of nicotinamide phosphoribosyltransferase (Nampt), which is the rate-limiting enzyme in the salvage pathway of NAD biosynthesis from nicotinamide, in the osteogenic differentiation of bone marrow stromal cells.

RESULTS

Differentiated bone marrow stromal cells isolated from Nampt^+/- mice presented with diminished osteogenesis, as evaluated by alkaline phosphatase (ALP) staining, ALP activity and osteoblast-mediated mineralization, compared to cells from Nampt^+/+ mice. Similar results were observed in differentiated Nampt-deficient C3H/10T1/2 and MC3T3-E1 cells. Further studies showed that Nampt promotes osteoblast differentiation through increased function and expression of Runx2 as tested by luciferase reporter assay, RT-PCR, and Western Blotting. Our data also demonstrated that Nampt regulates Runx2 transcription in part through epigenetic modification of H3-Lys9 acetylation.

CONCLUSION

Our study demonstrated that Nampt plays a critical role in osteoblast differentiation through epigenetic augmentation of Runx2 transcription. NAMPT may be a potential therapeutic target of aging-related osteoporosis.

Molecular Therapy for Degenerative Disc Disease: Clues from Secretome Analysis of the Notochordal Cell-Rich Nucleus Pulposus

Degenerative disc disease (DDD) is associated with spinal pain often leading to long-term disability. However, the non-chondrodystrophic canine intervertebral disc is protected from the development of DDD, ostensibly due to its retention of notochordal cells (NC) in the nucleus pulposus (NP). In this study, we hypothesized that secretome analysis of the NC-rich NP will lead to the identification of key proteins that delay the onset of DDD. Using mass-spectrometry, we identified 303 proteins including components of TGFβ- and Wnt-signaling, anti-angiogeneic factors and proteins that inhibit axonal ingrowth in the bioactive fractions of serum free, notochordal cell derived conditioned medium (NCCM). Ingenuity Pathway Analysis revealed TGFβ1 and CTGF as major hubs in protein interaction networks. In vitro treatment with TGFβ1 and CTGF promoted the synthesis of healthy extra-cellular matrix proteins, increased cell proliferation and reduced cell death in human degenerative disc NP cells. A single intra-discal injection of recombinant TGFβ1 and CTGF proteins in a pre-clinical rat-tail disc injury model restored the NC and stem cell rich NP. In conclusion, we demonstrate the potential of TGFβ1 and CTGF to mitigate the progression of disc degeneration and the potential use of these molecules in a molecular therapy to treat the degenerative disc.

Non-myogenic Contribution to Muscle Development and Homeostasis: The Role of Connective Tissues

Skeletal muscles belong to the musculoskeletal system, which is composed of bone, tendon, ligament and irregular connective tissue, and closely associated with motor nerves and blood vessels. The intrinsic molecular signals regulating myogenesis have been extensively investigated. However, muscle development, homeostasis and regeneration require interactions with surrounding tissues and the cellular and molecular aspects of this dialogue have not been completely elucidated. During development and adult life, myogenic cells are closely associated with the different types of connective tissue. Connective tissues are defined as specialized (bone and cartilage), dense regular (tendon and ligament) and dense irregular connective tissue. The role of connective tissue in muscle morphogenesis has been investigated, thanks to the identification of transcription factors that characterize the different types of connective tissues. Here, we review the development of the various connective tissues in the context of the musculoskeletal system and highlight their important role in delivering information necessary for correct muscle morphogenesis, from the early step of myoblast differentiation to the late stage of muscle maturation. Interactions between muscle and connective tissue are also critical in the adult during muscle regeneration, as impairment of the regenerative potential after injury or in neuromuscular diseases results in the progressive replacement of the muscle mass by fibrotic tissue. We conclude that bi-directional communication between muscle and connective tissue is critical for a correct assembly of the musculoskeletal system during development as well as to maintain its homeostasis in the adult.

(+)-Cholesten-3-one induces osteogenic differentiation of bone marrow mesenchymal stem cells by activating vitamin D receptor

In our previous reports, it was revealed that steroids in traditional Chinese medicine (TCM) have the therapeutic potential to treat bone disease. In the present study, an in vitro model of a vitamin D receptor response element (VDRE) reporter gene assay in mesenchymal stem cells (MSCs) was used to identify steroids that enhanced osteogenic differentiation of MSCs. (+)-cholesten-3-one (CN), which possesses a ketone group that is modified in cholesterol and cholesterol myristate, effectively promoted the activity of the VDRE promoter. Phenotypic cellular analysis indicated that CN induced differentiation of MSCs into osteogenic cells and increased expression of specific osteogenesis markers, including alkaline phosphatase, collagen II and Runt-related transcription factor 2. Furthermore, CN significantly increased the expression of osteopontin, the target of the vitamin D receptor (VDR), which indicated that CN may activate vitamin D receptor signaling. Over-expression of VDR or knockdown studies with VDR-small interfering RNA revealed that the pro-differentiation effects induced by CN required VDR. Furthermore, the present study determined that the C-terminal region of the VDR is responsible for the action of CN. Taken together, the present findings demonstrated that CN induced osteogenic differentiation of MSCs by activating VDR. The present study explored the regulation of stem cells by using a series of similar steroids and provided evidence to support a potential strategy for the screening of novel drugs to treat bone disease in the future.

A recurrent mutation in bone morphogenetic proteins-2-inducible kinase gene is associated with developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a complex disorder of the hip joint affecting 1-5‰ of newborns. While genetic influence on DDH has been long known, DDH has not been ascribed to any specific genetic event. The present study reported on variants contributing to DDH susceptibility in a family with four individuals affected across three generations. Whole-exome sequencing was performed in three affected and two unaffected individuals of a pedigree with DDH. Candidate variants were confirmed by Sanger sequencing and then validated in available family members and 37 sporadic DDH patients. Two novel heterozygous, inframe mutations causing multi-nucleotide substitution polymorphisms (c.1432_1440delCAGCAGCAG corresponding with p.Gln478_480del and c.1440_1441insCAG corresponding with p.Gln480ins) in exon 11 of chromosome 4 in bone morphogenetic proteins-2-inducible kinase (BMP2K) were identified; these were found in members of the pedigree affected by DDH and in the unaffected grandmother of the proband, who was deemed to be the carrier of potential mutations, but not in the unaffected normal control saunt of the proband. These two variants shared the same genomic coordinate but with different types of mutation in BMP2K. BMP2K is known to be associated with bone and cartridge development and heterozygous mutations were found to be present in 4/4 (100%) of the affected family members, 4/15 (26.7%) of the unaffected family members and 0/7 (0%) of the unaffected unrelated family members. Genotyping of 37 unrelated, sporadic DDH patients showed that three cases were positive for the BMP2K c.1432_1440delCAGCAGCAG variants (8.12%). These findings provided strong evidence for the role of BMP2K variants in causing DDH and demonstrated that the combination of pedigree information and next-generation sequencing is an effective method for identifying pathogenic sites associated with DDH.

Protective effects of remifentanil against H2O2-induced oxidative stress in human osteoblasts

BACKGROUND

Bone injury is common in many clinical situations, such as surgery or trauma. During surgery, excessive reactive oxygen species (ROS) production decreases the quality and quantity of osteoblasts. Remifentanil decreases ROS production, reducing oxidative stress and the inflammatory response. We investigated remifentanil's protective effects against H₂O₂-induced oxidative stress in osteoblasts.

METHODS

To investigate the effect of remifentanil on human fetal osteoblast (hFOB) cells, the cells were incubated with 1 ng/ml of remifentanil for 2 h before exposure to H₂O₂. For induction of oxidative stress, hFOB cells were then treated with 200 µM H₂O₂ for 2 h. To evaluate the effect on autophagy, a separate group of cells were incubated with 1 mM 3-methyladenine (3-MA) before treatment with remifentanil and H₂O₂. Cell viability and apoptotic cell death were determined via MTT assay and Hoechst staining, respectively. Mineralized matrix formation was visualized using alizarin red S staining. Western blot analysis was used to determine the expression levels of bone-related genes.

RESULTS

Cell viability and mineralized matrix formation increased on remifentanil pretreatment before exposure to H₂O₂-induced oxidative stress. As determined via western blot analysis, remifentanil pretreatment increased the expression of bone-related genes (Col I, BMP-2, osterix, and TGF-β). However , pretreatment with 3-MA before exposure to remifentanil and H₂O₂ inhibited remifentanil's protective effects on hFOB cells during oxidative stress.

CONCLUSIONS

We showed that remifentanil prevents oxidative damage in hFOB cells via a mechanism that may be highly related to autophagy. Further clinical studies are required to investigate its potential as a therapeutic agent.

Bone morphogenetic proteins and their antagonists: current and emerging clinical uses

Bone morphogenetic proteins (BMPs) are members of the TGFβ superfamily of secreted cysteine knot proteins that includes TGFβ1, nodal, activins and inhibins. BMPs were first discovered by Urist in the 1960s when he showed that implantation of demineralized bone into intramuscular tissue of rabbits induced bone and cartilage formation. Since this seminal discovery, BMPs have also been shown to play key roles in several other biological processes, including limb, kidney, skin, hair and neuronal development, as well as maintaining vascular homeostasis. The multifunctional effects of BMPs make them attractive targets for the treatment of several pathologies, including bone disorders, kidney and lung fibrosis, and cancer. This review will summarize current knowledge on the BMP signalling pathway and critically evaluate the potential of recombinant BMPs as pharmacological agents for the treatment of bone repair and tissue fibrosis in patients.

Effects of propofol-induced autophagy against oxidative stress in human osteoblasts

Background

Oxidative stress occurs during the aging process and other conditions such as bone fracture, bone diseases, and osteoporosis, but the role of oxidative stress in bone remodeling is unknown. Propofol exerts antioxidant effects, but the mechanisms of propofol preconditioning on oxidative stress have not been fully explained. Therefore, the aim of this study was to evaluate the protective effects of propofol against H₂O₂-induced oxidative stress on a human fetal osteoblast (hFOB) cell line via activation of autophagy.

Methods

Cells were randomly divided into the following groups: control cells were incubated in normoxia (5% CO₂, 21% O₂, and 74% N₂) without propofol. Hydrogen peroxide (H₂O₂) group cells were exposed to H₂O₂ (200 µM) for 2 h, propofol preconditioning (PPC)/H₂O₂ group cells were pretreated with propofol then exposed to H₂O₂, 3-methyladenine (3-MA)/PPC/H₂O₂ cells were pretreated with 3-MA (1 mM) and propofol, then were exposed to H₂O₂. Cell viability and apoptosis were evaluated. Osteoblast maturation was determined by assaying bone nodular mineralization. Expression levels of bone related proteins were determined by western blot.

Results

Cell viability and bone nodular mineralization were decreased significantly by H₂O₂, and this effect was rescued by propofol preconditioning. Propofol preconditioning effectively decreased H₂O₂-induced hFOB cell apoptosis. However, pretreatment with 3-MA inhibited the protective effect of propofol. In western blot analysis, propofol preconditioning increased protein levels of collagen type I, BMP-2, osterix, and TGF-β1.

Conclusions

This study suggests that propofol preconditioning has a protective effect on H₂O₂-induced hFOB cell death, which is mediated by autophagy activation.

Anabolic and Antiresorptive Modulation of Bone Homeostasis by the Epigenetic Modulator Sulforaphane, a Naturally Occurring Isothiocyanate

Bone degenerative pathologies like osteoporosis may be initiated by age-related shifts in anabolic and catabolic responses that control bone homeostasis. Here we show that sulforaphane (SFN), a naturally occurring isothiocyanate, promotes osteoblast differentiation by epigenetic mechanisms. SFN enhances active DNA demethylation viaTet1andTet2and promotes preosteoblast differentiation by enhancing extracellular matrix mineralization and the expression of osteoblastic markers (Runx2,Col1a1,Bglap2,Sp7,Atf4, andAlpl). SFN decreases the expression of the osteoclast activator receptor activator of nuclear factor-κB ligand (RANKL) in osteocytes and mouse calvarial explants and preferentially induces apoptosis in preosteoclastic cells via up-regulation of theTet1/Fas/Caspase 8 and Caspase 3/7 pathway. These mechanistic effects correlate with higher bone volume (∼20%) in both normal and ovariectomized mice treated with SFN for 5 weeks compared with untreated mice as determined by microcomputed tomography. This effect is due to a higher trabecular number in these mice. Importantly, no shifts in mineral density distribution are observed upon SFN treatment as measured by quantitative backscattered electron imaging. Our data indicate that the food-derived compound SFN epigenetically stimulates osteoblast activity and diminishes osteoclast bone resorption, shifting the balance of bone homeostasis and favoring bone acquisition and/or mitigation of bone resorptionin vivo Thus, SFN is a member of a new class of epigenetic compounds that could be considered for novel strategies to counteract osteoporosis.

BMP-2 Enhances Lgr4 Gene Expression in Osteoblastic Cells

Osteoporosis is one of the most prevalent diseases and the number of patients suffering from this disease is soaring due to the increase in the aged population in the world. The severity of bone loss in osteoporosis is based on the levels of impairment in the balance between bone formation and bone resorption, two arms of the bone metabolism, and bone remodeling. However, determination of bone formation levels is under many layers of control that are as yet fully defined. Bone morphogenetic protein (BMP) plays a key role in regulation of bone formation while its downstream targets are still incompletely understood. Lgr4 gene encodes an orphan receptor and has been identified as a genetic determinant for bone mass in osteoporotic patients. Here, we examine the effects of BMP on the expression of Lgr4 in osteoblastic cells. Lgr4 gene is expressed in an osteoblastic cell line, MC3T3E1 in a time dependent manner during the culture. BMP treatment enhances Lgr4 mRNA expression at least in part via transcriptional event. When Lgr4 mRNA is knocked down, the levels of BMP-induced increase in alkaline phosphatase (Alp) activity and Alp mRNA are suppressed. BMP enhancement of Lgr4 gene expression is suppressed by FGF and reversed by dexamethasone. BMP also enhances Lgr4 expression in primary cultures of calvarial osteoblasts. These data indicate that Lgr4 gene is regulated by BMP and is required for BMP effects on osteoblastic differentiation. J. Cell. Physiol. 231: 887-895, 2016. © 2015 Wiley Periodicals, Inc.

The effect of low-level diode laser therapy on early differentiation of osteoblast via BMP-2/TGF-β1 and its receptors

OBJECTIVES

The objective of this study was to determine the effect of LLDL therapy on the gene expression of osteoblast markers of growth and differentiation.

MATERIALS AND METHODS

The MG-63 cell line was exposed to diode laser (ezLase) of 940 nm at 1-1.5 W and 3-4 J, and gene expressions (Runx-2, alkaline phosphatase [ALP], type I collagen [Col-I], osterix [OSX], osteocalcin [OSC], osteoprotegerin [OPG], bone morphogenetic protein [BMP]-2 and -7, transforming growth factor-β1 [TGF-β1], and TGF-β receptors [TGF-β R1, TGF-β R2; TGF-β R3]) were evaluated by quantitative RT-PCR.

RESULTS

LLDL treatment stimulated the expression of osteoblast differentiation markers ALP, Col-I, Runx-2, and OSX in relation to the doses applied (P < 0.05), but no changes were detected in OSC, OPG, or BMP-7 at any study dose. This effect may be mediated by TGF-β1 and BMP-2, given that the treatment increased their expression and that of TGF-β receptors R1, R2, and R3 (P < 0.001).

CONCLUSION

These results suggest that the biostimulatory effect of laser therapy on osteoblasts may be attributable to the release of autocrine factors in response to the irradiation. A clinical trial is warranted to test its therapeutic usefulness in bone tissue regeneration and to define a treatment protocol.

TGF-β/BMP signaling and other molecular events: regulation of osteoblastogenesis and bone formation

Transforming growth factor-beta (TGF-β)/bone morphogenetic protein (BMP) plays a fundamental role in the regulation of bone organogenesis through the activation of receptor serine/threonine kinases. Perturbations of TGF-β/BMP activity are almost invariably linked to a wide variety of clinical outcomes, i.e., skeletal, extra skeletal anomalies, autoimmune, cancer, and cardiovascular diseases. Phosphorylation of TGF-β (I/II) or BMP receptors activates intracellular downstream Smads, the transducer of TGF-β/BMP signals. This signaling is modulated by various factors and pathways, including transcription factor Runx2. The signaling network in skeletal development and bone formation is overwhelmingly complex and highly time and space specific. Additive, positive, negative, or synergistic effects are observed when TGF-β/BMP interacts with the pathways of MAPK, Wnt, Hedgehog (Hh), Notch, Akt/mTOR, and miRNA to regulate the effects of BMP-induced signaling in bone dynamics. Accumulating evidence indicates that Runx2 is the key integrator, whereas Hh is a possible modulator, miRNAs are regulators, and β-catenin is a mediator/regulator within the extensive intracellular network. This review focuses on the activation of BMP signaling and interaction with other regulatory components and pathways highlighting the molecular mechanisms regarding TGF-β/BMP function and regulation that could allow understanding the complexity of bone tissue dynamics.

Skeletal muscle is an endocrine organ

Skeletal muscle plays a key role in postural retention as well as locomotion for maintaining the physical activities of human life. Skeletal muscle has a second role as an elaborate energy production and consumption system that influences the whole body's energy metabolism. Skeletal muscle is a specific organ that engenders a physical force, and exercise training has been known to bring about multiple benefits for human health maintenance and/or improvement. The mechanisms underlying the improvement of the human physical condition have been revealed: skeletal muscle synthesizes and secretes multiple factors, and these muscle-derived factors, so-called as myokines, exert beneficial effects on peripheral and remote organs. In this short review, we focus on the third aspect of skeletal muscle function - namely, the release of multiple types of myokines, which constitute a broad network for regulating the function of remote organs as well as skeletal muscle itself. We conclusively show that skeletal muscle is one of the endocrine organs and that understanding the mechanisms of production and secretion of myokines may lead to a new pharmacological approach for treatment of clinical disorders.

Effects of Remifentanil Preconditioning on Osteoblasts under Hypoxia-Reoxygenation Condition

BACKGROUND

Ischemia-reperfusion of bone occurs in a variety of clinical conditions, such as orthopedic arthroplasty, plastic gnathoplasty, spinal surgery, and amputation. Usually, cellular models of hypoxia-reoxygenation reflect in vivo models of ischemia-reperfusion. With respect to hypoxia-reoxygenation conditions, the effects of remifentanil on osteogenesis have received little attention. Therefore, we investigated the effects of remifentanil on the proliferation and differentiation of osteoblasts during hypoxic-reoxygenation.

METHODS

After remifentanil (0.1, 1 ng/mL) preconditioning for 2 hours, human osteoblasts were cultured under 1% oxygen tension for 24 hours. Thereafter, the cells were reoxygenated for 12 hours at 37 °C. The naloxone groups were treated with naloxone for 30 minutes before remifentanil treatment. We measured cell viability via MTT assay. Osteoblast maturation was determined by assay of bone nodular mineralization. Quantitative PCR and western blot methods were used to determine BMP-2, osteocalcin, Akt, type I collagen, osterix, TGF-β1, HIF-1α, and RUNX2 expression levels.

RESULTS

Osteoblast viability and bone nodular mineralization by osteoblasts is recovered by remifentanil preconditioning from hypoxia-reoxygenation insult. During hypoxic-reoxygenation condition, remifentanil preconditioning induced the expression of BMP-2, osteocalcin, Akt, type I collagen, osterix, TGF-β1, HIF-1α, and RUNX2 in osteoblasts.

CONCLUSIONS

Under hypoxia-reoxygenation conditions, remifentanil preconditioning enhanced the cell viability and maturation of osteoblasts, and stimulated the expression of proteins associated with osteoblast proliferation and differentiation of the osteoblast. Our results suggest that remifentanil may help in the treatment of bone stress injuries.

Proteomics approaches for the studies of bone metabolism

Bone is an active tissue, in which bone formation by osteoblast is followed by bone resorption by osteoclasts, in a repeating cycle. Proteomics approaches may allow the detection of changes in cell signal transduction, and the regulatory mechanism of cell differentiation. LC-MS/MS-based quantitative methods can be used with labeling strategies, such as SILAC, iTRAQ, TMT and enzymatic labeling. When used in combination with specific protein enrichment strategies, quantitative proteomics methods can identify various signaling molecules and modulators, and their interacting proteins in bone metabolism, to elucidate biological functions for the newly identified proteins in the cellular context. In this article, we will briefly review recent major advances in the application of proteomics for bone biology, especially from the aspect of cellular signaling. [BMB Reports 2014; 47(3): 141-148]

Acute-phase protein serum amyloid A3 is a novel paracrine coupling factor that controls bone homeostasis

Serum amyloid A (A-SAA/Saa3) was shown before to affect osteoblastic metabolism. Here, using RT-quantitative PCR and/or immunoblotting, we show that expression of mouse Saa3 and human SAA1 and SAA2 positively correlates with increased cellular maturation toward the osteocyte phenotype. Expression is not detected in C3H10T1/2 embryonic fibroblasts but is successively higher in preosteoblastic MC3T3-E1 cells, late osteoblastic MLO-A5 cells, and MLO-Y4 osteocytes, consistent with findings using primary bone cells from newborn mouse calvaria. Recombinant Saa3 protein functionally inhibits osteoblast differentiation as reflected by reductions in the expression of osteoblast markers and decreased mineralization in newborn mouse calvaria. Yet, Saa3 protein enhances osteoclastogenesis in mouse macrophages/monocytes based on the number of multinucleated and tartrate-resistant alkaline phosphatase-positive cells and Calcr mRNA expression. Depletion of Saa3 in MLO osteocytes results in the loss of the mature osteocyte phenotype. Recombinant osteocalcin, which is reciprocally regulated with Saa3 at the osteoblast/osteocyte transition, attenuates Saa3 expression in MLO-Y4 osteocytes. Mechanistically, Saa3 produced by MLO-Y4 osteocytes is integrated into the extracellular matrix of MC3T3-E1 osteoblasts, where it associates with the P2 purinergic receptor P2rx7 to stimulate Mmp13 expression via the P2rx7/MAPK/ERK/activator protein 1 axis. Our data suggest that Saa3 may function as an important coupling factor in bone development and homeostasis.

Roles of bone morphogenetic protein signaling in osteosarcoma

PURPOSE

Since the original extraction of bone morphogenetic proteins (BMPs) from bovine bone, research interest and clinical use has increased exponentially. With this, a concomitant analysis of BMP expression in bone tumours has been performed. BMP ligands, receptors, and signaling activity have been observed in diverse benign and malignant bone tumours. However, the reported expression, function, and importance of BMPs in bone tumours, and specifically osteosarcomas, have been far from uniform. This review highlights recent advances in understanding the role of BMP signaling in osteosarcoma biology, focusing on the sometimes divergent findings by various researchers and the challenges inherent in the study of osteosarcoma.

METHODS

We performed a literature review of all studies examining BMP signaling in osteosarcoma.

RESULTS

Overall, multiple BMP ligands and receptors are expressed in most osteosarcoma cell lines and subtypes, although BMP signaling may be reduced in comparison with benign bone-forming tumours. Studies suggest that osteosarcomas with different lineages of differentiation may have differential expression of BMP ligands. Although significant disagreement in the literature exists, the presence of BMP signaling in osteosarcoma may impart a worse prognosis. On the cellular level, BMP signaling appears to mediate promigratory effects in osteosarcoma and chondrosarcoma cell types, possibly via interaction and activation of Integrin β1.

CONCLUSIONS

BMP signaling has clear biologic importance in osteosarcoma, although it is not yet fully understood. Future questions for study include assessing the utility of BMP signaling in prognostication of osteosarcoma and the potential modulation of BMP signaling for inhibition of osteosarcomagenesis, growth and invasion.

FGFR3 induces degradation of BMP type I receptor to regulate skeletal development

Fibroblast growth factors (FGFs) and their receptors (FGFRs) play significant roles in vertebrate organogenesis and morphogenesis. FGFR3 is a negative regulator of chondrogenesis and multiple mutations with constitutive activity of FGFR3 result in achondroplasia, one of the most common dwarfisms in humans, but the molecular mechanism remains elusive. In this study, we found that chondrocyte-specific deletion of BMP type I receptor a (Bmpr1a) rescued the bone overgrowth phenotype observed in Fgfr3 deficient mice by reducing chondrocyte differentiation. Consistently, using in vitro chondrogenic differentiation assay system, we demonstrated that FGFR3 inhibited BMPR1a-mediated chondrogenic differentiation. Furthermore, we showed that FGFR3 hyper-activation resulted in impaired BMP signaling in chondrocytes of mouse growth plates. We also found that FGFR3 inhibited BMP-2- or constitutively activated BMPR1-induced phosphorylation of Smads through a mechanism independent of its tyrosine kinase activity. We found that FGFR3 facilitates BMPR1a to degradation through Smurf1-mediated ubiquitination pathway. We demonstrated that down-regulation of BMP signaling by BMPR1 inhibitor dorsomorphin led to the retardation of chondrogenic differentiation, which mimics the effect of FGF-2 on chondrocytes and BMP-2 treatment partially rescued the retarded growth of cultured bone rudiments from thanatophoric dysplasia type II mice. Our findings reveal that FGFR3 promotes the degradation of BMPR1a, which plays an important role in the pathogenesis of FGFR3-related skeletal dysplasia.

Molecular mechanisms of mesenchymal stem cell differentiation towards osteoblasts

Bone is a dynamic tissue that is constantly renewed by the coordinated action of two cell types, i.e., the bone-resorbing osteoclasts and the bone-forming osteoblasts. However, in some circumstances, bone regeneration exceeds bone self repair capacities. This is notably often the case after bone fractures, osteolytic bone tumor surgery, or osteonecrosis. In this regard, bone tissue engineering with autologous or allogenic mesenchymal stem cells (MSCs) is been widely developed. MSCs can be isolated from bone marrow or other tissues such as adipose tissue or umbilical cord, and can be implanted in bone defects with or without prior amplification and stimulation. However, the outcome of most pre-clinical studies remains relatively disappointing. A better understanding of the successive steps and molecular mechanisms involved in MSC-osteoblastic differentiation appears to be crucial to optimize MSC-bone therapy. In this review, we first present the important growth factors that stimulate osteoblastogenesis. Then we review the main transcription factors that modulate osteoblast differentiation, and the microRNAs (miRs) that inhibit their expression. Finally, we also discuss articles dealing with the use of these factors and miRs in the development of new bone MSC therapy strategies. We particularly focus on the studies using human MSCs, since significant differences exist between osteoblast differentiation mechanisms in humans and mice for instance.