Human bone sialoprotein. Deduced protein sequence and chromosomal localization

The immune duality of osteopontin and its therapeutic implications for kidney transplantation

Osteopontin (OPN) is a multifunctional glycoprotein with various structural domains that enable it to perform diverse functions in both physiological and pathological states. This review comprehensively examines OPN from multiple perspectives, including its protein structure, interactions with receptors, interactions with immune cells, and roles in kidney diseases and transplantation. This review explores the immunological duality of OPN and its significance and value as a biomarker and therapeutic target in kidney transplantation. In cancer, OPN typically promotes tumor evasion by suppressing the immune system. Conversely, in immune-related kidney diseases, particularly kidney transplantation, OPN activates the immune system by enhancing the migration and activation of immune cells, thereby exacerbating kidney damage. This immunological duality may stem from different OPN splice variants and the exposure, after cleavage, of different structural domains, which play distinct biological roles in cellular interactions. Additionally, OPN has a significant biological impact posttransplantation and on chronic kidney disease and, highlighting its importance as a biomarker and potential therapeutic target. Future research should further explore the specific mechanisms of OPN in kidney transplantation to improve treatment strategies and enhance patient quality of life.

Development of artificial bone graft via in vitro endochondral ossification (ECO) strategy for bone repair

Endochondral ossification (ECO) is a form of bone formation whereby the newly deposited bone replaces the cartilage template. A decellularized artificial cartilage graft (dLhCG), which is composed of hyaline cartilage matrixes, has been developed in our previous study. Herein, the osteogenesis of bone marrow-derived MSCs in the dLhCG through chondrogenic differentiation, chondrocyte hypertrophy, and subsequent transdifferentiation induction has been investigated by simulating the physiological processes of ECO for repairing critical-sized bone defects. The MSCs were recellularized into dLhCGs and subsequently allowed to undergo a 14-day proliferation period (mrLhCG). Following this, the mrLhCG constructs were subjected to two distinct differentiation induction protocols to achieve osteogenic differentiation: chondrogenic medium followed by chondrocytes culture medium with a high concentration of fetal bovine serum (CGCC group) and canonical osteogenesis inducing medium (OI group). The formation of a newly developed artificial bone graft, ossified dLhCG (OsLhCG), as well as its capability of aiding bone defect reconstruction were characterized by in vitro and in vivo trials, such as mRNA sequencing, quantitative real-time PCR (qPCR), immunohistochemistry, the greater omentum implantation in nude mice, and repair for the critical-sized femoral defects in rats. The results reveal that the differentiation induction of MSCs in the CGCC group can realize in vitro ECO through chondrogenic differentiation, hypertrophy, and transdifferentiation, while the MSCs in the OI group, as expected, realize ossification through direct osteogenic differentiation. The angiogenesis and osteogenesis of OsLhCG were proved by being implanted into the greater omentum of nude mice. Besides, the OsLhCG exhibits the capability to achieve the repair of critical-size femoral defects.

Silver-releasing bioactive glass nanoparticles for infected tissue regeneration

Bacterial infections represent a formidable challenge, often leaving behind significant bone defects post-debridement and necessitating prolonged antibiotic treatments. The rise of antibiotic-resistant bacterial strains further complicates infection management. Bioactive glass nanoparticles have been presented as a promising substitute for bone defects and as carriers for therapeutic agents against microorganisms. Achieving consistent incorporation of ions into BGNs has proven challenging and restricted to a maximum ion concentration, especially when reducing the particle size. This study presents a notable achievement in the synthesis of 10 nm-sized Ag-doped bioactive glass nanoparticles (Ag-BGNs) using a modified yet straightforward Stöber method. The successful incorporation of essential elements, including P, Ca, Al, and Ag, into the glass structure at the intended concentrations (i.e., CaO wt% above 20 %) was confirmed by EDS, signifying a significant advancement in nanoscale biomaterial engineering. While exhibiting a spherical morphology and moderate dispersity, these nanoparticles tend to form submicron-sized aggregates outside of a solution state. The antibacterial effectiveness against MRSA was established across various experimental conditions, with Ag-BGNs effectively sterilizing planktonic bacteria without the need for antibiotics. Remarkably, when combined with oxacillin or fosfomycin, Ag-BGNs demonstrated a potent synergistic effect, restoring antibacterial capabilities against MRSA strains resistant to these antibiotics when used alone. Ag-BGNs exhibited potential in promoting human mesenchymal stromal cell proliferation, inducing the upregulation of osteoblast gene markers, and significantly contributing to bone regeneration in mice. This innovative synthesis protocol holds substantial promise for the development of biomaterials dedicated to the regeneration of infected tissue.

Early induction of Hes1 by bone morphogenetic protein 9 plays a regulatory role in osteoblastic differentiation of a mesenchymal stem cell line

Bone morphogenic protein 9 (BMP9) is one of the most potent inducers of osteogenic differentiation among the 14 BMP members, but its mechanism of action has not been fully demonstrated. Hes1 is a transcriptional regulator with basic helix-loop-helix (bHLH) domain and is a well-known Notch effector. In this study, we investigated the functional roles of early induction of Hes1 by BMP9 in a mouse mesenchymal stem cell line, ST2. Hes1 mRNA was transiently and periodically induced by BMP9 in ST2, which was inhibited by BMP signal inhibitors but not by Notch inhibitor. Interestingly, Hes1 knockdown in ST2 by siRNA increased the expression of osteogenic differentiation markers such as Sp7 and Ibsp and matrix mineralization in comparison with control siRNA transfected ST2. In contrast, forced expression of Hes1 by using the Tet-On system suppressed the expression of osteogenic markers and matrix mineralization by BMP9. We also found that the early induction of Hes1 by BMP9 suppressed the expression of Alk1, an essential receptor for BMP9. In conclusion, BMP9 rapidly induces the expression of Hes1 via the SMAD pathway in ST2 cells, which plays a negative regulatory role in osteogenic differentiation of mesenchymal stem cells induced by BMP9.

Long-Term Changes in Adipose Tissue in the Newly Formed Bone Induced by Recombinant Human BMP-2 In Vivo

Recombinant human bone morphogenetic protein-2 (rhBMP-2) induces osteogenesis and adipogenesis in bone scaffolds. We evaluated rhBMP-2-induced long-term changes in adipose tissue in the newly formed bone in different scaffolds forms. Bovine bone particles and blocks were grafted along with rhBMP-2 in the subperiosteal space of a rat calvarial bone, and the formation of new bone and adipose tissue were evaluated at 6 and 16 weeks after the surgery. The bone mineral density (BMD) and trabecular thickness (TbTh) of the 16w particle group were significantly higher than those of the 6w particle group (p = 0.018 and 0.012, respectively). The BMD and TbTh gradually increased in the particle group from weeks 6 to 16. The average adipose tissue volume (ATV) of the 6w particle group was higher than that of the 16w particle group, although the difference was not significant (p > 0.05), and it decreased gradually. There were no significant changes in the bone volume (BV) and BMD between the 6w and 16w block groups. Histological analysis revealed favorable new bone regeneration in all groups. Adipose tissue was formed between the bone particles and at the center in the particle and block groups, respectively. The adipose tissue space decreased, and the proportion of new bone increased in the 16w particle group compared to that in the 6w group. To summarize, in the particle group, the adipose tissue decreased in a time-dependent manner, BMD and TbTh increased, and new bone formation increased from 6 to 16 weeks. These results suggest that rhBMP-2 effectively induces new bone formation in the long term in particle bone scaffolds.

Selective Grafting of Protease-Resistant Adhesive Peptides on Titanium Surfaces

In orthopedic, dental, and maxillofacial fields, joint prostheses, plates, and screws are widely used in the treatment of problems related to bone tissue. However, the use of these prosthetic systems is not free from complications: the fibrotic encapsulation of endosseous implants often prevents optimal integration of the prostheses with the surrounding bone. To overcome these issues, biomimetic titanium implants have been developed where synthetic peptides have been selectively grafted on titanium surfaces via Schiff base formation. We used the retro-inverted sequence (DHVPX) from [351-359] human Vitronectin and its dimer (D2HVP). Both protease-resistant peptides showed increased human osteoblast adhesion and proliferation, an augmented number of focal adhesions, and cellular spreading with respect to the control. D2HVP-grafted samples significantly enhance Secreted Phosphoprotein 1, Integrin Binding Sialoprotein, and Vitronectin gene expression vs. control. An estimation of peptide surface density was determined by Two-photon microscopy analysis on a silanized glass model surface labeled with a fluorescent analog.

Impact of Cross-Linked Hyaluronic Acid on Osteogenic Differentiation of SAOS-2 Cells in an Air-Lift Model

The aim of this study was to investigate the impact of cross-linked hyaluronic acid on osteoblast-like cells seeded on top of two collagen substrates, native porcine pericardium membrane (substrate A) and ribose cross-linked collagen membranes (substrate B), in an air-lift model. Substrates A or B, saturated with three hyaluronic acid concentrations, served as membranes for SAOS-2 cells seeded on top. Cultivation followed for 7 and 14 days in the air-lift model. Controls used the same substrates without hyaluronic pre-treatment. Cells were harvested, and four (Runx2, BGLAP, IBSP, Cx43) different osteogenic differentiation markers were assessed by qPCR. Triplicated experiment outcomes were statistically analyzed (ANOVA, t-test; SPSS). Supplementary histologic analysis confirmed the cells' vitality. After seven days, only few markers were overexpressed on both substrates. After 14 days, targeted genes were highly expressed on substrate A. The same substrate treated with 1:100 diluted xHyA disclosed statistically significant different expression level vs. substrate B (p = 0.032). Time (p = 0.0001), experimental condition as a function of time (p = 0.022), and substrate (p = 0.028) were statistically significant factors. Histological imaging demonstrated vitality and visualized nuclei. We conclude that the impact of hyaluronic acid resulted in a higher expression profile of SAOS-2 cells on substrate A compared to substrate B in an air-lift culture after two weeks.

Does the RGD region of certain proteins affect metabolic activity?

A better understanding of the role of mineralized tissues and their associated factors in governing whole-body metabolism should be of value toward informing clinical strategies to treat mineralized tissue and metabolic disorders, such as diabetes and obesity. This perspective provides evidence suggesting a role for the arginine-glycine-aspartic acid (RGD) region, a sequence identified in several proteins secreted by bone cells, as well as other cells, in modulating systemic metabolic activity. We focus on (a) two of the SIBLING (small integrin-binding ligand, N-linked glycoprotein) family genes/proteins, bone sialoprotein (BSP) and osteopontin (OPN), (b) insulin-like growth factor-binding protein-1 & 2 (IGFBP-1, IGFBP-2) and (c) developmental endothelial locus 1 (DEL1) and milk fat globule–EGF factor-8 (MFG-E8). In addition, for our readers to appreciate the mounting evidence that a multitude of bone secreted factors affect the activity of other tissues, we provide a brief overview of other proteins, to include fibroblast growth factor 23 (FGF23), phosphatase orphan 1 (PHOSPHO1), osteocalcin (OCN/BGLAP), tissue non-specific alkaline phosphatase (TNAP) and acidic serine aspartic-rich MEPE-associated motif (ASARM), along with known/suggested functions of these factors in influencing energy metabolism.

Comparative Transcriptome Analysis of Human Adipose-Derived Stem Cells Undergoing Osteogenesis in 2D and 3D Culture Conditions

Human adipose-derived stem cells (hADSCs) are types of mesenchymal stem cells (MSCs) that have been used as tissue engineering models for bone, cartilage, muscle, marrow stroma, tendon, fat and other connective tissues. Tissue regeneration materials composed of hADSCs have the potential to play an important role in reconstituting damaged tissue or diseased mesenchymal tissue. In this study, we assessed and investigated the osteogenesis of hADSCs in both two-dimensional (2D) and three-dimensional (3D) culture conditions. We confirmed that the hADSCs successfully differentiated into bone tissues by ARS staining and quantitative RT–PCR. To gain insight into the detailed biological difference between the two culture conditions, we profiled the overall gene expression by analyzing the whole transcriptome sequencing data using various bioinformatic methods. We profiled the overall gene expression through RNA-Seq and further analyzed this using various bioinformatic methods. During differential gene expression testing, significant differences in the gene expressions between hADSCs cultured in 2D and 3D conditions were observed. The genes related to skeletal development, bone development and bone remodeling processes were overexpressed in the 3D culture condition as compared to the 2D culture condition. In summary, our RNA-Seq-based study proves effective in providing new insights that contribute toward achieving a genome-wide understanding of gene regulation in mesenchymal stem cell osteogenic differentiation and bone tissue regeneration within the 3D culture system.

Silver-doped bioactive glass particles for in vivo bone tissue regeneration and enhanced methicillin-resistant Staphylococcus aureus (MRSA) inhibition

Infection is a significant risk factor for failed healing of bone and other tissues. We have developed a sol-gel (solution-gelation) derived bioactive glass doped with silver ions (Ag-BG), tailored to provide non-cytotoxic antibacterial activity while significantly enhancing osteoblast-lineage cell growth in vitro and bone regeneration in vivo. Our objective was to engineer a biomaterial that combats bacterial infection while maintaining the capability to promote bone growth. We observed that Ag-BG inhibits bacterial growth and potentiates the efficacy of conventional antibiotic treatment. Ag-BG microparticles enhance cell proliferation and osteogenic differentiation in human bone marrow stromal cells (hBMSC) in vitro. Moreover, in vivo tests using a calvarial defect model in mice demonstrated that Ag-BG microparticles induce bone regeneration. This novel system with dual biological and advanced antibacterial properties is a promising therapeutic for combating resistant bacteria while triggering new bone formation.

Synovial bone sialoprotein indicates aseptic failure in total joint arthroplasty

Background

Until today, a reliable diagnostic discrimination between periprosthetic joint infections (PJI) and aseptic failure (AF) after total joint arthroplasty (TJA) remains challenging. Nearly all recent research focused on synovial markers to be elevated in PJI rather than in AF patients. In this study, synovial bone sialoprotein (sBSP) was investigated in PJI and AF arthroplasty patients before revision surgery.

Methods

sBSP and C-reactive protein (CRP) were determined in synovial fluid samples of PJI (n = 13) patients fulfilling the MSIS criteria and AF (n = 25) patients. Beside descriptive analysis and comparison, computed statistics determined the area under the receiver operating characteristics curve (AUC) to evaluate the discrimination ability of the tested synovial markers.

Results

In patients with PJI according to the MSIS criteria, mean sBSP was significantly lower: 14.8 ng/ml (95% CI 5.5-24.1) vs. 38.2 ng/ml in the AF group (95% CI 31.1-45.3), p ≤ 0.001. Conversely, mean sCRP was significantly higher in PJI patients: 8.4 μg/ml (95% CI 0-17.2) vs. 1.8 μg/ml in the AF group (95% CI 0.9-2.8), p = 0.032. The AUC of sCRP in PJI patients was 0.71. The AUC of sBSP in AF revision arthroplasty patients was 0.83. The detection of osteolyses was not associated with higher sBSP concentrations.

Conclusions

Considering the MSIS criteria, significantly higher sBSP concentrations were found in synovial fluid samples of AF compared to PJI patients. sCRP showed only fair, sBSP good discrimination potential. If it is not clear whether PJI is present or not, sBSP may be considered as an add-on synovial marker.

Coral acid rich protein selects vaterite polymorph in vitro

Corals and other biomineralizing organisms use proteins and other molecules to form different crystalline polymorphs and biomineral structures. In corals, it’s been suggested that proteins such as Coral Acid Rich Proteins (CARPs) play a major role in the polymorph selection of their calcium carbonate (CaCO₃) aragonite exoskeleton. To date, four CARPs (1–4) have been characterized: each with a different amino acid composition and different temporal and spatial expression patterns during coral developmental stages. Interestingly, CARP3 is able to alter crystallization pathways in vitro, yet its function in this process remains enigmatic. To better understand the CARP3 function, we performed two independent in vitro CaCO₃ polymorph selection experiments using purified recombinant CARP3 at different concentrations and at low or zero Mg²⁺ concentration. Our results show that, in the absence of Mg²⁺, CARP3 selects for the vaterite polymorph and inhibits calcite. However, in the presence of a low concentration of Mg²⁺ and CARP3 both Mg-calcite and vaterite are formed, with the relative amount of Mg-calcite increasing with CARP3 concentration. In all conditions, CARP3 did not select for the aragonite polymorph, which is the polymorph associated to CARP3 in vivo, even in the presence of Mg²⁺ (Mg:Ca molar ratio equal to 1). These results further emphasize the importance of Mg:Ca molar ratios similar to that in seawater (Mg:Ca equal to 5) and the activity of the biological system in a aragonite polymorph selection in coral skeleton formation.

Stathmin regulates the proliferation and odontoblastic/osteogenic differentiation of human dental pulp stem cells through Wnt/β-catenin signaling pathway

Odontoblastic/osteogenic differentiation of human dental pulp stem cells (hDPSCs) is a key factor in tooth and pulp regeneration, but its mechanism still remains unknown. The purpose of this research is to look into the mechanism by which Stathmin affects the proliferation and odontoblastic/osteogenic differentiation of hDPSCs, and whether the Wnt/β- catenin is related to this regulation. First, the Stathmin expression was inhibited by lentiviral vector, after that the transcriptome sequencing technology was used to screen the differentially expressed genes, then we found Wnt5a which related to the regulation of Wnt/β-catenin was regulated. Comparing with hDPSC in the control group, the shRNA-Stathmin group inhibited proliferation and odontoblastic/osteogenic differentiation. The result of molecular analysis indicated that the Wnt/β-catenin was inhibited when Stathmin was silenced. After that, the shRNA-Stathmin group were added with LiCl (activator of Wnt/β-catenin), and the Wnt/β-catenin was significantly activated in β-catenin. After activation of the Wnt/β-catenin, the proliferation of hDPSCs was significantly increased and the expression of genes related to odontoblastic/osteogenic differentiation was also significantly increased. Taken together, these findings reveal for the first time that the Stathmin-Wnt/β-catenin plays a positive regulatory role in hDPSC proliferation and odontoblastic/osteogenic differentiation. SIGNIFICANCE: Transcriptome sequencing revealed that Stathmin interacts with Wnt/β-catenin signaling pathway-related proteins such as Wnt5a. At the same time, experiments have confirmed that Stathmin protein can affect the proliferation and odontogenetic differentiation of hDPSCs.The innovation of this paper is to link the Stathmin and Wnt/β-catenin signaling pathways for the first time, to explore the interaction of Stathmin and Wnt/β-catenin signaling pathways and the mechanism of this regulation on human dental pulp stem cells (hDPSCs) of odontoblastic/osteogenic differentiation and proliferation function. Especially for the regulation of odontoblastic/osteogenic differentiation, we have verified this mechanism at the molecular level and characterization leveland this regulation also provides new ideas for dental pulp tissue engineering. At the same time, more than 3000 proteins related to the change of Stathmin level were screened by transcriptome sequencing technology, which provided a possibility to further exploration of the regulation mechanism of Stathmin on various aspects of cell biological characteristics.

Combining information from multiple bone turnover markers as diagnostic indices for osteoporosis using support vector machines

CONTEXT

Osteoporosis (OP) is a progressive systemic bone disease. Dual-energy X-ray absorptiometry (DXA) is routinely employed and is considered the gold standard method for the diagnosis of OP.

OBJECTIVE

We aimed to investigate the potential use of combined information from multiple bone turnover markers (BTMs) as a clinical diagnostic tool for OP.

MATERIALS AND METHODS

A total of 9053 Chinese postmenopausal women (2464 primary OP patients and 6589 healthy controls) were recruited. Serum levels of six common BTMs, including BAP, BSP, CTX, OPG, OST and sRANKL were assayed. Models based on support vector machine (SVM) were constructed to explore the efficiency of different combinations of multiple BTMs for OP diagnosis.

RESULTS

Increasing the number of BTMs used in generating the models increased the predictive power of the SVM models for determining the disease status of study subjects. The highest kappa coefficient for the model with one BTM (BAP) compared to DXA was 0.7783. The full model incorporating all six BTMs resulted in a high kappa coefficient of 0.9786.

CONCLUSION

Our findings showed that although single BTMs were not sufficient for OP diagnosis, appropriate combinations of multiple BTMs incorporated into the SVM models showed almost perfect agreement with the DXA.

In vitro Models of Bone Remodelling and Associated Disorders

Disruption of bone remodelling by diseases such as osteoporosis results in an imbalance between bone formation by osteoblasts and resorption by osteoclasts. Research into these metabolic bone disorders is primarily performed in vivo; however, in the last decade there has been increased interest in generating in vitro models that can reduce or replace our reliance on animal testing. With recent advances in biomaterials and tissue engineering the feasibility of laboratory-based alternatives is growing; however, to date there are no established in vitro models of bone remodelling. In vivo, remodelling is performed by organised packets of osteoblasts and osteoclasts called bone multicellular units (BMUs). The key determinant of whether osteoclasts form and remodelling occurs is the ratio between RANKL, a cytokine which stimulates osteoclastogenesis, and OPG, its inhibitor. This review initially details the different circumstances, conditions, and factors which have been found to modulate the RANKL:OPG ratio, and fundamental factors to be considered if a robust in vitro model is to be developed. Following this, an examination of what has been achieved thus far in replicating remodelling in vitro using three-dimensional co-cultures is performed, before overviewing how such systems are already being utilised in the study of associated diseases, such as metastatic cancer and dental disorders. Finally, a discussion of the most important considerations to be incorporated going forward is presented. This details the need for the use of cells capable of endogenously producing the required cytokines, application of mechanical stimulation, and the presence of appropriate hormones in order to produce a robust model of bone remodelling.

Endogenous sialic acid-engineered micelles: a multifunctional platform for on-demand methotrexate delivery and bone repair of rheumatoid arthritis

Rheumatoid arthritis (RA) patients have suffered from the current drug therapeutic regimen because of its high toxicity and the absence of bone regeneration for existing erosion, seriously affecting the quality of life. Herein, a sialic acid-dextran-octadecanoic acid (SA-Dex-OA) conjugate was synthesized to form micelles with a 55.06 μg mL^-1 critical micelle concentration. The obtained micelles can encapsulate a disease-modifying anti-rheumatic drug, methotrexate (MTX), with 4.28% (w/w) drug content, featuring sustained drug release behavior over 48 h. In vitro and in vivo studies showed that SA-Dex-OA micelles significantly improved accumulation and transportation through a combination of SA and E-selectin receptors in inflamed cells and arthritic paws highly expressing E-selectin. MTX-loaded SA-Dex-OA micelles not only significantly inhibited the inflammatory response, but also diminished the adverse effects of MTX, as reflected by the reduced alanine aminotransferase, aspartate aminotransferase, creatinine, and urea nitrogen levels. Most importantly, the bone mineral density in rats treated with MTX-loaded SA-Dex-OA micelles was significantly higher as compared to in those treated with free MTX and Dex-OA/MTX micelles (increasing from 391.4 to 417.4 to 492.7 mg cc^-1), benefiting from the effects of endogenous sialic acid in promoting MC3T3-E1 cell differentiation and mineralization. It is anticipated that SA-based micelles with bone repair activities have great potential for RA treatment and other metabolic bone diseases with serious bone erosion.

Bone biomarker for the clinical assessment of osteoporosis: recent developments and future perspectives

Bone biomarkers included formation, resorption and regulator are released during the bone remodeling processes. These bone biomarkers have attracted much attention in the clinical assessment of osteoporosis treatment in the past decade. Combination with the measurement of bone mineral density, the clinical applications of bone biomarkers have provided comprehensive information for diagnosis of osteoporosis. However, the analytical approaches of the bone biomarkers are still the challenge for further clinical trials. In this mini-review, we have introduced the functions of bone biomarkers and then recently developed techniques for bone biomarker measurements have been systematically integrated to discuss the possibility for osteoporosis assessment in the early stage.

Smart biomaterials: Surfaces functionalized with proteolytically stable osteoblast-adhesive peptides

Engineered scaffolds for bone tissue regeneration are designed to promote cell adhesion, growth, proliferation and differentiation. Recently, covalent and selective functionalization of glass and titanium surfaces with an adhesive peptide (HVP) mapped on [351-359] sequence of human Vitronectin allowed to selectively increase osteoblast attachment and adhesion strength in in vitro assays, and to promote osseointegration in in vivo studies. For the first time to our knowledge, in this study we investigated the resistance of adhesion sequences to proteolytic digestion: HVP was completely cleaved after 5 h. In order to overcome the enzymatic degradation of the native peptide under physiological conditions we synthetized three analogues of HVP sequence. A retro-inverted peptide D-2HVP, composed of D amino acids, was completely stable in serum-containing medium. In addition, glass surfaces functionalized with D-2HVP increased human osteoblast adhesion as compared to the native peptide and maintained deposition of calcium. Interestingly, D-2HVP increased expression of IBSP, VTN and SPP1 genes as compared to HVP functionalized surfaces. Total internal reflection fluorescence microscope analysis showed cells with numerous filopodia spread on D-2HVP-functionalized surfaces. Therefore, the D-2HVP sequence is proposed as new osteoblast adhesive peptide with increased bioactivity and high proteolytic resistance.

Matrix Metallopeptidase 14 Plays an Important Role in Regulating Tumorigenic Gene Expression and Invasion Ability of HeLa Cells

OBJECTIVES

The objectives of this study were to investigate the functional effect of matrix metallopeptidase 14 (MMP14) on cell invasion in cervical cancer cells (HeLa line) and to study the underlying molecular mechanisms.

METHODS

Expression vector of short hairpin RNA targeting MMP14 was treated in HeLa cells, and then, transfection efficiency was verified by a florescence microscope. Transwell assay was used to investigate cell invasion ability in HeLa cells. Quantitative polymerase chain reaction and Western blotting analysis were used to detect the expression of MMP14 and relative factors in messenger RNA and protein levels, respectively.

RESULTS

Matrix metallopeptidase 14 short hairpin RNA expression vector transfection obviously decreased MMP14 expression in messenger RNA and protein levels. Down-regulation of MMP14 suppressed invasion ability of HeLa cells and reduced transforming growth factor β1 and vascular endothelial growth factor B expressions. Furthermore, MMP14 knockdown decreased bone sialoprotein and enhanced forkhead box protein L2 expression in both RNA and protein levels.

CONCLUSION

Matrix metallopeptidase 14 plays an important role in regulating invasion of HeLa cells. Matrix metallopeptidase 14 knockdown contributes to attenuating the malignant phenotype of cervical cancer cell.

Staphylococcus aureus vs. Osteoblast: Relationship and Consequences in Osteomyelitis

Bone cells, namely osteoblasts and osteoclasts work in concert and are responsible for bone extracellular matrix formation and resorption. This homeostasis is, in part, altered during infections by Staphylococcus aureus through the induction of various responses from the osteoblasts. This includes the over-production of chemokines, cytokines and growth factors, thus suggesting a role for these cells in both innate and adaptive immunity. S. aureus decreases the activity and viability of osteoblasts, by induction of apoptosis-dependent and independent mechanisms. The tight relationship between osteoclasts and osteoblasts is also modulated by S. aureus infection. The present review provides a survey of the relevant literature discussing the important aspects of S. aureus and osteoblast interaction as well as the ability for antimicrobial peptides to kill intra-osteoblastic S. aureus, hence emphasizing the necessity for new anti-infectious therapeutics.

Electrospun Scaffolds for Osteoblast Cells: Peptide-Induced Concentration-Dependent Improvements of Polycaprolactone

The design of hybrid poly-ε-caprolactone (PCL)-self-assembling peptides (SAPs) matrices represents a simple method for the surface functionalization of synthetic scaffolds, which is essential for cell compatibility. This study investigates the influence of increasing concentrations (2.5%, 5%, 10% and 15% w/w SAP compared to PCL) of three different SAPs on the physico-chemical/mechanical and biological properties of PCL fibers. We demonstrated that physico-chemical surface characteristics were slightly improved at increasing SAP concentrations: the fiber diameter increased; surface wettability increased with the first SAP addition (2.5%) and slightly less for the following ones; SAP-surface density increased but no change in the conformation was registered. These results could allow engineering matrices with structural characteristics and desired wettability according to the needs and the cell system used. The biological and mechanical characteristics of these scaffolds showed a particular trend at increasing SAP concentrations suggesting a prevailing correlation between cell behavior and mechanical features of the matrices. As compared with bare PCL, SAP enrichment increased the number of metabolic active h-osteoblast cells, fostered the expression of specific osteoblast-related mRNA transcripts, and guided calcium deposition, revealing the potential application of PCL-SAP scaffolds for the maintenance of osteoblast phenotype.

Sustained conditional knockdown reveals intracellular bone sialoprotein as essential for breast cancer skeletal metastasis

Increased bone sialoprotein (BSP) serum levels are related to breast cancer skeletal metastasis, but their relevance is unknown. We elucidated novel intracellular BSP functions by a conditional knockdown of BSP. Conditional MDA-MB-231 subclones were equipped with a novel gene expression cassette containing a tet-regulated miRNA providing knockdown of BSP production. These clones were used to assess the effect of BSP on morphology, proliferation, migration, colony formation and gene expression in vitro, and on soft tissue and osteolytic lesions in a xenograft model by three imaging methods. BSP knockdown caused significant anti-proliferative, anti-migratory and anti-clonogenic effects in vitro (p<0.001). In vivo, significant decreases of soft tissue and osteolytic lesions (p<0.03) were recorded after 3 weeks of miRNA treatment, leading to complete remission within 6 weeks. Microarray data revealed that 0.3% of genes were modulated in response to BSP knockdown. Upregulated genes included the endoplasmic reticulum stress genes ATF3 and DDIT3, the tumor suppressor gene EGR1, ID2 (related to breast epithelial differentiation), c-FOS and SERPINB2, whereas the metastasis associated genes CD44 and IL11 were downregulated. Also, activation of apoptotic pathways was demonstrated. These results implicate that intracellular BSP is essential for breast cancer skeletal metastasis and a target for treating these lesions.

Effects of interleukin-11 on the expression of human bone sialoprotein gene

Interleukin-11 (IL-11) is a bone marrow stromal fibroblast-derived cytokine with a wide spectrum of activities in different biological systems. IL-11 and IL-6 are two cytokines known to rely on osteoblast-osteoclast communication for their effects on osteoclast differentiation. Bone sialoprotein (BSP) is a mineralized connective tissue-specific protein expressed in differentiated osteoblasts, odontoblasts, and cementoblasts. To determine the molecular basis of the transcriptional regulation of the human BSP gene by IL-11, we conducted real-time polymerase chain reactions (PCR), transient transfection analyses with chimeric constructs of the human BSP gene promoter linked to a luciferase reporter gene, gel mobility shift assays, and a chromatin immunoprecipitation assay using human osteoblast-like Saos2 cells. IL-11 (20 ng/ml) increased BSP, Runx2, and Osterix mRNA levels at 6 h and the alkaline phosphatase (ALP) mRNA level at 12 h in osteoblast-like Saos2 cells. In a transient transfection assay, IL-11 (20 ng/ml, 12 h) increased luciferase activities of constructs between -60LUC and -868LUC including the human BSP gene promoter. Transcriptional stimulations by IL-11 were partially inhibited in the constructs that included 2-bp mutations in the cAMP response element 1 (CRE1, -72 to -79) and CRE2 (-667 to -674). When mutations were made in pairs of CRE1 and CRE2 in -868LUC, the effect of IL-11 on luciferase activity was almost totally abrogated. Transcriptional activities induced by IL-11 were inhibited by protein kinase A, tyrosine kinase, ERK1/2, and PI3-kinase inhibitors. Gel mobility shift analyses showed that IL-11 increased nuclear proteins binding to CRE1 and CRE2. CREB1, phospho-CREB1, c-Fos, and c-Jun antibodies disrupted the formation of CRE1 and CRE2 protein complexes. These data demonstrate that IL-11 stimulates BSP gene transcription via CRE1 and CRE2 elements in the human BSP gene promoter.

Not all carboxylates are created equal: differences in interaction of carboxylated peptides with a CaCO₃ dimer

The carboxylate group has been considered the "glue" for mineralizing proteins because of its ability to bind Ca(II). We propose the calcium salts of dicarboxylated dipeptides (Asp-Asp and Glu-Glu) as the smallest models of a mineralizing protein active site. Molecular dynamics/simulated annealing was used for conformational search of the dipeptide global minimum. Semiempirical blind docking was used for configurational search of all cluster-peptide complexes and structures were then optimized in the gas phase at the RI-MP2/SVP level of theory. Solvent effects were also taken into account. We found that the energy of interaction of the calcium carboxylates with a calcium carbonate dimer can be either favorable or unfavorable depending on side-chain length, so side-chain carboxylic groups belonging to different amino acids may show different affinities towards calcium carbonate.

Bone sialoprotein as a potential key factor implicated in the pathophysiology of osteoarthritis

OBJECTIVE

We previously identified an association between bone sialoprotein (BSP) and osteoarthritic (OA) chondrocyte hypertrophy but the precise role of BSP in ostearthritis (OA) has not been extensively studied. This study aimed to confirm the association between BSP and OA chondrocyte hypertrophy, to define its effect on molecules produced by chondrocytes and to analyse its association with cartilage degradation and vascular density at the osteochondral junction.

METHOD

Human OA chondrocytes were cultivated in order to increase hypertrophic differentiation. The effect of parathyroid hormone-related peptide (PTHrP), interleukin (IL)-1β or tumour necrosis factor (TNF)-α on BSP was analysed by real-time reverse transcription polymerase chain reaction (RT-PCR) and western blot. The effects of BSP on OA chondrocytes production of inflammatory response mediators (IL-6, nitric oxide), major matrix molecule (aggrecan), matrix metalloprotease-3 and angiogenic factors (vascular endothelial growth factor, basic fibroblast growth factor, IL-8, and thrombospondin-1) were investigated. BSP was detected by immunohistochemistry and was associated with cartilage lesions severity and vascular density.

RESULTS

PTHrP significantly decreased BSP, confirming its association with chondrocyte hypertrophy. In presence of IL-1β, BSP stimulated IL-8 synthesis, a pro-angiogenic cytokine but decreased the production of TSP-1, an angiogenesis inhibitor. The presence of BSP-immunoreactive chondrocytes in cartilage was associated with the severity of histological cartilage lesions and with vascular density at the osteochondral junction.

CONCLUSION

This study supports the implication of BSP in the pathology of OA and suggests that it could be a key mediator of the hypertrophic chondrocytes-induced angiogenesis. To control chondrocyte hypertrophic differentiation is promising in the treatment of OA.

Bone sialoprotein and osteopontin in bone metastasis of osteotropic cancers

The mechanisms underlying malignant cell metastasis to secondary sites such as bone are complex and no doubt multifactorial. Members of the small integrin-binding ligand N-linked glycoproteins (SIBLINGs) family, particularly bone sialoprotein (BSP) and osteopontin (OPN), exhibit multiple activities known to promote malignant cell proliferation, detachment, invasion, and metastasis of several osteotropic cancers. The expression level of BSP and OPN is elevated in a variety of human cancers, particularly those that metastasize preferentially to the skeleton. Recent studies suggest that the "osteomimicry" of malignant cells is not only conferred by transmembrane receptors bound by BSP and OPN, but includes the "switch" in gene expression repertoire typically expressed in cells of skeletal lineage. Understanding the role of BSP and OPN in tumor progression, altered pathophysiology of bone microenvironment, and tumor metastasis to bone will likely result in development of better diagnostic approaches and therapeutic regimens for osteotropic malignant diseases.

Infusion of human umbilical cord‑derived mesenchymal stem cells effectively relieves liver cirrhosis in DEN‑induced rats

Cirrhosis is the long‑term outcome of chronic hepatic injury and no effective therapy is currently available for this disease. Mesenchymal stromal cells (MSCs) are multipotent cells that are easily acquired and amplified, and may be potential candidates for cell therapy against cirrhosis. This study aimed to determine the therapeutic effects of human umbilical cord‑derived MSCs (hUCMSCs) for the treatment of liver cirrhosis and identify an effective method for engrafting MSCs. The model of liver cirrhosis was established by induction of diethylnitrosamine (DEN) in rats. The isolated hUCMSCs were identified by morphology, flow cytometry and multilineage differentiation; they were injected into the vein of DEN‑induced rats at varied cell doses and infusion times. Biochemical analyses of the serum and histopathological analysis of the liver tissues were performed to evaluate the therapeutic effects of hUCMSCs in all treatment groups. The results indicated that isolated hUCMSCs were capable of self‑replication and differentiated into multiple lineages, including osteoblast‑, adipocyte‑ and hepatocyte‑like cells. Compared with the control group, administration of hUCMSCs at different cell doses and infusion times relieved DEN‑induced cirrhosis to varying degrees. The therapeutic effects of hUCMSCs on liver cirrhosis gradually improved with increased cell dose and infusion times. The improvement of cirrhosis was due to the capacity of hUCMSCs to breakdown collagen fibers in the liver. It was demonstrated that infusion of hUCMSCs effectively relieved liver cirrhosis by facilitating the breakdown of collagen fibers in a dose‑dependent manner and multiple infusions caused a relatively greater improvement in cirrhosis compared with a single infusion of hUCMSCs.

PDGF-induced PI3K-mediated signaling enhances the TGF-β-induced osteogenic differentiation of human mesenchymal stem cells in a TGF-β-activated MEK-dependent manner

Transforming growth factor-β (TGF-β) is a critical regulator of osteogenic differentiation and the platelet-derived growth factor (PDGF) is a chemoattractant or mitogen of osteogenic mesenchymal cells. However, the combined effects of these regulators on the osteogenic differentiation of mesenchymal cells remains unknown. In this study, we investigated the effects of TGF-β and/or PDGF on the osteogenic differentiation of human mesenchymal stem cells (hMSCs). The TGF-β-induced osteogenic differentiation of UE7T-13 cells, a bone marrow-derived hMSC line, was markedly enhanced by PDGF, although PDGF alone did not induce differentiation. TGF-β induced extracellular signal-regulated kinase (ERK) phosphorylation and PDGF induced Akt phosphorylation. In addition, the mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor, U0126, suppressed the osteogenic differentiation induced by TGF-β alone. Moreover, U0126 completely suppressed the osteogenic differentiation synergistically induced by TGF-β and PDGF, whereas the phosphoinositide-3-kinase (PI3K) inhibitor, LY294002, only partially suppressed this effect. These results suggest that the enhancement of TGF-β-induced osteogenic differentiation by PDGF-induced PI3K/Akt-mediated signaling depends on TGF-β-induced MEK activity. Thus, PDGF positively modulates the TGF-β-induced osteogenic differentiation of hMSCs through synergistic crosstalk between MEK- and PI3K/Akt-mediated signaling.

Collagen scaffolds in bone sialoprotein-mediated bone regeneration

Decades of research in bioengineering have resulted in the development of many types of 3-dimentional (3D) scaffolds for use as drug delivery systems (DDS) and for tissue regeneration. Scaffolds may be comprised of different natural fibers and synthetic polymers as well as ceramics in order to exert the most beneficial attributes including biocompatibility, biodegradability, structural integrity, cell infiltration and attachment, and neovascularization. Type I collagen scaffolds meet most of these criteria. In addition, type I collagen binds integrins through RGD and non-RGD sites which facilitates cell migration, attachment, and proliferation. Type I collagen scaffolds can be used for bone tissue repair when they are coated with osteogenic proteins such as bone morphogenic protein (BMP) and bone sialoprotein (BSP). BSP, a small integrin-binding ligand N-linked glycoprotein (SIBLING), has osteogenic properties and plays an essential role in bone formation. BSP also mediates mineral deposition, binds type I collagen with high affinity, and binds αvβ₃ and αvβ₅ integrins which mediate cell signaling. This paper reviews the emerging evidence demonstrating the efficacy of BSP-collagen scaffolds in bone regeneration.

Osteoinduction: a review of old concepts with new standards

Since the discovery of osteoinduction in the early 20th century, innovative biomaterials with osteoinductive potential have emerged. Over the last 50 years, however, our ability to describe biological phenomena accurately has been improved dramatically by advancements in cell and molecular biology. The aim of this review is to divide the osteoinduction phenomenon into 3 principles: (1) mesenchymal cell recruitment, (2) mesenchymal differentiation to bone-forming osteoblasts, and (3) ectopic bone formation in vivo. Furthermore, this review formulates guidelines for in vitro and in vivo experimental testing for accurately defining new biomaterials as osteoinductive. The use of growth factors with osteoinductive potential in periodontal and oral surgery is discussed. These concepts and guidelines aim to guide the future direction of emerging biomaterials in bone regeneration.

Predictive value of serum bone sialoprotein in patients with bone metastasis of non-small cell lung cancer

BACKGROUND

The purpose of this study was to evaluate the diagnostic and prognostic significance of serum bone sialoprotein (BSP) in patients with bone metastasis (BM) from non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

A total of 146 patients diagnosed with NSCLC and 110 healthy controls were enrolled in this study. The clinical characteristics including clinical stage, pathological type, smoking status, and ECOG performance status were obtained. The mean serum BSP was detected by sandwich ELISA.

RESULTS

The mean serum BSP level in individuals with BM was significantly higher than those in non-BM NSCLC and controls (p < 0.001). Receiver operating characteristics (ROC) analysis showed that BSP discriminated patients with BM from non-BM NSCLC patients at the cutoff value of 33.56 ng/ml. Sensitivity and specificity were 77.8 and 81.1%, respectively. Kaplan-Meier analysis showed that subjects with higher BSP levels had a shorter BM-free period than those with lower BSP levels. Cox regression analysis revealed that the BSP level was a predictor for prognosis of BM from NSCLC.

CONCLUSION

Serum BSP is a useful biomarker for the diagnosis of BM from NSCLC, and can be regarded as an independent factor for predicting the prognosis of BM from NSCLC.

Calcium hydroxide regulates bone sialoprotein gene transcription in human osteoblast-like Saos2 cells

Bone sialoprotein (BSP) is a mineralized tissue-specific protein expressed in differentiated osteoblasts that appears to function in the initial mineralization of bone. Calcium hydroxide (Ca(OH)(2)) is a basic salt that has been widely used for a variety of applications in dentistry, due to its antimicrobial effects and its capability of inducing hard tissue formation. However, details of the mechanism involved in the mineralization induced by Ca(OH)(2) are still unclear. In the present study, Ca(OH)(2) (0.4 mM) was found to increase the levels of BSP and Runx2 mRNA at 3 h in human osteoblast-like Saos2 cells. Transient transfection assays were performed using chimeric constructs of the human BSP gene promoter linked to a luciferase reporter gene. Treatment of Saos2 cells with Ca(OH)(2) (0.4 mM) increased the luciferase activities of the constructs between -60LUC and -927LUC at 12 h. Gel shift analysis showed that Ca(OH)(2) (0.4 mM) increased the binding of nuclear protein to CRE1, CRE2 and FRE. Antibodies against CREB1, c-Fos, c-Jun, JunD, Fra2 and P300 disrupted the formation of the CRE1- and CRE2-protein complexes, and antibodies against Dlx5, Msx2, Runx2 and Smad1 disrupted the formation of the FRE-protein complex. These findings demonstrate that Ca(OH)(2) stimulates BSP transcription by targeting the CRE1, CRE2 and FRE elements in the human BSP gene promoter.

Effect of bone sialoprotein on proliferation and osteodifferentiation of human bone marrow-derived mesenchymal stem cells in vitro

We performed this study to investigate the effects of recombinant human bone sialoprotein (BSP) on the proliferation and osteodifferentiation of human BMSCs(hBMSCs). The hBMSC cultures were divided into 4 groups: control group, 10(-10) M BSP group (BSP group), osteogenic medium group (10 nM dexamethasone, 10 mM β-glycerophosphate, and 50 mg/L ascorbic acid, OM group) and BSP + OM group (OM plus10(-10) M BSP). Compared with the control group, cell growth of the other three groups slowed down, while fluorescence at the G(0)/G(1) phase increased. After 28 days, in the OM group and the BSP + OM group, the proportion of STRO-1-positive cells decreased by 22.7% and 38.4% and ALP activity increased by 50% and 71.43%, respectively. CD271 mRNA expression decreased while Cbfa1, osteocalcin and osterix mRNA levels increased in the OM and BSP + OM groups, and the mRNA level change was greater in the BSP + OM group. After 28 days, the number of nodules in the BSP + OM group was 112.5% more than that in the OM group, but nodules did not formed in the control or BSP group. We conclude that BSP is capable of inhibiting hBMSCs proliferation and enhancing their osteogenic differentiation and mineralization in the presence of OM.

Transcriptional regulation of bone sialoprotein gene by interleukin-11

Interleukin-11 (IL-11) is a stromal cell-derived cytokine that belongs to the interleukin-6 family of cytokines. IL-11 has many biological activities and has roles in hematopoiesis, immune responses, the nervous system and bone metabolism. Bone sialoprotein (BSP) is a mineralized tissue-specific protein expressed in differentiated osteoblasts that appears to function in the initial mineralization of bone. IL-11 (20 ng/ml) increased BSP mRNA and protein levels at 12h in osteoblast-like ROS 17/2.8 cells. In a transient transfection assay, IL-11 (20 ng/ml) increased luciferase activity of the construct (-116 to +60) in ROS 17/2.8 cells and rat bone marrow stromal cells. Introduction of 2 bp mutations to the luciferase constructs showed that the effects of IL-11 were mediated by a cAMP response element (CRE), a fibroblast growth factor 2 response element (FRE) and a homeodomain protein-binding site (HOX). Luciferase activities induced by IL-11 were blocked by protein kinase A inhibitor, tyrosine kinase inhibitor and ERK1/2 inhibitor. Gel shift analyses showed that IL-11 (20 ng/ml) increased nuclear protein binding to CRE, FRE and HOX. CREB1, phospho-CREB1, c-Fos, c-Jun, JunD and Fra2 antibodies disrupted the formation of CRE-protein complexes. Dlx5, Msx2, Runx2 and Smad1 antibodies disrupted FRE- and HOX-protein complex formations. These studies demonstrate that IL-11 stimulates BSP transcription by targeting CRE, FRE and HOX sites in the proximal promoter of the rat BSP gene. Moreover, phospho-CREB1, c-Fos, c-Jun, JunD, Fra2, Dlx5, Msx2, Runx2 and Smadl transcription factors appear to be key regulators of IL-11 effects on BSP transcription.

Wnt5a promotes differentiation of human dental papilla cells

AIM

To investigate the role of Wnt5a in the process of differentiation of human dental papilla cells (HDPCs).

METHODOLOGY

Recombinant adenovirus encoding full-length Wnt5a cDNA was constructed to investigate the biological role of Wnt5a on the differentiation of HDPCs. The effect of Wnt5a on HDPCs differentiation was determined by ALP activity assay, ALP staining and mineral induction assay. Mineralization-related gene expressions were assessed by RT-PCR.

RESULTS

Immunostaining revealed Wnt5a expression in the odontoblast layer and dental papilla tissue. Over-expression of Wnt5a by transfecting HDPCs with an Wnt5a-carrying construct increased ALPase activity and the formation of mineralized nodules of HDPCs. RT-PCR analysis showed that the expressions of mineralization-related genes, such as bone sialoprotein, collagen type I, osteonectin, osteopontin (OCN), dentine matrix protein-1 were up-regulated by Wnt5a.

CONCLUSIONS

Wnt5a promoted differentiation of HDPCs.

How does bone sialoprotein promote the nucleation of hydroxyapatite? A molecular dynamics study using model peptides of different conformations

Bone sialoprotein (BSP) is a highly phosphorylated, acidic, noncollagenous protein in bone matrix. Although BSP has been proposed to be a nucleator of hydroxyapatite (Ca(5)(PO(4))(3)OH), the major mineral component of bone, no detailed mechanism for the nucleation process has been elucidated at the atomic level to date. In the present work, using a peptide model, we apply molecular dynamics (MD) simulations to study the conformational effect of a proposed nucleating motif of BSP (a phosphorylated, acidic, 10 amino-acid residue sequence) on controlling the distributions of Ca(2+) and inorganic phosphate (Pi) ions in solution, and specifically, we explore whether a nucleating template for orientated hydroxyapatite could be formed in different peptide conformations. Both the alpha-helical conformation and the random coil structure have been studied, and inorganic solutions without the peptide are simulated as reference. Ca(2+) distributions around the peptide surface and interactions between Ca(2+) and Pi in the presence of the peptide are examined in detail. From the MD simulations, although in some cases for the alpha-helical conformation, we observe that a Ca(2+) equilateral triangle forms around the surface of peptide, which matches the distribution of Ca(2+) ions on the (001) face of the hydroxyapatite crystal, we do not consistently find a stable nucleating template formation in general for either the helical conformation or the random coil structure. Therefore, independent of conformations, the BSP nucleating motif is more likely to help nucleate an amorphous calcium phosphate cluster, which ultimately converts to crystalline hydroxyapatite.

Force-induced craniosynostosis in the murine sagittal suture

BACKGROUND

The cause of nonsyndromic craniosynostosis remains elusive. Although compressive forces have been implicated in premature suture fusion, conclusive evidence of force-induced craniosynostosis is lacking. The purpose of this study was to determine whether cyclical loading of the murine calvaria could induce suture fusion.

METHODS

Calvarial coupons from postnatal day-21, B6CBA, wild-type mice (n = 18) were harvested and cultured. A custom appliance capable of delivering controlled, cyclical, compressive loads was applied perpendicular to the sagittal suture within the coupon in vitro. Nine coupons were subjected to 0.3 g of force for 30 minutes each day for a total of 14 days. A control group of nine coupons was clamped in the appliance without loading. Analysis of suture phenotype was performed using alkaline phosphatase and hematoxylin and eosin staining techniques and in situ hybridization analysis using bone sialoprotein.

RESULTS

Control group sagittal sutures-which normally remain patent in mice-showed their customary histologic appearance. In contradistinction, sagittal sutures subjected to cyclic loading showed histologic evidence of premature fusion (craniosynostosis). In addition, alkaline phosphatase activity and bone sialoprotein expression were observed to be increased in the experimental group when compared with matched controls.

CONCLUSIONS

An in vitro model of force-induced craniosynostosis has been devised. Premature fusion of the murine sagittal suture was induced with the application of controlled, cyclical, compressive loads. These results implicate abnormal forces in the development of nonsyndromic craniosynostosis, which supports our global hypothesis that epigenetic phenomena play a crucial role in the pathogenesis of craniosynostosis.

Small integrin-binding proteins as serum markers for prostate cancer detection

PURPOSE

The small integrin-binding ligand N-linked glycoprotein (SIBLING) gene family includes bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), matrix extracellular phosphoglycoprotein (MEPE), and osteopontin (OPN). Previous studies have separately reported elevated expression of BSP, OPN, or DSPP in prostate tumor paraffin sections. We hypothesized that SIBLINGs may be informative serum markers for subjects with prostate cancer.

METHODS

Expression levels of SIBLINGs in biopsies of normal tissue and tumors from prostate were determined by cDNA array and by immunohistochemical staining with monoclonal antibodies. Competitive ELISAs for measuring total BSP, DSPP, MEPE, and OPN were applied to a test group of 102 subjects with prostate cancer and 110 normal subjects and a validation group of 90 subjects.

RESULTS

BSP, DMP1, DSPP, and OPN exhibited elevated mRNA expression and protein levels in biopsies. BSP, DSPP, and OPN were elevated in serum from prostate cancer subjects, with serum DSPP exhibiting the greatest difference, yielding an area under the receiver operator characteristic curve value of 0.98. Serum BSP and OPN levels were significantly elevated only in late stages, whereas DSPP was significantly elevated at all stages. Optimal serum value cutoff points derived for BSP, OPN, and DSPP were applied as a validation test to a new group of 90 subjects and DSPP yielded a sensitivity of 90% and a specificity of 100%.

CONCLUSION

Of the SIBLING gene family members, DSPP appears to be a strong candidate for use in serum assays for prostate cancer detection.

Modulation of bone resorption by phosphorylation state of bone sialoprotein

We have determined transmembrane protein tyrosine phosphorylation (outside-in signaling) in cultured osteoclasts and macrophages in response to added native purified bone sialoprotein (nBSP) and its dephosphorylated form (dBSP). There were selective/differential and potent inhibitory effects by dBSP and minimal effect by nBSP on intracellular tyrosine phosphorylation in macrophages and osteoclasts. Further studies on the downstream gene expression effects led to identification of a large number of differentially expressed genes in response to nBSP relative to dBSP in both macrophages and osteoclasts. These studies were extended to a bone resorption model using live mouse neonatal calvarial bone organ cultures stimulated by parathyroid hormone (PTH) to undergo bone resorption. Inclusion of nBSP in such cultures showed no effect on type I collagen telopeptide fragment release, hence overall bone resorption, whereas addition of dBSP abolished the PTH-induced bone resorption. The inhibition of bone resorption by dBSP was shown to be unique since in complementary experiments use of integrin receptor binding ligand, GRGDS peptide, offered only partial reduction on overall bone resorption. Quantitative RANKL analysis indicated that mechanistically the PTH-induced bone resorption was inhibited by dBSP via down-regulation of the osteoblastic RANKL production. This conclusion was supported by the RANKL analysis in cultured MC3T3-E1 osteoblast cells. Overall, these studies provided direct evidence for the involvement of covalently bound phosphates on BSP in receptor mediated "outside-in" signaling via transmembrane tyrosine phosphorylation with concurrent effects on downstream gene expressions. The use of a live bone organ culture system augmented these results with further evidence that links the observed in vivo variable state of phosphorylation with bone remodeling.

Applications of transgenics in studies of bone sialoprotein

Bone sialoprotein (BSP) is a major non-collagenous protein in mineralizing connective tissues such as dentin, cementum and calcified cartilage tissues. As a member of the Small Integrin-Binding Ligand, N-linked Glycoprotein (SIBLING) gene family of glycoproteins, BSP is involved in regulating hydroxyapatite crystal formation in bones and teeth, and has long been used as a marker gene for osteogenic differentiation. In the most recent decade, new discoveries in BSP gene expression and regulation, bone remodeling, bone metastasis, and bone tissue engineering have been achieved with the help of transgenic mice. In this review, we discuss these new discoveries obtained from the literatures and from our own laboratory, which were derived from the use of transgenic mouse mutants related to BSP gene or its promoter activity.

Parathyroid hormone regulation of the human bone sialoprotein gene transcription is mediated through two cAMP response elements

Parathyroid hormone (PTH) regulates serum calcium and inorganic phosphate levels through its actions on kidney and bone. Bone sialoprotein (BSP) is an early marker of osteoblast differentiation and bone metabolism. We here report that two cAMP response elements (CRE) in the human BSP gene promoter are target of PTH. In human osteoblast-like Saos2 cells, PTH (human 1-34 PTH, 10 nM) increased BSP mRNA and protein levels at 3 h. From transient transfection assays, 2- to 2.5-fold increase in transcription by PTH was observed at 3 and 6 h in -184, -211, -428, -868, and -927 luciferase constructs that included the human BSP gene promoter. Effect of PTH was abrogated by 2 bp mutations in either the CRE1 (-79 to -72) or CRE2 (-674 to -667). Luciferase activities induced by PTH were blocked by protein kinase A inhibitor H89 and tyrosine kinase inhibitor herbimycin A. Gel shift analyses showed that PTH increased binding of nuclear proteins to the CRE1 and CRE2 elements. The CRE1-protein and CRE2-protein complexes were disrupted by CRE binding protein 1 (CREB1) antibodies and supershifted by phospho-CREB1 antibody. ChIP assays detected binding of CREB1 and phospho-CREB1 to a chromatin fragment containing CRE1 and CRE2, and increased binding of phospho-CREB1 to the both sites. These studies demonstrate that PTH stimulates human BSP gene transcription by targeting the two CREs in the promoter of the human BSP gene.

Targeted overexpression of BSP in osteoclasts promotes bone metastasis of breast cancer cells

Bone is one of the most common sites of breast cancer metastasis while bone sialoprotein (BSP) is thought to play an important role in bone metastasis of malignant tumors. The objective of this study is to determine the role of BSP overexpression in osteolytic metastasis using two homozygous transgenic mouse lines in which BSP expression is elevated either in all the tissues (CMV-BSP mice) or only in the osteoclasts (CtpsK-BSP mice). The results showed that skeletal as well as systemic metastases of 4T1 murine breast cancer cells were dramatically increased in CMV-BSP mice. In CtpsK-BSP mice, it was found that targeted BSP overexpression in osteoclasts promoted in vitro osteoclastogenesis and activated osteoclastic differentiation markers such as Cathepsin K, TRAP and NFAT2. MicroCT scan demonstrated that CtpsK/BSP mice had reduced trabecular bone volume and bone mineral density (BMD). The real-time IVIS Imaging System showed that targeted BSP overexpression in osteoclasts promoted bone metastasis of breast cancer cells. The osteolytic lesion area was significantly larger in CtpsK/BSP mice than in the controls as demonstrated by both radiographic and histomorphometric analyses. TRAP staining demonstrated a twofold increase in the number of osteoclasts in the bone lesion area from CtpsK/BSP mice compared with that from wild type mice. We conclude that host tissue-derived BSP also plays important roles in breast cancer metastasis through inducing tumor cell seeding into the remote host tissues. Furthermore, osteoclast-derived BSP promotes osteoclast differentiation in an autocrine manner and consequently promotes osteolytic bone metastasis of breast cancer.

Dentin matrix protein-1 isoforms promote differential cell attachment and migration

Dentin matrix protein-1 (DMP1), bone sialoprotein (BSP), and osteopontin (OPN) are three SIBLINGs (small integrin-binding ligand, N-linked glycoproteins) co-expressed/secreted by skeletal and active ductal epithelial cells. Although etiological mechanisms remain unclear, DMP1 is the only one of these three genes currently known to have mutations resulting in human disease, and yet it remains the least studied. All three contain the highly conserved integrin-binding tripeptide, RGD, and experiments comparing the cell attachment and haptotactic migration-enhancing properties of DMP1 to BSP and OPN were performed using human skeletal (MG63 and primary dental pulp cells) and salivary gland (HSG) cells. Mutation of any SIBLING's RGD destroyed all attachment and migration activity. Using its alphaVbeta5 integrin, HSG cells attached to BSP but not to DMP1 or OPN. However, HSG cells could not migrate onto BSP in a modified Boyden chamber assay. Expression of alphaVbeta3 integrin enhanced HSG attachment to DMP1 and OPN and promoted haptotactic migration onto all three proteins. Interchanging the first four coding exons or the conserved amino acids adjacent to the RGD of DMP1 with corresponding sequences of BSP did not enhance the ability of DMP1 to bind alphaVbeta5. For alphaVbeta3-expressing cells, intact DMP1, its BMP1-cleaved C-terminal fragment, and exon six lacking all post-translational modifications worked equally well but the proteoglycan isoform of DMP1 had greatly reduced ability for cell attachment and migration. The sequence specificity of the proposed BMP1-cleavage site of DMP1 was verified by mutation analysis. Direct comparison of the three proteins showed that cells discriminate among these SIBLINGs and among DMP1 isoforms.

Membrane potential controls adipogenic and osteogenic differentiation of mesenchymal stem cells

BACKGROUND

Control of stem cell behavior is a crucial aspect of developmental biology and regenerative medicine. While the functional role of electrophysiology in stem cell biology is poorly understood, it has become clear that endogenous ion flows represent a powerful set of signals by means of which cell proliferation, differentiation, and migration can be controlled in regeneration and embryonic morphogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

We examined the membrane potential (V(mem)) changes exhibited by human mesenchymal stem cells (hMSCs) undergoing adipogenic (AD) and osteogenic (OS) differentiation, and uncovered a characteristic hyperpolarization of differentiated cells versus undifferentiated cells. Reversal of the progressive polarization via pharmacological modulation of transmembrane potential revealed that depolarization of hMSCs prevents differentiation. In contrast, treatment with hyperpolarizing reagents upregulated osteogenic markers.

CONCLUSIONS/SIGNIFICANCE

Taken together, these data suggest that the endogenous hyperpolarization is a functional determinant of hMSC differentiation and is a tractable control point for modulating stem cell function.