Constitutive expression of non-bone/liver/kidney alkaline phosphatase in human osteosarcoma cell lines

Titanium dioxide nanoparticles affect osteoblast-derived exosome cargos and impair osteogenic differentiation of human mesenchymal stem cells

Titanium (Ti) and its alloys are the most widely used metallic biomaterials in total joint replacement; however, increasing evidence supports the degradation of its surface due to corrosion and wear processes releasing debris (ions, and micro and nanoparticles) and contribute to particle-induced osteolysis and implant loosening. Cell-to-cell communication involving several cell types is one of the major biological processes occurring during bone healing and regeneration at the implant-bone interface. In addition to the internal response of cells to the uptake and intracellular localization of wear debris, a red flag is the ability of titanium dioxide nanoparticles (mimicking wear debris) to alter cellular communication with the tissue background, disturbing the balance between osseous tissue integrity and bone regenerative processes. This study aims to understand whether titanium dioxide nanoparticles (TiO₂ NPs) alter osteoblast-derived exosome (Exo) biogenesis and whether exosomal protein cargos affect the communication of osteoblasts with human mesenchymal stem/stromal cells (HMSCs). Osteoblasts are derived from mesenchymal stem cells coexisting in the bone microenvironment during development and remodelling. We observed that TiO₂ NPs stimulate immature osteoblast- and mature osteoblast-derived Exo secretion that present a distinct proteomic cargo. Functional tests confirmed that Exos derived from both osteoblasts decrease the osteogenic differentiation of HMSCs. These findings are clinically relevant since wear debris alter extracellular communication in the bone periprosthetic niche, contributing to particle-induced osteolysis and consequent prosthetic joint failure.

Osseointegrating and phase-oriented micro-arc-oxidized titanium dioxide bone implants

Here, we present a bone implant system of phase-oriented titanium dioxide (TiO₂) fabricated by the micro-arc oxidation method (MAO) on β-Ti to facilitate improved osseointegration. This (101) rutile-phase-dominant MAO TiO₂ (R-TiO₂) is biocompatible due to its high surface roughness, bone-mimetic structure, and preferential crystalline orientation. Furthermore, (101) R-TiO₂ possesses active and abundant hydroxyl groups that play a significant role in enhancing hydroxyapatite formation and cell adhesion and promote cell activity leading to osseointegration. The implants had been elicited their favorable cellular behavior in vitro in the previous publications; in addition, they exhibit excellent shear strength and promote bone-implant contact, osteogenesis, and tissue formation in vivo. Hence, it can be concluded that this MAO R-TiO₂ bone implant system provides a favorable active surface for efficient osseointegration and is suitable for clinical applications.

Dietary Cadmium Chloride Supplementation Impairs Renal Function and Bone Metabolism of Laying Hens

This study was conducted to evaluate the toxic effects of cadmium (Cd) on the kidney function and bone development in laying hens. A total of 480 Hy-line laying hens aged 38 weeks were randomly allocated into five treatments, each of which included six replicates of 16 birds. The concentrations of Cd in the diets of the five groups were 0.47, 7.58, 15.56, 30.55, and 60.67 mg/kg. Results showed that serum calcium (Ca) levels decreased significantly in the 60.67 mg Cd/kg diet group (p < 0.05). The activities of serum alkaline phosphatase (ALP) and bone ALP (BALP) decreased significantly in the 15.56, 30.55 and 60.67 mg Cd/kg diet groups (p < 0.05). The levels of parathyroid hormone (PTH) increased significantly in the 30.55 and 60.67 mg Cd/kg diet groups, and the estradiol (E2), 1,25-(OH)2-D3 and calcitonin (CT) decreased significantly with the increase of dietary Cd supplementation (p < 0.05). Histological results presented enlargements of renal tubules and tubular fibrosis in the kidney and decreased trabecular bone in the tibia. Tartrate-resistant acidic phosphatase (TRAP) staining results of tibia showed that osteoclast was significantly increased at the relatively high dose of dietary Cd (p < 0.05). In addition, the renal function indicators of blood urea nitrogen (BUN), urea acid (UA), and creatinine were significantly increased in Cd supplemented groups compared with the control group (p < 0.05). Low dose Cd exposure induced antioxidant defenses accompanying the increase in activities of catalase (CAT), glutathione peroxidase (GSH-Px), and the levels of glutathione (GSH) in renal tissue. At the same time, with the increased Cd levels, the activities of CAT, GSH-Px decreased significantly, and the level of malondialdehyde (MDA) increased significantly (p < 0.05). The activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase decreased significantly in the relatively high levels of dietary Cd (p < 0.05). These results suggest that Cd can damage renal function and induce disorders in bone metabolism of laying hens.

The Predictive Value of Albumin-to-Alkaline Phosphatase Ratio for Overall Survival of Hepatocellular Carcinoma Patients Treated with Trans-Catheter Arterial Chemoembolization Therapy

Background: We have previously reported the prognostic value of the albumin-to-alkaline phosphatase ratio (AAPR) for advanced hepatocellular carcinoma (HCC) patients who are not receiving any standard anticancer therapy. However, the prognostic value of the AAPR for HCC patients treated with trans-catheter arterial chemoembolization therapy (TACE) was not investigated.

Methods: We retrospectively analysed 372 HCC patients treated with TACE (the training cohort) and applied receiver operating characteristic curves (ROC curves) to identify the best cut-off value for the AAPR in this cohort. Then, univariate analyses by the Kaplan-Meier method and multivariate analysis by a Cox proportional hazards regression model were conducted. Both comparisons of the ROC curves and the likelihood ratio test (LRT) were employed to evaluate the abilities of different factors in predicting the survival of patients in this cohort. Finally, the prognostic value of the AAPR was validated in two cohorts: one included 202 HCC patients treated with supportive care (validation cohort I), and the other included 82 HCC patients treated with TACE (validation cohort II).

Results: We identified 0.439 as the best cut-off value of the AAPR by ROC curve analysis. An AAPR > 0.439 was significantly correlated with a lower frequency of Child-Pugh grade B, portal vein tumour thrombus (PVTT), T3-4 and lymph node metastasis (P < 0.05). The median overall survival (OS) of the patients with an AAPR > 0.439 was significantly longer than that of those with an AAPR ≤ 0.439 (58.4 m vs 17.8 m, respectively, P < 0.001). The AAPR was identified as an independent prognostic factor after univariate and multivariate analyses (HR = 0.636, P = 0.003). The independent prognostic value of the AAPR was also confirmed in validation cohorts I and II. Additionally, we substituted the AAPR for the Child-Pugh grade in the CLIP system and integrated the AAPR into the TNM system. We found that the area under the curve (AUC) of the AAPR-CLIP system was significantly larger than that of the CLIP and the TNM when predicting 3-month, 6-month, 1-year and 2-year survival (P < 0.05). There was no significant difference between the AUCs for the AAPR-CLIP and the AAPR-TNM. The LRT suggested that both AAPR-CLIP and AAPR-TNM had significantly larger χ2 values and smaller AIC values than that of their corresponding primary system (P < 0.05).

Conclusions: The AAPR was an independent prognostic index for the HCC patients treated with TACE. Both AAPR-CLIP and AAPR-TNM outperformed their corresponding primary system in predicting OS in the current study.

Immunohistochemical Validation of Spontaneously Arising Canine Osteosarcoma as a Model for Human Osteosarcoma

Osteosarcoma (OS) originates from bone-forming mesenchymal cells and represents one of the primary bone tumours. It is the most common primary bone tumour in dogs and man. The characterization of an appropriate natural disease animal model to study human OS is essential to elucidate the pathogenesis of the disease. This study aimed to validate canine OS as a model for the human disease by evaluating immunohistochemically the expression of markers known to be important in human OS. The immunohistochemical panel included vimentin, alkaline phosphatase (ALP), desmin, S100, neuron-specific enolase (NSE), runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 4 (BMP4). Immunohistochemistry was conducted on formalin-fixed, paraffin wax-embedded tissue sections from 59 dogs with confirmed primary OS. Vimentin, ALP, Runx2 and BMP4 were highly expressed by all tumours, while desmin, S100 and NSE were expressed variably. The findings were similar to those described previously for human OS and suggest that canine OS may represent a useful model for the study of the human disease.

Prognostic value of combined preoperative lactate dehydrogenase and alkaline phosphatase levels in patients with resectable pancreatic ductal adenocarcinoma

Serum enzymes, including lactate dehydrogenase (LDH) and alkaline phosphatase (ALP), have recently been reported to play important roles in tumor growth. Increases in LDH and ALP have been confirmed to predict poor prognosis in patients with various cancers. However, their prognostic value in pancreatic cancer has not been well studied. Therefore, we reviewed the preoperative data on LDH and ALP in 185 pancreatic ductal adenocarcinoma (PDAC) patients who underwent surgery between July 2005 and December 2010 to explore the prognostic value of these markers. The cutoff points were determined based on the upper limit of their normal values. The Chi-square test was used to analyze the relationships between LDH/ALP and clinical characteristics. Univariate and multivariate analyses were performed to identify the predictive value of the above factors for disease-free survival (DFS) and overall survival (OS). We found that elevation of LDH was related to carbohydrate antigen 19-9 (CA19-9), lymph node involvement, tumor size, TNM, distant metastasis, and recurrence. Additionally, ALP was correlated to perineural invasion. After multivariate analysis, LDH and ALP were identified as independent prognostic factors for DFS and OS, and elevation of LDH/ALP was correlated with poor DFS and OS. Notably, there was a positive correlation between LDH and ALP. The predictive power of LDH combined with ALP was more sensitive than that of either one alone. Therefore, we conclude that the preoperative LDH and ALP values are prognostic factors for PADC, and the prognostic accuracy of testing can be enhanced by the combination of LDH and ALP.

The predictive value of alkaline phosphatase and lactate dehydrogenase for overall survival in patients with esophageal squamous cell carcinoma

The elevation of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) has been demonstrated to predict worse prognosis in various malignancies; however, their prognostic value in esophageal squamous cell carcinoma has not been well studied. We conducted a retrospective study of 906 patients with esophageal squamous cell carcinoma to explore their prognostic value for overall survival. The optimal cutoff points for ALP and LDH were determined. We analyzed the association between the levels of ALP and LDH and clinicopathological characteristics. Their prognostic value for overall survival was explored by univariate and multivariate analysis. We also proposed the ALP and LDH classification and examined its prognostic value in the general population and subgroups. The optimal cutoff points of ALP and LDH to predict overall survival were 90.7 and 361.5 U/L respectively. Higher levels of ALP and LDH were both associated with more advanced TNM stage (P = 0.003 and 0.002, respectively) and more distant metastasis (P = 0.001 and P < 0.001, respectively). Both ALP (≤90.7/>90.7 U/L) and LDH (≤361.5/>361.5 U/L) were independent prognostic factors for overall survival in esophageal squamous cell carcinoma (P = 0.004 and P < 0.001 by multivariate analysis). The ALP and LDH classification categorized patients into three subgroups with distinct prognosis (P < 0.001 by multivariate analysis) and identified a small group of patients who had extremely poor overall survival with a median of 4.2 months. In conclusion, ALP and LDH were both independent prognostic factors for overall survival. A combination of the two indexes might contribute to further identification of survival differences in esophageal squamous cell carcinoma.

Reinforced Portland cement porous scaffolds for load-bearing bone tissue engineering applications

Modified Portland cement porous scaffolds with suitable characteristics for load-bearing bone tissue engineering applications were manufactured by combining the particulate leaching and foaming methods. Non-crosslinked polydimethylsiloxane was evaluated as a potential reinforcing material. The scaffolds presented average porosities between 70 and 80% with mean pore sizes ranging from 300 μm up to 5.0 mm. Non-reinforced scaffolds presented compressive strengths and elastic modulus values of 2.6 and 245 MPa, respectively, whereas reinforced scaffolds exhibited 4.2 and 443 MPa, respectively, an increase of ∼62 and 80%. Portland cement scaffolds supported human osteoblast-like cell adhesion, spreading, and propagation (t = 1-28 days). Cell metabolism and alkaline phosphatase activity were found to be enhanced at longer culture intervals (t ≥ 14 days). These results suggest the possibility of obtaining strong and biocompatible scaffolds for bone repair applications from inexpensive, yet technologically advanced materials such as Portland cement.

Tissue-nonspecific alkaline phosphatase is activated in enterocytes by oxidative stress via changes in glycosylation

BACKGROUND

Intestinal inflammation produces an induction of alkaline phosphatase (AP) activity that is attributable in part to augmented expression, accompanied by a change in isoform, in epithelial cells.

METHODS

This study focuses on induction of AP in intestinal epithelial cells in vitro.

RESULTS

Treatment with the oxidants H2O2, monochloramine, or tButOOH increases AP activity in vitro in Caco-2, HT29, and IEC18 cells. We selected IEC18 cells for further testing. Basal AP activity in IEC18 cells is of the tissue-nonspecific (bone-liver-kidney) type, as indicated by Northern and Western blot analysis. Oxidative stress augments AP activity and the sensitivity of the enzyme to levamisole, homoarginine, and heat in IEC18 cells. Increased immunoreactivity to tissue-nonspecific AP antibodies suggests an isoform shift from liver to either kidney or bone type. This effect occurs without changes at the mRNA level and is sensitive to tunicamycin, an inhibitor of N-glycosylation, and neuraminidase digestion. Saponin and deoxycholate produce similar effects to oxidants. Butyrate but not proinflammatory cytokines or LPS can induce a similar effect but without toxicity. The AP increase is not prevented by modulators of the MAPK, NF-κB, calcium, and cyclic adenosine monophosphate (cAMP) pathways, and is actually enhanced by actinomycin D via higher cell stress.

CONCLUSIONS

Oxidative stress causes a distinct increase in enterocyte AP activity together with cell toxicity via changes in the glycosylation of the enzyme that correspond to a shift in isotype within the tissue-nonspecific paradigm. We speculate that this may have physiological implication for gut defense.

Possible prognostic role of IL-17R in osteosarcoma

PURPOSE

An intense vascularization of primary tumor mass is associated with a fatal outcome in various types of invasive solid tumors. Interleukin 17 (IL-17), a CD4+ T-cell-derived cytokine, stimulates some tumor cells to secrete angiogenic factors, among which venous endothelial growth factor (VEGF). We assessed whether the expression of IL-17 receptor (IL-17R) represents a marker for the metastasizing ability of osteosarcoma (OS), a very malignant bone tumor.

METHODS

We immunoassayed the amount of VEGF secreted by three OS cell lines expressing IL-17R in differing amounts: HOS, MG63 and U-2 OS, and their sensitivity to IL-17 stimulation to secrete VEGF.

RESULTS

U-2 OS, which best expresses IL-17R, secreted the highest amounts of VEGF and was the most sensitive to IL-17, whereas MG63 expressed the lowest level of IL-17R, secreted the lowest amount of VEGF and was not sensitive to IL-17. IL-17R expression correlated with VEGF secretion and IL-17 sensitivity. U-2 OS expressed the most dedifferentiated phenotype, which is associated with tumor malignancy.

CONCLUSIONS

These results suggest that IL-17R in OS might represent a marker of tumor metastasis potential.

Bioactive glass nanofiber-collagen nanocomposite as a novel bone regeneration matrix

Nanoscale organized organic-inorganic nanocomposite systems have great potential in the development of biomaterials with advanced properties. Herein, we developed a novel nanocomposite biomaterial consisting of bioactive glass nanofiber (BGNF) and collagen reconstituted fibrous matrix for bone regenerative medicine. A sol-gel derived glass with a bioactive composition (58SiO(2). 38CaO.4P(2)O(5)) was electrospun to a nanoscale fiber with an average diameter of approximately 320 nm. The BGNF was subsequently hybridized with type I collagen, which is the main organic constituent of bone matrix. The BGNF and self-assembled collagen sol were combined in aqueous solution, and then crosslinked to produce a BGNF-collagen nanocomposite, in the form of either a thin membrane or a macroporous scaffold, by adopting appropriate processing conditions. The BGNF was observed to be distributed uniformly within the collagen reconstituted nanofibrous matrix. The nanocomposite matrices induced rapid formation of bone-like apatite minerals on their surfaces when incubated in a simulated body fluid, exhibiting excellent bioactivity in vitro. Osteoblastic cells showed favorable growth on the BGNF-collagen nanocomposite. In particular, the alkaline phosphatase activity of the cells on the nanocomposite was significantly higher than that on the collagen. This novel BGNF-collagen nanocomposite is believed to have significant potential in bone regeneration and tissue engineering applications.

A novel bioactive porous CaSiO3 scaffold for bone tissue engineering

The aim of this study was to fabricate bioactive porous CaSiO3 scaffolds and examine their effects on proliferation and differentiation of osteoblast-like cells. In this study, porous CaSiO3 scaffolds were obtained by sintering a ceramic slip-coated polymer foam at 1350 degrees C. X-ray diffraction (XRD) of the scaffolds indicated that the products were essentially pure alpha-CaSiO3. The obtained scaffolds had a well-interconnected porous structure with pore sizes ranging from several micrometers to more than 100 microm and porosities of 88.5 +/- 2.8%. The in vitro bioactivity of the scaffolds was investigated by soaking them in simulated body fluid (SBF) for 7 days and then characterizing them by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis. The results indicated that hydroxyapatite (HAp) was formed on the surface of the scaffolds. In addition, the scaffolds were incubated in Ringer's solution at 37 degrees C to study the in vitro degradation by measurement of weight loss after incubation, which showed that the CaSiO3 scaffolds were degradable. The cellular responses to the scaffolds were assessed in terms of cell proliferation and differentiation. Osteoblast-like cells were seeded into the CaSiO3 scaffolds. SEM observations showed that there was significant cell adhesion, as the cells spread and grew in the scaffolds. In addition, the proliferation rate and alkaline phosphatase (ALP) activity of the cells in the scaffolds were improved as compared to the controls. These studies demonstrate initial in vitro cell compatibility and their potential application to bone tissue engineering.

Induction of alkaline phosphatase in the inflamed intestine: a novel pharmacological target for inflammatory bowel disease

This study demonstrates the upregulation of alkaline phosphatase and the mechanisms involved in experimental colitis. All models of ileal and colonic inflammation examined, which were characterized by significant oxidative stress and neutrophil infiltration, resulted in an increase in alkaline phosphatase activity which was attributable to both epithelial cells and cells of the lamina propria, mainly leukocytes. The increase in alkaline phosphatase sensitivity to the inhibitors levamisole and homoarginine, together with changes in the apparent molecular size and in the sialization of the enzyme, indicated a change in the isoform expressed. An increase in tissue non-specific alkaline phosphatase expression was observed by Western blotting. Treatment with the bone/kidney alkaline phosphatase inhibitor levamisole or a monoclonal antibody resulted in significant protection from colonic inflammation. Taken together, these results indicate that the kidney isoform is a marker of intestinal inflammation and that it might even constitute a target for pharmacological intervention.

Dissolution control and cellular responses of calcium phosphate coatings on zirconia porous scaffold

Different types of calcium phosphates [hydroxyapatite (HA), fluorapatite (FA), tricalcium phosphate (TCP), and their composites (HA + FA, HA + TCP)] were coated on a zirconia (ZrO(2)) porous scaffold using a powder slurry method. The ZrO(2) porous scaffold was intended for a load-bearing implant, and the apatite layers were coated to improve osteoconductivity. The insertion of an FA intermediate layer between the coating layer and ZrO(2) scaffold effectively suppressed the reaction between the calcium phosphate and ZrO(2) and maintained the coating layer at the initial powder composition. The obtained coating layer, of a thickness of approximately 30 microm, was relatively microporous and firmly adherent to the ZrO(2) scaffold. Dissolution tests in physiological solution showed typical differences depending on the coating layers, with the dissolution rate increasing in the order TCP > HA + TCP > HA > HA + FA > FA. This result suggests the functional coating of the calcium phosphates in view of tailoring the solubility. Osteoblast-like cells, MG63 and HOS, responded similarly in terms of cell growth, morphology, and proliferation rate regardless of the coating types, indicating favorable and comparable cell viability. However, the alkaline phosphatase (ALP) activity of the cells on the pure HA and HA composite coatings (HA + FA and HA + TCP) expressed at higher levels compared to those on pure FA and pure TCP coatings for both MG63 and HOS cells, suggesting a selective cell activity depending on the coating types. All the calcium phosphate-coated-ZrO(2) scaffolds showed higher ALP levels compared to pure ZrO(2) scaffold.

Hydroxyapatite coating on titanium substrate with titania buffer layer processed by sol–gel method

Hydroxyapatite (HA) was coated onto a titanium (Ti) substrate with the insertion of a titania (TiO2) buffer layer by the sol-gel method. The HA layer was employed to enhance the bioactivity and osteoconductivity of the Ti substrate, and the TiO2 buffer layer was inserted to improve the bonding strength between the HA layer and Ti substrate, as well as to prevent the corrosion of the Ti substrate. The HA layer coated over the TiO2 showed a typical apatite phase at 400 degrees C and the phase intensity increased above 450 degrees C. The sol-gel derived HA and TiO2 films, with thicknesses of approximately 800 and 200 nm, respectively, adhered tightly to each other and to the Ti substrate. The bonding strength of the HA/TiO2 double layer coating on Ti was markedly improved when compared to that of the HA single coating on Ti. The highest strength of the double layer coating was 55 MPa after heat treatment at 500 degrees C. The improvement in bonding strength with the insertion of TiO2 was attributed to the resulting enhanced chemical affinity of TiO2 toward the HA layer, as well as toward the Ti substrate. Human osteoblast-like cells, cultured on the HA/TiO2 coating surface, proliferated in a similar manner to those on the TiO2 single coating and on the pure Ti surfaces. However, the alkaline phosphatase activity of the cells on the HA/TiO2 double layer was expressed to a higher degree than that on the TiO2 single coating and pure Ti surfaces. The corrosion resistance of Ti was improved by the presence of the TiO2 coating, as confirmed by a potentiodynamic polarization test.

IL-17 enhances the susceptibility of U-2 OS osteosarcoma cells to NK cell lysis

We investigated the effect of the proinflammatory cytokine interleukin 17 (IL-17) on the lysis of osteosarcoma cells by human NK cells. NK cells and U-2 OS, MG-63, HOS osteosarcoma cell lines express the IL-17 receptor, the highest amount being found on U-2 OS. Pre-incubation of NK cells with IL-17 did not affect the cytotoxicity against osteosarcomas, that was increased when U-2 OS were pre-incubated with IL-17. In IL-17 treated U-2 OS osteosarcoma cells FACS analysis demonstrated an increased expression of fibronectin among the panel of adhesion molecules assayed, and the treatment with anti-fibronectin antibodies decreased the NK cytotoxicity. The comparison between interferon gamma (IFN-gamma) treated and IFN-gamma/IL-17-treated U-2 OS showed a decreased susceptibility to NK lysis associated with a reduced expression of CD49f on U-2 OS treated with IFN-gamma/IL-17. IL-17 appears to be a modulator of NK adhesion molecules on U-2 OS cells but antagonizes with IFN-gamma on NK lysis.

Porous ZrO2 bone scaffold coated with hydroxyapatite with fluorapatite intermediate layer

Highly porous zirconia (ZrO(2)) bone scaffolds, fabricated by a replication technique using polymeric sponge, were coated with hydroxyapatite (HA). To prevent the chemical reactions between ZrO(2) and HA, an intermediate fluorapatite (FA) layer was introduced. The strength of the porous ZrO(2) was higher than that of pure HA by a factor of 7, suggesting the feasibility of ZrO(2) porous scaffolds as load-bearing part applications. The coated HA/FA layer, with a thickness of about 30 microm, was firmly adhered to the ZrO(2) body with a bonding strength of 22MPa. The osteoblast-like cells were attached and spread well on the coating layer throughout the porous scaffolds. The alkaline phosphatase activity of the proliferated cells on the HA/FA coated ZrO(2) was comparable to that on pure HA and higher than that on pure ZrO(2).

Expression of osteocalcin and its transcriptional regulators core-binding factor alpha 1 and MSX2 in osteoid-forming tumours

Osteosarcoma, fibrous dysplasia, and myositis ossificans contain osteoid-producing cells that are not necessarily morphologically typical osteoblasts. Nevertheless, these pathologic cells may share differentiation steps with osteoblasts at the molecular level. Osteocalcin, a bone-specific extracellular matrix protein, is a marker of mature osteoblasts. Osteocalcin is upregulated by the transcription factor core-binding factor alpha 1, which is responsible for commitment to the osteoblastic lineage, and is downregulated by MSX2, a homeobox-containing transcription factor expressed during the early proliferative phase of osteoblast differentiation. Semiquantitative reverse transcription-polymerase chain reaction was used to compare expression levels of osteocalcin, core-binding factor alpha 1, and MSX2 in 34 osteosarcoma, five fibrous dysplasia, and five myositis ossificans specimens, as well as in seven normal cortical bone samples. Despite normal or elevated levels of core-binding factor alpha-1 expression in most specimens, osteocalcin expression was low or undetectable in most cases of osteosarcoma (25 of 34) and myositis ossificans (4 of 5). Single-strand conformation polymorphism and sequencing did not identify any mutations in the DNA-binding domain of core-binding factor alpha 1. However, a high level of MSX2 expression was demonstrated in these lesions, which may inhibit osteocalcin transcription. The presence of moderate levels of osteocalcin in fibrous dysplasia may contribute to the characteristic disconnected appearance of trabeculae in that entity because osteocalcin is a negative regulator of bone formation.