Local Bone Metabolism Research Articles

18F]NaF PET/CT as a Marker for Fibrodysplasia Ossificans Progressiva: From Molecular Mechanisms to Clinical Applications in Bone Disorders.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic bone disorder characterized by episodic flare-ups in connective tissue, which are frequently followed by the formation of heterotopic ossification. The absence of available plasma-soluble biomarkers for flare-ups or heterotopic bone formation poses severe challenges to the monitoring of disease activity to measure or predict disease progression. Recently, 18-fluor-sodium fluoride positron emission tomography/computed tomography ([18F]NaF PET/CT) was introduced as a potential marker for ossifying FOP activity. This review discusses the pharmacokinetics of [18F]NaF in relation to the pathophysiology of FOP, and its use as a marker of local bone metabolism in a variety of bone-related disorders. In addition, the review specifically addresses the applicability of [18F]NaF PET/CT imaging in FOP as a monitoring modality.

3D-printed bone regeneration scaffolds modulate bone metabolic homeostasis through vascularization for osteoporotic bone defects

The treatment of osteoporotic bone defects poses a challenge due to the degradation of the skeletal vascular system and the disruption of local bone metabolism within the osteoporotic microenvironment. However, it is feasible to modulate the disrupted local bone metabolism imbalance through enhanced vascularization, a theory termed "vascularization-bone metabolic balance". This study developed a 3D-printed polycaprolactone (PCL) scaffold modified with EPLQLKM and SVVYGLR peptides (PCL-SE). The EPLQLKM peptide attracts bone marrow-derived mesenchymal stem cells (BMSCs), while the SVVYGLR peptide enhances endothelial progenitor cells (EPCs) vascular differentiation, thus regulating bone metabolism and fostering bone regeneration through the paracrine effects of EPCs. Further mechanistic research demonstrated that PCL-SE promoted the vascularization of EPCs, activating the Notch signaling pathway in BMSCs, leading to the upregulation of osteogenesis-related genes and the downregulation of osteoclast-related genes, thereby restoring bone metabolic balance. Furthermore, PCL-SE facilitated the differentiation of EPCs into "H"-type vessels and the recruitment of BMSCs to synergistically enhance osteogenesis, resulting in the regeneration of normal microvessels and bone tissues in cases of femoral condylar bone defects in osteoporotic SD rats. This study suggests that PCL-SE supports in-situ vascularization, remodels bone metabolic translational balance, and offers a promising therapeutic regimen for osteoporotic bone defects.

Tantalum Particles Promote M2 Macrophage Polarization and Regulate Local Bone Metabolism via Macrophage-Derived Exosomes Influencing the Fates of BMSCs.

In this study, the regulatory role and mechanisms of tantalum (Ta) particles in the bone tissue microenvironment are explored. Ta particle deposition occurs in both clinical samples and animal tissues following porous Ta implantation. Unlike titanium (Ti) particles promoting M1 macrophage (Mϕ) polarization, Ta particles regulating calcium signaling pathways and promoting M2 Mϕ polarization. Ta-induced M2 Mϕ enhances bone marrow-derived mesenchymal stem cells (BMSCs) proliferation, migration, and osteogenic differentiation through exosomes (Exo) by upregulating miR-378a-3p/miR-221-5p and downregulating miR-155-5p/miR-212-5p. Ta particles suppress the pro-inflammatory and bone resorption effects of Ti particles in vivo and in vitro. In a rat femoral condyle bone defect model, artificial bone loaded with Ta particles promotes endogenous Mϕ polarization toward M2 differentiation at the defect site, accelerating bone repair. In conclusion, Ta particles modulate Mϕ polarization toward M2 and influence BMSCs osteogenic capacity through Exo secreted by M2 Mϕ, providing insights for potential bone repair applications.

Increased local bone turnover in patients with chronic periprosthetic joint infection.

The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI. Periprosthetic femoral trabecular bone specimens were obtained from patients suffering from chronic PJI of the hip and knee (n = 20). Microbiological analysis was performed on preoperative joint aspirates and tissue specimens obtained during revision surgery. Microstructural and cellular bone parameters were analyzed in bone specimens by histomorphometry on undecalcified sections complemented by tartrate-resistant acid phosphatase immunohistochemistry. Data were compared with control specimens obtained during primary arthroplasty (n = 20) and aseptic revision (n = 20). PJI specimens exhibited a higher bone volume, thickened trabeculae, and increased osteoid parameters compared to both control groups, suggesting an accelerated bone turnover with sclerotic microstructure. On the cellular level, osteoblast and osteoclast parameters were markedly increased in the PJI cohort. Furthermore, a positive association between serum (CRP) but not synovial (white blood cell (WBC) count) inflammatory markers and osteoclast indices could be detected. Comparison between different pathogens revealed increased osteoclastic bone resorption parameters without a concomitant increase in osteoblasts in bone specimens from patients with Staphylococcus aureus infection, compared to those with detection of Staphylococcus epidermidis and Cutibacterium spp. This study provides insights into the local bone metabolism in chronic PJI, demonstrating osteosclerosis with high bone turnover. The fact that Staphylococcus aureus was associated with distinctly increased osteoclast indices strongly suggests early surgical treatment to prevent periprosthetic bone alterations.

Study on the association of the microstructure and bone metabolism in the osteoporotic femoral head

BackgroundWe compared the bone microstructure and metabolism of the femoral heads in patients with osteoporosis (OP) and non-OP patients to investigate the pathologic mechanism of OP and guide clinical treatment.Methods and resultsFrom January 2020 to June 2021, we obtained femoral head samples from 30 patients undergoing hip replacement due to femoral neck fracture. All patients were women aged approximately 67 to 80 years (mean age, 74 years). According to the dual-energy X-ray results, the femoral head samples were divided into the OP (T< − 2.5) and non-OP (T > − 1.5) groups. Microcomputed tomography scanning, bone metrology analysis, hematoxylin and eosin staining, and Masson’s trichrome staining were used to compare the local bone trabecular microstructure changes. Quantitative reverse transcription PCR was performed to identify changes in the osteogenesis-related genes and the osteoclast-related genes in specific regions to reflect osteogenic and osteoclastic activities. Femoral heads with OP showed significant changes in the local bone microstructure. Bone density, bone volume fraction, and the number and thickness of the bone trabeculae decreased. Local bone metabolism was imbalanced in the areas with microstructural changes in femoral heads with OP, with increased osteoclast activity and decreased osteoblast activity.ConclusionsDeterioration of bone microstructure is closely related to abnormal bone metabolism associated with the activity of osteoblasts and osteoclasts in osteoporotic femoral heads. Promoting bone formation by improving local bone metabolism, enhancing osteogenic activity and inhibiting osteoclast activity may be a promising way of preventing local OP and osteoporotic fractures.

Do Clinical Parameters Reflect Local Bone Metabolism in Heterotopic Ossification After Septic or Aseptic THA?

Do Clinical Parameters Reflect Local Bone Metabolism in Heterotopic Ossification After Septic or Aseptic THA?

Local bone metabolism during the consolidation process of spinal interbody fusion.

Although computed tomography (CT) can identify the presence of eventual bony bridges following lumbar interbody fusion (LIF) surgery, it does not provide information on the ongoing formation process of new bony structures. 18F sodium fluoride (18F-NaF) positron emission tomography (PET) could be used as complementary modality to add information on the bone metabolism at the fusion site. However, it remains unknown how bone metabolism in the operated segment changes early after surgery in uncompromised situations. This study aimed to quantify the changes in local bone metabolism during consolidation of LIF. Six skeletally mature sheep underwent LIF surgery. 18F-NaF PET/CT scanning was performed 6 and 12weeks postoperatively to quantify the bone volume and metabolism in the operated segment. Bone metabolism was expressed as a function of bone volume. Early in the fusion process, bone metabolism was increased at the endplates of the operated vertebrae. In a next phase, bone metabolism increased in the center of the interbody region, peaked, and declined to an equilibrium state. During the entire postoperative time period of 12weeks, bone metabolism in the interbody region was higher than that of a reference site in the spinal column. Following LIF surgery, there is a rapid increase in bone metabolism at the vertebral endplates that develops towards the center of the interbody region. Knowing the local bone metabolism during uncompromised consolidation of spinal interbody fusion might enable identification of impaired bone formation early after LIF surgery using 18F-NaF PET/CT scanning.

Local bone metabolism balance regulation via double-adhesive hydrogel for fixing orthopedic implants

The effective osteointegration of orthopedic implants is a key factor for the success of orthopedic surgery. However, local metabolic imbalance around implants under osteoporosis condition could jeopardize the fixation effect. Inspired by the bone structure and the composition around implants under osteoporosis condition, alendronate (A) was grafted onto methacryloyl hyaluronic acid (H) by activating the carboxyl group of methacryloyl hyaluronic acid to be bonded to inorganic calcium phosphate on trabecular bone, which is then integrated with aminated bioactive glass (AB) modified by oxidized dextran (O) for further adhesion to organic collagen on the trabecular bone. The hybrid hydrogel could be solidified on cancellous bone in situ under UV irradiation and exhibits dual adhesion to organic collagen and inorganic apatite, promoting osteointegration of orthopedic implants, resulting in firm stabilization of the implants in cancellous bone areas. In vitro, the hydrogel was evidenced to promote osteogenic differentiation of embryonic mouse osteoblast precursor cells (MC3T3-E1) as well as inhibit the receptor activator of nuclear factor-κ B ligand (RANKL)-induced osteoclast differentiation of macrophages, leading to the upregulation of osteogenic-related gene and protein expression. In a rat osteoporosis model, the bone-implant contact (BIC) of the hybrid hydrogel group increased by 2.77, which is directly linked to improved mechanical stability of the orthopedic implants. Overall, this organic-inorganic, dual-adhesive hydrogel could be a promising candidate for enhancing the stability of orthopedic implants under osteoporotic conditions.

Osteocalcin: the relationship between bone metabolism and glucose homeostasis in diabetes mellitus

Recent studies have demonstrated the importance of bone as an endocrine organ that produces biologically active substances, which regulate both local bone metabolism and metabolic functions throughout the body. In the process of bone remodeling (formation/destruction), the active cells secrete specific biomarkers that help detect osteometabolic dysfunction. Among bone hormones, osteocalcin plays an important role as a coordinator of bone modeling processes, energy homeostasis, metabolism of glucose, lipids and minerals. Osteocalcin is a structural protein of the bone matrix, which is synthesized by osteoblasts and enters the bloodstream in the process of bone resorption. The level of osteocalcin in the serum is used as a specific marker of bone formation. Osteocalcin promotes pancreatic β-cell proliferation and insulin secretion, and also affects the insulin sensitivity of peripheral tissues. The inverse association of glycemia with the level of osteocalcin was revealed. Patients with type 2 diabetes mellitus usually have normal or even slightly elevated bone mineral density compared to age-appropriate controls. Decreased bone quality and increased risk of fractures are associated with changes in bone microarchitecture and local humoral environment. An imbalance in osteoblast/osteoclast activity may be due to oxidative stress and the accumulation of glycosylation end products, which contributes to chronic inflammation and bone resorbtion in patients with diabetes. It is shown that the level of osteocalcin in the blood serum is significantly reduced compared to healthy controls, both in patients with type 1 diabetes mellitus and, especially, in type 2 diabetes mellitus. Given the importance of developing new approaches to the diagnosis and correction of metabolic disorders in diabetic patients, the study of the influence of bone hormones on hormonal and metabolic parameters and bone status, including the risk of fractures, remains relevant in modern diabetology.

Assessment of bone metabolism and quality of life in knee osteoarthritis patients with low bone mineral density

Purpose: Osteoarthritis (OA) and Osteoporosis (OP) are two respective diseases in skeletal system correlated with aging. They are different diseases but often coexist in one patient. The relationship between them is complicated and controversial. With the update of OA definition, a new conception called “Bone-driven OA subtype” was put forward, suggesting that abnormal bone metabolism plays a key role in OA development. OA complicated with OP may be a separate subtype of OA, with its own features different from neither OA nor OP. However, the underlying researches on this subtype are still sparse. The current cross-sectional study was conducted by recruiting people aged between 40∼80 years old to: (i) investigate the prevalence and risk factors of OA patients complicated with low BMD; (ii) assess their bone metabolism status; (iii) evaluate their general health status. Methods: The study was conducted in accordance with the World Medical Association Declaration of Helsinki-Ethical Principles for Medical Research Involving Human Subjects. All participants provided written informed consent to participate in this research, which was approved by the Ethics Committee of the First Affiliated Hospital of Xi’an Jiaotong University (the approval number of ethics is KYLLSL-2018-231). Physical examination of knee joints was performed. To measure the degree of functional impairment and to identify the severity of disease in patients with KOA, we included Western Ontario questionnaire and the McMaster Universities Osteoarthritis Index (WOMAC)as well as SF-36. The free and informed consent, as well as a questionnaire were applied by the researcher. Bone mineral density (BMD) of the lumbar spine and bilateral proximal femora was performed by a Dual Energy X-Ray Absorptiometry (DEXA) machine. Blood samples were collected and laboratory tests performed for detection of bone turn-over markers (β-CrossLaps, PINP and N-MID Osteocalcin N). Radiographs in AP+P load of bilateral knees were evaluated and a radiological classification was performed by two independent observers using the Kellgren-Lawrence (KL) scores. Data were expressed as means ± standard deviations for continuous variables and as numbers and percentages for categorical data. The Student t-test, one-way ANOVA test and the chi-square test were used. Significance value was p<0.05 at 95% confidence interval. Results: Prevalence of KOA with low BMD 956 subjects were enrolled. There were 164 (17.15%) KOA patients complicated with low BMD, accounting for 72.25% of KOA patients. Their mean age was 57.70±7.68 years, and mean BMI was 25.00±2.98 kg/m2. When stratified with age and gender, the prevalence elevated along with age and was significantly higher in menopausal women (72.9%, P<0.001) (Table 1). There was a trend that the prevalence of KL scores ≥2 (28.7%, n=47) in these patients was higher than that (22.2%, n=14) in KOA with normal BMD group. BMD and Serum bone turnover markers in KOA with low BMD The serum levels of bone formation markers (ALP, PINP and N-MID Osteocalcin) and bone absorption markers (β-CrossLaps) in KOA with low BMD patients were significantly higher than that in KOA with normal BMD group and healthy control group (P<0.001) (Table 1). Mean BMD and T-scores at lumbar, femoral neck and total hip of these patients were significantly lower than that in KOA with normal BMD group and healthy control group (p<0.001). There also appeared to be an inverse relationship between severity of KOA and mean BMD at total hip and femoral neck (Fig. 1). General health status in KOA with low BMD Evaluated with SF-36, mean values of all the dimensions reflecting body health and mental health (except for MH) in KOA with low BMD patients were significantly lower than that in OP and healthy control group (P<0.05). Conclusions: OA is a heterogenous disease with a variety of pathophysiologic drivers leading to multiple phenotypes. Bone-driven OA is a specific subtype that associated with OP and osteopenia, characterized as active bone turnover rate caused by local or systemic abnormal bone metabolism in early stage of OA. For these patients, low BMD is a risk factor of OA development. Evaluation of health outcome by SF-36 showed that both body health and mental health of these patients had severely suffered. Therefore, this subtype will progress rapidly and present specific bone metabolism features. Our findings shed new light on patient stratification and the development of precision medicines for OA. New and effective approaches have to be developed to focus on abnormal bone metabolism in the treatment of Bone-driven OA.

An in vitro Three-Dimensional Co-Culture System for Ameloblastoma Modelling

Ameloblastoma, the most clinically significant odontogenic epithelial tumor, is a locally-invasive and destructive lesion in the jawbones. However, the nature of this infiltrativeness and destructive behavior remains ill-understood. To address this, we established an in vitro three-dimensional (3D) co-culture system to simulate an amelobastoma disease model aimed at investigating the interactions between tumor cells and osteoblasts. Osteoblastic cell lines (KUSA/A1 and MC3T3-E1) and one stromal cell line (ST2) were separately co-seeded with ameloblastoma-derived cell line (AM-1) in a collagen scaffold (representing the extracellular bone matrix) and incubated with mineralization medium. Immunohistochemistry, double immunofluorescence and mineralization assay were performed. Only AM-1/KUSA-A1 co-culture showed a significant increase in AM-1 cell count, suggesting that heterotypic cell-cell interaction promotes tumoral cell growth, while formation of visible AM-1 epithelial nest-like structures resembling ameloblastoma cells in their native state, suggest morphodifferentiation. A RANK-high, RANKL-low and osteoprotegerin-low immunoprofile in co-culture AM-1 cells implies deregulated osteoclastogenesis. Mineralization assays showed diminished calcification in AM-1/KUSA-A1 co-culture extracellular matrix suggesting an altered local bone metabolism. In contrast, KUSA/A1 monocultures showed abundant extracellular matrix calcification. Taken together, these results suggest that a 3D co-culture system as an amelobastoma disease model provides insights that bidirectional ameloblastoma-osteoblastic interactions might play a role in modulating tumor growth and osteoclastogenesis.

Basis of bone metabolism around dental implants during osseointegration and peri-implant bone loss.

Despite the growing number of publications in the field of implant dentistry, there are limited studies to date investigating the biology and metabolism of bone healing around dental implants and their implications in peri-implant marginal bone loss. The aim of this review article is to provide a thorough understanding of the biological events taking place during osseointegration and the subsequent early and late phases of bone remodeling around dental implants. An update on the coupling mechanism occurring during bone resorption-bone remodeling is provided, focused on the relevance of the osteocytes, bone lining cells and immune cells during bone maintenance. An electronic and manual literature search was conducted by three independent reviewers in several databases, including MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Oral Health Group Trials Register databases for articles up to September 2016 with no language restriction. Local bone metabolism is subject to signals from systemic calcium-phosphate homeostasis and bone remodeling. Three areas of interest were reviewed due to recent reported compromises in bone healing including the putative effects of (1) cholesterol, (2) hyperlipidemia, and (3) low vitamin D intake. Moreover, the prominent influence of osteocytes and immune cells is discussed as being key regulators during dental implant osseointegration and maintenance. These cells are of crucial importance in the presence of biofilm accumulation and their associated byproducts that leads to hard and soft tissue breakdown; the so called peri-implantitis. Factors that could negatively impact osteoclastogenesis or osteal macrophage activation should be monitored in future research including implant placement/torque protocols, bone characteristics, as well as meticulous maintenance programs to favor osseointegration and future long-term stability and success of dental implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2075-2089, 2017.

Analysis of the Influence of Hormone Replacement Therapy on Osteocalcin Gene Expression in Postmenopausal Women.

Background. Osteocalcin (OC) contributes to the process of bone mineralization. Present study was designed to investigate the changes in OC gene expression of postmenopausal women treated with hormone replacement therapy (HRT). Study was also designed to evaluate OC gene expression in cells which are not part of connective tissue. Material and Methods. Research was carried out on 30 postmenopausal women not treated and 30 treated with HRT. Examination of OC gene expression was conducted on peripheral blood lymphocytes (PBL) and buccal epithelial lining (BEL). Densitometry was conducted on femur and mandible. Results. Tests revealed OC gene expression in BEL and PBL. BMD was higher in groups treated with HRT. Assessment of correlation between the OC gene expression in BEL and BMD of mandible revealed significant positive relation. Conclusions. OC gene expression can be stated BEL and PBL. Analysis of correlation between OC gene expression in oral cavity and mandible BMD showed significant correlation between local OC expression and local bone metabolism. The relation between OC gene expression and bone metabolism is complex and further research is needed to clear all of the uncertainties.

Effect of odanacatib on root resorption and alveolar bone metabolism during orthodontic tooth movement.

The aim of this study was to investigate the effect of local administration of odanacatib (ODN) on orthodontic root resorption and the status of alveolar bone metabolism in rat molars. All specimens were scanned using microcomputed tomography and then the raw images were reconstructed. The total volume of the root resorption craters of the 60 g-NS (normal saline) group was higher than in the 60 g-ODN group and the control group. In the 60 g-NS group, the bone volume fraction values of alveolar bone were significantly decreased compared with the other 2 groups. There were no significant differences in the bone volume fraction values of the tibiae among the 3 groups. The results of tartrate-resistant acid phosphatase-positive (TRAP+) numbers showed that there was no difference between the 60 g-NS group and the 60 g-ODN group. The expression of cathepsin K was decreased significantly in the 60 g-ODN group. These results indicate that ODN reduces orthodontics-induced external root resorption and increases alveolar bone metabolism. This may be because ODN inhibits the activity of odontoclasts, but maintains the quantity of odontoclasts and enhances bone formation. ODN promotes local alveolar bone metabolism, but does not affect systemic bone metabolism.

RANK, RANKL, and OPG in recurrent solid/multicystic ameloblastoma: their distribution patterns and biologic significance.

To determine the distribution patterns of bone resorption regulators, receptor activator of nuclear factor κ-B (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) in recurrent ameloblastoma (RAs) and to clarify their impact on the biologic behavior of these neoplasms. Fifteen paraffin-embedded RA cases were subjected to immunohistochemistry for expression of RANK, RANKL, and OPG. The RANK-RANKL-OPG triad was heterogeneously detected in RA samples. RANK, essential for osteoclast differentiation, was strongly expressed in tumoral epithelium. Conversely, RANKL, an osteoclast activator, was markedly underexpressed, and protein localization was predominantly stromal. OPG, an osteoclastogenesis inhibitory factor, was detected in neoplastic epithelium more than in stroma, suggesting functional inactivation of RANKL. Most RA (n= 12/15; 80%) exhibited a bimolecular spatial expression pattern, the most common being RANK-positive/OPG-positive (n= 8/15; 53.3%). All three proteins showed no significant correlation with the clinical/histopathologic parameters in RA patients (P>.05). The RANK(+)/RANKL(low/-)/OPG(+) phenotype observed in RA suggests an altered local bone metabolism characterized by low bone resorptive activity in these recurrent tumors.

Osteocyte-specific deletion of Fgfr1 suppresses FGF23.

Increases in fibroblastic growth factor 23 (FGF23 or Fgf23) production by osteocytes result in hypophosphatemia and rickets in the Hyp mouse homologue of X-linked hypophosphatemia (XLH). Fibroblastic growth factor (FGF) signaling has been implicated in the pathogenesis of Hyp. Here, we conditionally deleted FGF receptor 1 (FGFR1 or Fgfr1) in osteocytes of Hyp mice to investigate the role of autocrine/paracrine FGFR signaling in regulating FGF23 production by osteocytes. Crossing dentin matrix protein 1 (Dmp1)-Cre;Fgfr1 null/+ mice with female Hyp;Fgfr1 flox/flox mice created Hyp and Fgfr1 (Fgfr1Dmp1-cKO)-null mice (Hyp;Fgfr1 Dmp1-cKO) with a 70% decrease in bone Fgfr1 transcripts. Fgfr1Dmp1-cKO-null mice exhibited a 50% reduction in FGF23 expression in bone and 3-fold reduction in serum FGF23 concentrations, as well as reductions in sclerostin (Sost), phosphate regulating endopeptidase on X chromosome (PHEX or Phex), matrix extracellular phosphoglycoprotein (Mepe), and Dmp1 transcripts, but had no demonstrable alterations in phosphate or vitamin D homeostasis or skeletal morphology. Hyp mice had hypophosphatemia, reductions in 1,25(OH)2D levels, rickets/osteomalacia and elevated FGF2 expression in bone. Compared to Hyp mice, compound Hyp;Fgfr1 Dmp1-cKO-null mice had significant improvement in rickets and osteomalacia in association with a decrease in serum FGF23 (3607 to 1099 pg/ml), an increase in serum phosphate (6.0 mg/dl to 9.3 mg/dl) and 1,25(OH)2D (121±23 to 192±34 pg/ml) levels, but only a 30% reduction in bone FGF23 mRNA expression. FGF23 promoter activity in osteoblasts was stimulated by FGFR1 activation and inhibited by overexpression of a dominant negative FGFR1(TK−), PLCγ and MAPK inhibitors. FGF2 also stimulated the translation of an FGF23 cDNA transfected into osteoblasts via a FGFR1 and PI3K/Akt-dependent mechanism. Thus, activation of autocrine/paracrine FGF pathways is involved in the pathogenesis of Hyp through FGFR1-dependent regulation of FGF23 by both transcriptional and post-transcriptional mechanisms. This may serve to link local bone metabolism with systemic phosphate and vitamin D homeostasis.

Increased bone mineral density at the hypoxia prone site of the juxta-articular metacarpal bone in patients with limited systemic sclerosis: a cross-sectional study.

Low levels of oxygen has been shown to be involved in the induction of osteogenesis, particularly in bone repair. It is unknown whether hypoxia leads to osteogenesis at the hypoxia prone skeletal sites in limited systemic sclerosis. This study determined the total and trabecular volumetric bone mineral density (vBMD) at the hypoxia prone site of the juxta-articular metacarpal bone. In this cross-sectional study, female patients with limited systemic sclerosis were included and compared to healthy controls. Peripheral quantitative computed tomography was used to measure cross-sectional area, total vBMD, and trabecular vBMD at the radius, the tibia and the third metacarpal bone. Disease severity was assessed by the modified Rodnan Skin Score. Twenty consecutive patients were included in the sclerosis group and 20 in the control group. Mean age was 60 years (range 52-68 years), and mean disease duration was 45 months (range 4-156 months). Age, height, and weight were comparable between the groups. The mean modified Rodnan Skin Score was 1.78 (range 0 to 8). The sclerosis group showed both higher total and trabecular vBMD at the distal metacarpal bone (p=0.05 and 0.04, respectively). vBMD of the tibia and radius did not differ in both groups. vBMD at the juxta-articular metacarpal bone in patients with limited systemic sclerosis is increased, possibly due to an alteration in local bone metabolism and hypoxia induced local osteogenesis.

A bone substitute with high affinity for vitamin D‐binding protein―relationship with niche of osteoclasts

The biological activity of osteoblasts and osteoclasts is regulated not only by hormones but also by local growth factors, which are expressed in neighbouring cells or included in bone matrix. Previously, we developed hydroxyapatite (HA) composed of rod-shaped particles using applied hydrothermal methods (HHA), and it revealed mild biodegradability and potent osteoclast homing activity. Here, we compared serum proteins adsorbed to HHA with those adsorbed to conventional HA composed of globular-shaped particles (CHA). The two ceramics adsorbed serum albumin and γ-globulin to similar extents, but affinity for γ-globulin was much greater than that to serum albumin. The chemotactic activity for macrophages of serum proteins adsorbed to HHA was significantly higher than that of serum proteins adsorbed to CHA. Quantitative proteomic analysis of adsorbed serum proteins revealed preferential binding of vitamin D-binding protein (DBP) and complements C3 and C4B with HHA. When implanted with the femur of 8-week-old rats, HHA contained significantly larger amount of DBP than CHA. The biological activity of DBP was analysed and it was found that the chemotactic activity for macrophages was weak. However, DBP-macrophage activating factor, which is generated by the digestion of sugar chains of DBP, stimulated osteoclastogenesis. These results confirm that the microstructure of hydroxyapatite largely affects the affinity for serum proteins, and suggest that DBP preferentially adsorbed to HA composed of rod-shaped particles influences its potent osteoclast homing activity and local bone metabolism.

Promotion of normal healing of bone defects under estrogen deficiency by implantation of beta‐tricalcium phosphate composed of rod‐shaped particles

We compared the healing of bone defects in ovariectomized rats implanted with beta-tricalcium phosphate (b-TCP)composed of rod-shaped particles, which were prepared using the applied hydrothermal method (HTCP), and that of bone defects implanted with conventional b-TCP composed of globular-shaped particles (CTCP), which were prepared by normal sintering. Eight week-old female Wistar rats were ovariectomized, and 2 weeks after the operation, 0.5- to 0.6-mm diameter spherical granules of each ceramic were implanted in a bone defect created in the distal end of the femur. Four, 8, and 12 weeks after implantation, the amount of newly formed bone implanted with HTCP was significantly larger than that implanted with CTCP and was equivalent to that in non-ovariectomized sham-operated rats. Without implantation, spontaneous repair of the trabecular bone was barely observed. The physiological structure of the trabecular network was maintained in the region implanted with HTCP, but that in the region implanted with CTCP was severely destroyed. Gene expression microarray analysis revealed that the expression of genes involved in interferon signaling pathways was upregulated in osteoclasts cultured on HTCP compared with that cultured on CTCP. Our results suggest that the microstructure of b-TCP affected the biological behavior of osteoclasts and regulated local bone metabolism.

Behaviour of co-cultured human osteoclastic and osteoblastic cells exposed to endodontic sealers’ extracts

Bone tissue is constantly being moulded and shaped by the coordinated action of bone-resorbing osteoclasts and bone-synthesizing osteoblasts. This study addresses the long-term effects of endodontic sealers' extracts (AH Plus™, GuttaFlow™, Tubliseal™, Sealapex™ and RealSeal™) on co-cultures of human osteoclastic and osteoblastic cells. The sealers were mixed according to the manufacturer's instructions, freshly extracted with culture medium (1.3 cm(2)/ml; 24 h; 37 °C, 5% CO2/air) and diluted (1:20-1:2,500). Co-cultures of osteoclastic and osteoblastic cells, established from precursors present in human peripheral blood mononuclear cells and bone marrow cells, respectively, were exposed to the extracts for 21 days. Co-cultures were characterized for the osteoclastic and osteoblastic response. The sealers caused a dose-dependent decrease on TRAP and ALP activities, respectively, an osteoclastic and an osteoblastic marker. The resorbing ability of the osteoclastic cells and the expression of osteoclastic and osteoblastic genes were also decreased; in addition, the extracts affected several intracellular signalling pathways. Inhibition was higher during the two first weeks, followed by adaptive cell responses. Osteoblastic response was more sensitive to the extracts' toxicity and showed lower adaptive ability. A correlation to the clinical situation cannot be predicted; however, the results suggest that the sealers' eluents might disrupt the highly regulated interaction between osteoblastic and osteoclastic cells, compromising the local bone metabolism. Also, the higher susceptibility of the osteoblastic response might be particularly relevant in the initial stages of the healing of periapical lesions, due to the significant role of the bone formation events.