The Role of Bone Sialoprotein in Bone Healing.

Bone sialoprotein (BSP) is a multi-functional extracellular matrix (ECM) protein associated with mineralized tissues, particularly bone and cementum. The amino acid sequence of BSP includes three evolutionarily conserved functional domains which contribute to functions of the protein: an N-terminal collagen-binding domain, polyglutamic acid (polyE) sequences involved in hydroxyapatite nucleation and crystal growth, and a C-terminal arginine-glycine-aspartic acid (RGD) integrin-binding domain. BSP promotes attachment and differentiation of osteogenic and osteoclastic cells. Genetic ablation of BSP in mice results in skeletal and dental developmental defects and impaired bone healing in both appendicular bone and alveolar bone of the jaw. Several studies demonstrated positive effects of BSP on bone healing in rodent models, though other experiments show negligible results. Native (harvested from rat bones) BSP cross-linked to collagen induced slight improvements in calvarial bone healing in rats. Recombinant BSP and collagen delivered in a polylactide (PLA) cylinder improved bone defect healing in rat femurs. Both native and recombinant BSP delivered in a collagen gel improved alveolar bone healing in wild-type and BSP-deficient mice. These advances suggest BSP is a new player in bone healing that has potential to be an alternative or complimentary to other bioactive factors. Future studies are necessary to understand mechanisms of how BSP influences bone healing and optimize delivery and dose in different types of bone defects and injuries.

Adverse effect of botulinum toxin-A injections on mandibular bone: A systematic review and meta-analysis.

INTRODUCTION: Botulinum toxin-A (BTX) is a potent neurotoxin that is emerging in the scope of dental practice for its ability to temporarily paralyse musculature and reduce hyperfunction. This may be desirable in diseases/disorders associated with hyperactive muscles such as the muscles of mastication, most implicated in painful temporomandibular disorders (TMDs). The use of BTX extends beyond its indications with off-label use in TMD's and other conditions, while potential adverse effects remain understudied. BTX is well-established hindlimb paralysis model in animals leading to significant bone loss with underlying mechanisms remaining unclear. The objective of this study is to systematically review the literature for articles investigating changes in mandibular bone following BTX injections and meta-analyse available data on reported bone outcomes. METHODS: Comprehensive search of Medline, Embase and Web of Science retrieved 934 articles. Following the screening process, 36 articles in animals and humans were included for quantitative synthesis. Articles in human individuals (6) and three different animal species (14) presented mandibular bone outcomes that were included in the meta-analysis. RESULTS: The masseter and temporalis muscles were frequently injected across all species. In humans, we observe a decrease of about 6% in cortical thickness of mandibular regions following BTX injection with no evident changes in either volume or density of bone structures. In animals, bone loss in the condylar region is significantly high in both cortical and trabecular compartments. DISCUSSION: Our analysis supports the concept of BTX-induced bone-loss model in animal mandibles. Further, bone loss might be confined to the cortical compartments in humans. Most studies did not address the reality of repeated injections and excessive dosing, which occur due to the reversible action of BTX. More rigorous trials are needed to draw a full picture of potential long-term adverse effects on bone.

Postmenopausal women with HIV have increased tooth loss.

BACKGROUND: With effective antiretroviral therapy, people with HIV (PWH) are living longer and aging; the majority of PWH in the United States are now over the age of 50 and in women have gone through the menopause transition. Menopause potentiates skeletal bone loss at the spine, hip, and radius in PWH. The alveolar bone which surronds the teeth is different than long bones because it is derived from the neural crest. However, few studies have assessed the oral health and alveolar bone in middle aged and older women with HIV. Therefore, the objective of this study was to evaluate periodontal disease and alveolar bone microarchitecture in postmenopausal women with HIV. METHODS: 135 self-reported postmenopausal women were recruited (59 HIV-, 76 HIV + on combination antiretroviral therapy with virological suppression) from a single academic center. The following parameters were measured: cytokine levels (IFN-γ, TNF-α, IL-1ß, IL-2, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, IL-13, IL-17 A, OPG, and RANKL) in gingival crevicular fluid, bleeding on probing, probing depth, clinical attachment loss, number of teeth present, alveolar crestal height, and alveolar bone microarchitecture. RESULTS: The mean age of participants was 57.04+/-6.25 years and a greater proportion of women with HIV were black/African American (HIV + 68.42%, HIV- 23.73%; p < 0.001). There was no significant difference in bleeding on probing (p = 0.17) and attachment loss (p = 0.39) between women who were HIV infected vs. HIV uninfected. Women with HIV had significantly higher RANKL expression in Gingival Crevicular Fluid (HIV + 3.80+/-3.19 pg/ul, HIV- 1.29+/-2.14 pg/ul ; p < 0.001), fewer teeth present (HIV + 17.75+/-7.62, HIV- 22.79+/-5.70; p < 0.001), ), lower trabecular number (HIV + 0.08+/-0.01, HIV- 0.09+/-0.02; p = 0.004) and greater trabecular separation (HIV + 9.23+/-3.11, HIV- 7.99+/-3.23; p = 0.04) compared to women without HIV that remained significant in multivariate logistic regression analysis in a sub-cohort after adjusting for age, race/ethnicity, smoking status, and diabetes. CONCLUSION: Postmenopausal women with HIV have deterioration of the alveolar trabecular bone microarchitecture that may contribute to greater tooth loss.

[Latest Findings on the Role of RUNX1 in Bone Development and Disorders]. / RUNX1åœ¨éª¨å‘è‚²åŠéª¨ç›¸å ³ç–¾ç— ä¸­çš„ä½œç”¨ç ”ç©¶è¿›å±•.

Runt-related transcription factor (RUNX1) is a transcription factor closely involved in hematopoiesis. RUNX1 gene mutation plays an essential pathogenic role in the initiation and development of hematological tumors, especially in acute myeloid leukemia. Recent studies have shown that RUNX1 is also involved in the regulation of bone development and the pathological progression of bone-related diseases. RUNX1 promotes the differentiation of mesenchymal stem cells into chondrocytes and osteoblasts and modulates the maturation and extracellular matrix formation of chondrocytes. The expression of RUNX1 in mesenchymal stem cells, chondrocytes, and osteoblasts is of great significance for maintaining normal bone development and the mass and quality of bones. RUNX1 also inhibits the differentiation and bone resorptive activities of osteoclasts, which may be influenced by sexual dimorphism. In addition, RUNX1 deficiency contributes to the pathogenesis of osteoarthritis, delayed fracture healing, and osteoporosis, which was revealed by the RUNX1 conditional knockout modeling in mice. However, the roles of RUNX1 in regulating the hypertrophic differentiation of chondrocytes, the sexual dimorphism of activities of osteoclasts, as well as bone loss in diabetes mellitus, senescence, infection, chronic inflammation, etc, are still not fully understood. This review provides a systematic summary of the research progress concerning RUNX1 in the field of bone biology, offering new ideas for using RUNX1 as a potential target for bone related diseases, especially osteoarthritis, delayed fracture healing, and osteoporosis.

Resveratrol prevents ovariectomy-induced bone quality deterioration by improving the microarchitectural and biophysicochemical properties of bone.

INTRODUCTION: Osteoporosis is a major health problem that is very common worldwide and is characterized by both low bone density and deterioration in bone quality. New treatment options without side effects have become an active area of research in recent years. This study was designed to investigate the preventive effects of resveratrol on bone quality deterioration caused by ovariectomy. MATERIALS AND METHODS: Sixty rats were randomly divided into five groups (12 animals per group): Control, Sham-operated (SHAM), ovariectomized (OVX), OVX + Resveratrol-40 mg/kg/day (OVX + Res40), OVX + Resveratrol-80 mg/kg/day (OVX + Res80). Resveratrol was administered by oral gavage (40 and 80 mg/kg/day) for ten weeks. Micro-CT measurements, biomechanical testing, Raman spectroscopy analysis, and RT-PCR analysis were performed. ALP, OCN, TAS, and TOS levels were also measured from blood serum. RESULTS: Bone strength, bone volume/total volume, trabecular volume, and trabecular thickness were higher in the OVX + RES-80 group than in the OVX group. Resveratrol increased osteogenic differentiation, as the expression of osteogenic markers ALP, Col1A1, Runx2, OPG, OCN increased in both OVX + RES-80 and OVX + RES-40 groups compared to the OVX group. 80 mg/kg/day resveratrol administration decreased the levels of ALP, OCN and TOS in ovariectomized rats. Raman spectroscopy findings showed a preventive effect of resveratrol administration against ovariectomy-induced deterioration in biophysiochemical properties of bone tissue. CONCLUSION: This study revealed that administration of different doses of 80 mg/kg/day and 40 mg/kg/day of resveratrol had protective effects on bone quality deterioration caused by ovariectomy.

Bone Trans-omics: Integrating Omics to Unveil Mechanistic Molecular Networks Regulating Bone Biology and Disease.

PURPOSE OF REVIEW: Recent advancements in "omics" technologies and bioinformatics have afforded researchers new tools to study bone biology in an unbiased and holistic way. The purpose of this review is to highlight recent studies integrating multi-omics data gathered from multiple molecular layers (i.e.; trans-omics) to reveal new molecular mechanisms that regulate bone biology and underpin skeletal diseases. RECENT FINDINGS: Bone biologists have traditionally relied on single-omics technologies (genomics, transcriptomics, proteomics, and metabolomics) to profile measureable differences (both qualitative and quantitative) of individual molecular layers for biological discovery and to investigate mechanisms of disease. Recently, literature has grown on the implementation of integrative multi-omics to study bone biology, which combines computational and informatics support to connect multiple layers of data derived from individual "omic" platforms. This emerging discipline termed "trans-omics" has enabled bone biologists to identify and construct detailed molecular networks, unveiling new pathways and unexpected interactions that have advanced our mechanistic understanding of bone biology and disease. While the era of trans-omics is poised to revolutionize our capacity to answer more complex and diverse questions pertinent to bone pathobiology, it also brings new challenges that are inherent when trying to connect "Big Data" sets. A concerted effort between bone biologists and interdisciplinary scientists will undoubtedly be needed to extract physiologically and clinically meaningful data from bone trans-omics in order to advance its implementation in the field.

Entering, Linked with the Sphinx: Lysophosphatidic Acids Everywhere, All at Once, in the Oral System and Cancer.

Oral health is crucial to overall health, and periodontal disease (PDD) is a chronic inflammatory disease. Over the past decade, PDD has been recognized as a significant contributor to systemic inflammation. Here, we relate our seminal work defining the role of lysophosphatidic acid (LPA) and its receptors (LPARs) in the oral system with findings and parallels relevant to cancer. We discuss the largely unexplored fine-tuning potential of LPA species for biological control of complex immune responses and suggest approaches for the areas where we believe more research should be undertaken to advance our understanding of signaling at the level of the cellular microenvironment in biological processes where LPA is a key player so we can better treat diseases such as PDD, cancer, and emerging diseases.

Development of an in vivo radiographic method with potential for use in improving bone quality and the welfare of laying hens through genetic selection.

1. Genetic selection for bone quality can improve this, as it is heritable. A method was established using digital X-ray which took around 40 s in total and gave an image that allowed quantification of bone density from many appendicular bones.2. The tibiotarsus measurement of bone density on the live hen across the different experiments had correlations with post-mortem whole bone radiographic density from 0.62 to 0.7, similar to that between density and material properties for example. Differences between groups of hens, where calcium and phosphorus in the diet were manipulated, were detected within 3 weeks of treatment using live hen measurement (P < 0.001, n = 24).3. In a gage analysis, 'hen' explained more than 86% of the variance, demonstrating the ability to observe clear differences between hens. The effect of different operators' analysis on the contribution to variance was very low as was the repeated measurement of the same hen.4. The measurement of bone density on the live hen described in this paper represented major progress to a usable method for genetic selection to improve bone strength in laying hens. The method has the potential to reduce the number of animals needed to test nutritional and management interventions to improve bone health.

Molecular structure, expression, and the emerging role of Siglec-15 in skeletal biology and cancer.

Siglec-15, a Siglec family member and type-1 transmembrane protein, is expressed mainly in human macrophages and dendritic cells. It is comprised of a lysine-containing transmembrane domain, two extracellular immunoglobulin (Ig)-like domains and a short cytoplasmic domain. Siglec-15 is highly conserved in vertebrates and acts as an immunoreceptor. It exerts diverse functions on osteoclast physiology as well as the tumor microenvironment. Siglec-15 interacts with adapter protein DAP12 - Syk signaling pathway to regulate the RANKL/RANK-mediated PI3K, AKT, and ERK signaling pathways during osteoclast formation in vitro. Consistently, the lack of the Siglec-15 gene in mice leads to impaired osteoclast activity and osteopetrosis in vivo. In addition, Siglec-15 is expressed by tumor-associated macrophages (TAMs) and regulates the tumor microenvironment by activating the SYK/MAPK signaling pathway. Interestingly, Siglec-15 shares sequence homology to programmed death-ligand 1 (PD-L1) and has a potential immune-regulatory role in cancer immunology. Thus, Siglec-15 might also represent an alternative target for the treatment of cancers that do not respond to anti-PD-L1/PD-1 immunotherapy. Understanding the role of Siglec-15 in osteoclastogenesis and the tumor microenvironment will help us to develop new treatments for bone disorders and cancer.

Bone markers and bone mineral density associates with periodontitis in females with poly-cystic ovarian syndrome.

INTRODUCTION: Studies suggest an association between poly-cystic ovarian syndrome (PCOS) and chronic periodontitis (CP), both being inflammatory conditions. However, insufficient evidence assesses the impact of this inflammation on bone metabolism and bone turnover markers (BTMs). The present study aimed to determine the association between BTMs, bone mineral density (BMD), and clinical periodontal parameters in PCOS women with CP. MATERIALS AND METHODS: Three groups, each with 40 newly diagnosed (1) PCOS+CP, (2) PCOS alone, (3) CP alone, and fourth group (n = 20) systemically and periodontally healthy females aged 18-30 years were included in the study. Full mouth clinical periodontal parameters, C-terminal telopeptides of type I collagen (CTX), bone alkaline phosphatase (ALP), BMD and 25-hydroxyvitamin D (VD) were recorded for all. RESULTS: Low BMD (0.89 ± 0.11 g/cm2), increased CTX levels (2.76 ± 4.64 ng/ml), decreased bone ALP levels (11.09 ± 6.86 ng/ml), higher VD levels (289.02 ± 168.28 nmol/l) and poor clinical periodontal status were observed in PCOS + CP females. BMD-spine showed weak positive correlation with CTX, bone ALP, VD (r = 0.02, r = 0.07, r = 0.15, respectively) in PCOS + CP group. ANCOVA depicted covariates had no confounding effect. Multiple regression model explained 21.0% for BMD-spine and 12.7% for BMD-femur of total variability signifying association with all measured parameters among all groups. CONCLUSION: Enhanced inflammatory thrust by periodontitis increases CTX levels and decreases bone ALP and BMD levels in women with PCOS. Screening PCOS women for periodontal disease and vice versa may have a direct bearing on overall bone health.

Latex proteins from Plumeria pudica reduce ligature-induced periodontitis in rats.

BACKGROUND: Previous studies have shown that latex proteins from Plumeria pudica (LPPp) have anti-inflammatory and antioxidant activity. Therefore, the aim of this study was to evaluate the effects in rats of LPPp on ligature-induced periodontitis, an inflammatory disease. METHODS: The animals were divided into groups: saline (animals without induction of periodontitis), periodontitis (induced periodontitis and untreated) and LPPp (induced periodontitis and treated with 40 mg/kg). The following parameters were evaluated after 20 consecutive days of treatment: gingival bleeding index (GBI), probing pocket depth (PPD), alveolar bone height (ABH) and gingival myeloperoxidase (MPO) activity. In the hepatic tissue, malondialdehyde (MDA), glutathione (GSH) and histopathological alterations were evaluated. Blood levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured. RESULTS: Significant reduction in GBI, PPD and gingival MPO activity and ABH was seen in animals treated with LPPp compared with periodontitis. Values of GSH, MDA, ALT and histopathological evaluation were preserved in animals treated with LPPp. CONCLUSIONS: Treatment with LPPp improved clinical aspects of periodontitis, reduced the blood and hepatic alterations and prevented alveolar bone loss. Data suggest that LPPp have potential for treatment of periodontitis.

Cranial Base Synchondrosis Lacks PTHrP-Expressing Column-Forming Chondrocytes.

The cranial base contains a special type of growth plate termed the synchondrosis, which functions as the growth center of the skull. The synchondrosis is composed of bidirectional opposite-facing layers of resting, proliferating, and hypertrophic chondrocytes, and lacks the secondary ossification center. In long bones, the resting zone of the epiphyseal growth plate houses a population of parathyroid hormone-related protein (PTHrP)-expressing chondrocytes that contribute to the formation of columnar chondrocytes. Whether PTHrP+ chondrocytes in the synchondrosis possess similar functions remains undefined. Using Pthrp-mCherry knock-in mice, we found that PTHrP+ chondrocytes predominantly occupied the lateral wedge-shaped area of the synchondrosis, unlike those in the femoral growth plate that reside in the resting zone within the epiphysis. In vivo cell-lineage analyses using a tamoxifen-inducible Pthrp-creER line revealed that PTHrP+ chondrocytes failed to establish columnar chondrocytes in the synchondrosis. Therefore, PTHrP+ chondrocytes in the synchondrosis do not possess column-forming capabilities, unlike those in the resting zone of the long bone growth plate. These findings support the importance of the secondary ossification center within the long bone epiphysis in establishing the stem cell niche for PTHrP+ chondrocytes, the absence of which may explain the lack of column-forming capabilities of PTHrP+ chondrocytes in the cranial base synchondrosis.

Maximum insertion torque loss after miniscrew placement in orthodontic patients: A randomized controlled trial.

OBJECTIVES: To compare torque recordings of immediately loaded orthodontic miniscrews between insertion time and different post-placement timepoints (2 weeks, 4 weeks and removal time, respectively). SETTING AND SAMPLE POPULATION: Parallel trial with an allocation ratio of 1:1. Eligibility criteria were needs of fixed orthodontic treatment, no systemic disease and absence of using drugs altering bone metabolism. MATERIAL AND METHODS: Patients received miniscrews, 2.0 mm diameter and 10 mm length. All miniscrews underwent inter-radicular placement, and they were placed in the maxilla or in the mandible, palatally or buccally. No pre-drilling was performed. Miniscrews were loaded immediately after the insertion and were used for distalization, intrusion, extrusion, mesialization or indirect anchorage. Patients were randomly divided into three groups. For each patient, Maximum Insertion Torque (MIT) was evaluated at baseline. MIT was measured again after 2 weeks and after 4 weeks by tightening the screw a quarter of turn in Groups 1 and 2, respectively. At the end of the treatment, maximal removal torque was evaluated in Group 3. Torque variation with respect to insertion time was considered as the primary outcome. Baseline and longitudinal differences were tested using the linear mixed-effects (LME) model. RESULTS: Forty seven patients and 74 miniscrews were followed up. An association existed between maximum insertion torque and the observation time. A torque decrease of 26.9% and 30% after 2 weeks was observed for mandibular and maxillary miniscrews, respectively. After 1 month, torque values were similar to the baseline records. The overall success rate was 79.7%. No serious harm was observed. CONCLUSIONS: Maximum insertion torque undergoes a loss during the first 2 weeks, and its values may depend on the insertion site and the anchorage purpose. Removal torque value is almost the same as the initial torque after 1 month.

Deferoxamine Reduces Inflammation and Osteoclastogenesis in Avulsed Teeth.

Replacement and inflammatory resorption are serious complications associated with the delayed replantation of avulsed teeth. In this study, we aimed to assess whether deferoxamine (DFO) can suppress inflammation and osteoclastogenesis in vitro and attenuate inflammation and bone resorption in a replanted rat tooth model. Cell viability and inflammation were evaluated in RAW264.7 cells. Osteoclastogenesis was confirmed by tartrate-resistant acid phosphatase staining, reactive oxygen species (ROS) measurement, and quantitative reverse transcriptase-polymerase chain reaction in teeth exposed to different concentrations of DFO. In vivo, molars of 31 six-week-old male Sprague-Dawley rats were extracted and stored in saline (n = 10) or DFO solution (n = 21) before replantation. Micro-computed tomography (micro-CT) imaging and histological analysis were performed to evaluate inflammation and root and alveolar bone resorption. DFO downregulated the genes related to inflammation and osteoclastogenesis. DFO also reduced ROS production and regulated specific pathways. Furthermore, the results of the micro-CT and histological analyses provided evidence of the decrease in inflammation and hard tissue resorption in the DFO group. Overall, these results suggest that DFO reduces inflammation and osteoclastogenesis in a tooth replantation model, and thus, it has to be further investigated as a root surface treatment option for an avulsed tooth.

Computed tomography assessment of maxillary bone density for orthodontic mini-implant placement with respect to vertical growth patterns.

OBJECTIVE: To quantitatively measure and report bone density of maxilla in the interradicular (alveolar and basal bone) and infrazygomatic crest (IZC) region in various growth patterns among Dravidian individuals. DESIGN: This was a retrospective spiral computed tomography (CT) study. SETTING: The study was conducted at the Department of Orthodontics, Saveetha Dental College and Hospital, Tamil Nadu, India. METHODS: Sixty CT scans (24 men, 36 women; mean age = 25.3 years and 23.8 years, respectively) divided equally into three groups based on vertical facial proportions were included. Bone density measurements in Hounsfield units (HU) were performed using Philips and RadiAnt DICOM viewers. Buccal cortical, palatal cortical and cancellous bone regions were analysed in a Philips DICOM viewer and IZC region was analysed in a RadiAnt DICOM viewer. Statistical analysis with one-way ANOVA and post-hoc Tukey HSD test was done. RESULTS: The hypodivergent group had a significantly higher bone density at the buccal cortex in posterior region (P < 0.05) when compared to the normodivergent and hyperdivergent groups. Buccal basal bone was denser than buccal alveolar bone (P < 0.05) in all three groups. In the IZC region, hypodivergent groups had significantly higher density values when compared to the normodivergent and hyperdivergent groups (P < 0.05). CONCLUSION: The present study concluded that cancellous bone density in the interradicular regions was greatest in the anterior sites and was not influenced by growth pattern. Hypodivergent groups tend to have higher density in the posterior regions (buccal and palatal cortical bone) and at the IZC region compared to normodivergent and hyperdivergent groups.

Concurrent Local Delivery of Diflunisal Limits Bone Destruction but Fails To Improve Systemic Vancomycin Efficacy during Staphylococcus aureus Osteomyelitis.

Staphylococcus aureus osteomyelitis is a debilitating infection of bone. Treatment of osteomyelitis is impaired by the propensity of invading bacteria to induce pathological bone remodeling that may limit antibiotic penetration to the infectious focus. The nonsteroidal anti-inflammatory drug diflunisal was previously identified as an osteoprotective adjunctive therapy for osteomyelitis, based on the ability of this compound to inhibit S. aureus quorum sensing and subsequent quorum-dependent toxin production. When delivered locally during experimental osteomyelitis, diflunisal significantly limits bone destruction without affecting bacterial burdens. However, because diflunisal's "quorum-quenching" activity could theoretically increase antibiotic recalcitrance, it is critically important to evaluate this adjunctive therapy in the context of standard-of-care antibiotics. The objective of this study is to evaluate the efficacy of vancomycin to treat osteomyelitis during local diflunisal treatment. We first determined that systemic vancomycin effectively reduces bacterial burdens in a murine model of osteomyelitis and identified a dosing regimen that decreases bacterial burdens without eradicating infection. Using this dosing scheme, we found that vancomycin activity is unaffected by the presence of diflunisal in vitro and in vivo Similarly, locally delivered diflunisal still potently inhibits osteoblast cytotoxicity in vitro and bone destruction in vivo in the presence of subtherapeutic vancomycin. However, we also found that the resorbable polyester urethane (PUR) foams used to deliver diflunisal serve as a nidus for infection. Taken together, these data demonstrate that diflunisal does not significantly impact standard-of-care antibiotic therapy for S. aureus osteomyelitis, but they also highlight potential pitfalls encountered with local drug delivery.

Three-dimensional characterization of osteocyte volumes at multiple scales, and its relationship with bone biology and genome evolution in ray-finned fishes.

Osteocytes, cells embedded within the bone mineral matrix, inform on key aspects of vertebrate biology. In particular, a relationship between volumes of the osteocytes and bone growth and/or genome size has been proposed for several tetrapod lineages. However, the variation in osteocyte volume across different scales is poorly characterized and mostly relies on incomplete, two-dimensional information. In this study, we characterize the variation of osteocyte volumes in ray-finned fishes (Actinopterygii), a clade including more than half of modern vertebrate species in which osteocyte biology is poorly known. We use X-ray synchrotron micro-computed tomography (SRµCT) to achieve a three-dimensional visualization of osteocyte lacunae and direct measurement of their size (volumes). Our specimen sample is designed to characterize variation in osteocyte lacuna morphology at three scales: within a bone, among the bones of one individual and among species. At the intra-bone scale, we find that osteocyte lacunae vary noticeably in size between zones of organized and woven bone (being up to six times larger in woven bone), and across cyclical bone deposition. This is probably explained by differences in bone deposition rate, with larger osteocyte lacunae contained in bone that deposits faster. Osteocyte lacuna volumes vary 3.5-fold among the bones of an individual, and this cannot readily be explained by variation in bone growth rate or other currently observable factors. Finally, we find that genome size provides the best explanation of variation in osteocyte lacuna volume among species: actinopterygian taxa with larger genomes (polyploid taxa in particular) have larger osteocyte lacunae (with a ninefold variation in median osteocyte volume being measured). Our findings corroborate previous two-dimensional studies in tetrapods that also observed similar patterns of intra-individual variation and found a correlation with genome size. This opens new perspectives for further studies on bone evolution, physiology and palaeogenomics in actinopterygians, and vertebrates as a whole.

PTH and PTHrP Actions on Bone.

Parathyroid hormone (PTH), PTH-related peptide (PTHrP), PTHR, and their cognate G protein-coupled receptor play defining roles in the regulation of extracellular calcium and phosphate metabolism and in controlling skeletal growth and repair. Acting through complex signaling mechanisms that in many instances proceed in a tissue-specific manner, precise control of these processes is achieved. A variety of direct and indirect disease processes, along with genetic anomalies, can cause these schemes to become dysfunctional. Here, we review the basic components of this regulatory network and present both the well-established elements and emerging findings and concepts with the overall objective to provide a framework for understanding the elementary aspects of how PTH and PTHrP behave and as a call to encourage further investigation that will yield more comprehensive understanding of the physiological and pathological steps at play, with a goal toward novel therapeutic interventions.

Mutant hFGF23(A12D) stimulates osteoblast differentiation through FGFR3.

Fibroblast growth factor (FGF) 23 is a member of the FGF family involved in bone development by interacting with FGFRs. In a previous study, we discovered a mutant human FGF (hFGF) 23 (A12D) in the mandibular prognathism (MP) pedigree. However, the exact role of hFGF23(A12D) during bone formation remains unclear. The aim of this study was to identify the function of hFGF23(A12D) in bone formation. We infected isolated rat calvaria (RC) cells with the recombinant lentivirus containing mutant hFGF23(A12D) and WT hFGF23 respectively. Real-time PCR, western blot and enzyme-linked immunosorbent assay confirmed that hFGF23(A12D) failed to be secreted. We measured cell growth via the CCK-8 assay based on Zsgreen expression, detected cell differentiation ability via alkaline phosphatase staining, performed RT-PCR and found that hFGF23(A12D) inhibited proliferation of RC cells and stimulated the differentiation of RC cells to osteoblasts. Through RNA sequencing, RT-PCR and western blot, we found increased expression of FGFR3. Through co-immunoprecipitation assays and immunofluorescence staining, we revealed that hFGF23(A12D) activated the mitogen-activated protein kinase signalling pathway through interactions with the intracellular domain of FGFR3. In summary, we determined the mechanisms of hFGF23(A12D) involved in osteoblast generation and formation which is specifically due to its interaction with FGFR3.

Exercise-induced loading increases ilium cortical area in a selectively bred mouse model.

OBJECTIVES: Little is known about how ilium cortical bone responds to loading. Using a mouse model, this study presents data testing the hypothesis that iliac cross-sectional properties are altered in response to increased activity. MATERIALS AND METHODS: The sample derives from lines of High Runner (HR) mice bred for increased wheel-running activity. Four treatment groups of female mice were tested: non-selected control lines housed without (N = 19) and with wheels (N = 20), and HR mice housed without (N = 17) and with wheels (N = 18) for 13 weeks beginning at weaning. Each pelvis was µCT-scanned, cross-sectional properties (cortical area-Ct.Ar, total area-Tt.Ar, polar moment of area, and polar section modulus) were determined from the ilium midshaft, and robusticity indices (ratio of the square root of Ct.Ar or Tt.Ar to caudal ilium length) were calculated. Mixed models were implemented with linetype, wheel access, and presence of the mini-muscle phenotype as fixed effects, replicate line nested within linetype as a random effect, and body mass as a covariate. RESULTS: Results demonstrate that the mouse ilium morphologically resembles a long bone in cross section. Body mass and the mini-muscle phenotype were significant predictors of iliac cross-sectional properties. Wheel access only had a statistically significant effect on Ct.Ar and its robusticity index, with greater values in mice with wheel access. DISCUSSION: These results suggest that voluntary exercise increases cortical area, but does not otherwise strengthen the ilium in these mice, corroborating previous studies on the effect of increased wheel-running activity on femoral and humeral cross-sectional properties in these mice.