Bone Maintenance Research Articles

The Membrane Transporter OAT7 (SLC22A9) Is Not a Susceptibility Factor for Osteoporosis in Europeans

Bone production, maintenance, and modeling are a well-balanced process involving mineralization by osteoblasts and resorption by osteoclasts. Sex steroid hormones, including their conjugated forms, contribute majorly to maintaining this balance. Recently, variants in the SLC22A9 gene have been associated with osteoporosis in Korean females. We had recently shown that SLC22A9, encoding organic anion transporter 7 (OAT7), is an uptake transporter of estrone sulfate and identified several genetic variants in Europeans leading to functional consequences in vitro. We therefore hypothesized that SLC22A9 genetic variants may contribute to the pathophysiology of osteoporosis in Europeans. To test this hypothesis, we examined the associations of SLC22A9 variants with bone quality, fractures, and bone turnover markers. We genotyped SLC22A9 variants in 5,701 (2,930 female) subjects (age range, 20–93 years) extracted from the population-based Study of Health in Pomerania (SHIP and SHIP-TREND) covered by the Illumina Infinium HumanExome BeadChip version v1.0 (Exome Chip). Descriptive data (e.g., history of fractures), ultrasonography of the calcaneus, as well as serum concentrations of carboxy-terminal telopeptide of type I collagen, amino-terminal propeptide of type I procollagen, and vitamin D were determined. Comprehensive statistical analyses revealed no association between low-frequency and rare SLC22A9 variants and bone quality, fractures, and bone turnover markers. Our results indicate that single genetic SLC22A9 variants do not have a major impact on osteoporosis risk prediction in Europeans, yet findings need to be replicated in larger-scale studies.

Abstract 3055: Xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, shows efficacy in a human breast cancer model of bone metastasis

Abstract Bone metastases are a frequent complication of cancer and are associated with considerable morbidity. Bones provide a permissive environment for metastatic colonization due to their dynamic turnover and an abundance of secreted factors that are required for bone maintenance. Insulin-like growth factors (IGF) are the most abundant growth factors in bone and are required for normal skeletal development and function. IGFs also promote cancer progression, aggressiveness, and treatment resistance via activation of the IGF-1 receptor (IGF-1R) and insulin receptor variant A (IR-A). Of specific relevance to bone metastases, excessive bone destruction in osteolytic metastatic lesions leads to a release of IGF-1 from the bone matrix, thus promoting proliferation of metastatic tumor cells, stimulating tumor cell homing to bones, and contributing to further enhancement of bone destruction. Therapeutic targeting of the IGF axis may therefore provide an effective method for treating bone metastases. The aim of this study was to explore the efficacy of the IGF-1/-2 ligand blocking antibody, xentuzumab (BI 836845[1]), alone and in combination with the mTOR inhibitor everolimus, in a breast cancer bone metastasis xenograft model. MDA-231-BoM cells[2], a subline of MDA-MB-231 selected in vivo for enhanced metastatic ability to bone, were injected intra-cardiacly to form bone metastases, and via tail vein to form lung/visceral metastases and treated with xentuzumab, everolimus, and the combination thereof. Tumor burden was monitored by bioluminescence imaging, and metastasis-associated osteolysis was measured by quantitative bone micro-computed tomography. Tumor-associated morbidity was evaluated by a multi-parameter health scoring scheme. Metastatic tumor burden in the bone was significantly reduced upon treatment with xentuzumab in monotherapy and in combination with everolimus vs. placebo. Xentuzumab (±everolimus) reduced the number and size of osteolytic lesions, delayed and diminished bone metastasis-associated morbidity, and prolonged survival. In contrast, the growth of lung/visceral metastases developing upon intravenous injection of tumor cells was not inhibited by xentuzumab. In summary, the IGF-1/-2 neutralizing antibody xentuzumab showed efficacy in a breast cancer bone metastasis model (with and without everolimus) but did not affect metastatic tumor growth in lung/visceral organs. A phase II trial evaluating the xentuzumab/ everolimus/ exemestane triple combination in HR+BC patients with non-visceral disease is currently ongoing (NCT03659136). [1] Friedbichler et al, 2014. Mol Cancer Ther 13(2):399 [2] Kang et al, 2003. Cancer Cell 3:537 Citation Format: Ulrike Weyer-Czernilofsky, Izabela Krecioch, Stephan Handschuh, Martin Glösmann, Mario Kuttke, Robin Jacob, Anna C. Obenauf. Xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, shows efficacy in a human breast cancer model of bone metastasis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3055.

The Role of Insulin-Like Growth Factor-2 on the Cellular Viability and Differentiation to the Osteogenic Lineage and Mineralization of Stem Cells Cultured on Deproteinized Bovine Bone Mineral

Insulin-like growth factors (IGFs) plays various roles, including differentiation and mitogenesis, and IGFs are reported to regulate the bone growth and maintenance. This study was performed to analyze the enhancing effects of IGF-2 on osteogenic differentiation and the mineralization of stem cells cultured on deproteinized bovine bone mineral. Stem cell loaded bone graft material was cultured in the presence of the IGF-2 at final concentrations of 10 and 100 ng/mL and the morphology of the cells was observed on Days 1, 3, and 7. The commercially available, two-color assay based on plasma membrane integrity and esterase activity was also used for qualitative analyses on Days 1, 3, and 7. The level of alkaline phosphatase activity and anthraquinone dye assay were used to evaluate osteogenic differentiation on Days 7 and 14. Real-time polymerase chain reaction was applied in order to identify the mRNA expression of BGLAP, Runx2, and β-catenin. The stem cells were well-attached with fibroblast morphology and most of the stem cells produced a high intensity of green fluorescence, indicating that there were live cells on Day 1. The relative cellular viability assay values for IGF-2 groups at 0, 10, and 100 ng/mL on Day 1 were 0.419 ± 0.015, 0.427 ± 0.013, and 0.500 ± 0.030, respectively (p < 0.05). The absorbance values at 405 nm for alkaline phosphatase activity on Day 7 for IGF-2 at 0, 10, and 100 ng/mL were 2.112 ± 0.152, 1.897 ± 0.144, and 2.067 ± 0.128, respectively (p > 0.05). The mineralization assay results at Day 7 showed significantly higher values for IGF-2 groups at 10 and 100 ng/mL concentration when compared to the control (p < 0.05). The application of IGF-2 groups of 10 and 100 ng/mL produced a significant increase of BGLAP. Conclusively, this study indicates that the use of IGF-2 on stem cell loaded bone graft increased cellular viability, Alizarin red staining, and BGLAP expression of stem cells. This report suggests the combined approach of stem cells and IGF-2 with scaffold may have synergistic effects on osteogenesis.

Biologically structured materials

Biomimetics, biomechanics, and tissue engineering are three multidisciplinary fields that have been contemplated in this research to attain the objective of improving prosthetic implants reliability. Since testing and mathematical methods are closely interlaced, a promising approach seemed to be the combination of in vitro and in vivo experiments with computer simulations (in silico). An innovative biomimetics and biomechanics approach, and a new synthetic structure providing a microenvironment, which is mechanically coherent and nutrient conducive for tissue osteoblast cell cultures used in regenerative medicine, are presented. The novel hybrid ceramic-polymeric nanocomposites are mutually investigated by finite element analysis (FEA) biomimetic modeling, anatomic reconstruction, quantitative-computed-tomography characterization, computer design of tissue scaffold. The starting base materials are a class of innovative highly bioactive hybrid ceramic-polymeric materials set-up by the proponent research group that will be used as a bioactive matrix for the preparation of in situ bio-mineralized techno- structured porous nanocomposites. This study treats biomimetics, biomechanics and tissue engineering as strongly correlated multidisciplinary fields combined to design bone tissue scaffolds. The growth, maintenance, and ossification of bone are fundamental and are regulated by the mechanical cues that are imposed by physical activities: this biomimetic/biomechanical approach will be pursued in designing the experimental procedures for in vitro scaffold mineralization and ossification. Bio-tissue mathematical modeling serves as a central repository to interface design, simulation, and tissue fabrication. Finite element computer analyses will be used to study the role of local tissue mechanics on endochondral ossification patterns, skeletal morphology and mandible thickness distributions using single and multi-phase continuum material representations of clinical cases of patients implanted with the traditional protocols. New protocols will be hypothesized for the use of the new biologically techno-structured hybrid materials.

Bovine Milk Extracellular Vesicles Are Osteoprotective by Increasing Osteocyte Numbers and Targeting RANKL/OPG System in Experimental Models of Bone Loss

Studying effects of milk components on bone may have a clinical impact as milk is highly associated with bone maintenance, and clinical studies provided controversial associations with dairy consumption. We aimed to evaluate the impact of milk extracellular vesicles (mEVs) on the dynamics of bone loss in mice. MEVs are nanoparticles containing proteins, mRNA and microRNA, and were supplemented into the drinking water of mice, either receiving diet-induced obesity or ovariectomy (OVX). Mice receiving mEVs were protected from the bone loss caused by diet-induced obesity. In a more severe model of bone loss, OVX, higher osteoclast numbers in the femur were found, which were lowered by mEV treatment. Additionally, the osteoclastogenic potential of bone marrow-derived precursor cells was lowered in mEV-treated mice. The reduced stiffness in the femur of OVX mice was consequently reversed by mEV treatment, accompanied by improvement in the bone microarchitecture. In general, the RANKL/OPG ratio increased systemically and locally in both models and was rescued by mEV treatment. The number of osteocytes, as primary regulators of the RANKL/OPG system, raised in the femur of the OVX mEVs-treated group compared to OVX non-treated mice. Also, the osteocyte cell line treated with mEVs demonstrated a lowered RANKL/OPG ratio. Thus, mEVs showed systemic and local osteoprotective properties in two mouse models of bone loss reflected in reduced osteoclast presence. Data reveal mEV potential in bone modulation, acting via osteocyte enhancement and RANKL/OPG regulation. We suggest that mEVs could be a therapeutic candidate for the treatment of bone loss.

Bone Marrow Microvasculature.

The skeleton is highly vascularized due to the various roles blood vessels play in the homeostasis of bone and marrow. For example, blood vessels provide nutrients, remove metabolic by-products, deliver systemic hormones, and circulate precursor cells to bone and marrow. In addition to these roles, bone blood vessels participate in a variety of other functions. This article provides an overview of the afferent, exchange and efferent vessels in bone and marrow and presents the morphological layout of these blood vessels regarding blood flow dynamics. In addition, this article discusses how bone blood vessels participate in bone development, maintenance, and repair. Further, mechanical loading-induced bone adaptation is presented regarding interstitial fluid flow and pressure, as regulated by the vascular system. The role of the sympathetic nervous system is discussed in relation to blood vessels and bone. Finally, vascular participation in bone accrual with intermittent parathyroid hormone administration, a medication prescribed to combat age-related bone loss, is described and age- and disease-related impairments in blood vessels are discussed in relation to bone and marrow dysfunction. © 2020 American Physiological Society. Compr Physiol 10:1009-1046, 2020.

CCN1/Cyr61 Is Required in Osteoblasts for Responsiveness to the Anabolic Activity of PTH

CCN1/Cyr61 is a dynamically expressed matricellular protein that serves regulatory functions in multiple tissues. Previous studies from our laboratory demonstrated that CCN1 regulates bone maintenance. Using an osteoblast and osteocyte conditional knockout mouse model (Ccn1OCN ), we found a significant decrease in trabecular and cortical bone mass in vivo, in part through suppression of Wnt signaling since the expression of the Wnt antagonist sclerostin (SOST) is increased in osteoblasts lacking CCN1. It has been established that parathyroid hormone (PTH) signaling also suppresses SOST expression in bone. We therefore investigated the interaction between CCN1 and PTH-mediated responses in this study. We find that loss of Ccn1 in osteoblasts leads to impaired responsiveness to anabolic intermittent PTH treatment in Ccn1OCN mice in vivo and in osteoblasts from these mice in vitro. Analysis of Ccn1OCN mice demonstrated a significant decrease in parathyroid hormone receptor-1 (PTH1R) expression in osteoblasts in vivo and in vitro. We investigated the regulatory role of a non-canonical integrin-binding domain of CCN1 because several studies indicate that specific integrins are critical to mechanotransduction, a PTH-dependent response, in bone. These data suggest that CCN1 regulates the expression of PTH1R through interaction with the αvβ3 and/or αvβ5 integrin complexes. Osteoblasts that express a mutant form of CCN1 that cannot interact with αvβ3/β5 integrin demonstrate a significant decrease in mRNA and protein expression of both PTH1R and αv integrin. Overall, these data suggest that the αvβ3/β5-binding domain of CCN1 is required to endow PTH signaling with anabolic activity in bone cells. © 2020 American Society for Bone and Mineral Research (ASBMR).

Immediate fixed rehabilitation supported by pterygoid implants for participants with severe maxillary atrophy: 1-Year postloading results from a prospective cohort study

Statement of problemFew investigations concerning the use of pterygoid implants have reported reproducible and consistent data, making survival data controversial. PurposeThe purpose of this clinical study was to investigate the 1-year survival and success rates of pterygoid implants and prostheses in participants affected by severe atrophy of the posterior maxilla requiring a complete-arch immediate fixed prosthesis. Material and methodsFifteen participants, either completely edentulous or with failing dentition in the maxillary arch and with severe atrophy of the posterior maxilla, were enrolled in the study. All participants underwent prosthodontic rehabilitation after implant placement in both the anterior maxilla areas and the pterygoid regions. The survival data of the implants were evaluated at the time of abutment connection by means of a mobility test for each implant. After placement of the prostheses, survival was assessed by means of marginal bone maintenance as assessed by panoramic radiographs and the absence of pain or symptoms of infection. The t test was used for evaluating the difference in age between men and women (α=.05). Correlations between categorical variables (Fisher exact test) were used to evaluate the possible association between the number of implants and both the age and presence of comorbidities (α=.05). ResultsDuring the 1-year follow-up, high prosthesis stability and no implant loss were observed for all participants. In addition, participants did not report any pain or paresthesia. No peri-implant radiolucency was detected in the panoramic radiographs. Survival and success rates in the follow-up period were 100%. ConclusionsThe present study supports the conclusion that pterygoid implants have a high success rate with minimal or no complications.

Boron as Boric Acid Induces mRNA Expression of the Differentiation Factor Tuftelin in Pre-Osteoblastic MC3T3-E1 Cells.

The effects of boron on the formation and maintenance of mineralized structures at the molecular level are still not clearly defined. Thus, a study was conducted using MC3T3-E1 cells to determine whether boron affected mRNA expressions of genes associated with bone/alveolar bone formation around the teethMC3T3-E1 (clone 4) cells were cultured in media treated with boric acid at concentrations of 0, 0.1, 10, 100, or 1000ng/ml. Total RNAs of each group were isolated on day 3. Gene expression profiles were determined by using RT2 Profiler PCR micro-array that included 84 genes associated with osteogenic differentiation. Tuftelin1 mRNA expression was upregulated by all boron treatments. The upregulation was confirmed by quantitative RT-PCR using the tuftelin probe. While 100ng/ml had no effect on the integrin-α2 (Itga2) transcript and 1ng/ml boric acid induced Itga2 mRNA expression (2.1-fold), 0.1, 10, and 1000ng/ml boric acid downregulated the integrin-α2 gene transcript 2.2-, 1.5-, and 2.1-fold respectively. While 0.1ng/ml boric acid induced BMP6, increased BMP1r mRNA expression (1.5 fold) was observed in 1000ng/ml boric acid treatment. The findings suggest that boron affects the regulation of the tuftelin1 gene in osteoblastic cells. Further studies are needed to establish that the beneficial actions of boron on alveolar bone and tooth formation and maintenance include an effect on the expression of the tuftelin1 gene.

Irisin deficiency disturbs bone metabolism.

Balancing the process of bone formation and resorption is important in the maintenance of healthy bone. Therefore, the discovery of novel factors that can regulate bone metabolism remains needed. Irisin is a newly identified hormone-like peptide. Recent studies have reported the involvement of irisin in many physiological and pathological conditions with bone mineral density changes, including osteopenia and osteoporotic fractures. In this study, we generated the first line of Osx-Cre:FNDC5/irisin KO mice, in which FNDC5/irisin was specifically deleted in the osteoblast lineage. Gene and protein expressions of irisin were remarkably decreased in bones but no significant differences in other tissues were observed in knockout mice. FNDC5/irisin deficient mice showed a lower bone density and significantly delayed bone development and mineralization from early-stage to adulthood. Ourphenotypical analysis exhibited decreased osteoblast-related gene expression and increased osteoclast-related gene expression in bone tissues, and reduced adipose tissue browning due to bone-born irisin deletion. By harvesting and culturing MSCs from the knockout mice, we found that osteoblastogenesis was inhibited and osteoclastogenesis was increased. By using irisin stimulated wildtype primary cells as a gain-of-function model, we further revealed the effects and mechanisms of irisin on promoting osteogenesis and inhibiting osteoclastogenesis in vitro. In addition, positive effects of exercise, including bone strength enhancement and body weight loss were remarkably weakened due to irisin deficiency. Interestingly, these changes can be rescued by supplemental administration of recombinant irisin during exercise. Our study indicates that irisin plays an important role in bone metabolism and the crosstalk between bone and adipose tissue. Irisin represents a potential molecule for the prevention and treatment of bone metabolic diseases.

A Review of Vitamin D in Spinal Surgery: Deficiency Screening, Treatment, and Outcomes.

In this review, we discuss the demonstrated value of vitamin D in bone maintenance, fracture resistance, spinal health, and spine surgery outcomes. Despite this, the effect of vitamin D levels in spine surgery has not been well described. Through this review of literature, several conclusions were drawn. First, despite the fact that a high number of spine surgery patients are vitamin D deficient, screening is not commonly performed. Second, adequate vitamin D levels will not be achieved in a majority of these patients without supplementation. Last, inadequate vitamin D levels may increase the risk of pseudarthrosis. Given these findings, we suggest that many patients undergoing spinal surgery could be treated with vitamin D supplementation prior to surgery without the need for confirmatory testing for vitamin D deficiency. This is a more cost-effective method than screening all patients. However, future randomized trials and cost-effectiveness analyses are needed to determine the ultimate effects of vitamin D supplementation on clinical morbidity and surgical outcomes.

Is Zinc an Important Trace Element on Bone-Related Diseases and Complications? A Meta-analysis and Systematic Review from Serum Level, Dietary Intake, and Supplementation Aspects.

Bone-related diseases are very common problems, especially in the elderly population. Zinc takes part in the growth and maintenance of healthy bones. This meta-analysis aims to evaluate the effects of zinc supplementation or dietary zinc intake on serum zinc levels and bone turnover markers. A systematical research was performed with 2899 articles in PubMed, WoS, and Scopus for relevant articles in English which have mean/standard deviation values of serum zinc levels, dietary zinc intake/zinc supplementation (mg/day), and bone turnover markers up to February 2020. In the overall analysis, serum zinc level was significantly lower in patients with osteoporosis compared with controls (p 0.0002). Dietary zinc intake decreased in the fracture group compared with controls according to subgroup analysis patients with fracture (p 0.02). Zinc supplementation was effective on the femoral neck (p< 0.0001) and lumbar spine (p 0.05) bone mineral density (BMD). In the correlation analysis of the data obtained from all of the included studies, serum osteocalcin (p 0.0106, r - 0.9148) correlated with serum zinc level. In conclusion, serum zinc level and dietary zinc intake could have an essential role in preventing osteoporosis. Zinc supplementation might improve bone turnover markers for bone formation such as serum osteocalcin and serum alkaline phosphatase and also, BMD at the site of the femoral neck.

Fabrication of tooth supported overdenture using customized metal short copings: A case report

Overdenture has been a proven mainstay of conservative prosthodontic treatment when proper diagnosis, treatment planning, and most importantly, patient compliance are achieved. Despite recent developments in dental implantology, the conservative approach to root preservation followed by an overdenture is still valid. The many advantages of root retention include- alveolar bone maintenance, better prosthesis support, proprioceptive feedback, aesthetics and psychological benefits. This paper presents a case report of rehabilitation of an edentulous patient with a tooth supported overdenture. Keywords: Short copings, Tooth supported, Overdenture.

Endogenous Collagenases Regulate Osteoclast Fusion.

The precise regulation of osteoclast differentiation and function is crucial for the maintenance of healthy bone. Despite several reports of collagenase expression in bone tissues, the precise isoform expression as well as the role in osteoclasts are still unclear. In the present report, the expression of matrix metalloprotease (MMP)8 and MMP13 was confirmed in mouse bone marrow macrophage osteoclast precursors. The mRNA and protein expressions of both collagenases were significantly reduced by receptor activator of nuclear factor κB ligand (RANKL) stimulation. Notably, either inhibition of MMP expression by siRNA or treatment of cells with collagenase inhibitor Ro 32-3555 significantly augmented osteoclast fusion and resorption activity without affecting the osteoclast number. The inhibition of collagenase by Ro 32-3555 increased the expression of osteoclast fusion genes, Atp6v0d2 and Dcstamp, without affecting nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) protein expression. The enhanced osteoclast fusion by collagenase inhibition appears to be mediated through an extracellular signal regulated kinase (ERK)-dependent pathway. Collectively, these data provide novel information on the regulation of osteoclast fusion process.

Prosthetic resolution of malpositioned dental implants with 5-year follow-up

The poor positioning of dental implants directly influences the functional and esthetic result of the implant-supported prosthesis. And as an alternative to correcting the positioning, prosthetic components such as prefabricated and customized abutments may be used. The current study aims to present an alternative resolution for malpositioned dental implants, with the hopes of minimizing damage to osseointegration and gingival tissues. A 53-year-old female patient had two implants in regions 11 and 21 with a height discrepancy of approximately 7 mm between them. The following treatment plan was proposed: the manufacture of two metal-free crowns and the use of a customized abutment to correct the height of the implant. A metal UCLA (Universal Long Castable Abutment) was used as a healer. The case includes 5 years of follow-up. It can be concluded that the use of a customized abutment as a prosthetic solution for an implant installed far below the cervical region of the tooth presented satisfactory esthetic and functional results with peri-implant bone maintenance and long-term gingival health.Descriptors: Dental Implantation; Dental Prosthesis, Esthetics, Dental.ReferênciasGoodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. Clinical complications with implants and implant prostheses. J Prosthet Dent. 2003;90(2):121-32.Branemark PI, Hansson BO, Adell R, Breine U, Lindström J, Hallén O, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl. 1977;16:1-132.Simensen AN, Bøe OE, Berg E, Leknes KN. Patient knowledge and expectations prior to receiving implant-supported restorations. Int J Oral Maxillofac Implants. 2015;30(1):41-7.Hyland R, Ellis J, Thomason M, El-Feky A, Moynihan P. A qualitative study on patient perspectives of how conventional and implant-supported dentures affect eating. J Dent. 2009;37(9):718-23.Arunyanak SP, Pollini A, Ntounis A, Morton D. Clinician assessments and patient perspectives of single-tooth implant restorations in the esthetic zone of the maxilla: A systematic review. J Prosthet Dent. 2017;118(1):10-17. Higginbottom FL. Implants as an option in the esthetic zone. J Oral Maxillofac Surg. 2005; 63(9 Suppl 2):33-44.Moráguez OD, Vailati F, Belser UC. Malpositioned implants in the anterior maxilla: a novel restorative approach to reestablish peri-implant tissue health and acceptable esthetics. Part II: Case report and discussion. Int J Esthet Dent. 2015;10(4):522-32.Pelekanos S, Pozi di G, Kourtis S. Restoration of divergent implants with a 2-piece screw-retained fixed, complete dental implant prostheses. J Prosthet Dent. 2016;115(4):389-92.DeFuria C, Weber HP, Kudara Y, Papaspyridakos P. Management of a Malpositioned Implant in the Anterior Maxilla. Compend Contin Educ Dent. 2017;38(3):e9-e12.Scutellà F, Weinstein T, Lazzara R, Testori T. Buccolingual implant position and vertical abutment finish line geometry: two strictly related factors that may influence the implant esthetic outcome. Implant Dent. 2015;24(3):343-8.Funato A, Salama MA, Ishikawa T, Garber DA, Salama H. Timing, positioning, and sequential staging in esthetic implant therapy: a four-dimensional perspective. Int J Periodontics Restorative Dent. 2007;27(4):313-23.Pjetursson BE, Asgeirsson AG, Zwahlen M, Sailer I. Improvements in implant dentistry over the last decade: comparison of survival and complication rates in older and newer publications. Int J Oral Maxillofac Implants. 2014;29 Suppl:308-24.Fuentealba R, Jofré J. Esthetic failure in implant dentistry. Dent Clin North Am. 2015;59(1):227-46.Kim DG, Elias KL, Jeong YH, Kwon HJ, Clements M, Brantley WA, et al. Differences between buccal and lingual bone quality and quantity of peri-implant regions. J Mech Behav Biomed Mater. 2016;60:48-55.Arai K, Takeda Y, Mori Y, Terauchi R, Furumori T, Tanaka S, et al. Analysis of factors associated with maintenance discontinuation in implant patients. Springerplus. 2015;12;4:767.

Bone blood flow regulation in humans

Bone is a highly vascularized organ with an extensive network of arteries, arterioles, and capillaries that is critical for bone development, maintenance, and repair. Despite the importance of bone circulation to bone health, the regulation of blood flow to bone is not well understood in humans. One of the potential factors controlling bone blood flow is the sympathetic nervous system, bone vasculature being innervated by a rich network of sympathetic nerves. While no human studies have been conducted, animal data suggests that sympathetic activation reduces bone blood flow. If this were not the case, bone vasculature would respond simply as a passive pressure system. Therefore, we characterized bone blood flow regulation in health young individuals (N=12 (8M; 4F), 23±0.7 years) in response to isometric handgrip to fatigue (IHE). Sustained IHE is a profound pressor stimulus, resulting in active vasoconstriction in the nonactive leg and progressive increases in blood pressure. During IHE at 30% of maximal voluntary contraction, we measured blood pressure, whole leg blood flow (via Doppler ultrasound), and tibial blood perfusion (via near infrared spectroscopy). Tibial blood perfusion was determined as changes from resting baseline in oxygenated and deoxygenated hemoglobin content. Data is presented as mean change from resting baseline ± standard error. To account for different IHE time courses, all variables were normalized to 100% duration and averaged across individuals. Blood pressure increased progressively to end of IHE (at 10%: 5.46 ± 1.30 mmHg; at 100%: 48.0 ± 4.32 mmHg). Whole leg blood flow decreased progressively throughout IHE, suggesting active sympathetic vasoconstriction in the leg (at 10%: −0.70 ± 0.28 cm/s; at 100%: −2.26 ± 0.50 cm/s). Similarly, tibial oxygenated hemoglobin decreased progressively throughout the test (at 10%: −0.21 ± 0.31 μM; at 100%: −1.19 ± 1.12 μM) whereas tibial deoxygenated hemoglobin did not change significantly throughout IHE (at 10%: 0.06 ± 0.07 μM; at 100%: −0.4 ± 0.32 μM). This indicates that arterial flow (oxygenated hemoglobin) declined while bone metabolism (deoxygenated hemoglobin) remained unchanged in response to IHE. It should be noted that the decline in oxygenated hemoglobin was slower and lesser than that in whole leg blood flow. This data suggests that sympathetic activity is involved in controlling bone circulation, but vasoconstrictor responses is not as fast or as robust in bone as it is in the whole leg.Support or Funding InformationParalyzed Veterans of America (AED)

Characterization of the pathophysiological processes of osteoarthritis using RNA sequencing data of subchondral bone

Purpose: Osteoarthritis (OA) has a considerable genetic component and genetic research has resulted in many insights into underlying disease pathways. Most recent large-scale genomic association studies have identified TGFA , MGP, CHADL as compelling genes involved in the aetiology of OA. The functions of these genes confirm that deviations in both cartilage and bone maintenance processes are major pathways underlying OA pathology in humans. Moreover, follow-up studies have shown that risk SNPs frequently modulate pathology due to altering transcription of the genes in cis both in bone and cartilage. Nonetheless, follow up study of these genes towards underlying biological mechanisms, preclinical studies on target discovery and eventually drug testing have thus far focused on gene expression profiling in articular cartilage. The aim of the current study was to characterize interactive pathophysiological processes of subchondral bone and articular cartilage in human osteoarthritis (OA) in large human cohort RNA sequencing. Methods: We performed RNA sequencing on macroscopically preserved and lesioned OA subchondral bone of patients that underwent a joint replacement surgery due to OA (N=24 pairs; 6 hips, 18 knees, RAAK-study). Unsupervised hierarchical clustering and differential expression analysis were performed on the data. Gene enrichment was performed using the online tool DAVID. Moreover, we compared the differentially expressed genes identified here to our previously reported differentially expressed genes in OA articular cartilage. Results: Upon performing cluster analysis we identified two clusters; one representing hips and the other representing knees. Due to the low hip sample size, differential expression analysis was performed on knee samples only. As shown in Figure 1, we identified 1757 significantly differentially expressed genes between lesioned and preserved subchondral bone. The most significantly downregulated gene was FRZB (FC=0.48, FDR=3.07x10-12), encoding the frizzled receptor protein and is a well-known cartilage OA gene. The most significantly upregulated gene was CNTNAP2 (FC=2.90, FDR=3.38x10-6), encoding the contactin-associated protein-like 2 protein (CASPR2). Among the 1757 differentially expressed genes, 102 genes showed an absolute foldchange of 2 or higher. The highest upregulated gene was STMN2 (FC=23.0, FDR=1.8x10-4), encoding stathmin 2, while the most downregulated gene was CHRDL2 (FC=0.09, FDR=4.13x10-6), encoding chordin-like protein 2 and is also known to be involved in OA in cartilage. Enrichment of the differentially expressed genes resulted in significant enrichment of GO-terms regarding the extracellular matrix. To investigate whether the subchondral bone and the articular cartilage show similarities in the OA pathophysiological processes, we compared the results presented here with our previously reported results on differentially expressed genes in OA articular cartilage. As a result, we identified 398 genes that were differentially expressed in both tissues, of which 361 showed similar directions of effect, including the genes IL11, encoding Interleukin 11, and CHADL, encoding Chondroadherin-Like Protein. Conclusions: To our knowledge, we are the first to report on the differential expression pattern of OA subchondral bone using RNA sequencing on a large sample size while integrating these with differential expression patterns of cartilage of the same individuals. By performing cluster analysis on our RNA sequencing data, we identified two clusters representing hips and knees, respectively. These clusters indicate distinct OA pathophysiological processes in the subchondral bone between the two joint sites, which was not previously seen with similar analyses of the cartilage. Among the most consistently differentially expressed genes with OA pathophysiology in bone and cartilage are IL11, and CHADL. Notably, these genes were recently found in large GWA studies on OA indicating also their causal involvement in the OA pathophysiology. Moreover, IL11 was recognized as being targeted by FDA approved drugs. As such, we advocate that IL11 could be an attractive potential drug for OA patients with a therapeutic effect both in cartilage and subchondral.

A study on vitamin D status among orthopaedic patients

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; There is an alarmingly high prevalence of hypovitaminosis D in orthopaedic patients, regardless of whether or not, they require surgical intervention. Vitamin D plays an essential role in bone formation, maintenance, and remodelling, as well as muscle function and deficiency could affect adversely in multiple ways. Many reports recently demonstrated high rates of vitamin D deficiency, in numerous segments of Indian population, but there is no study reported so far from India, which focuses specifically on vitamin D status in orthopaedic patients.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; It is a descriptive study to&lt;strong&gt; &lt;/strong&gt;estimate vitamin D levels in patients scheduled to undergo orthopaedic surgery. Vitamin D, calcium, phosphorus and alkaline phosphatase (ALP) levels in 310 patients, who were admitted at our institution, from December 2015 to August 2017 were measured.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Out of 310 patients included in our study, 189 (61%) were males and 121 (39%) females. Vitamin D deficiency (&amp;lt;20 ng/ml) was present in 232 patients, insufficiency (&amp;lt;30 ng/ml) was present in 63 patients and only 15 patients had desirable levels (&amp;gt;30 ng/ml). Patients younger than 60 years and males had more prevalence of Vitamin D abnormality. 168 (72.4%) of the patients, with deficiency presented in winter, compared to 64 (27.6%) in summer.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; Statistically significant vitamin D deficiency was seen during winter months, in patients undergoing hip hemiarthroplasty, and in patients admitted for degenerative disease of the spine, hip and knee. Screening and treating hypovitaminosis D appears to be important in orthopaedic patients as vitamin D deficiency is prevalent across all age groups in the population studied.&lt;/p&gt;

Efficacy of Alveolar Ridge Preservation: A Randomized Controlled Trial

Alveolar ridge preservation (ARP) therapy is indicated to attenuate the physiologic resorptive events that occur as a consequence of tooth extraction with the purpose of facilitating tooth replacement therapy. This randomized controlled trial was primarily aimed at testing the efficacy of ARP as compared with unassisted socket healing. A secondary objective was to evaluate the effect that local phenotypic factors play in the volumetric reduction of the alveolar bone. A total of 53 subjects completed the study. Subjects were randomized into either the control group, which involved only tooth extraction (EXT n = 27), or the experimental group, which received ARP using a combination of socket grafting with a particulate bone allograft and socket sealing with a nonabsorbable membrane (dPTFE) following tooth extraction (ARP n = 26). A set of clinical, linear, volumetric, implant-related, and patient-reported outcomes were assessed during a 14-wk healing period. All linear bone assessments (horizontal, midbuccal, and midlingual reduction) revealed that ARP is superior to EXT. Likewise, volumetric bone resorption was significantly higher in the control group (mean ± SD: EXT = −15.83% ± 4.48%, ARP = −8.36% ± 3.81%, P < 0.0001). Linear regression analyses revealed that baseline buccal bone thickness is a strong predictor of alveolar bone resorption in both groups. Interestingly, no significant differences in terms of soft tissue contour change were observed between groups. Additional bone augmentation to facilitate implant placement in a prosthetically acceptable position was deemed necessary in 48.1% of the EXT sites and only 11.5% of the ARP sites (P < 0.004). Assessment of perceived postoperative discomfort at each follow-up visit revealed a progressive decrease over time, which was comparable between groups. Although some extent of alveolar ridge remodeling occurred in both groups, ARP therapy was superior to EXT as it was more efficacious in the maintenance of alveolar bone and reduced the estimated need for additional bone augmentation at the time of implant placement (ClinicalTrials.gov NCT01794806).

Control of XPR1-dependent cellular phosphate efflux by InsP8 is an exemplar for functionally-exclusive inositol pyrophosphate signaling

Homeostasis of cellular fluxes of inorganic phosphate (Pi) supervises its structural roles in bones and teeth, its pervasive regulation of cellular metabolism, and its functionalization of numerous organic compounds. Cellular Pi efflux is heavily reliant on Xenotropic and Polytropic Retrovirus Receptor 1 (XPR1), regulation of which is largely unknown. We demonstrate specificity of XPR1 regulation by a comparatively uncharacterized member of the inositol pyrophosphate (PP-InsP) signaling family: 1,5-bis-diphosphoinositol 2,3,4,6-tetrakisphosphate (InsP8). XPR1-mediated Pi efflux was inhibited by reducing cellular InsP8 synthesis, either genetically (knockout [KO] of diphosphoinositol pentakisphosphate kinases [PPIP5Ks] that synthesize InsP8) or pharmacologically [cell treatment with 2.5 µM dietary flavonoid or 10 µM N2-(m-trifluorobenzyl), N6-(p-nitrobenzyl) purine], to inhibit inositol hexakisphosphate kinases upstream of PPIP5Ks. Attenuated Pi efflux from PPIP5K KO cells was quantitatively phenocopied by KO of XPR1 itself. Moreover, Pi efflux from PPIP5K KO cells was rescued by restoration of InsP8 levels through transfection of wild-type PPIP5K1; transfection of kinase-dead PPIP5K1 was ineffective. Pi efflux was also rescued in a dose-dependent manner by liposomal delivery of a metabolically resistant methylene bisphosphonate (PCP) analog of InsP8; PCP analogs of other PP-InsP signaling molecules were ineffective. High-affinity binding of InsP8 to the XPR1 N-terminus (Kd = 180 nM) was demonstrated by isothermal titration calorimetry. To derive a cellular biology perspective, we studied biomineralization in the Soas-2 osteosarcoma cell line. KO of PPIP5Ks or XPR1 strongly reduced Pi efflux and accelerated differentiation to the mineralization end point. We propose that catalytically compromising PPIP5K mutations might extend an epistatic repertoire for XPR1 dysregulation, with pathological consequences for bone maintenance and ectopic calcification.