Central control of bone remodelling

Effects of Amnion Lyophilization Sterile Radiation against the Number of Osteoblasts and Osteocytes in Nonunion Fractures: An Experimental Research Study

Background: This study used an experimental posttest-only control group design that involved white rats of the Sprague Dawley strain. Methods: The samples used were 8-week-old rats, weighing 250–350 grams of the male sex. The study was conducted on five groups of rats with a total of seven rats per group. Results: The mean value of osteocytes in the control group was 00.00 ± 00.00 and in the ALSR group it was 87.14 ± 44.85. The mean value of osteoblasts in the control group was 50.06 ± 5.76 and in the ALSR group it was 283.63 ± 22.86. This study showed that there were differences in the number of osteocytes and osteoblasts in the two groups. Conclusion: The study reported that the ALSR group had significantly different numbers of osteoblasts and osteocytes than the control group.

Pathophysiological mechanisms of root resorption after dental trauma: a systematic scoping review

Background

The objective of this scoping review was to systematically explore the current knowledge of cellular and molecular processes that drive and control trauma-associated root resorption, to identify research gaps and to provide a basis for improved prevention and therapy.

Methods

Four major bibliographic databases were searched according to the research question up to February 2021 and supplemented manually. Reports on physiologic, histologic, anatomic and clinical aspects of root resorption following dental trauma were included. Duplicates were removed, the collected material was screened by title/abstract and assessed for eligibility based on the full text. Relevant aspects were extracted, organized and summarized.

Results

846 papers were identified as relevant for a qualitative summary. Consideration of pathophysiological mechanisms concerning trauma-related root resorption in the literature is sparse. Whereas some forms of resorption have been explored thoroughly, the etiology of others, particularly invasive cervical resorption, is still under debate, resulting in inadequate diagnostics and heterogeneous clinical recommendations. Effective therapies for progressive replacement resorptions have not been established. Whereas the discovery of the RANKL/RANK/OPG system is essential to our understanding of resorptive processes, many questions regarding the functional regulation of osteo-/odontoclasts remain unanswered.

Conclusions

This scoping review provides an overview of existing evidence, but also identifies knowledge gaps that need to be addressed by continued laboratory and clinical research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01510-6.

Interaction of bone and brain: osteocalcin and cognition

INTRODUCTION

Bone has conventionally been considered to be a passive organ that only receives external control, but according to recent findings, it has become clear that bone is an endocrine organ that actively regulates systemic metabolism through osteocalcin (OC).

METHODS

We focus on the relationship between the brain and bone and summarize the effects of OC on cognitive function as well as the association between OC and improved cognitive function through exercise.

RESULTS

The findings suggest that the decrease in OC produced by bone is responsible for the decrease in cognitive function associated with aging. Furthermore, positive effect of improving cognitive function can generally be recognized in exercise interventions conducted for healthy elderly people and those with MCI, and moderate exercise is particularly effective for dementia prevention.

CONCLUSION

The improving bone health with aging may exert beneficial effects on cognition.

Acetylcholinesterase Inhibitors Are Associated with Reduced Fracture Risk among Older Veterans with Dementia

Acetylcholinesterase inhibitors (AChEIs) have been noted to increase bone density and quality in mice. Human studies are limited but suggest an association with improved bone healing after hip fracture. We examined the relationship between AChEI use and fracture risk in a national cohort of 360,015 male veterans aged 65 to 99 years with dementia but without prior fracture using Veterans Affairs (VA) hospital, Medicare, and pharmacy records from 2000 to 2010. Diagnosis of dementia, any clinical fracture (excluding facial and digital), comorbidities, and medications were identified using ICD-9 and drug class codes. Cox proportional hazard models considering AChEI use as a time-varying covariate and adjusting for fall and fracture risk factors compared the time-to-fracture in AChEI users versus non-AChEI users. Potential confounders included demographics (age, race, body mass index), comorbidities associated with fracture or falls (diabetes, lung disease, stroke, Parkinson's, seizures, etc.) and medications associated with fracture or falls (bisphosphonates, glucocorticoids, androgen deprivation therapy [ADT], proton pump inhibitors [PPIs], selective serotonin receptor inhibitors [SSRIs], etc.). Competing mortality risk was considered using the methods of Fine and Gray. To account for persistent effects on bone density or quality that might confer protection after stopping the medication, we completed a secondary analysis using the medication possession ratio (MPR) as a continuous variable in logistic regression models and also compared MPR increments of 10% to minimal/no use (MPR 0 to <0.10). Among older veterans with diagnosis of dementia, 20.1% suffered a fracture over an average of 4.6 years of follow-up. Overall, 42.3% of the cohort were prescribed AChEIs during the study period. The hazard of any fracture among AChEI users compared with those on other/no dementia medications was significantly lower in fully adjusted models (hazard ratio [HR] = 0.81; 95% confidence interval [CI] 0.75-0.88). After considering competing mortality risk, fracture risk remained 18% lower in veterans using AChEIs (HR = 0.82; 95% CI 0.76-0.89). © 2019 American Society for Bone and Mineral Research. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.

Health-Related Quality of Life and Medical Resource Use in Patients with Osteoporosis and Depression: A Cross-Sectional Analysis from the National Health and Nutrition Examination Survey

Background: Patients with either osteoporosis or depression are prone to develop other diseases and require more medical resources than do the general population. However, there are no studies on health-related quality of life (HRQoL) and medical resource use by osteoporosis patients with comorbid depression. We conducted this study for clarifying it. Methods: This cross-sectional study from 2005 to 2010 (6 years) analyzed 9776 National Health and Nutrition Examination Survey (NHANES) patients > 40 years old. Each patient was assigned to one of four groups: osteoporosis-positive⁽⁺⁾ and depression-positive⁽⁺⁾ (O⁺/D⁺); O⁺/D⁻; O⁻/D⁺; O⁻/D⁻. We used multivariate linear and logistic regression model to analyze the HRQoL and medical resource use between groups. Results: The O⁺/D⁺ group reported more unhealthy days of physical health, more unhealthy days of mental health, and more inactive days during a specified 30 days. The adjusted odds ratios (AORs) of O⁺/D⁺ patients who had poor general health (7.40, 95% CI = 4.80–11.40), who needed healthcare (3.25, 95% CI = 2.12–5.00), and who had been hospitalized overnight (2.71, 95% CI = 1.89–3.90) were significantly highest. Conclusions: Low HRQoL was significantly more prevalent in D⁺/O⁺ patients. We found that depression severity more significantly affected HRQoL than did osteoporosis. However, both diseases significantly increased the risk of high medical resource use.

The alliance between nerve fibers and stem cell populations in bone marrow: life partners in sickness and health

The bone marrow (BM) is the central hematopoietic organ in adult mammals, with great potential to be used as a tool to improve the efficacy of the body's response to a number of malignancies and stressful conditions. The nervous system emerges as a critical regulatory player of the BM both under homeostatic and pathologic settings, with essential roles in cellular anchorage and egress, stem cell differentiation, and endothelial cell permeability. This review collects the current knowledge on the interplay between the nervous system and the BM cell populations, with a focus on how the nervous system modulates hematopoietic stem and progenitor cell, mesenchymal stromal cell, and endothelial progenitor cell activity in BM. We have also highlighted the pathologies that have been associated with disturbances in the neuronal signaling in BM and discussed if targeting the nervous system, either by modulating the activity of specific neuronal circuits or by pharmacologically leveling the activity of sympathetic and sensorial signaling-responsive cells in BM, is a promising therapeutic approach to tackling pathologies from BM origin.-Leitão, L., Alves, C. J., Sousa, D. M., Neto, E., Conceição, F., Lamghari, M. The alliance between nerve fibers and stem cell populations in bone marrow: life partners in sickness and health.

A bone-targeting drug-delivery system based on Semaphorin 3A gene therapy ameliorates bone loss in osteoporotic ovariectomized mice

Osteoporosis is a serious health problem worldwide. Semaphorins (Sema) have been described as key molecules involved in the cross-talk between bone cells (osteoblasts/osteoclasts). In this study, we investigated whether plasmid containing Sema3a could ameliorate bone loss in an ovariectomized (OVX) mouse model via (AspSerSer)₆, a selectively bone-targeting moiety. Plasmid pcDNA3.1(+)-Sema3a-GFP was fabricated and transfected cells with the plasmid demonstrated statistically higher levels of Sema3A in vitro (p < 0.001). Mice were ovariectomized and injected twice weekly with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP for four weeks. The aim of the study was twofold: firstly to design an effective bone-targeting drug-delivery system (AspSerSer)₆. Secondly, the effects of Sem3A gene therapy on bone loss was investigated. Here, the targeting selectivity of pcDNA3.1(+)-Sema3a-GFP via (AspSerSer)₆ to the trabecular bone surface was firstly verified by histological observation of frozen sections and immunofluorescence staining. Then, bone microstructure analysis by Micro-CT indicated significantly less bone loss in mice treated with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP compared to the control group (p < 0.05). Furthermore,H&E staining and Safranin O staining of the decalcified sections demonstrated statistically significantly higher bone area/total area in the mice that were injected with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP (p < 0.001, p < 0.01,respectively). TRAP staining and immunohistochemistry staining of COL I demonstrated lower numbers of osteoclasts and significantly increased numbers of osteoblasts in the bone-targeting moiety delivering pcDNA3.1(+)-Sema3a-GFP group, when compared to the control group (p < 0.01, p < 0.001,respectively). Together, our findings have identified that, (AspSerSer)₆, a bone-targeting drug-delivery system based on semaphorin3A gene therapy, ameliorated bone loss in osteoporotic ovariectomized mice, by suppressing osteoclastic bone resorption and simultaneously increasing osteoblastic bone formation. Gene therapy by local site-specific Sema3A overexpression might be a potential new strategy for treating osteoporosis and bone defects.

The Effect of Previous Methylphenidate Use on Incidence of Stress Fractures in Military Recruits: A Retrospective Cohort

BACKGROUND

Previous research has detected an increased risk of stress fractures among subjects who reported previous use of methylphenidate. Conversely, stimulant medication use has been associated with traumatic fracture risk reduction, possibly because of the improved control of the underlying symptoms of attention deficit hyperactivity disorder (ADHD). The goal of this study was to investigate the effect of previous methylphenidate use on the incidence of traumatic and stress fractures among combat soldiers with previously treated and untreated ADHD.

METHODS

The retrospective cohort included 100,000 combat soldiers recruited to the Israeli Defense Forces from 2005 through 2015. Diagnosis of ADHD and previous exposure to methylphenidate were determined on the basis of self-reported recruitment questionnaires and medical records. Accordingly, the cohort was divided into 3 groups: subjects with ADHD who were previously treated with methylphenidate (n = 689), untreated subjects with ADHD reporting no medication use (n = 762), and controls having no ADHD diagnosis (n = 98,549). Logistic regressions were fitted to determine the odds ratios (ORs) of study subjects for stress and non-stress (traumatic) fractures. Multivariate analysis incorporated baseline characteristics, including age, sex, weight, duration of service, and diagnosis of anemia, at some point during the service.

RESULTS

After adjustment for sex, anemia, weight, age, and duration of service, the risk of traumatic fractures was increased in both subjects with treated ADHD (OR, 1.03 [95% confidence interval (CI), 1.00 to 1.05]) and subjects with untreated ADHD (OR, 1.04 [95% CI, 1.02 to 1.07]) compared with controls. Subjects in the treated ADHD group were at a higher risk of stress fractures (OR, 1.04 [95% CI, 1.02 to 1.07]). Interestingly, a diagnosis of anemia was an independent predictor of stress fractures (OR, 1.05 [95% CI, 1.04 to 1.06]).

CONCLUSIONS

Methylphenidate use is associated with an increased risk of stress fractures but a decreased risk of traumatic fractures in individuals diagnosed with ADHD. These and previous findings may serve as sufficient basis for screening for other risk factors and perhaps taking prevention measures in all those using stimulant medications, especially those planning to engage in strenuous physical activity.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Osteoclast-secreted SLIT3 coordinates bone resorption and formation

Coupling is the process that links bone resorption to bone formation in a temporally and spatially coordinated manner within the remodeling cycle. Several lines of evidence point to the critical roles of osteoclast-derived coupling factors in the regulation of osteoblast performance. Here, we used a fractionated secretomic approach and identified the axon-guidance molecule SLIT3 as a clastokine that stimulated osteoblast migration and proliferation by activating β-catenin. SLIT3 also inhibited bone resorption by suppressing osteoclast differentiation in an autocrine manner. Mice deficient in Slit3 or its receptor, Robo1, exhibited osteopenic phenotypes due to a decrease in bone formation and increase in bone resorption. Mice lacking Slit3 specifically in osteoclasts had low bone mass, whereas mice with either neuron-specific Slit3 deletion or osteoblast-specific Slit3 deletion had normal bone mass, thereby indicating the importance of SLIT3 as a local determinant of bone metabolism. In postmenopausal women, higher circulating SLIT3 levels were associated with increased bone mass. Notably, injection of a truncated recombinant SLIT3 markedly rescued bone loss after an ovariectomy. Thus, these results indicate that SLIT3 plays an osteoprotective role by synchronously stimulating bone formation and inhibiting bone resorption, making it a potential therapeutic target for metabolic bone diseases.

Bone turnover after bariatric surgery

OBJECTIVE

The aim of the present study was to evaluate parameters of bone and mineral metabolism after bariatric surgery.

SUBJECTS AND METHODS

This sectional study included data from medical records from 61 bariatric surgery (BS) patients (minimum period of 6 months after the procedure) and from 30 class II and III obese patients as a control group (Cont), consisting of daily dietary intake of macronutrients, calcium and sodium, serum 25(OH)D and parathyroid hormone (PTH) and other biochemical serum and urinary parameters. Bone alkaline phosphatase (BAP), leptin, fibroblast growth factor-23 (FGF-23) and deoxypyridinoline (DPYD) were determined from available banked serum and urinary samples.

RESULTS

Mean body mass index (BMI), median energy, carbohydrate, protein and sodium chloride consumption were significantly lower in the BS versus Cont, but calcium and lipids were not. No significant differences were found in ionized calcium, 25(OH)D, PTH and fibroblast growth factor 23 (FGF-23) between groups. Mean serum BAP was significantly higher for BS versus Cont and had a positive correlation with time after the surgical procedure. Mean serum leptin was significantly lower and median urinary DPYD higher in BS versus Cont.

CONCLUSION

The present study showed an increase in bone markers of both bone formation and resorption among bariatric patients up to more than 7 years after the surgical procedure, suggesting that an increased bone turnover persists even at a very long-term follow-up in such patients.

The Role of Semaphorin 3A in Bone Remodeling

Bone remodeling occurs at the bone surface throughout adult life and associates bony quantity and quality. This process is a balance between the osteoblastic bone formation and osteoclastic bone resorption, which cross-talks together. Semaphorin 3A is a membrane-associated secreted protein and regarded as a diffusible axonal chemorepellent, which has been identified in the involvement of bone resorption and formation synchronously. However, the role of Semaphorin 3A in bone homeostasis and diseases remains elusive, in particular the association to osteoblasts and osteoclasts. In this review article, we summarize recent progress of Semaphorin 3A in the bone mass, homeostasis, and diseases and discuss the novel application of nerve-based bone regeneration. This will facilitate the understanding of Semaphorin 3A in skeletal biology and shed new light on the modulation and potential treatment in the bone disorders.

Temporal sequence of hard and soft tissue healing around titanium dental implants

The objective of the present review was to summarize the evidence available on the temporal sequence of hard and soft tissue healing around titanium dental implants in animal models and in humans. A search was undertaken to find animal and human studies reporting on the temporal dynamics of hard and soft tissue integration of titanium dental implants. Moreover, the influence of implant surface roughness and chemistry on the molecular mechanisms associated with osseointegration was also investigated. The findings indicated that the integration of titanium dental implants into hard and soft tissue represents the result of a complex cascade of biological events initiated by the surgical intervention. Implant placement into alveolar bone induces a cascade of healing events starting with clot formation and continuing with the maturation of bone in contact with the implant surface. From a genetic point of view, osseointegration is associated with a decrease in inflammation and an increase in osteogenesis-, angiogenesis- and neurogenesis-associated gene expression during the early stages of wound healing. The attachment and maturation of the soft tissue complex (i.e. epithelium and connective tissue) to implants becomes established 6-8 weeks following surgery. Based on the findings of the present review it can be concluded that improved understanding of the mechanisms associated with osseointegration will provide leads and targets for strategies aimed at enhancing the clinical performance of titanium dental implants.

Long-Term Oral Toxicity and Anti-osteoporotic Effect of Sintered Dicalcium Pyrophosphate in Rat Model of Postmenopausal Osteoporosis

Sintered dicalcium pyrophosphate (SDCP), a synthetic pyrophosphate analog, has shown potential for the management of osteoporosis. The long-term oral toxicity and anti-osteoporotic effect of SDCP in a postmenopausal osteoporosis rat model were evaluated in this study. SDCP was orally administered to bilateral ovariectomized (OVX) Wistar rats at a dose of 0.75 mg/kg daily for 24 weeks following by 2 weeks of observation. There were no abnormal findings in clinical signs of toxicity, food consumption, body weight, blood examination, necropsy, and histological inspection attributable to the ingestion of SDCP. The serum level of type I collagen fragments, a bone resorption marker, decreased in SDCP-treated rats, and the bone formation markers alkaline phosphatase, osteocalcin, and osteopontin significantly decreased. These findings indicate that the bone turnover rate decreased in SDCP-treated animals. Relative to OVX rats, the increase in serum tartrate-resistant acid phosphatase 5b level represents an increase in bony tissues in the SDCP-treated rats. Histological examinations of distal femoral metaphyses further revealed that the ingestion of SDCP improved the trabecular bone architecture and decreased bone porosity. Analysis of limb bone ashes showed a significant increase in bone mineral content. Our results show that SDCP inhibits bone resorption to restore bone mass in OVX rats without deleterious effects, and therefore that SDCP has potential in the management of osteoporosis.

Naringin ameliorates bone loss induced by sciatic neurectomy and increases Semaphorin 3A expression in denervated bone

Naringin maintains bone mass in various osteoporosis models, while its effect on bone in disuse osteoporosis has not been reported. The present study explores whether naringin can prevent disuse osteoporosis induced by unilateral sciatic neurectomy (USN) and whether the Semaphorin 3A-induced Wnt/β-catenin signalling pathway is involved in the osteoprotection of naringin. Naringin dose-dependently prevented the deterioration of bone mineral density (BMD), trabecular structure and biomechanical strength in femur due to USN. Naringin increased bone formation but inhibited resorption, as indicated by bone-turnover markers in blood and urine and the histological staining of Osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP) in femur. Semaphorin 3A (Sema3A) and active β-catenin protein decreased after USN and could be restored by naringin to the levels of the sham-operated rats. In addition, naringin in vitro promoted the differentiation of osteoblasts and inhibited osteoclastic differentiation. Our studies suggest that the down-regulation of Sema3A and the subsequent inactivation of Wnt/β-catenin signalling may be some of the mechanisms involved in USN-induced osteoporosis. Naringin could increase the expression of Sema3A and the activation of Wnt/β-catenin signalling to prevent disuse osteoporosis induced by denervation. Thus, naringin functions in bone maintenance and could be a promising therapeutic alternative in preventing disuse osteoporosis.

Sim1 inhibits bone formation by enhancing the sympathetic tone in male mice

Single-minded 1 (Sim1) is a basic helix-loop-helix Per-Arnt-Sim transcription factor that is important for neuronal development in the hypothalamus. Loss-of-function mutation of Sim1 causes early-onset obesity. However, it is unknown whether and how Sim1 regulates bone remodeling. In this study, we found that adult-onset Sim1 deletion increases bone formation, leading to high bone mass. In contrast, Sim1-overexpressing transgenic mice exhibit decreased bone formation and low bone mass. Sim1 does not directly regulate osteoblastogenesis, because bone marrow mesenchymal stem cells from Sim1 mutant mice display a normal capacity for osteoblast differentiation. Instead, Sim1 inhibits bone formation via stimulating the sympathetic nervous system, because sympathetic tone is decreased by Sim1 deletion but increased by Sim1 overexpression. Treatment with the β-adrenergic agonist isoproterenol effectively reverses the high bone mass in Sim1-knockout mice. These findings reveal Sim1 as a critical yet previously unrecognized modulator of skeletal homeostasis that functions through a central relay.

Endocrinology of bone/brain crosstalk

Bone metabolism is regulated by the action of two skeletal cells: osteoblasts and osteoclasts. This process is controlled by many genetic, hormonal and lifestyle factors, but today more and more studies have allowed us to identify a neuronal regulation system termed 'bone-brain crosstalk', which highlights a direct relationship between bone tissue and the nervous system. The first documentation of an anatomic relationship between nerves and bone was made via a wood cut by Charles Estienne in Paris in 1545. His diagram demonstrated nerves entering and leaving the bones of a skeleton. Later, several studies were conducted on bone innervation and, as of today, many observations on the regulation of bone remodeling by neurons and neuropeptides that reside in the CNS have created a new research field, that is, neuroskeletal research.

Impact on bone and muscle area after spinal cord injury

Spinal cord injury (SCI) causes inactivation and consequent unloading of affected skeletal muscle and bone. This cross-sectional study investigated correlations of muscle and bone in spinal cord-injured subjects compared with able-bodied subjects. Thirty-one complete SCI paraplegics were divided according to the neurological level of injury (NLoI) into group A (n=16, above thoracic 7 NLoI, age: 33±16 years, duration of paralysis (DoP): 6±6 years) and group B (n=15, thoracic 8-12, age: 39±14 years, DoP: 5.6±6 years), compared with 33 controls (group C). All were examined with peripheral quantitative computed tomography at 66% of tibia length (bone and muscle area, bone/muscle area ratio). In able-bodied subjects, muscle area was correlated with bone area (P<0.001, r=0.88). Groups A and B differed significantly from the control group in terms of bone and muscle area (P<0.001). In paraplegics, less muscle per unit of bone area (bone/muscle area ratio) was found compared with controls (P<0.001). Bone area was negatively correlated with the DoP in the total paraplegic group (r=-0.66, P<0.001) and groups A and B (r=-0.77, P=0.001 vs r=-0.52, P=0.12, respectively). Muscle area and bone/muscle ratio area correlations in paraplegic groups with DoP were weak. Paraplegic subjects who performed standing and therapeutic walking had significantly higher bone area (P=0.02 and P=0.013, respectively). The relationship between bone and muscle was consistent in able-bodied subjects and it was predictably altered in those with SCI, a clinical disease affecting bone and muscle.

Gene expression profiling of peri-implant healing of PLGA-Li+ implants suggests an activated Wnt signaling pathway in vivo

Bone development and regeneration is associated with the Wnt signaling pathway that, according to literature, can be modulated by lithium ions (Li+). The aim of this study was to evaluate the gene expression profile during peri-implant healing of poly(lactic-co-glycolic acid) (PLGA) implants with incorporated Li+, while PLGA without Li+ was used as control, and a special attention was then paid to the Wnt signaling pathway. The implants were inserted in rat tibia for 7 or 28 days and the gene expression profile was investigated using a genome-wide microarray analysis. The results were verified by qPCR and immunohistochemistry. Histomorphometry was used to evaluate the possible effect of Li+ on bone regeneration. The microarray analysis revealed a large number of significantly differentially regulated genes over time within the two implant groups. The Wnt signaling pathway was significantly affected by Li+, with approximately 34% of all Wnt-related markers regulated over time, compared to 22% for non-Li+ containing (control; Ctrl) implants. Functional cluster analysis indicated skeletal system morphogenesis, cartilage development and condensation as related to Li+. The downstream Wnt target gene, FOSL1, and the extracellular protein-encoding gene, ASPN, were significantly upregulated by Li+ compared with Ctrl. The presence of β-catenin, FOSL1 and ASPN positive cells was confirmed around implants of both groups. Interestingly, a significantly reduced bone area was observed over time around both implant groups. The presence of periostin and calcitonin receptor-positive cells was observed at both time points. This study is to the best of the authors' knowledge the first report evaluating the effect of a local release of Li+ from PLGA at the fracture site. The present study shows that during the current time frame and with the present dose of Li+ in PLGA implants, Li+ is not an enhancer of early bone growth, although it affects the Wnt signaling pathway.

Netrin-4 derived from murine vascular endothelial cells inhibits osteoclast differentiation in vitro and prevents bone loss in vivo

Bone is a highly vascularized organ, thus angiogenesis is a vital process during bone remodeling. However, the role of vascular systems in bone remodeling is not well recognized. Here we show that netrin-4 inhibits osteoclast differentiation in vitro and in vivo. Co-cultures of bone marrow macrophages with vascular endothelial cells markedly inhibited osteoclast differentiation. Adding a neutralizing antibody, or RNA interference against netrin-4, restored in vitro osteoclast differentiation. Administration of netrin-4 prevented bone loss in an osteoporosis mouse model by decreasing the osteoclast number. We propose that vascular endothelial cells interact with bone in suppressing bone through netrin-4.

Role of leptin in Legg-Calvé-Perthes disease

Obesity is considered a clinical risk sign for Legg-Calvé-Perthes disease (LCPD). Leptin is primarily secreted by adipocytes, and it regulates adipose tissue mass and body weight. Furthermore, obesity is clearly associated with increased leptin levels. We investigated the roles of leptin and the soluble leptin receptor (sOB-R) in LCPD. This matched case-control study included 38 male and 3 female patients with LCPD, and an equal number of age-(range was 4-12) and sex-matched control patients with healthy fractures. Serum leptin and sOB-R levels were quantified with ELISA. The free leptin index (FLI) was defined as the ratio of leptin to sOB-R levels. Serum leptin levels, sOB-R, and FLI were compared between groups. The relationship between leptin, disease severity, and treatment outcomes were analyzed in the LCPD group. There were no significant differences between groups in terms of age, sex, and body mass index (BMI) percentile. Mean leptin levels (p = 0.042), sOB-R levels (p = 0.003), and FLI (p = 0.013) differed significantly between groups. In the LCPD group, the serum leptin levels, sOB-R levels, and FLI differed significantly between the lateral pillar and Stulberg classification groups (p < 0.05). Also, the leptin levels and FLI increased significantly according to the lateral pillar and Stulberg classifications even after adjusting for age and BMI percentile (p < 0.05). Circulating leptin and FLI were significantly higher in the LCPD group. Furthermore, leptin, disease severity, and treatment outcomes were associated. This correlation suggests that leptin might play an important role in LCPD pathogenesis.

Cannabinoid receptor signaling in progenitor/stem cell proliferation and differentiation

Cannabinoids, the active components of cannabis (Cannabis sativa) extracts, have attracted the attention of human civilizations for centuries, much earlier than the discovery and characterization of their substrate of action, the endocannabinoid system (ECS). The latter is an ensemble of endogenous lipids, their receptors [in particular type-1 (CB1) and type-2 (CB2) cannabinoid receptors] and metabolic enzymes. Cannabinoid signaling regulates cell proliferation, differentiation and survival, with different outcomes depending on the molecular targets and cellular context involved. Cannabinoid receptors are expressed and functional from the very early developmental stages, when they regulate embryonic and trophoblast stem cell survival and differentiation, and thus may affect the formation of manifold adult specialized tissues derived from the three different germ layers (ectoderm, mesoderm and endoderm). In the ectoderm-derived nervous system, both CB1 and CB2 receptors are present in neural progenitor/stem cells and control their self-renewal, proliferation and differentiation. CB1 and CB2 show opposite patterns of expression, the former increasing and the latter decreasing along neuronal differentiation. Recently, endocannabinoid (eCB) signaling has also been shown to regulate proliferation and differentiation of mesoderm-derived hematopoietic and mesenchymal stem cells, with a key role in determining the formation of several cell types in peripheral tissues, including blood cells, adipocytes, osteoblasts/osteoclasts and epithelial cells. Here, we will review these new findings, which unveil the involvement of eCB signaling in the regulation of progenitor/stem cell fate in the nervous system and in the periphery. The developmental regulation of cannabinoid receptor expression and cellular/subcellular localization, together with their role in progenitor/stem cell biology, may have important implications in human health and disease.

Bone health and associated metabolic complications in neuromuscular diseases

This article reviews the recent literature regarding bone health as it relates to the patient living with neuromuscular disease (NMD). Studies defining the scope of bone-related disease in NMD are scant. The available evidence is discussed, focusing on abnormal calcium metabolism, increased fracture risk, and the prevalence of both scoliosis and hypovitaminosis D in Duchenne muscular dystrophy, amyotrophic lateral sclerosis, and spinal muscular atrophy. Future directions are discussed, including the urgent need for studies both to determine the nature and extent of poor bone health, and to evaluate the therapeutic effect of available osteoporosis treatments in patients with NMD.

The nervous system's potential role in multiple sclerosis associated bone loss

Osteoporosis is a degenerative bone disease that causes significant morbidity and mortality in multiple sclerosis (MS) patients; the pathogenesis of this disease being poorly understood in the context of MS. Osteoporosis is seen more frequently in MS patients than in healthy controls matched for age and sex. Extensively studied factors, including impaired ambulation and the use of steroids, do not appear to completely account for the phenomenon. This review summarizes common risk factors, physiologic and genetic, that may contribute to the etiology and progression of osteoporosis in MS patients as well as providing insight into nervous system control of bone metabolism and homeostasis.

Transgenic overexpression of tartrate-resistant acid phosphatase is associated with induction of osteoblast gene expression and increased cortical bone mineral content and density

Bone remodeling is a central event in the maintenance of skeletal tissue, and involves cycles of resorption followed by the formation of bone tissue. The activity of osteoclasts and osteoblasts during these cycles is tightly regulated by systemic and local factors coupling the action of these cells. Tartrate-resistant acid phosphatase (TRAP) is predominantly expressed in bone by osteoclasts but has also been detected in osteoblasts and osteocytes. Moreover, TRAP can stimulate the differentiation of mesenchymal lineage cells, i.e. progenitors of osteoblasts and adipocytes. In order to further explore the effects of TRAP on bone turnover, the structural and molecular phenotypes of osteoclasts and osteoblasts were assessed in TRAP-overexpressing transgenic mice. Transgenic mice of both sexes display increased cortical bone mineral content and density, which cannot be accounted for by decreased bone resorption since osteoclast numbers and resorptive activity do not differ from wild-type mice. Examination of the osteoblast phenotype revealed that markers of bone formation, i.e. procollagen type I N-terminal propeptides, and osteoblast lineage markers as well as the TRAP 1B mRNA transcript are increased in TRAP-overexpressing mice. Expression of the osteoclast-selective TRAP 1C mRNA is not increased in TRAP transgenic mice. Elevated expression of TRAP mRNA and protein were detected in osteoblasts, osteocytes and in the bone matrix of TRAP transgenic mice, suggesting that TRAP overexpression in osteoblast lineage cells is associated with increased cortical bone mineral content and density. The data presented here support the hypothesis that TRAP overexpression in the osteoblastic cell lineage stimulates the differentiation and/or activation of these cells.

Interactions between Serum Adipokines and Osteocalcin in Older Patients with Hip Fracture

Introduction. Experiments on genetically modified animals have discovered a complex cross-regulation between adipokines (leptin, adiponectin) and osteocalcin. The relationships between these molecules in human osteoporosis are still unclear. We evaluated the hypothesis of a bidirectional link between adipokines and osteocalcin. Materials and Methods. In a cross-sectional study of 294 older patients with osteoporotic hip fracture, we estimated serum concentrations of leptin, adiponectin, resistin, osteocalcin, parameters of mineral metabolism, and renal function. Results. After adjustment for multiple potential confounders, serum osteocalcin concentration was inversely associated with resistin and positively with leptin, leptin/resistin ratio, and adiponectin/resistin ratio. In multivariate regression models, osteocalcin was an independent predictor of serum leptin, resistin, leptin/resistin, and adiponectin/resistin ratios. Conclusions. Our data support the bidirectional regulation between osteocalcin and adipokines, but contrary to the genetically modified animal models, in older subjects with osteoporotic hip fracture, serum osteocalcin is positively associated with leptin and inversely with resistin.

Oxytocin and bone remodelling: relationships with neuropituitary hormones, bone status and body composition

PURPOSE

There is growing evidence that oxytocin, which regulates appetite, plays a role in bone remodelling and improves osteoporosis. We previously showed a significant decrease in circulating oxytocin levels in postmenopausal osteoporotic women compared to healthy controls. However, factors involved in the pathophysiology of osteoporosis, such as estrogens and leptin, are known to regulate oxytocin secretion. Herein, we evaluated the relationships between oxytocin and other hormonal factors known to regulate bone remodeling and body composition in postmenopausal osteoporotic women, compared to healthy controls.

METHODS

In 20 postmenopausal women with severe osteoporosis compared to 16 healthy controls, we measured serum levels of oxytocin, high sensitive estradiol, testosterone, FSH, LH, SHBG, TSH, osteocalcin, serum type I collagen carboxy-terminal telopeptide, leptin. Bone mineral density and body composition were also measured with DXA.

RESULTS

Osteoporotic women had significantly lower oxytocin, leptin and LH serum levels and higher CTX and SHBG; all other biological parameters were similar in both groups. Fat mass and lean mass were significantly decreased in osteoporotic women. Oxytocin serum levels were significantly correlated to bone mineral density but not to any other measured parameter, including leptin, estradiol and age. In a logistic regression analysis, osteoporosis remained significantly correlated to oxytocin, regardless of age.

CONCLUSIONS

Low oxytocin serum levels appeared to be associated with severe osteoporosis, independently of other factors associated with osteoporosis or known to regulate oxytocin serum levels, such as estradiol or leptin, reinforcing the concept that oxytocin may be involved in the pathophysiology of postmenopausal osteoporosis.

Preproenkephalin (Penk) is expressed in differentiated osteoblasts, and its deletion in Hyp mice partially rescues their bone mineralization defect

Although our understanding of the molecular mechanisms controlling osteoblast differentiation and function is steadily increasing, there are still many open questions, especially regarding the regulation of bone matrix mineralization. For instance, while there is hallmark evidence for the importance of the endopeptidase Phex, whose inactivation in Hyp mice or human patients causes X-linked hypophosphatemic rickets, it is still largely unknown how Phex controls bone mineralization since a physiological substrate for its endopeptidase activity has not been identified yet. Using a genome-wide expression analysis comparing primary calvarial osteoblasts, we have identified preproenkephalin (Penk) as a gene that is selectively expressed in mineralized cultures. Since a role of enkephalin in the regulation of bone remodeling has been suggested previously and since Leu-enkephalin is known to be cleaved by Phex, we analyzed whether Penk expression in osteoblasts is physiologically relevant. Through skeletal analysis of a Penk-deficient mouse model, we found that Penk expression is dispensable for bone development and remodeling since we could not detect any defect following nondecalcified bone histology and histomorphometry compared to wild-type littermates. When Penk was deleted in Phex-deficient Hyp mice, however, we observed a significant reduction of the osteoid enrichment at 24 weeks of age, whereas their disturbance of mineral homeostasis was not affected by the additional absence of the Penk gene. Taken together, our data provide the first in vivo analysis concerning the role of Penk in osteoblasts.

Serum markers of bone turnover are increased at six and 18 months after Roux-en-Y bariatric surgery: correlation with the reduction in leptin

OBJECTIVE

The aim of the study was to examine serum markers of bone turnover at 6 and 18 months after Roux-en-Y gastric bypass surgery.

PARTICIPANTS

Ten women and 10 men [body mass index (BMI), 50.2 +/- 8.4 kg/m(2)] were studied at 6 months; 10 women and nine men (BMI, 47.2 +/- 6.6 kg/m(2)) were studied at 18 months after surgery.

MAIN OUTCOME MEASURES

Serum osteocalcin, bone specific alkaline phosphatase (BAP), N-telopeptide of type 1 collagen (NTX), PTH, 25-hydroxy vitamin D, and leptin were measured.

RESULTS

BMI was reduced 32.7 +/- 6.2% at 6 months after surgery. Serum osteocalcin (6.9 +/- 2.4 to 10.9 +/- 2.6 ng/ml; P < 0.0001), BAP (14.2 +/- 3.7 to 16.4 +/- 4.5 ng/ml; P = 0.04), and NTX (10.9 +/- 1.7 to 19.6 +/- 5.3 nm bone collagen equivalents; P < 0.0001) were increased. Calcium, phosphate, and PTH were unchanged, but 25-hydroxy vitamin D increased (16.0 +/- 8.9 vs. 26.9 +/- 10.6 ng/ml; P <0.0001). The increase in NTX correlated with reduction in serum leptin (r = 0.58; P = 0.007). BMI was reduced 40.9 +/- 7.5% at 18 months after surgery. Serum BAP (17.6 +/- 5.3 to 22.2 +/- 7.8 ng/ml; P = 0.0017) and NTX (10.8 +/- 2.7 to 16.9 +/- 5.5 nm bone collagen equivalents; P < 0.0001) were increased. Calcium, phosphate, and PTH were unchanged, but 25-hydroxy vitamin D increased (17.7 +/- 7.6 to 25.6 +/- 6.8 ng/ml; P < 0.0001). The increase in NTX correlated with reduction in BMI (r = 0.58; P = 0.009) and leptin (r = 0.45; P = 0.04) and the increase in serum 25-hydroxy vitamin D (r = 0.43; P = 0.05). In multiple regression (adjusted model R(2) 0.263; P = 0.013), reduction in leptin was a significant predictor of increase in NTX (P = 0.016), but changes in BMI and 25-hydroxy vitamin D were not.

CONCLUSIONS

Weight loss after bariatric surgery is associated with long-term increase in serum markers of bone turnover. The increase in NTX is related to the decrease in leptin, which may signal caloric restriction to the skeleton.

Pathogenesis of adolescent idiopathic scoliosis in girls - a double neuro-osseous theory involving disharmony between two nervous systems, somatic and autonomic expressed in the spine and trunk: possible dependency on sympathetic nervous system and hormones with implications for medical therapy

Anthropometric data from three groups of adolescent girls - preoperative adolescent idiopathic scoliosis (AIS), screened for scoliosis and normals were analysed by comparing skeletal data between higher and lower body mass index subsets. Unexpected findings for each of skeletal maturation, asymmetries and overgrowth are not explained by prevailing theories of AIS pathogenesis. A speculative pathogenetic theory for girls is formulated after surveying evidence including: (1) the thoracospinal concept for right thoracic AIS in girls; (2) the new neuroskeletal biology relating the sympathetic nervous system to bone formation/resorption and bone growth; (3) white adipose tissue storing triglycerides and the adiposity hormone leptin which functions as satiety hormone and sentinel of energy balance to the hypothalamus for long-term adiposity; and (4) central leptin resistance in obesity and possibly in healthy females. The new theory states that AIS in girls results from developmental disharmony expressed in spine and trunk between autonomic and somatic nervous systems. The autonomic component of this double neuro-osseous theory for AIS pathogenesis in girls involves selectively increased sensitivity of the hypothalamus to circulating leptin (genetically-determined up-regulation possibly involving inhibitory or sensitizing intracellular molecules, such as SOC3, PTP-1B and SH2B1 respectively), with asymmetry as an adverse response (hormesis); this asymmetry is routed bilaterally via the sympathetic nervous system to the growing axial skeleton where it may initiate the scoliosis deformity (leptin-hypothalamic-sympathetic nervous system concept = LHS concept). In some younger preoperative AIS girls, the hypothalamic up-regulation to circulating leptin also involves the somatotropic (growth hormone/IGF) axis which exaggerates the sympathetically-induced asymmetric skeletal effects and contributes to curve progression, a concept with therapeutic implications. In the somatic nervous system, dysfunction of a postural mechanism involving the CNS body schema fails to control, or may induce, the spinal deformity of AIS in girls (escalator concept). Biomechanical factors affecting ribs and/or vertebrae and spinal cord during growth may localize AIS to the thoracic spine and contribute to sagittal spinal shape alterations. The developmental disharmony in spine and trunk is compounded by any osteopenia, biomechanical spinal growth modulation, disc degeneration and platelet calmodulin dysfunction. Methods for testing the theory are outlined. Implications are discussed for neuroendocrine dysfunctions, osteopontin, sympathoactivation, medical therapy, Rett and Prader-Willi syndromes, infantile idiopathic scoliosis, and human evolution. AIS pathogenesis in girls is predicated on two putative normal mechanisms involved in trunk growth, each acquired in evolution and unique to humans.

Depression as a risk factor for osteoporosis

Osteoporosis is a major public health threat. Multiple studies have reported an association between depression and low bone mineral density, but a causal link between these two conditions is disputed. Here we review the endocrine and immune alterations secondary to depression that might affect bone mass. We also discuss the possible role of poor lifestyle in the etiology of osteoporosis in subjects with depression and the potential effect of antidepressants on bone loss. We propose that depression induces bone loss and osteoporotic fractures, primarily via specific immune and endocrine mechanisms, while poor lifestyle habits and use of specific antidepressants are potential contributory factors.

Cross-talk among bone cells

PURPOSE OF REVIEW

Bone cells such as osteoclasts, osteoblasts, and osteocytes 'talk' to each other throughout adult life to maintain bone integrity. This review highlights frontier areas of research on intercellular communication among bone cells.

RECENT FINDINGS

Bone cells communicate to regulate the balance between bone resorption and bone formation. Recent findings have suggested that bone remodeling compartment is critical for osteoclast-osteoblast communication during bone remodeling. New molecules and mechanisms for bone cell communication, including 'coupling' of bone formation to resorption, have been revealed. Osteoclastic regulation of pH within the bone remodeling compartment is a mechanism that has been posited to rapidly activate osteoblastic bone formation, whereas osteocytes in the bone matrix regulate osteoclasts and osteoblasts on the bone surface through the lacuno-canaliculi network.

SUMMARY

Differentiation, activation, and apoptosis of bone cells are often dependent on the status of other types of bone cells. Bone cells in different lineages achieve intercellular communication not only by ligand-receptor interactions but also by molecules and ions traveling in the extracellular space or across gap junctions, processes that depend profoundly on the four-dimensional (space and time) architecture of bone tissue.

Improved bone status by the beta-blocker propranolol in an animal model of nutritional growth retardation

The aim of the present research was to study if the beta-blocker propranolol, which is known to increase bone mass, could reverse the adverse skeletal effects of mild chronic food restriction in weanling rats. Male Wistar rats were divided into four groups: control, control+propranolol (CP), nutritional growth retardation (NGR) and nutritional growth retardation+propranolol (NGRP). Control and CP rats were fed freely with the standard diet. NGR and NGRP rats received, for 4 weeks, 80 % of the amount of food consumed by the control and CP rats, respectively. Results were expressed as mean values and sem. Food restriction induced detrimental effects on body and femur weight and length (P < 0.05) and bone structural and geometrical properties (P < 0.001), confirming results previously shown in our laboratory. However, the beta-blocker overcame the deleterious effect of nutritional stress on load-bearing capacity, yielding load, bone stiffness, cross-sectional cortical bone area and second moment of inertia of the cross-section in relation to the horizontal axis without affecting anthropometric, histomorphometric and bone morphometric parameters. The results suggest that propranolol administration to mildly chronically undernourished rats markedly attenuates the impaired bone status in this animal model of growth retardation.

Transcriptional analysis of fracture healing and the induction of embryonic stem cell-related genes

Fractures are among the most common human traumas. Fracture healing represents a unique temporarily definable post-natal process in which to study the complex interactions of multiple molecular events that regulate endochondral skeletal tissue formation. Because of the regenerative nature of fracture healing, it is hypothesized that large numbers of post-natal stem cells are recruited and contribute to formation of the multiple cell lineages that contribute to this process. Bayesian modeling was used to generate the temporal profiles of the transcriptome during fracture healing. The temporal relationships between ontologies that are associated with various biologic, metabolic, and regulatory pathways were identified and related to developmental processes associated with skeletogenesis, vasculogenesis, and neurogenesis. The complement of all the expressed BMPs, Wnts, FGFs, and their receptors were related to the subsets of transcription factors that were concurrently expressed during fracture healing. We further defined during fracture healing the temporal patterns of expression for 174 of the 193 genes known to be associated with human genetic skeletal disorders. In order to identify the common regulatory features that might be present in stem cells that are recruited during fracture healing to other types of stem cells, we queried the transcriptome of fracture healing against that seen in embryonic stem cells (ESCs) and mesenchymal stem cells (MSCs). Approximately 300 known genes that are preferentially expressed in ESCs and approximately 350 of the known genes that are preferentially expressed in MSCs showed induction during fracture healing. Nanog, one of the central epigenetic regulators associated with ESC stem cell maintenance, was shown to be associated in multiple forms or bone repair as well as MSC differentiation. In summary, these data present the first temporal analysis of the transcriptome of an endochondral bone formation process that takes place during fracture healing. They show that neurogenesis as well as vasculogenesis are predominant components of skeletal tissue formation and suggest common pathways are shared between post-natal stem cells and those seen in ESCs.

Frequency of osteoporosis in 46 men with methamphetamine abuse hospitalized in a National Hospital

BACKGROUND

Methamphetamine, a derivative of amphetamine, has been well known to cause mental problems in humans; however, its physical effects are little known. Despite relevant information on the effect of methamphetamine abuse on bone quality being available, data regarding the frequency of osteoporosis in methamphetamine abusers are limited.

METHODS

We selected 46 hospitalized male methamphetamine abusers and 188 reference male controls in whom any conditions affecting bone metabolism were ruled out. Bone mineral density (BMD) in the lumbar spine was measured by dual energy X-ray absorptiometry (DXA). We compared the BMD between methamphetamine abusers and controls and evaluated the frequency of osteoporosis in both groups.

RESULTS

The mean BMD value was lower in methamphetamine abusers (mean+/-SD, 0.71+/-0.07 g/cm(2)) than in the controls (mean+/-SD, 0.98+/-0.14 g/cm(2)). The frequency of osteoporosis was 22% according to WHO diagnostic guidelines, and osteopenia at the lumbar spine was 76%. The correlation between the extent of methamphetamine abuse and BMD was very clear.

CONCLUSION

There was considerable loss of bone mineral in a high percentage of methamphetamine abusers. Our study is the first clinical study to determine the frequency of osteoporosis in male methamphetamine abusers.