Guidelines for Dual Energy X-Ray Absorptiometry Analysis of Trabecular Bone-Rich Regions in Mice: Improved Precision, Accuracy, and Sensitivity for Assessing Longitudinal Bone Changes

Guava leaf extract attenuated muscle proteolysis in dexamethasone induced muscle atrophic mice via ubiquitin proteasome system, mTOR-autophagy, and apoptosis pathway

Muscle atrophy is the waste or loss of muscle mass and is caused by physical inactivity, aging, or diseases such as diabetes, cancer, and heart failure. The number of patients suffering from musculoskeletal disorders is expected to increase in the future. However, intervention for muscle atrophy is limited, so research on treatment for muscle wasting is needed. This study hypothesized that guava leaf (Psidium guajava L. [GL]) would have ameliorative effects on muscle atrophy by regulation of protein degradation pathways in a dexamethasone (DEX)-induced muscle atrophy mice model. Muscle atrophy was induced by DEX injection for 28 days in 7 week-old-male ICR mice. Then, low-dose GL (LGL, 200 mg/kg) or high-dose GL (HGL, 500 mg/kg) extract (GLE) was supplemented by oral gavage for 21 days. Muscle strength, calf thickness, and body composition were analyzed. Histopathological changes in the gastrocnemius muscle were examined using hematoxylin and eosin staining, and molecular pathways related to muscle degradation were analyzed by western blots. GLE treatment regardless of dose increased muscle strength in mice with muscle atrophy accompanied by attenuating autophagy related pathway in the DEX-induced muscle atrophy mice. Moreover, a high dose of GLE treatment ameliorated ubiquitin proteasome system and apoptosis in the DEX-induced muscle atrophy mice. This study suggested that GLE could be helpful to improve muscle health and alleviate proteolysis by regulation of the ubiquitin-proteasome system, autophagy, and apoptosis, which are involved in muscle degradation. In conclusion, GLE could be a potential nutraceutical to prevent muscle atrophy.

Computed Tomography Provides Improved Quantification of Trabecular Lumbar Spine Bone Loss Compared to Dual-Energy X-Ray Absorptiometry in Ovariectomized Sheep

Early detection of osteoporosis using advanced imaging is imperative to the successful treatment and prevention of high morbidity fractures in aging patients. In this preclinical study, we aimed to compare dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) to quantify bone mineral density (BMD) changes in the sheep lumbar spine. We also aimed to determine the relationship of BMD to microarchitecture in the same animals as an estimate of imaging modality precision. Osteoporosis was induced in 10 ewes via laparoscopic ovariectomy and administration of high-dose corticosteroids. We performed DXA and QCT imaging to measure areal BMD (aBMD) and trabecular volumetric BMD (Tb.vBMD)/cortical vBMD (Ct.vBMD), respectively, at baseline (before ovariectomy) and at 3, 6, 9, and 12 months after ovariectomy. Iliac crest bone biopsies were collected at each time point for micro-computed tomography (microCT) analysis; bone volume fraction (BV/TV), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp) were reported. aBMD and Tb.vBMD both decreased significantly by 3 and 6 months (p < 0.05) compared with baseline, whereas no changes to Ct.vBMD were observed. Combined (Tb. and Ct.) vBMD was significantly correlated with aBMD at all time points (all p < 0.05). Additionally, greater significant correlations were found between BV/TV and Tb.vBMD at all five time points (R 2 = 0.54, 0.57, 0.66, 0.46, and 0.56, respectively) than with aBMD values (R 2 = 0.23, 0.55, 0.41, 0.20, and 0.19, respectively). The higher correlation of microCT values with QCT than with DXA indicates that QCT provides additional detailed information regarding bone mineral density changes in preclinical settings. Because trabecular bone is susceptible to rapid density loss and structural changes during osteoporosis, QCT can capture these subtle changes more precisely than DXA in a large animal preclinical model. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Hounsfield Unit-Calculated Bone Mineral Density Loss Following Combat-Related Lower Extremity Amputations

BACKGROUND

After combat-related lower extremity amputations, patients rapidly lose bone mineral density (BMD). As serial dual x-ray absorptiometry (DXA) scans are rarely performed in this setting, it is difficult to determine the timeline for bone loss and recovery or the role of interventions. However, a strong correlation has been demonstrated between DXA BMD and computed tomography (CT) signal attenuation. We sought to leverage multiple CT scans obtained after trauma to develop a predictive model for BMD after combat-related lower extremity amputations.

METHODS

We reviewed amputations performed within the United States military between 2003 and 2016 in patients with multiple CT scans. We collected pertinent clinical information, including amputation level(s), complications, and time to weight-bearing. The primary outcome measure was the development of low BMD, estimated in Hounsfield units (HU) from CT scans with use of a previously validated method. One hundred and twenty-eight patients with 613 femoral neck CT scans were available for analysis. A least absolute shrinkage and selection operator (LASSO) multiple logistic regression analysis was applied to determine the effects of modifiable and non-modifiable variables on BMD. A random-effects model was applied to determine which factors were most predictive of low BMD and to quantify their effects.

RESULTS

Both amputated and non-amputated extremities demonstrated substantial BMD loss, which stabilized approximately 3 years after the injury. Loss of BMD followed a logarithmic pattern, stabilizing after 1,000 days. On average, amputated limbs lost approximately 100 HU of BMD after 1,000 days. Other factors identified by the mixed-effects model included nonambulatory status (-33.5 HU), age at injury (-3.4 HU per year), surgical complications delaying weight-bearing (-21.3 HU), transtibial amputation (20.9 HU), and active vitamin-D treatment (-19.7 HU).

CONCLUSIONS

Patients with combat-related lower extremity amputations experience an initially rapid decline in BMD in both intact and amputated limbs as a result of both modifiable and non-modifiable influences, including time to walking, amputation level, surgical complications, and age. The paradoxical association of vitamin-D supplementation with lower HU likely reflects this treatment being assigned to patients with low BMD. This model may assist with clinical decision-making prior to performing lower extremity amputation and also may assist providers with postoperative decision-making to optimize management for prophylaxis against osteoporosis.

LEVEL OF EVIDENCE

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

Bisphosphonate conjugation enhances the bone-specificity of NELL-1-based systemic therapy for spaceflight-induced bone loss in mice

Microgravity-induced bone loss results in a 1% bone mineral density loss monthly and can be a mission critical factor in long-duration spaceflight. Biomolecular therapies with dual osteogenic and anti-resorptive functions are promising for treating extreme osteoporosis. We previously confirmed that NELL-like molecule-1 (NELL-1) is crucial for bone density maintenance. We further PEGylated NELL-1 (NELL-polyethylene glycol, or NELL-PEG) to increase systemic delivery half-life from 5.5 to 15.5 h. In this study, we used a bio-inert bisphosphonate (BP) moiety to chemically engineer NELL-PEG into BP-NELL-PEG and specifically target bone tissues. We found conjugation with BP improved hydroxyapatite (HA) binding and protein stability of NELL-PEG while preserving NELL-1's osteogenicity in vitro. Furthermore, BP-NELL-PEG showed superior in vivo bone specificity without observable pathology in liver, spleen, lungs, brain, heart, muscles, or ovaries of mice. Finally, we tested BP-NELL-PEG through spaceflight exposure onboard the International Space Station (ISS) at maximal animal capacity (n = 40) in a long-term (9 week) osteoporosis therapeutic study and found that BP-NELL-PEG significantly increased bone formation in flight and ground control mice without obvious adverse health effects. Our results highlight BP-NELL-PEG as a promising therapeutic to mitigate extreme bone loss from long-duration microgravity exposure and musculoskeletal degeneration on Earth, especially when resistance training is not possible due to incapacity (e.g., bone fracture, stroke).

Juvenile Bone Toxicity: Study Considerations, Regulations, and Techniques for Assessment

Recommendations on study designs that adequately evaluate the in-life effects leading to juvenile bone toxicity, the various imaging modalities that can aid interpretation of the bone effects, biomarkers that may be useful, and regulatory issues were presented in this 2020 ACT symposium. The pathologies encountered in past studies were briefly mentioned. The first speaker covered study design and the numbers of juveniles that may be necessary to power the evaluation. Changes in the International Council for Harmonisation (IHC) guidelines were reviewed. The second speaker launched the rest of the symposium by describing the tools that may help assess juvenile bone toxicity, specifically those used to monitor bone toxicity, healing, and remodeling as they relate or drive the study design including model, species selection, and age. The third speaker addressed in more depth the micro-Computed Tomography (CT) applications in juvenile toxicology for evaluation of skeletal elements and bone growth in both embryo-fetal development (EFD) and pre and postnatal development (PPND) studies. Lastly, a regulatory perspective on strategies to assess juvenile bone toxicity and the concerns of the regulatory agency with respect to these potential changes in the juvenile population was addressed.

Allolobophora caliginosa coelomic fluid and extract alleviate glucocorticoid-induced osteoporosis in mice by suppressing oxidative stress and regulating osteoblastic/osteoclastic-related markers

Allolobophora calignosa (Ac) is a folk medicine for millennia, as it possesses many biological activities. This study aimed to investigate the chemo-preventive activity of A.calignosa coelomic fluid (AcCF) and A.calignosa extract (AcE) on glucocorticoid-induced osteoporosis (GIOP) in mice. Characterization and in vitro biological activity of AcE and AcCF has been assessed. Male CD-1 mice were subcutaneously received dexamethasone (DEX) (1 mg/kg, 5 times/week) and concurrently intraperitoneally treated with either AcCF (20 mg/kg) or AcE (45 mg/kg) every other day for 28 days. Serum and bone homogenates were subjected for qPCR and biochemical analysis. AcE and AcCF treatment significantly increased bone mineral density (BMD), bone mineral content (BMC), calcium (Ca), phosphorus (P), and calcitonin levels, whereas activity of serum alkaline phosphatase (ALP), bone alkaline phosphatase (BALP), serum acidic phosphatase (ACP), bone acidic phosphatase (BACP) and parathyroid hormone (PTH) levels were significantly reduced compare with untreated GIOP mice. Treatment with AcE and AcCF modulates oxidative stress and downregulated Rank and Mmp9 expression, as well as increased glycosaminoglycan content in the organic bone matrix, resulting in osteoclastogenesis inhibition. Overall, AcCF and AcE show a chemo-preventive activity against GIOP by inhibiting oxidative stress and regulating expression and/or activity of osteoblast/osteoclast-related markers.

Augmenting Skeletal Muscle Estrogen Does not Prevent or Rescue Obesity-linked Metabolic Impairments in Female Mice

AIMS

We developed a novel mouse model with increased skeletal muscle estrogen content via inducible, skeletal-muscle-specific aromatase overexpression (SkM-Arom↑). We proposed to examine the effect that increased skeletal muscle estrogen both in gonadally intact and ovariectomized (OVX) female mice has on preventing or rescuing high-fat diet (HFD)-induced obesity.

METHODS

In the prevention experiment, gonadally intact and OVX SkM-Arom↑ mice and littermate controls were fed a low-fat diet (LFD) or HFD for 13 weeks. SkM-Arom↑ was induced at the initiation of dietary treatment. In the intervention experiment, gonadally intact and OVX SkM-Arom↑ mice and littermate controls were fed an HFD for 14 weeks before induction of SkM-Arom↑ for 6 weeks. Glucose tolerance, insulin action, adipose tissue inflammation, and body composition were assessed. Liquid chromatography-mass spectrometry was used to determine circulating and skeletal muscle steroid content.

RESULTS

SkM-Arom↑ significantly increased skeletal muscle 17β-estradiol (E2) and estrone (E1) in both experiments. Interestingly, this resulted in leakage of estrogens into circulation, producing a physiologically relevant E2 concentration. Consequently, bone mineral density (BMD) was enhanced and adipose tissue inflammation was reduced in the prevention experiment only. However, no benefits were seen with respect to changes in adiposity or metabolic outcomes.

CONCLUSION

We show that increasing skeletal muscle estrogen content does not provide a metabolic benefit in gonadally intact and OVX female mice in the setting of obesity. However, a chronic physiological concentration of circulating E2 can improve BMD and reduce adipose tissue inflammation independently of a metabolic benefit or changes in adiposity.

Suppression of high bone remodelling by E'Jiao in ovariectomised rats

The current prevention options for postmenopausal osteoporosis are very limited. E'Jiao is a collagen-rich traditional Chinese medicine with the potential to prevent osteoporosis but more comprehensive investigations are lacking. This study aimed to investigate the skeletal protective effects of E'Jiao in a rat model of osteoporosis caused by ovariectomy. Female Sprague Dawley rats (n = 42) were randomly assigned into baseline, sham, ovariectomised (OVX) control, OVX-treated with low-dose (0.26 g/kg), medium dose (0.53 g/kg) and high dose E'Jiao (1.06 g/kg), as well as calcium carbonate (1% w/v) groups. Daily treatment through oral gavage was initiated 7 days after OVX. The rats were euthanised after eight weeks of treatment. Bone mineral density and content were measured at baseline, 1 and 2 months after treatment. Blood was collected for the measurement of bone remodelling markers. Femur and tibial bones were collected for histomorphometry and biomechanical strength analysis. Untreated OVX rats showed high bone remodelling marked by the increased bone formation and bone resorption markers, as well as increased mineralising surface/bone surface ratio. In addition, osteoclast surface and single-labelled surface were increased while mineral apposition rate was reduced in the untreated OVX rats. These changes were antagonised by E'Jiao at all doses. However, the structural, cellular and biomechanical parameters were not affected by ovariectomy and treatment. In conclusion, E'Jiao prevented high bone remodelling during oestrogen deficiency but a long-term study will be required to establish its effects on structural and biomechanical changes due to oestrogen deficiency.

Genetic and pharmacologic suppression of PPARγ enhances NELL-1-stimulated bone regeneration

Recent investigations into mechanisms behind the development of osteoporosis suggest that suppressing PPARγ-mediated adipogenesis can improve bone formation and bone mineral density. In this study, we investigated a co-treatment strategy to enhance bone formation by combining NELL-1, an osteogenic molecule that has been extensively studied for its potential use as a therapeutic for osteoporosis, with two methods of PPARγ suppression. First, we suppressed PPARγ genetically using lentiviral PPARγ-shRNA in immunocompromised mice for a proof of concept. Second, we used a PPARγ antagonist to suppress PPARγ pharmacologically in immunocompetent senile osteopenic mice for clinical transability. We found that the co-treatment strategy significantly increased bone formation, increased the proliferation stage cell population, decreased late apoptosis of primary mouse BMSCs, and increased osteogenic marker mRNA levels in comparison to the single agent treatment groups. The addition of PPARγ suppression to NELL-1 therapy enhanced NELL-1's effects on bone formation by upregulating anabolic processes without altering NELL-1's inhibitory effects on osteoclastic and adipogenic activities. Our findings suggest that combining PPARγ suppression with therapeutic NELL-1 may be a viable method that can be further developed as a novel strategy to reverse bone loss and decrease marrow adiposity in age-related osteoporosis.

Early effects of ovariectomy on bone microstructure, bone turnover markers and mechanical properties in rats

Background

Fragility fracture is one of the most serious consequences of female aging, which can increase the risk of death. Therefore, paying attention to the pathogenesis of postmenopausal osteoporosis (PMOP) is very important for elderly women.

Methods and materials

Forty 12-week-old female rats were divided into two groups including the ovariectomy (OVX) group and the control group. Four rats in each group were selected at 1, 4, 8, 12 and 16 weeks after operation. Vertebral bones and femurs were dissected completely for micro-Computed Tomography (micro-CT) scanning, biological modulus detection and histomorphological observation.

Results

In OVX group, bone volume/total volume (BV/TV), bone trabecular connection density (Conn.D) and trabecular bone number (Tb.N) decreased significantly with time (P < 0.05). The elastic modulus of femur in OVX group was lower than that in control group, but there was no significant difference between them (P > 0.05). Over time, the tartrate resistant acid phosphatase (TRAP), osteocalcin (BGP), type I procollagen amino terminal propeptide (PINP) and type I collagen carboxy terminal peptide (CTX-I) in OVX group increased significantly (P < 0.05). The micrographs of the OVX group showed sparse loss of the trabecular interconnectivity and widening intertrabecular spaces with time.

Conclusion

The bone loss patterns of vertebral body and femur were different in the early stage of estrogen deficiency. The bone turnover rate of OVX rats increased, however the changes of biomechanical properties weren’t obvious.

Bone Phenotyping Approaches in Human, Mice and Zebrafish - Expert Overview of the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal traits TranslatiOnal NEtwork")

A synoptic overview of scientific methods applied in bone and associated research fields across species has yet to be published. Experts from the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal Traits translational Network") Working Group 2 present an overview of the routine techniques as well as clinical and research approaches employed to characterize bone phenotypes in humans and selected animal models (mice and zebrafish) of health and disease. The goal is consolidation of knowledge and a map for future research. This expert paper provides a comprehensive overview of state-of-the-art technologies to investigate bone properties in humans and animals - including their strengths and weaknesses. New research methodologies are outlined and future strategies are discussed to combine phenotypic with rapidly developing -omics data in order to advance musculoskeletal research and move towards "personalised medicine".

The Use of Dual Energy X-Ray Bone Density Scan in Assessment of Alveolar Cleft Grafting Using Bone Marrow Stem Cells Concentrate/Platelet-Rich Fibrin Regenerative Technique

OBJECTIVES

To determine the densitometric quality of regenerated bone at the site of bone marrow and platelet-rich membrane grafting technique at unilateral alveolar cleft region using dual energy x-ray bone density scan (DEXA).

METHODS

The present prospective cohort study included 16 unilateral alveolar cleft patients who were selected randomly from the outpatient maxillofacial surgery clinic and suffered from unilateral alveolar cleft. Bone marrow aspirate and platelet-rich fibrin (PRF) (bone marrow stem cells + PRF) were used as the grafting material. Six months of follow-up have been conducted for all patients' including clinical and radiographic assessments with (DEXA scan).

RESULTS

Sixteen unilateral patients with a mean age of 12.56 ± 1.71 years were included in the sample and the majority of patients were females with a frequency of 56.2 percent. The current research revealed no infection or wound dehiscence. After surgery, the pain and edema scores were reasonable. Our findings showed that, after 6 months of regenerative graft, the average bone mineral density of the cleft side DEXA scan value was 1.56 ± 0.32 gm/cm2, compared to 1.51 ± 0.488 gm/cm2 on the normal side of the noncleft scan. There was no statistically significant difference in DEXA bone mineral content measurements between the cleft and standard sides (P = 0.461).

CONCLUSIONS

The bone marrow stem cells + PRF regenerative graft technique has been successfully integrated, and the DEXA scan approach for measuring regenerated grafted bone mineral content was found to be appropriate for simple and inexpensive follow-up of alveolar cleft lip patients.

The hepcidin regulator erythroferrone is a new member of the erythropoiesis-iron-bone circuitry

Background

Erythroblast erythroferrone (ERFE) secretion inhibits hepcidin expression by sequestering several bone morphogenetic protein (BMP) family members to increase iron availability for erythropoiesis.

Methods

To address whether ERFE functions also in bone and whether the mechanism of ERFE action in bone involves BMPs, we utilize the Erfe-/- mouse model as well as β-thalassemic (Hbbth3/+) mice with systemic loss of ERFE expression. In additional, we employ comprehensive skeletal phenotyping analyses as well as functional assays in vitro to address mechanistically the function of ERFE in bone.

Results

We report that ERFE expression in osteoblasts is higher compared with erythroblasts, is independent of erythropoietin, and functional in suppressing hepatocyte hepcidin expression. Erfe-/- mice display low-bone-mass arising from increased bone resorption despite a concomitant increase in bone formation. Consistently, Erfe-/- osteoblasts exhibit enhanced mineralization, Sost and Rankl expression, and BMP-mediated signaling ex vivo. The ERFE effect on osteoclasts is mediated through increased osteoblastic RANKL and sclerostin expression, increasing osteoclastogenesis in Erfe-/- mice. Importantly, Erfe loss in Hbbth3/+mice, a disease model with increased ERFE expression, triggers profound osteoclastic bone resorption and bone loss.

Conclusions

Together, ERFE exerts an osteoprotective effect by modulating BMP signaling in osteoblasts, decreasing RANKL production to limit osteoclastogenesis, and prevents excessive bone loss during expanded erythropoiesis in β-thalassemia.

Funding

YZG acknowledges the support of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (R01 DK107670 to YZG and DK095112 to RF, SR, and YZG). MZ acknowledges the support of the National Institute on Aging (U19 AG60917) and NIDDK (R01 DK113627). TY acknowledges the support of the National Institute on Aging (R01 AG71870). SR acknowledges the support of NIDDK (R01 DK090554) and Commonwealth Universal Research Enhancement (CURE) Program Pennsylvania.

Femoral Neck Hounsfield Units as an Adjunct for Bone Mineral Density After Combat-Related Lower Extremity Amputation

OBJECTIVES

To correlate femoral neck Hounsfield units (HUs) measured on a computed tomography (CT) scan to dual-energy x-ray absorptiometry (DEXA) T-scores allowing evaluation of bone mineral density (BMD) over time after lower extremity trauma-related amputation.

DESIGN

Retrospective cohort study.

SETTING

United States military trauma referral center.

PATIENTS

Military combat-related lower extremity amputees with both DEXA and CT scans within 6 months of each other.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Correlation between femoral neck comprehensive mean HUs and BMD and HUs threshold for low BMD.

RESULTS

Regression model correlation (r) between CT HU and DEXA T-score was r = 0.84 [95% confidence interval (CI) 0.52-0.94] and r = 0.81 (95% CI 0.57-0.92) when CT imaging was separated from DEXA by less than 4 and 5 months, respectively. Beyond 5 months separation, correlation decreased to r = 0.60 (95% CI 0.29-0.80). Using a receiver operator characteristic curve for mean comprehensive HUs to determine low BMD with 4-month cut-off, a threshold of 151 HUs was 97% sensitive and 84% specific to identify low BMD, whereas 98 HUs was 100% sensitive and 100% specific to identify osteoporosis.

CONCLUSION

Using opportunistic CT, clinicians can reliably estimate BMD in trauma-related amputees. This information will inform providers making decisions regarding weightbearing and bisphosphonate therapy to limit further loss. Future phases of this study will aim to use this correlation to study the effects of weightbearing advancement timing, bisphosphonate therapy, and interventions on the natural history of bone density after amputation.

LEVEL OF EVIDENCE

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Severe injury-induced osteoporosis and skeletal muscle mineralization: Are these related complications?

Severely injured patients are beleaguered by complications during convalescence, such as dysregulated biomineralization. Paradoxically, severely injured patients experience the loss of bone (osteoporosis), resulting in diminished skeletal integrity and increased risk of fragility fractures; yet they also accrue mineralization in soft tissues, resulting in complications such as heterotopic ossification (HO). The pathophysiology leading to dysregulated biomineralization in severely injured patients is not well defined. It has been postulated that these pathologies are linked, such that mineralization is "transferred" from the bone to soft tissue compartments. The goal of this study was to determine if severe injury-induced osteoporosis and soft tissue calcification are temporally coincident following injury. Using a murine model of combined burn and skeletal muscle injury to model severe injury, it was determined that mice developed significant progressive bone loss, detectable as early as 3 days post injury, and marked soft tissue mineralization by 7 days after injury. The observed temporal concordance between the development of severe injury-induced osteoporosis and soft tissue mineralization indicates the plausibility that these complications share a common pathophysiology, though further experiments are required.

Computer-aided osteoporosis detection from DXA imaging

BACKGROUND AND OBJECTIVE

Osteoporosis is a skeletal disease caused by a high rate of bone tissue loss, and it is a major cause of bone fracture. In contemporary society, osteoporosis is more common than cancer and stroke and results in a higher rate of morbidity and mortality in the human population. Osteoporosis can conclusively be diagnosed with dual energy X-ray absorptiometry (DXA). In this study, we propose a computer-aided osteoporosis detection (CAOD) technique that automatically measures bone mineral density (BMD) and generates an osteoporosis report from a DXA scan.

METHODS

The CAOD model denoise and segments DXA images using a non-local mean filter, Machine learning pixel label random forest respectively, and locates regions of interest with higher accuracy. Pixel label random forest classifies a pixel either bone or soft tissue; then contours are extracted from binary image to locate regions of interest and calculate BMD from bone and soft tissues pixels. Mean standard deviation and correlation coefficients statistical analysis were used to evaluate the consistency and accuracy of BMD measurements.

RESULTS

During a consistency test of BMD measurements using three consecutive scans from Computerized Imaging Reference Systems' Bona Fide Phantom (CIRS-BFP) for the spine, the CAOD model showed an averaged standard deviation of 0.0029 while the standard deviation from manual measurements on the same data set by three different individuals was recorded as 0.1199. During another correlation study of BMD measurements evaluating real human scan images by the CAOD model versus manual measurement, the model scored a correlation coefficient of R² = 0.9901 while the CIRS-BFP study scored a correlation coefficient of R² = 0.9709.

CONCLUSIONS

The CAOD model increases the preciseness and accuracy of BMD measurements. This CAOD method will help clinicians, untrained DXA operators, and researchers (medical scientists, doctors, and bone researchers) use the DXA system with reliable accuracy and overcome workload challenges. It will also improve osteoporosis diagnosis from DXA systems and increase system performance and value.

Mouse Models and Online Resources for Functional Analysis of Osteoporosis Genome-Wide Association Studies

Osteoporosis is a complex genetic disease in which the number of loci associated with the bone mineral density, a clinical risk factor for fracture, has increased at an exponential rate in the last decade. The identification of the causative variants and candidate genes underlying these loci has not been able to keep pace with the rate of locus discovery. A large number of tools and data resources have been built around the use of the mouse as model of human genetic disease. Herein, we describe resources available for functional validation of human Genome Wide Association Study (GWAS) loci using mouse models. We specifically focus on large-scale phenotyping efforts focused on bone relevant phenotypes and repositories of genotype-phenotype data that exist for transgenic and mutant mice, which can be readily mined as a first step toward more targeted efforts designed to deeply characterize the role of a gene in bone biology.

The Effect of β-Aminopropionitrile on Skeletal Micromorphology and Osteogenesis

Collagen cross-linking, as a form of collagen post-translational modification, plays a crucial role in maintaining bone mechanical properties as well as in regulating cell biological functions. Shifts in cross-links profile are found apparently correlated to kinds of skeletal pathology and diseases, whereas little is known about the relationship between collagen cross-links and osteogenesis. Here, we hypothesized that the inhibition of collagen cross-links could impair skeletal microstructure and inhibit osteogenesis. A mouse model of collagen cross-linking defects has been established using subcutaneous injection of 350 mg/kg β-aminopropionitrile (BAPN) daily for 4 weeks, and same dose of phosphate buffered saline (PBS) served as control group. The analysis of bone microstructural parameters revealed a significant decrease of bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), and increase of bone surface ratio (BS/BV), structure model index (SMI) as well as trabecular separation (Tb.Sp) in the experimental group (p < 0.05), whereas there was no difference observed in bone mineral density (BMD). Histological staining displayed that the BAPN treatment caused thinner trabeculae and decrease of collagen content in proximal tibiae. The analysis of osteogenesis PCR (Polymerase Chain Reaction) array reflected that BAPN remarkably influenced the expression of Alpl, Bglap, Bgn, Bmp5, Col10a1, Col1a1, Col1a2, Col5a1, Itga2b, and Serpinh1. The results of immunohistochemistry displayed a significant reduction in the mean optical densities of OCN and COL1 at the presence of BAPN. The overall results of this study suggested that BAPN alters bone microstructure and hinders the expression of osteogenic genes without affecting mineralization processes, indicating the influences of collagen cross-links on osteogenesis may be a potential pathological mechanism in skeletal diseases.