Serum serotonin levels and bone in rheumatoid arthritis patients.

In rheumatoid arthritis (RA), a disease characterized by bone loss, increased levels of serotonin have been reported. Recent studies have demonstrated a role for circulating serotonin as a regulator of osteoblastogenesis, inhibiting bone formation. Thus, we measured serum serotonin levels (SSL) in a Portuguese sample of 205 RA patients and related these to anthropometric variables, disease parameters, serum bone biomarkers, and bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry at several sites (total proximal femur, lumbar spine, left hand, and left second proximal phalange). SSL were inversely associated with body mass index (BMI) in RA women (r = - 0.218; p = 0.005), independent of exposure to biologics and/or bisphosphonates. Among biologic naïves, there was an inverse association between SSL and osteoprotegerin in RA women (r = - 0.260; p = 0.022). Serum ß-CTX and dickkopf-1 were strongly associated with SSL in RA men not treated with bisphosphonates (r = 0.590; p < 0.001/r = 0.387; p = 0.031, respectively). There was also an inverse association between SSL and sclerostin in RA men (r = - 0.374; p < 0.05), stronger among biologic naïve or bisphosphonates-unexposed RA men. In crude models, SSL presented as a significant negative predictor of total proximal femur BMD in RA women as well as in postmenopausal RA women. After adjustment for BMI, disease duration, and years of menopause, SSL remained a significant negative predictor of total proximal femur BMD only in postmenopausal RA women. Our data reinforce a role, despite weak, for circulating serotonin in regulating bone mass in RA patients, with some differences in terms of gender and anatomical sites.

CHD7 regulates craniofacial cartilage development via controlling HTR2B expression.

Mutations in the Chromodomain helicase DNA-binding protein 7 - coding gene (CHD7) cause CHARGE syndrome (CS). Although craniofacial and skeletal abnormalities are major features of CS patients, the role of CHD7 in bone and cartilage development remain largely unexplored. Here, using a zebrafish (Danio rerio) CS model, we show that chd7-/- larvae display abnormal craniofacial cartilage development and spinal deformities. The craniofacial and spine defects are accompanied by a marked reduction of bone mineralization. At the molecular level, we show that these phenotypes are associated with significant reduction in the expression levels of osteoblast differentiation markers. Additionally, we detected a marked depletion of collagen 2α1 in the cartilage of craniofacial regions and vertebrae, along with significantly reduced number of chondrocytes. Chondrogenesis defects are at least in part due to downregulation of htr2b, which we found to be also dysregulated in human cells derived from an individual with CHD7 mutation-positive CS. Overall, this study thus unveils an essential role for CHD7 in cartilage and bone development, with potential clinical relevance for the craniofacial defects associated with CS.

Patients with CHARGE syndrome exhibit skeletal defects. CHARGE syndrome is primarily caused by mutations in the chromatin remodeler-coding gene CHD7. To investigate the poorly characterized role of CHD7 in cartilage and bone development, here, we examine the craniofacial and bone anomalies in a zebrafish chd7-/- mutant model. We find that zebrafish mutant larvae exhibit striking dysmorphism of craniofacial structures and spinal deformities. Notably, we find a significant reduction in osteoblast, chondrocyte, and collagen matrix markers. This work provides important insights to improve our understanding of the role of chd7 in skeletal development.

Blood cadmium is associated with increased fracture risk in never-smokers - results from a case-control study using data from the Malmö Diet and Cancer cohort.

BACKGROUND: Several studies have shown associations between cadmium (Cd) exposure and an increased risk of fractures. However, the size of the risk is still unclear and proper adjustment for smoking is a challenge. The aim of this study was to quantify the association between dietary cadmium measured in blood and fracture risk in the general Swedish population through a large population-based case-control study in never-smokers. METHODS: The study included 2113 incident cases with osteoporosis-related fractures and the same number of age- and sex-matched controls in never-smokers from the Swedish population-based Malmö Diet and Cancer study cohort. Cd in blood (B-Cd) was analyzed at baseline (1991-1996). Incident osteoporosis-related fractures (of the hip, distal radius, and proximal humerus) up to the year 2014 were identified using the National Patient Register. Associations between B-Cd and fractures were analyzed using logistic regression. RESULTS: Median B-Cd was 0.22 µg/L (P25 = 0.16, P75 = 0.31) among 2103 cases and 0.21 (P25 = 0.15, P75 = 0.30) among 2105 controls. The risk of fracture was significantly increased (OR 1.58; 95 % confidence interval 1.08-2.31, per µg/L of B-Cd), after adjustment for age, sex, BMI, physical activity, and fiber consumption. In analyses by cadmium quartiles, the OR increased monotonically and was significant in the highest quartile of B-Cd (for B-Cd > 0.31 versus B-Cd < 0.15 µg/L; OR 1.21; 95 % confidence interval 1.01-1.45). CONCLUSION: Even modestly increased blood cadmium in never-smokers is associated with increased risk of incident osteoporosis-related fractures.

Complex clinical encounter series: osteoporosis presenting during pregnancy and lactation: wait and reassess.

Two months after her first pregnancy, a 35-yr-old exclusively breastfeeding woman bent to move her baby in the car seat and experienced sudden, severe pain from 5 spontaneous vertebral compression fractures. Genomic screen was negative but she had mild ankylosing spondylitis previously well controlled on etanercept. She was vegetarian with a high phytate intake. A lactation consultant had advised her to pump and discard milk between feeds, leading her to believe she produced twice as much milk as her baby ingested. She presented with a LS Z score of -3.6 and a TH Z score of -1.6. After 6 mo postweaning, she was treated with teriparatide (14 mo intermittently over 18 mo) and ultimately achieved a 50% increase in LS bone density and an 8% increase in TH bone density. Her fragility is explained by normal lactational bone loss amplified by excessive milk production and phytate-induced impairment of intestinal calcium absorption, ankylosing spondylitis, and the bend-and-lift maneuver. The marked increase in bone density resulted from the combined effects of spontaneous recovery and pharmacotherapy. Spontaneous recovery of bone mass and strength should occur during 12 mo after weaning in all women, including those who have fractured.

Identification of an novel genetic variant associated with osteoporosis: insights from the Taiwan Biobank Study.

Purpose: The purpose of this study was to identify new independent significant SNPs associated with osteoporosis using data from the Taiwan Biobank (TWBB). Material and Methods: The dataset was divided into discovery (60%) and replication (40%) subsets. Following data quality control, genome-wide association study (GWAS) analysis was performed, adjusting for sex, age, and the top 5 principal components, employing the Scalable and Accurate Implementation of the Generalized mixed model approach. This was followed by a meta-analysis of TWBB1 and TWBB2. The Functional Mapping and Annotation (FUMA) platform was used to identify osteoporosis-associated loci. Manhattan and quantile-quantile plots were generated using the FUMA platform to visualize the results. Independent significant SNPs were selected based on genome-wide significance (P < 5 × 10-8) and independence from each other (r2 < 0.6) within a 1 Mb window. Positional, eQTL(expression quantitative trait locus), and Chromatin interaction mapping were used to map SNPs to genes. Results: A total of 29 084 individuals (3154 osteoporosis cases and 25 930 controls) were used for GWAS analysis (TWBB1 data), and 18 918 individuals (1917 cases and 17 001 controls) were utilized for replication studies (TWBB2 data). We identified a new independent significant SNP for osteoporosis in TWBB1, with the lead SNP rs76140829 (minor allele frequency = 0.055, P-value = 1.15 × 10-08). Replication of the association was performed in TWBB2, yielding a P-value of 6.56 × 10-3. The meta-analysis of TWBB1 and TWBB2 data demonstrated a highly significant association for SNP rs76140829 (P-value = 7.52 × 10-10). In the positional mapping of rs76140829, 6 genes (HABP2, RP11-481H12.1, RNU7-165P, RP11-139 K1.2, RP11-57H14.3, and RP11-214 N15.5) were identified through chromatin interaction mapping in mesenchymal stem cells. Conclusions: Our GWAS analysis using the Taiwan Biobank dataset unveils rs76140829 in the VTI1A gene as a key risk variant associated with osteoporosis. This finding expands our understanding of the genetic basis of osteoporosis and highlights the potential regulatory role of this SNP in mesenchymal stem cells.

Equivalence trial of proposed denosumab biosimilar GP2411 and reference denosumab in postmenopausal osteoporosis: the ROSALIA study.

Denosumab is a monoclonal antibody used to reduce risk of fractures in osteoporosis. ROSALIA was a multicenter, double-blind, randomized, integrated phase I/phase III study comparing the efficacy, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and safety of proposed biosimilar denosumab GP2411 with reference denosumab (REF-DMAb) (Prolia®; Amgen). Postmenopausal women with osteoporosis were randomized 1:1 to 2 60-mg doses of GP2411 or REF-DMAb, one at study start and one at week 26. At week 52, the REF-DMAb group was re-randomized 1:1 to a third dose of REF-DMAb or switch to GP2411. The primary efficacy endpoint was percentage change from baseline (%CfB) in LS-BMD at week 52. Secondary efficacy endpoints were %CfB in LS-BMD, FN-BMD, and TH-BMD at weeks 26 and 78 (and week 52 for FN-BMD and TH-BMD). Primary PK and PD endpoints were the area under the serum concentration-time curve extrapolated to infinity and maximum drug serum concentration at week 26, and the area under the effect-time curve of the %CfB in serum CTX at week 26. Secondary PK and PD endpoints included drug serum concentrations and %CfB in serum CTX and P1NP during the study period. Similar efficacy was demonstrated at week 52, with 95% CIs of the difference in %CfB in LS-BMD between treatment groups fully contained within prespecified equivalence margins. Similarity in PK and PD was demonstrated at week 26. Immunogenicity was similar between groups and was not impacted by treatment switch. The rate of new vertebral fractures was comparable. Treatment-emergent adverse events were comparable between groups (63.6% [GP2411/GP2411]; 76.0% [REF-DMAb/REF-DMAb]; 76.6% [REF-DMAb/GP2411]). In conclusion, ROSALIA showed similar efficacy, PK and PD, and comparable safety and immunogenicity of GP2411 to REF-DMAb in postmenopausal osteoporosis.

Denosumab is a biologic treatment that stops bone breakdown. This clinical trial evaluated how similar GP2411 (a denosumab biosimilar in development) is compared with European-approved reference denosumab in women with post-menopausal osteoporosis. Biosimilars are highly similar to the original treatment ('reference denosumab') and may have a lower price. 263 patients were randomly assigned to receive GP2411 and 264 to reference denosumab. Treatment was given at the study beginning, at Week 26 and at Week 52. 124 patients were re-assigned at Week 52 to test the effect of changing from reference denosumab to GP2411. The study showed similarity in how the body interacts with the treatments, what effects the treatment has (both measured over 26 weeks), and bone mineral density (measured over 78 weeks). Antibody responses to GP2411 were detected in similar proportions of patients on each treatment. Reported adverse events were similar between treatments before Week 52, and from Week 52 to 78, and <5% of patients experienced serious adverse events. A change of treatment from reference denosumab to GP2411 did not affect outcomes. These results showed similarity between GP2411 and reference denosumab in this population. In future, GP2411 may enable more patients to benefit from denosumab.

Safety, pharmacokinetics, and pharmacodynamics of efzimfotase alfa, a second-generation enzyme replacement therapy: phase 1, dose-escalation study in adults with hypophosphatasia.

Hypophosphatasia (HPP) is a rare, inherited metabolic disease caused by deficient activity of tissue-nonspecific alkaline phosphatase (TNSALP). Efzimfotase alfa (ALXN1850) is a second-generation TNSALP enzyme replacement therapy in development for HPP. This first-in-human open-label, dose-escalating phase 1 trial evaluated efzimfotase alfa safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity. Fifteen adults (5/cohort) with HPP received efzimfotase alfa in doses of 15 mg (cohort 1), 45 mg (cohort 2), or 90 mg (cohort 3) as one intravenous (i.v.) dose followed by 3 weekly subcutaneous (s.c.) doses. The primary objective was to assess safety and tolerability. Secondary objectives included pharmacokinetics, pharmacodynamics of ALP substrates known to be biomarkers of disease (inorganic pyrophosphate [PPi] and pyridoxal 5'-phosphate [PLP]) and immunogenicity. Treatment-emergent adverse events (TEAEs) occurred in 12 (80%) participants. Eight (53%) participants had injection site reactions (ISRs), observed after 10 of 41 (24%) s.c. injections. Most ISR TEAEs were mild and resolved within 1-2 d. Peak and total exposures of efzimfotase alfa increased in a greater-than-dose proportional manner over the range of 15-90 mg after i.v. and s.c. dosing. The arithmetic mean elimination half-life was approximately 6 d; absolute bioavailability was 28.6%-36.8% over the s.c. dose range of 15-90 mg. Dose-dependent reductions in plasma concentrations of PPi and PLP relative to baseline reached nadir in the first week after i.v. dosing and were sustained for 3-4 wk after the last s.c. dose. Four (27%) participants tested positive for antidrug antibodies (ADAs), 3 of whom were ADA positive before the first dose of efzimfotase alfa. ADAs had no apparent effect on efzimfotase alfa pharmacokinetics/pharmacodynamics. No participants had neutralizing antibodies. Efzimfotase alfa demonstrated acceptable safety, tolerability, and pharmacokinetic profiles and was associated with sustained reductions in biomarkers of disease in adults with HPP, supporting further evaluation in adult and pediatric patients. Registration: ClinicalTrials.gov NCT04980248 (https://clinicaltrials.gov/study/NCT04980248).

Hypophosphatasia (HPP) is a rare metabolic disease caused by low activity of tissue nonspecific alkaline phosphatase (TNSALP), which is an enzyme involved in the formation and healing of bone and function of other body systems. People with HPP experience fractures, difficulty moving and walking, muscle weakness, pain, fatigue (tiredness), and teeth problems. Babies with HPP often have life-threatening breathing problems, craniosynostosis (early closure of skull bones), seizures that respond to treatment with vitamin B6, failure to thrive (inability to gain weight), and weak and abnormally shaped bones. Enzyme replacement therapy (ERT) for HPP was developed to supplement defective TNSALP with active enzyme, thus improving bone health and the symptoms of HPP. Asfotase alfa, the first ERT approved for the treatment of HPP, is given by subcutaneous injection either 3 or 6 times per week. Efzimfotase alfa is a second-generation ERT that is being developed for the treatment of HPP. Although similar to asfotase alfa, efzimfotase alfa has incorporated several changes that have the potential to require lower doses and reduce injection volume and dosing frequency, thereby potentially improving the treatment experience for patients. This first-in-human study investigated the safety, tolerability, pharmacokinetics (how a drug is absorbed into, distributed throughout, and removed from the body), pharmacodynamics (effects of the drug within the body), and immunogenicity (ability of a drug to provoke an undesirable immune response) of 4 injections of efzimfotase alfa when given by intravenous and subcutaneous routes of administration to adults with HPP. Our results showed that efzimfotase alfa has acceptable safety and pharmacokinetics and is effective for reducing biomarkers (measurable substances that reflect underlying disease) when given once weekly by subcutaneous injection, supporting further evaluation of efzimfotase alfa in planned clinical trials in adult and pediatric patients with HPP.

Goal-directed osteoporosis treatment: ASBMR/BHOF task force position statement 2024.

The overarching goal of osteoporosis management is to prevent fractures. A goal-directed approach to long-term management of fracture risk helps ensure that the most appropriate initial treatment and treatment sequence is selected for individual patients. Goal-directed treatment decisions require assessment of clinical fracture history, vertebral fracture identification (using vertebral imaging as appropriate), measurement of bone mineral density (BMD), and consideration of other major clinical risk factors. Treatment targets should be tailored to each patient's individual risk profile and based on the specific indication for beginning treatment, including recency, site, number and severity of prior fractures, and BMD levels at the total hip, femoral neck, and lumbar spine. Instead of first-line bisphosphonate treatment for all patients, selection of initial treatment should focus on reducing fracture risk rapidly for patients at very high and imminent risk, such as in those with recent fractures. Initial treatment selection should also consider the probability that a BMD treatment target can be attained within a reasonable period of time and the differential magnitude of fracture risk reduction and BMD impact with osteoanabolic versus antiresorptive therapy. This position statement of the ASBMR/BHOF Task Force on Goal-Directed Osteoporosis Treatment provides an overall summary of the major clinical recommendations about treatment targets and strategies to achieve those targets based on the best evidence available, derived primarily from studies in older postmenopausal women of European ancestry.

Goal-directed treatment can help healthcare providers recommend the best treatments for individual patients to prevent fractures. The goal-directed strategy considers the site, number, and recency of prior fractures. This may require imaging for spine fractures, which may not have caused pain. Treatment decisions also require bone mineral density (BMD) measurement and consideration of other major risk factors. In contrast to the standard approach, same first treatment for all, treatment selection is tailored to an individual's risk. In patients with recent fractures of the spine, hip, or pelvis, fracture risk is very high and treatment should rapidly reduce that risk. For others, the target is a specific BMD level and should consider the likelihood that the treatment target can be attained within a reasonable period of time, which differs for osteoporosis medications. After initial therapy, BMD should be assessed to determine if the target has been achieved. If so, strategies should focus on maintaining BMD. If the target is not yet achieved, treatment should be intensified, or continued if it is already the most potent option. This position statement represents a consensus of expert recommendations about treatment targets and strategies to achieve those targets based on the best available evidence.

Affinity targeting of therapeutic proteins to the bone surface-local delivery of sclerostin-neutralizing antibody enhances efficacy.

Currently available biotherapeutics for the treatment of osteoporosis lack explicit mechanisms for bone localization, potentially limiting efficacy and inducing off-target toxicities. While various strategies have been explored for targeting the bone surface, critical aspects remain poorly understood, including the optimal affinity ligand, the role of binding avidity and circulation time, and, most importantly, whether or not this strategy can enhance the functional activity of clinically relevant protein therapeutics. To investigate, we generated fluorescent proteins (eg, mCherry) with site-specifically attached small molecule (bisphosphonate) or peptide (deca-aspartate, D10) affinity ligands. While both affinity ligands successfully anchored fluorescent protein to the bone surface, quantitative radiotracing revealed only modest femoral and vertebral accumulation and suggested a need for enhanced circulation time. To achieve this, we fused mCherry to the Fc fragment of human IgG1 and attached D10 peptides to each C-terminus. The mCherry-Fc-D10 demonstrated an ~80-fold increase in plasma exposure and marked increases in femoral and vertebral accumulation (13.6% ± 1.4% and 11.4% ± 1.3% of the injected dose/g [%ID/g] at 24 h, respectively). To determine if bone surface targeting could enhance the efficacy of a clinically relevant therapeutic, we generated a bone-targeted sclerostin-neutralizing antibody, anti-sclerostin-D10. The targeted antibody demonstrated marked increases in bone accumulation and retention (20.9 ± 2.5% and 19.5 ± 2.5% ID/g in femur and vertebrae at 7 days) and enhanced effects in a murine model of ovariectomy-induced bone loss (bone volume/total volume, connectivity density, and structure model index all increased [P < .001] vs untargeted anti-sclerostin). Collectively, our results indicate the importance of both bone affinity and circulation time in achieving robust targeting of therapeutic proteins to the bone surface and suggest that this approach may enable lower doses and/or longer dosing intervals without reduction in biotherapeutic efficacy. Future studies will be needed to determine the translational potential of this strategy and its potential impact on off-site toxicities.

Several biologic therapies have been approved for osteoporosis, but they lack means of localization to bone tissue, potentially limiting their efficacy and leading to off-target toxicities. This manuscript investigates strategies for targeting biotherapeutics to the bone surface and asks the question of whether or not this approach can enhance functional activity and allow for lower or less frequent dosing. To define the key determinants of bone surface targeting, we begin by synthesizing fluorescent model proteins with different bone targeting tags. We show that even 1 tag is enough to make the surface of the femur and vertebrae fluorescent following systemic administration. The results are relatively modest at first, but when we combine the bone targeting tag with a second modification that makes the protein circulate in the body for a longer period of time, we observe a huge increase in bone surface delivery. We then synthesize a bone surface targeted version of a sclerostin-inhibiting antibody and show that it is more effective than the untargeted antibody and provides near complete protection of bone density despite relatively low dose. Our findings could have translational implications for existing bone therapies and help guide design of future strategies for optimized bone surface targeting.

A retrospective audit with subsequent cost and environmental analysis of a denosumab self-injection program.

The Metabolic Bone Health Department, Cardiff and Vale University Health Board, serves a local population of approximately 445 000 people. A retrospective audit of attendance data regarding the denosumab treatment clinic (the traditional treatment pathway) and the denosumab Self-Injection Program (SIP) was conducted to determine whether the SIP is both cost-effective and environmentally beneficial, compared to the traditional treatment pathway. Cost analysis was then conducted by the Finance Department. The audit was conducted over 3 years following the implementation of the service development; 233 patients had enrolled in the program at the time of the audit and 69 had completed 3 years of self-injected treatment. A control group of 497 patients were identified by the service. This group remained on the historical pathway and had consistent attendance activity over the 3-yr period from 2017 to 2019. Pre- and post-period activity of all patients on the program was compared, together with the activity for the independent control group. The SIP resulted in a reduction in clinical contacts, with financial analysis showing a total opportunity cost saving per patient of £420 per annum. There were obvious benefits to the patient of a reduced number of visits to a clinical site, which also resulted in an estimated carbon footprint reduction of 59 kg CO2 per patient per annum. The cost analysis is based on our organization's 2022 charges. The SIP demonstrates that by focusing on care "closer to home", it is possible to maximize resources, improve the patient experience through reduced travel, and reduce the environmental impact of healthcare.

Giant cell arteritis associated with intravenous zoledronic acid administration.

Bisphosphonates frequently provoke a cytokine-driven acute clinical response (ACR) characterized by fever, chills, arthralgias, and myalgias. More rarely, an association between aminobisphosphonates, such as alendronate and zoledronic acid, and rheumatologic and/or immune-mediated syndromes (RIMS) has been described. Herein we report 2 patients, one with a prior history of rheumatic disease and one without, who developed giant cell arteritis meeting the American College of Rheumatology 2022 criteria following zoledronic acid infusion. We subsequently review existing mechanistic and clinical literature supporting this link. The duration of symptoms and elevation of inflammatory markers may serve as indicators for differentiating between the more common ACR and less frequent but potentially morbid RIMS. Although the benefit of bisphosphonates will outweigh the risk of RIMS for most patients with high fracture risk, clinicians should be aware of this phenomenon to assist earlier diagnosis and treatment in affected individuals.

Demographic and disease-related factors impact bone turnover and vitamin D in children with hemato-oncological diseases.

Children with hemato-oncological diseases may have significant skeletal morbidity, not only during and after treatment but also at the time of diagnosis before cancer treatment. This study was designed to evaluate the vitamin D status and circulating bone metabolic markers and their determinants in children at the time of diagnostic evaluation for hemato-oncological disease. This cross-sectional study included 165 children (91 males, median age 6.9 yr range 0.2-17.7 yr). Of them, 76 patients were diagnosed with extracranial or intracranial solid tumors, 83 with leukemia, and 6 with bone marrow failure. Bone metabolism was assessed by measuring serum 25OHD, PTH, bone alkaline phosphatase, intact N-terminal propeptide of type I procollagen, and C-terminal cross-linked telopeptide of type I collagen. Vitamin D deficiency was found in 30.9% of children. Lower 25OHD levels were associated with older age, lack of vitamin D supplementation, season outside summer, and a country of parental origin located between latitudes -45° and 45°. Children diagnosed with leukemia had lower levels of markers of bone formation and bone resorption than those who had solid tumors or bone marrow failure. In conclusion, vitamin D deficiency was observed in one-third of children with newly diagnosed cancer. Bone turnover markers were decreased in children with leukemia, possibly because of the suppression of osteoblasts and osteoclasts by leukemic cells. The identification of patients with suboptimal vitamin D status and compromised bone remodeling at cancer diagnosis may aid in the development of supportive treatment to reduce the adverse effects of cancer and its treatment.

Hypophosphatemic rickets and short stature.

An 18-month-old male presented with gross motor delay and poor growth (weight z-score -2.21, length z-score -4.26). Radiographs showed metaphyseal irregularities suggesting metaphyseal dysplasia and sagittal craniosynostosis. Biochemical evaluation supported hypophosphatemic rickets [serum phosphorus 2.3 mg/dL (reference range (RR) 4.3-6.8), alkaline phosphatase 754 unit/L (RR 156-369)] due to renal phosphate wasting (TmP/GFR 4.3 mg/dL, normal for age 4.3-6.8), with C-terminal fibroblast growth factor 23 (FGF23) 125 RU/mL (>90 during hypophosphatemia suggests FGF23-mediated hypophosphatemia). Treatment was initiated with calcitriol and phosphate. Genetic analysis showed a pathogenic variant of FGF23: c.527G > A (p.Arg176Gln) indicative of autosomal dominant hypophosphatemic rickets (ADHR). Consistent with reports linking iron deficiency with the ADHR phenotype, low ferritin was detected. Following normalization of ferritin level (41 ng/mL) with oral ferrous sulfate replacement, biochemical improvement was demonstrated (FGF23 69 RU/mL, phosphorus 5.0 mg/dL and alkaline phosphatase 228 unit/L). Calcitriol and phosphate were discontinued. Three years later, the patient demonstrated improved developmental milestones, linear growth (length Z-score -2.01), radiographic normalization of metaphyses, and stabilization of craniosynostosis. While the most common cause of hypophosphatemic rickets is X-linked hypophosphatemia, other etiologies should be considered as treatment differs. In ADHR, normalization of iron leads to biochemical and clinical improvement.

Bacterial Lipopolysaccharides Exacerbate Neurogenic Heterotopic Ossification Development.

Neurogenic heterotopic ossifications (NHO) are heterotopic bones that develop in periarticular muscles after severe central nervous system (CNS) injuries. Several retrospective studies have shown that NHO prevalence is higher in patients who suffer concomitant infections. However, it is unclear whether these infections directly contribute to NHO development or reflect the immunodepression observed in patients with CNS injury. Using our mouse model of NHO induced by spinal cord injury (SCI) between vertebrae T11 to T13 , we demonstrate that lipopolysaccharides (LPS) from gram-negative bacteria exacerbate NHO development in a toll-like receptor-4 (TLR4)-dependent manner, signaling through the TIR-domain-containing adapter-inducing interferon-ß (TRIF/TICAM1) adaptor rather than the myeloid differentiation primary response-88 (MYD88) adaptor. We find that T11 to T13 SCI did not significantly alter intestinal integrity nor cause intestinal bacteria translocation or endotoxemia, suggesting that NHO development is not driven by endotoxins from the gut in this model of SCI-induced NHO. Relevant to the human pathology, LPS increased expression of osteoblast markers in cultures of human fibro-adipogenic progenitors isolated from muscles surrounding NHO biopsies. In a case-control retrospective study in patients with traumatic brain injuries, infections with gram-negative Pseudomonas species were significantly associated with NHO development. Together these data suggest a functional association between gram-negative bacterial infections and NHO development and highlights infection management as a key consideration to avoid NHO development in patients. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Impaired Bone Architecture in Peripubertal Children With HIV, Despite Treatment With Antiretroviral Therapy: A Cross-Sectional Study From Zimbabwe.

HIV infection has multi-system adverse effects in children, including on the growing skeleton. We aimed to determine the association between chronic HIV infection and bone architecture (density, size, strength) in peripubertal children. We conducted a cross-sectional study of children aged 8 to 16 years with HIV (CWH) on antiretroviral therapy (ART) and children without HIV (CWOH) recruited from schools and frequency-matched for age strata and sex. Outcomes, measured by tibial peripheral quantitative computed tomography (pQCT), included 4% trabecular and 38% cortical volumetric bone mineral density (vBMD), 4% and 38% cross-sectional area (CSA), and 38% stress-strain index (SSI). Multivariable linear regression tested associations between HIV status and outcomes, stratified by sex and puberty (Tanner 1-2 versus 3-5), adjusting for age, height, fat mass, physical activity, and socioeconomic and orphanhood statuses. We recruited 303 CWH and 306 CWOH; 50% were female. Although CWH were similar in age to CWOH (overall mean ± SD 12.4 ± 2.5 years), more were prepubertal (ie, Tanner 1; 41% versus 23%). Median age at ART initiation was 4 (IQR 2-7) years, whereas median ART duration was 8 (IQR 6-10) years. CWH were more often stunted (height-for-age Z-score <-2) than those without HIV (33% versus 7%). Both male and female CWH in later puberty had lower trabecular vBMD, CSA (4% and 38%), and SSI than those without HIV, whereas cortical density was similar. Adjustment explained some of these differences; however, deficits in bone size persisted in CWH in later puberty (HIV*puberty interaction p = 0.035 [males; 4% CSA] and p = 0.029 [females; 38% CSA]). Similarly, puberty further worsened the inverse association between HIV and bone strength (SSI) in both males (interaction p = 0.008) and females (interaction p = 0.004). Despite long-term ART, we identified deficits in predicted bone strength in those living with HIV, which were more overt in the later stages of puberty. This is concerning, as this may translate to higher fracture risk later in life. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Role of the Mitochondrial Permeability Transition in Bone Metabolism and Aging.

The mitochondrial permeability transition pore (MPTP) and its positive regulator, cyclophilin D (CypD), play important pathophysiological roles in aging. In bone tissue, higher CypD expression and pore activity are found in aging; however, a causal relationship between CypD/MPTP and bone degeneration needs to be established. We previously reported that CypD expression and MPTP activity are downregulated during osteoblast (OB) differentiation and that manipulations in CypD expression affect OB differentiation and function. Using a newly developed OB-specific CypD/MPTP gain-of-function (GOF) mouse model, we here present evidence that overexpression of a constitutively active K166Q mutant of CypD (caCypD) impairs OB energy metabolism and function, and bone morphological and biomechanical parameters. Specifically, in a spatial-dependent and sex-dependent manner, OB-specific CypD GOF led to a decrease in oxidative phosphorylation (OxPhos) levels, higher oxidative stress, and general metabolic adaptations coincident with the decreased bone organic matrix content in long bones. Interestingly, accelerated bone degeneration was present in vertebral bones regardless of sex. Overall, our work confirms CypD/MPTP overactivation as an important pathophysiological mechanism leading to bone degeneration and fragility in aging. © 2023 American Society for Bone and Mineral Research (ASBMR).

Trends in Serum Cytokine Expression in Pediatric Skeletal Dysplasia.

The skeletal dysplasias are a heterogeneous group of genetic conditions caused by abnormalities of growth, development, and maintenance of bone and cartilage. Little is known about the roles that cytokines play in the inflammatory and non-inflammatory pathophysiology of skeletal dysplasia. We sought to test our hypothesis that cytokines would be differentially expressed in children with skeletal dysplasia as compared to typically growing controls. Cytokine levels were analyzed using the Cytokine Human Magnetic 25-Plex Panel (Invitrogen, Waltham, MA, USA); 136 growing individuals with skeletal dysplasia and compared to a cohort of 275 healthy pediatric control subjects. We focused on the expression of 12 cytokines across nine dysplasia cohorts. The most common skeletal dysplasia diagnoses were: achondroplasia (58), osteogenesis imperfecta (19), type II collagenopathies (11), multiple epiphyseal dysplasia (MED: 9), diastrophic dysplasia (8), metatropic dysplasia (8), and microcephalic osteodysplastic primordial dwarfism type II (MOPDII: 8). Of the 108 specific observations made, 45 (41.7%) demonstrated statistically significant differences of expression between controls and individuals with skeletal dysplasia. Four of the 12 analyzed cytokines demonstrated elevated expression above control levels in all of the dysplasia cohorts (interleukin 12 [IL-12], IL-13, interferon γ-induced protein 10 kDa [IP-10], regulated on activation, normal T cell expressed and secreted [RANTES]) and two demonstrated expression below control levels across all dysplasia cohorts (monocyte chemoattractant protein 1 [MCP-1], macrophage inflammatory protein-1ß [MIP-1ß]). The highest levels of overexpression were seen in MOPDII, with expression levels of IP-10 being increased 3.8-fold (p < 0.0001). The lowest statistically significant levels of expressions were in type II collagenopathies, with expression levels of MCP-1 being expressed 0.43-fold lower (p < 0.005). With this data, we hope to lay the groundwork for future directions in dysplasia research that will enhance our understanding of these complex signaling pathways. Looking forward, validating these early trends in cytokine expression, and associating the observed variations with trends in the progression of dysplasia may offer new candidates for clinical biomarkers or even new therapeutics. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Antibiotic Treatment Prior to Injury Abrogates the Detrimental Effects of LPS in STR/ort Mice Susceptible to Osteoarthritis Development.

Post traumatic osteoarthritis (PTOA) is a form of secondary osteoarthritis (OA) that develops in ~50% of cases of severe articular joint injuries and leads to chronic and progressive degradation of articular cartilage and other joint tissues. PTOA progression can be exacerbated by repeated injury and systemic inflammation. Few studies have examined approaches for blunting or slowing down PTOA progression with emphasis on systemic inflammation; most arthritis studies focused on the immune system have been in the context of rheumatoid arthritis. To examine how the gut microbiome affects systemic inflammation during PTOA development, we used a chronic antibiotic treatment regimen starting at weaning for 6 weeks before anterior cruciate ligament (ACL) rupture in STR/ort mice combined with lipopolysaccharide (LPS)-induced systemic inflammation. STR/ort mice develop spontaneous OA as well as a more severe PTOA phenotype than C57Bl/6J mice. By 6 weeks post injury, histological examination showed a more robust cartilage staining in the antibiotic-treated (AB) STR/ort mice than in the untreated STR/ort controls. Furthermore, we also examined the effects of AB treatment on systemic inflammation and found that the effects of LPS administration before injury are also blunted by AB treatment in STR/ort mice. The AB- or AB+LPS-treated STR/ort injured joints more closely resembled the C57Bl/6J VEH OA phenotypes than the vehicle- or LPS-treated STR/ort, suggesting that antibiotic treatment has the potential to slow disease progression and should be further explored therapeutically as prophylactic post injury. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Reduced Bone Regeneration in Rats With Type 2 Diabetes Mellitus as a Result of Impaired Stromal Cell and Osteoblast Function-A Computer Modeling Study.

Bone has the fascinating ability to self-regenerate. However, under certain conditions, such as type 2 diabetes mellitus (T2DM), this ability is impaired. T2DM is a chronic metabolic disease known by the presence of elevated blood glucose levels that is associated with reduced bone regeneration capability, high fracture risk, and eventual non-union risk after a fracture. Several mechanical and biological factors relevant to bone regeneration have been shown to be affected in a diabetic environment. However, whether impaired bone regeneration in T2DM can be explained due to mechanical or biological alterations remains unknown. To elucidate the relevance of either one, the aim of this study was to investigate the relative contribution of T2DM-related alterations on either cellular activity or mechanical stimuli driving bone regeneration. A previously validated in silico computer modeling approach that was capable of explaining bone regeneration in uneventful conditions of healing was further developed to investigate bone regeneration in T2DM. Aspects analyzed included the presence of mesenchymal stromal cells (MSCs), cellular migration, proliferation, differentiation, apoptosis, and cellular mechanosensitivity. To further verify the computer model findings against in vivo data, an experimental setup was replicated, in which regeneration was compared in healthy and diabetic after a rat femur bone osteotomy stabilized with plate fixation. We found that mechanical alterations had little effect on the reduced bone regeneration in T2DM and that alterations in MSC proliferation, MSC migration, and osteoblast differentiation had the highest effect. In silico predictions of regenerated bone in T2DM matched qualitatively and quantitatively those from ex vivo µCT at 12 weeks post-surgery when reduced cellular activities reported in previous in vitro and in vivo studies were included in the model. The presented findings here could have clinical implications in the treatment of bone fractures in patients with T2DM. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Coxa Vara Deformity in Fibrous Dysplasia/McCune-Albright Syndrome: Prevalence, Natural History and Risk Factors: A Two-Center Study.

This study aimed to evaluate the prevalence of and risk factors for coxa vara deformity in patients with fibrous dysplasia/McCune-Albright syndrome (FD/MAS). This study was conducted at the National Institutes of Health and Leiden University Medical Center. All patients with any subtype of FD/MAS, FD involving the proximal femur, one or more X-rays available and age <30 years were included. X-rays were scored for the neck-shaft angle (NSA). Varus deformity was defined as NSA <110 degrees or >10 degrees below age-specific values. Risk factors for deformity were assessed by nested case-control analysis, comparing patients and femurs with and without deformity, and by linear mixed effects model, modeling temporal NSA decrease (the natural course of the NSA) in non-operated femurs with two or more X-rays. Assessed variables included growth hormone excess, hyperthyroidism, hypophosphatemia, >25% of the femur affected, calcar destruction, radiolucency, and bilateral involvement. In total 180 patients were studied, 57% female. Mean ± SD baseline age was 13.6 ± 7.5 years; median follow-up 5.4 (interquartile range [IQR], 11.1) years. Sixty-three percent (63%) were diagnosed with MAS. A total of 94 patients were affected bilaterally; 274 FD femurs were analyzed; 99 femurs had a varus deformity (36%). In the nested case-control analysis, risk factors were as follows: presence of MAS (p < 0.001), hyperthyroidism (p < 0.001), hypophosphatemia (p < 0.001), high percentage of femur affected (p < 0.001), and calcar destruction (p < 0.001). The linear mixed effects model included 114 femurs, identified risk factors were: growth hormone excess (ß = 7.2, p = 0.013), hyperthyroidism (ß = 11.3, p < 0.001), >25% of the femur affected (ß = 13.2, p = 0.046), calcar destruction (ß = 8.3, p = 0.004), radiolucency (ß = 3.9, p = 0.009), and bilateral involvement (ß = 9.8, p = 0.010). Visual inspection of the graph of the model demonstrated most progression of deformity if NSA <120 degrees with age < 15 years. In conclusion, in tertiary care centers, the prevalence of FD/MAS coxa vara deformity was 36%. Risk factors included presence of MAS, high percentage of femur affected, calcar destruction, radiolucency, NSA <120 degrees and age < 15 years. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).