An update on clinical presentation and responses to therapy of patients with hereditary hypophosphatemic rickets with hypercalciuria (HHRH).

Pathogenic variants in solute carrier family 34, member 3 (SLC34A3), the gene encoding the sodium-dependent phosphate cotransporter 2c (NPT2c), cause hereditary hypophosphatemic rickets with hypercalciuria (HHRH). Here, we report a pooled analysis of clinical and laboratory records of 304 individuals from 145 kindreds, including 20 previously unreported HHRH kindreds, in which two novel SLC34A3 pathogenic variants were identified. Compound heterozygous/homozygous carriers show above 90% penetrance for kidney and bone phenotypes. The biochemical phenotype for heterozygous carriers is intermediate with decreased serum phosphate, tubular reabsorption of phosphate (TRP (%)), fibroblast growth factor 23, and intact parathyroid hormone, but increased serum 1,25-dihydroxy vitamin D, and urine calcium excretion causing idiopathic hypercalciuria in 38%, with bone phenotypes still observed in 23% of patients. Oral phosphate supplementation is the current standard of care, which typically normalizes serum phosphate. However, although in more than half of individuals this therapy achieves correction of hypophosphatemia it fails to resolve the other outcomes. The American College of Medical Genetics and Genomics score correlated with functional analysis of frequent SLC34A3 pathogenic variants in vitro and baseline disease severity. The number of mutant alleles and baseline TRP (%) were identified as predictors for kidney and bone phenotypes, baseline TRP (%) furthermore predicted response to therapy. Certain SLC34A3/NPT2c pathogenic variants can be identified with partial responses to therapy, whereas with some overlap, others present only with kidney phenotypes and a third group present only with bone phenotypes. Thus, our report highlights important novel clinical aspects of HHRH and heterozygous carriers, raises awareness to this rare group of disorders and can be a foundation for future studies urgently needed to guide therapy of HHRH.

Klotho Overexpression Is Frequently Associated With Upstream Rearrangements in Fusion-Negative Phosphaturic Mesenchymal Tumors of Bone and Sinonasal Tract.

Phosphaturic mesenchymal tumors (PMT) are uncommon neoplasms that cause hypophosphatemia/osteomalacia mainly by secreting fibroblast growth factor 23. We previously identified FN1::FGFR1/FGF1 fusions in nearly half of the PMTs and frequent KL (Klotho or α-Klotho) overexpression in only those with no known fusion. Here, we studied a larger cohort of PMTs for KL expression and alterations. By FN1 break-apart fluorescence in situ hybridization (FISH) and reappraisal of previous RNA sequencing data, 6 tumors previously considered "fusion-negative" (defined by negative results of FISH for FN1::FGFR1 fusion and FGF1 break-apart and/or of RNA sequencing) were reclassified as fusion-positive PMTs, including 1 containing a novel FN1::ZACN fusion. The final cohort of fusion-negative PMTs included 33 tumors from 32 patients, which occurred in the bone (n = 18), soft tissue (n = 10), sinonasal tract (n = 4), and brain (n = 1). In combination with previous work, RNA sequencing, RNA in situ hybridization, and immunohistochemistry showed largely concordant results and demonstrated KL/α-Klotho overexpression in 17 of the 28 fusion-negative and none of the 10 fusion-positive PMTs studied. Prompted by a patient in this cohort harboring germline KL upstream translocation with systemic α-Klotho overexpression and multifocal PMTs, FISH was performed and revealed KL rearrangement in 16 of the 33 fusion-negative PMTs (one also with amplification), including 14 of the 17 cases with KL/α-Klotho overexpression and none of the 11 KL/α-Klotho-low fusion-negative and 11 fusion-positive cases studied. Whole genomic sequencing confirmed translocation and inversion in 2 FISH-positive cases involving the KL upstream region, warranting further investigation into the mechanism whereby these rearrangements may lead to KL upregulation. Methylated DNA immunoprecipitation and sequencing suggested no major role of promoter methylation in KL regulation in PMT. Interestingly, KL-high/-rearranged cases seemed to form a clinicopathologically homogeneous group, showing a predilection for skeletal/sinonasal locations and typically matrix-poor, cellular solitary fibrous tumor-like morphology. Importantly, FGFR1 signaling pathways were upregulated in fusion-negative PMTs regardless of the KL status compared with non-PMT mesenchymal tumors by gene set enrichment analysis, perhaps justifying FGFR1 inhibition in treating this subset of PMTs.

Improving care pathways for people living with rare bone diseases (RBDs): outcomes from the first RBD Summit.

INTRODUCTION: Rare bone diseases (RBDs) are a heterogenous group of disorders that are poorly understood and challenging to treat. This creates a plethora of unmet needs for people with RBDs as well as their families and care providers, including diagnostic delays, limited access to expert care, and a lack of specialized treatments. The RBD Summit, which took place across 2 days in November 2021, was a virtual meeting of 65 RBD experts from clinical, academic, and patient communities as well as the pharmaceutical industry. The first meeting of its kind, the RBD Summit aimed to facilitate dialog and information exchange between delegates to advance knowledge and awareness of RBDs and improve patient outcomes. METHODS: Key challenges were discussed, and actions for overcoming them were proposed, including how obstacles to diagnosis can be overcome by (a) improving awareness of RBDs, (b) the implementation of a person-centered care pathway, and (c) how to narrow the communication gap between patients and healthcare professionals. RESULTS: Agreed actions were categorized as short term and long term, and priorities determined. CONCLUSION: In this position paper, we provide an overview of key discussions from the RBD Summit, summarize the subsequent action plan, and discuss the next steps in this continued collaboration.

Novel PHEX gene locus-specific database: Comprehensive characterization of vast number of variants associated with X-linked hypophosphatemia (XLH).

X-linked hypophosphatemia (XLH), the most common form of hereditary hypophosphatemia, is caused by disrupting variants in the PHEX gene, located on the X chromosome. XLH is inherited in an X-linked pattern with complete penetrance observed for both males and females. Patients experience lifelong symptoms resulting from chronic hypophosphatemia, including impaired bone mineralization, skeletal deformities, growth retardation, and diminished quality of life. This chronic condition requires life-long management with disease-specific therapies, which can improve patient outcomes especially when initiated early in life. To centralize and disseminate PHEX variant information, we have established a new PHEX gene locus-specific database, PHEX LSDB. As of April 30, 2021, 870 unique PHEX variants, compiled from an older database of PHEX variants, a comprehensive literature search, a sponsored genetic testing program, and XLH clinical trials, are represented in the PHEX LSDB. This resource is publicly available on an interactive, searchable website (https://www.rarediseasegenes.com/), which includes a table of variants and associated data, graphical/tabular outputs of genotype-phenotype analyses, and an online submission form for reporting new PHEX variants. The database will be updated regularly with new variants submitted on the website, identified in the published literature, or shared from genetic testing programs.

Efficacy of Burosumab in Adults with X-linked Hypophosphatemia (XLH): A Post Hoc Subgroup Analysis of a Randomized Double-Blind Placebo-Controlled Phase 3 Study.

The anti-fibroblast growth factor 23 monoclonal antibody burosumab corrects hypophosphatemia in adults with X-linked hypophosphatemia (XLH) and improves pain, stiffness, physical function, and fatigue. This post hoc subgroup analysis used data from the 24-week placebo-controlled period of a phase 3 study in 134 adults with XLH (ClinicalTrials.gov NCT02526160), to assess whether the benefits of burosumab are evident in 14 clinically relevant subgroups defined by baseline demographic and functional criteria, including sex, Brief Pain Inventory-short form (BPI-SF) Average And Worst Pain, region, race, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC®) Stiffness, Physical Function and Pain domains and total score, use of opioid/other pain medication, active fractures/pseudo-fractures, and 6-min walk test distance. There were no statistically significant interactions between any of the subgroups and treatment arm for any endpoint. Higher proportions of subjects achieved mean serum phosphate concentration above the lower limit of normal (the primary endpoint) with burosumab than with placebo in all subgroups. For the key secondary endpoints (WOMAC Stiffness and Physical Function; BPI-SF Worst Pain) individual subgroup categories showed improvements with burosumab relative to placebo. For additional efficacy endpoints, burosumab was favored in some subgroups but differences were not significant and confidence intervals were wide. For some endpoints the treatment effect is small at 24 weeks in all subjects. This subgroup analysis shows that burosumab was largely superior to placebo across endpoints in the 14 clinically relevant subgroup variables at 24 weeks and is likely to benefit all symptomatic adults with active XLH.

Burosumab Therapy in Children with X-Linked Hypophosphatemia.

BACKGROUND: X-linked hypophosphatemia is characterized by increased secretion of fibroblast growth factor 23 (FGF-23), which leads to hypophosphatemia and consequently rickets, osteomalacia, and skeletal deformities. We investigated burosumab, a monoclonal antibody that targets FGF-23, in patients with X-linked hypophosphatemia. METHODS: In an open-label, phase 2 trial, we randomly assigned 52 children with X-linked hypophosphatemia, in a 1:1 ratio, to receive subcutaneous burosumab either every 2 weeks or every 4 weeks; the dose was adjusted to achieve a serum phosphorus level at the low end of the normal range. The primary end point was the change from baseline to weeks 40 and 64 in the Thacher rickets severity total score (ranging from 0 to 10, with higher scores indicating greater disease severity). In addition, the Radiographic Global Impression of Change was used to evaluate rachitic changes from baseline to week 40 and to week 64. Additional end points were changes in pharmacodynamic markers, linear growth, physical ability, and patient-reported outcomes and the incidence of adverse events. RESULTS: The mean Thacher rickets severity total score decreased from 1.9 at baseline to 0.8 at week 40 with every-2-week dosing and from 1.7 at baseline to 1.1 at week 40 with every-4-week dosing (P<0.001 for both comparisons); these improvements persisted at week 64. The mean serum phosphorus level increased after the first dose in both groups, and more than half the patients in both groups had levels within the normal range (3.2 to 6.1 mg per deciliter [1.0 to 2.0 mmol per liter]) by week 6. Stable serum phosphorus levels were maintained through week 64 with every-2-week dosing. Renal tubular phosphate reabsorption increased from baseline in both groups, with an overall mean increase of 0.98 mg per deciliter (0.32 mmol per liter). The mean dose of burosumab at week 40 was 0.98 mg per kilogram of body weight with every-2-week dosing and 1.50 mg per kilogram with every-4-week dosing. Across both groups, the mean serum alkaline phosphatase level decreased from 459 U per liter at baseline to 369 U per liter at week 64. The mean standing-height z score increased in both groups, with greater improvement seen at all time points with every-2-week dosing (an increase from baseline of 0.19 at week 64) than with every-4-week dosing (an increase from baseline of 0.12 at week 64). Physical ability improved and pain decreased. Nearly all the adverse events were mild or moderate in severity. CONCLUSIONS: In children with X-linked hypophosphatemia, treatment with burosumab improved renal tubular phosphate reabsorption, serum phosphorus levels, linear growth, and physical function and reduced pain and the severity of rickets. (Funded by Ultragenyx Pharmaceutical and Kyowa Hakko Kirin; ClinicalTrials.gov number, NCT02163577 ; EudraCT number, 2014-000406-35 ).

Minimal Physiologically Based Pharmacokinetic-Pharmacodynamic (mPBPK-PD) Model of N-Acetylgalactosamine-Conjugated Small Interfering RNA Disposition and Gene Silencing in Preclinical Species and Humans.

Conjugation of small interfering RNA (siRNA) to tris N-acetylgalactosamine [(GalNAc)3] can enable highly selective, potent, and durable knockdown of targeted proteins in the liver. However, potential knowledge gaps between in vitro experiments, preclinical species, and clinical scenarios remain. A minimal physiologically based pharmacokinetic-pharmacodynamic model for GalNAc-conjugated siRNA (GalNAc-siRNA) was developed using published data for fitusiran (ALN-AT3), an investigational compound targeting liver antithrombin (AT), to delineate putative determinants governing the whole-body-to-cellular pharmacokinetic (PK) and pharmacodynamic (PD) properties of GalNAc-siRNA and facilitate preclinical-to-clinical translation. The model mathematically linked relevant mechanisms: 1) hepatic biodistribution, 2) tris-GalNAc binding to asialoglycoprotein receptors (ASGPRs) on hepatocytes, 3) ASGPR endocytosis and recycling, 4) endosomal transport and escape of siRNA, 5) cytoplasmic RNA-induced silencing complex (RISC) loading, 6) degradation of target mRNA by bound RISC, and 7) knockdown of protein. Physiologic values for 36 out of 48 model parameters were obtained from the literature. Kinetic parameters governing (GalNAc)3-ASGPR binding and internalization were derived from published studies of uptake in hepatocytes. The proposed model well characterized reported pharmacokinetics, RISC dynamics, and knockdown of AT mRNA and protein by ALN-AT3 in mice. The model bridged multiple PK-PD data sets in preclinical species (mice, rat, monkey) and successfully captured reported plasma pharmacokinetics and AT knockdown in a phase I ascending-dose study. Estimates of in vivo potency were similar (∼2-fold) across species. Subcutaneous absorption and serum AT degradation rate constants scaled across species by body weight with allometric exponents of -0.29 and -0.22. The proposed mechanistic modeling framework characterizes the unique PK-PD properties of GalNAc-siRNA. SIGNIFICANCE STATEMENT: Tris N-acetylgalactosamine (GalNAc)3-conjugated small interfering RNA (siRNA) therapeutics enable liver-targeted gene therapy and precision medicine. Using a translational and systems-based minimal physiologically based pharmacokinetic-pharmacodynamic (mPBPK-PD) modeling approach, putative determinants influencing GalNAc-conjugated siRNA (GalNAc-siRNA) functionality in three preclinical species and humans were investigated. The developed model successfully integrated and characterized relevant published in vitro-derived biomeasures, mechanistic PK-PD profiles in animals, and observed clinical PK-PD responses for an investigational GalNAc-siRNA (fitusiran). This modeling effort delineates the disposition and liver-targeted pharmacodynamics of GalNAc-siRNA.

Negative Emotionality Interacts with Trauma Exposure to Prospectively Predict Posttraumatic Stress Disorder Symptoms During Firefighters' First 3 Years of Service.

Firefighters (FFs) protect the public despite significant risks to their health and well-being stemming from frequent trauma exposure and other occupational stressors. A minority of FFs develop posttraumatic stress disorder (PTSD) or related mental health problems, whereas most remain remarkably resilient despite enormous stress. This points toward substantial variability in responses to traumatic stress among FFs. Personality, particularly negative emotionality (NEM), has been shown to predict the development of PTSD in other trauma-exposed populations, yet has not been prospectively studied in relation to PTSD in FFs. The aim of this secondary analysis from a broader study of mental health in FFs was to test whether preemployment NEM predicted PTSD symptom severity over time by influencing how FFs respond to traumatic experiences. In this first prospective study of the development of PTSD symptoms in professional FFs, 322 FFs were recruited from seven urban fire academies across the United States and followed over their first 3 years of fire service. We assessed NEM during the fire academy as well as trauma exposure and both self-reported and clinician-rated PTSD symptoms at 1-, 2-, and 3-year follow-ups. Level of trauma exposure and NEM predicted PTSD symptoms over time, and NEM moderated the effect of trauma exposure on clinician-rated PTSD symptoms across both trauma exposure measures at 1- and 3-year follow-ups, f2 = .03-.10, but not at 2-year follow-up nor for self-reported PTSD symptoms. These findings indicate that NEM, assessed upon entry into a high-risk occupation, is useful in predicting PTSD symptom development.

Severity of reduced bone mineral density and risk of fractures in long-term survivors of childhood leukemia and lymphoma undergoing guideline-recommended surveillance for bone health.

BACKGROUND: Survivors of childhood leukemia/lymphoma are at increased risk for reduced bone mineral density (BMD). The authors sought to determine the frequency of reduced BMD detected by off-therapy surveillance, factors associated with reduced BMD, and the association of reduced BMD with fractures. METHODS: This cross-sectional study included childhood leukemia/lymphoma survivors attending 2 survivorship clinics who received guideline-recommended BMD surveillance ≥2 years post-therapy with dual-energy x-ray absorptiometry (from January 1, 2004 to August 31, 2016). Lumbar spine BMD z-scores were height-for-age-adjusted. Low and very low BMD were >1 SD and >2 SDs below norms, respectively. Treatment, chronic conditions, and fractures were abstracted from medical records. Logistic regression was used to examine the association of low BMD with patient/treatment factors and fractures. RESULTS: In total, 542 patients (51.5% female) with a mean age of 15.5 years (range, 4.4-52.2 years) who were 6 years post-therapy (range, 2.0-35.1 years) were evaluated, including 116 who reported post-therapy fractures. Lumbar spine low BMD was identified in 17.2% of survivors, and very low BMD was identified in 3.5% of survivors, but frequencies varied considerably between subgroups; 10.8% of survivors aged 15 to 19 years at diagnosis had very low BMD. In multivariable analyses, older age at diagnosis, white race, and being underweight were significantly associated with low BMD. Survivors with low BMD had greater odds of nondigit fractures (odds ratio, 2.2; 95% CI, 1.3-3.7) and specifically long-bone fractures (odds ratio, 2.7; 95% CI, 1.5-4.7). CONCLUSIONS: In this study of childhood leukemia/lymphoma survivors undergoing guideline-recommended dual-energy x-ray absorptiometry surveillance, patients who were older at diagnosis, white, and underweight were at the highest risk for lumbar spine low BMD. Low BMD was associated with a greater risk of fractures, emphasizing the clinical importance of surveillance.

Frequent overexpression of klotho in fusion-negative phosphaturic mesenchymal tumors with tumorigenic implications.

Phosphaturic mesenchymal tumors (PMT) are tumors that cause hypophosphatemia/osteomalacia chiefly by secreting FGF23. We have identified FN1-FGFR1/FGF1 fusion genes in nearly half of PMT, suggesting a central role of FGFR1 pathways in the pathogenesis of PMT. Tumorigenic drivers are unknown for tumors where previous study detected neither fusion, including many in bone, where FISH failed because of tissue decalcification. To identify alternative fusions in PMT without known fusions, as well as to validate the positive FISH results and characterize the fusion junctions, 34 PMT were studied, including 12 with known FN1-FGFR1 fusion by FISH (Group A), 2 with FN1-FGF1 (B), 12 with neither fusion (C), and 8 with previous acid-based decalcification and hence unknown fusion status (D). In total, 23 archival samples were subjected to anchored multiplex PCR-based RNA-sequencing (AMP-seq) with primers targeting FN1, genes encoding the FGF/FGFR families, and KL (α-Klotho); five Group C cases were also studied with whole-transcriptomic and exome-captured RNA sequencing, respectively. The AMP-seq results were consistent with previous FISH and/or transcriptomic sequencing data, except in one old Group A sample. One case had a novel FGFR1 exon 9 breakpoint, confirmed by genomic DNA sequencing. One Group D bone tumor was found to harbor FN1-FGF1. All 3 RNA-sequencing platforms failed to identify convincing fusion genes in Group C (N = 10), which instead expressed significantly higher levels of either KL or KLB. This result was further confirmed with KL and KLB RNA CISH semi-quantification (RNAscope). Our results demonstrated the utility of AMP-seq, which was compromised by decalcification and prolonged archiving. Of potential importance, fusion-negative PMT frequently overexpressed α-Klotho (or instead ß-Klotho less commonly), whose role as an obligatory co-receptor for FGF23-FGFR1 binding suggests its aberrant expression in osteocytes/osteoblasts might result in an FGF23-FGFR1 autocrine loop that in turn drives the overexpression of FGF23 and tumorigenesis through activated FGFR pathways.

Effects of Iron Isomaltoside vs Ferric Carboxymaltose on Hypophosphatemia in Iron-Deficiency Anemia: Two Randomized Clinical Trials.

Importance: Intravenous iron enables rapid correction of iron-deficiency anemia, but certain formulations induce fibroblast growth factor 23-mediated hypophosphatemia. Objective: To compare risks of hypophosphatemia and effects on biomarkers of mineral and bone homeostasis of intravenous iron isomaltoside (now known as ferric derisomaltose) vs ferric carboxymaltose. Design, Setting, and Participants: Between October 2017 and June 2018, 245 patients aged 18 years and older with iron-deficiency anemia (hemoglobin level ≤11 g/dL; serum ferritin level ≤100 ng/mL) and intolerance or unresponsiveness to 1 month or more of oral iron were recruited from 30 outpatient clinic sites in the United States into 2 identically designed, open-label, randomized clinical trials. Patients with reduced kidney function were excluded. Serum phosphate and 12 additional biomarkers of mineral and bone homeostasis were measured on days 0, 1, 7, 8, 14, 21, and 35. The date of final follow-up was June 19, 2018, for trial A and May 29, 2018, for trial B. Interventions: Intravenous administration of iron isomaltoside, 1000 mg, on day 0 or ferric carboxymaltose, 750 mg, infused on days 0 and 7. Main Outcomes and Measures: The primary end point was the incidence of hypophosphatemia (serum phosphate level <2.0 mg/dL) between baseline and day 35. Results: In trial A, 123 patients were randomized (mean [SD] age, 45.1 [11.0] years; 95.9% women), including 62 to iron isomaltoside and 61 to ferric carboxymaltose; 95.1% completed the trial. In trial B, 122 patients were randomized (mean [SD] age, 42.6 [12.2] years; 94.1% women), including 61 to iron isomaltoside and 61 to ferric carboxymaltose; 93.4% completed the trial. The incidence of hypophosphatemia was significantly lower following iron isomaltoside vs ferric carboxymaltose (trial A: 7.9% vs 75.0% [adjusted rate difference, -67.0% {95% CI, -77.4% to -51.5%}], P < .001; trial B: 8.1% vs 73.7% [adjusted rate difference, -65.8% {95% CI, -76.6% to -49.8%}], P < .001). Beyond hypophosphatemia and increased parathyroid hormone, the most common adverse drug reactions (No./total No.) were nausea (iron isomaltoside: 1/125; ferric carboxymaltose: 8/117) and headache (iron isomaltoside: 4/125; ferric carboxymaltose: 5/117). Conclusions and Relevance: In 2 randomized trials of patients with iron-deficiency anemia who were intolerant of or unresponsive to oral iron, iron isomaltoside (now called ferric derisomaltose), compared with ferric carboxymaltose, resulted in lower incidence of hypophosphatemia over 35 days. However, further research is needed to determine the clinical importance of this difference. Trial Registration: ClinicalTrials.gov Identifiers: NCT03238911 and NCT03237065.

Continued Beneficial Effects of Burosumab in Adults with X-Linked Hypophosphatemia: Results from a 24-Week Treatment Continuation Period After a 24-Week Double-Blind Placebo-Controlled Period.

Burosumab, a fully human monoclonal antibody to FGF23, is the only approved treatment for X-linked hypophosphatemia (XLH), a rare genetic disorder characterized by renal phosphate wasting and substantial cumulative musculoskeletal morbidity. During an initial 24-week randomized, controlled trial, 134 adults with XLH received burosumab 1 mg/kg (n = 68) or placebo (n = 66) every 4 weeks. After 24 weeks, all subjects received open-label burosumab until week 48. This report describes the efficacy and safety of burosumab during the open-label treatment period. From weeks 24-48, serum phosphorus concentrations remained normal in 83.8% of participants who received burosumab throughout and were normalized in 89.4% who received burosumab after placebo. By week 48, 63.1% of baseline fractures/pseudofractures healed fully with burosumab, compared with 35.2% with burosumab after placebo. In both groups, burosumab was associated with clinically significant and sustained improvement from baseline to week 48 in scores for patient-reported outcomes of stiffness, pain, physical function, and total distance walked in 6 min. Rates of adverse events were similar for burosumab and placebo. There were no fatal adverse events or treatment-related serious adverse events. Nephrocalcinosis scores did not change from baseline by more than one grade at either week 24 or 48. These data demonstrate that in participants with XLH, continued treatment with burosumab is well tolerated and leads to sustained correction of serum phosphorus levels, continued healing of fractures and pseudofractures, and sustained improvement in key musculoskeletal impairments.

Supply-Inverted Bipolar Pulser and Tx/Rx Switch for CMUTs Above the Process Limit for High Pressure Pulse Generation.

A combined supply-inverted bipolar pulser and a Tx/Rx switch is proposed to drive capacitive micromachined ultrasonic transducers (CMUTs). The supply-inverted bipolar pulser adopts a bootstrap circuit combined with stacked transistors, which guarantees high voltage (HV) operation above the process limit without lowering device reliability. This circuit generates an output signal with a peak-to-peak voltage that is almost twice the supply level. It generates a bipolar pulse with only positive supply voltages. The Tx/Rx switch adopts a diode-bridge structure with the protection scheme dedicated to this proposed pulser. A proof- of-concept ASIC prototype has been implemented in 0.18-µm HV CMOS/DMOS technology with 60 V devices. Measurement results show that the proposed pulser can safely generate a bipolar pulse of -34.6 to 45 V, from a single 45 V supply voltage. The Tx/Rx switch blocks the HV bipolar pulse, resulting in less than 1.6 V at the input of the receiver. Acoustic measurements are performed connecting the pulser to CMUTs with 2 pF capacitance and 8 MHz center frequency. The variation of acoustic output pressures for different pulse shapes were simulated with the large signal CMUT model and compared with the experimental results for transmit pressure optimization. A potential implementation of the methods using MEMS fabrication methods is also described.

Survey-software implicit association tests: A methodological and empirical analysis.

The implicit association test (IAT) is widely used in psychology. Unfortunately, the IAT cannot be run within online surveys, requiring researchers who conduct online surveys to rely on third-party tools. We introduce a novel method for constructing IATs using online survey software (Qualtrics); we then empirically assess its validity. Study 1 (student n = 239) revealed good psychometric properties, expected IAT effects, and expected correlations with explicit measures for survey-software IATs. Study 2 (MTurk n = 818) showed predicted IAT effects across four survey-software IATs (ds = 0.82 [Black-White IAT] to 2.13 [insect-flower IAT]). Study 3 (MTurk n = 270) compared survey-software IATs and IATs run via Inquisit, yielding nearly identical results and intercorrelations that would be expected for identical IATs. Survey-software IATs appear to be reliable and valid, offer numerous advantages, and make IATs accessible for researchers who use survey software to conduct online research. We present all the materials, links to tutorials, and an open-source tool that rapidly automates survey-software IAT construction and analysis.

Three-Month Randomized Clinical Trial of Nasal Calcitonin in Adults with X-linked Hypophosphatemia.

Previous work has demonstrated that a single subcutaneous dose of salmon calcitonin leads to a transient decline in circulating levels of FGF23 in patients with X-linked hypophosphatemia (XLH). Since the calcitonin receptor is expressed on osteocytes, this raises the possibility that interdicting signals through that receptor could modulate circulating levels of FGF23 in XLH. In the present study, 21 subjects with XLH were randomly assigned to receive either placebo nasal spray or 400 IU of nasal salmon calcitonin daily for three months. On the first and last day of the study, serial measurements of FGF23, 1,25-dihydroxyvitamin D, and TmP/GFR were made over 27 h. At the beginning of Visit 2 (the first day of month 2) and the beginning of Visit 3 (the first day of month 3), single, first-morning, fasting measurements of these same parameters were made before the next administered dose of study drug. Following the initial or final dose of study drug, there were no differences in area under the curve, based on treatment assignment, for the three principal outcome variables. Similarly, there were no differences in the fasting measures taken at the beginning of Visit 2 or Visit 3 compared to the fasting values on either day 2 of Visit 1 or the fasting values on day 2 of Visit 4. There were also no significant changes over time in serum phosphorus, serum calcium, circulating levels of PTH, CTx, or P1NP. The reasons why nasal salmon calcitonin did not recapitulate the findings with subcutaneously administered drug may relate to the kinetics of drug delivery, the bioavailability of drug or peak drug dose achieved. It remains possible, however, that other means of altering calcitonin receptor signaling may still provide an opportunity for regulating FGF23 production.

Pigment epithelium-derived factor restoration increases bone mass and improves bone plasticity in a model of osteogenesis imperfecta type VI via Wnt3a blockade.

Null mutations in for pigment epithelium-derived factor (PEDF), the protein product of the SERPINF1 gene, are the cause of osteogenesis imperfecta (OI) type VI. The PEDF-knockout (KO) mouse captures crucial elements of the human disease, including diminished bone mineralization and propensity to fracture. Our group and others have demonstrated that PEDF directs human mesenchymal stem cell (hMSC) commitment to the osteoblast lineage and modulates Wnt/ß-catenin signaling, a major regulator of bone development; however, the ability of PEDF to restore bone mass in a mouse model of OI type VI has not been determined. In this study, PEDF delivery increased trabecular bone volume/total volume by 52% in 6-mo-old PEDF-KO mice but not in wild-type mice. In young (19-d-old) PEDF-KO mice, PEDF restoration increased bone volume fraction by 35% and enhanced biomechanical parameters of bone plasticity. A Wnt-green fluorescent protein reporter demonstrated dynamic changes in Wnt/ß-catenin signaling characterized by early activation and marked suppression during terminal differentiation of hMSCs. Continuous Wnt3a exposure impeded mineralization of hMSCs, whereas the combination of Wnt3a and PEDF potentiated mineralization. Interrogation of the PEDF sequence identified a conserved motif found in other Wnt modulators, such as the dickkopf proteins. Mutation of a single amino acid on a 34-mer PEDF peptide increased mineralization of hMSC cultures compared with the native peptide sequence. These results indicate that PEDF counters Wnt signaling to allow for osteoblast differentiation and provides a mechanistic insight into how the PEDF null state results in OI type VI.-Belinsky, G. S., Sreekumar, B., Andrejecsk, J. W., Saltzman, W. M., Gong, J., Herzog, R. I., Lin, S., Horsley, V., Carpenter, T. O., Chung, C. Pigment epithelium-derived factor restoration increases bone mass and improves bone plasticity in a model of osteogenesis imperfecta type VI via Wnt3a blockade.

Hypophosphatemia promotes lower rates of muscle ATP synthesis.

Hypophosphatemia can lead to muscle weakness and respiratory and heart failure, but the mechanism is unknown. To address this question, we noninvasively assessed rates of muscle ATP synthesis in hypophosphatemic mice by using in vivo saturation transfer [31P]-magnetic resonance spectroscopy. By using this approach, we found that basal and insulin-stimulated rates of muscle ATP synthetic flux (VATP) and plasma inorganic phosphate (Pi) were reduced by 50% in mice with diet-induced hypophosphatemia as well as in sodium-dependent Pi transporter solute carrier family 34, member 1 (NaPi2a)-knockout (NaPi2a-/-) mice compared with their wild-type littermate controls. Rates of VATP normalized in both hypophosphatemic groups after restoring plasma Pi concentrations. Furthermore, VATP was directly related to cellular and mitochondrial Pi uptake in L6 and RC13 rodent myocytes and isolated muscle mitochondria. Similar findings were observed in a patient with chronic hypophosphatemia as a result of a mutation in SLC34A3 who had a 50% reduction in both serum Pi content and muscle VATP After oral Pi repletion and normalization of serum Pi levels, muscle VATP completely normalized in the patient. Taken together, these data support the hypothesis that decreased muscle ATP synthesis, in part, may be caused by low blood Pi concentrations, which may explain some aspects of muscle weakness observed in patients with hypophosphatemia.-Pesta, D. H., Tsirigotis, D. N., Befroy, D. E., Caballero, D., Jurczak, M. J., Rahimi, Y., Cline, G. W., Dufour, S., Birkenfeld, A. L., Rothman, D. L., Carpenter, T. O., Insogna, K., Petersen, K. F., Bergwitz, C., Shulman, G. I. Hypophosphatemia promotes lower rates of muscle ATP synthesis.