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18?F-Fluoride positron emission tomography/computed tomography for noninvasive in vivo quantification of pathophysiological bone metabolism in experimental murine arthritis.

ABSTRACT: INTRODUCTION: Evaluation of disease severity in experimental models of rheumatoid arthritis is inevitably associated with assessment of structural bone damage. A noninvasive imaging technology allowing objective quantification of pathophysiological alterations of bone structure in rodents could substantially extend the methods used to date in preclinical arthritis research for staging of autoimmune disease severity or efficacy of therapeutical intervention. Sodium 18?F-fluoride (18?F-NaF) is a bone-seeking tracer well-suited for molecular imaging. Therefore, we systematically examined the use of 18?F-NaF positron emission tomography/computed tomography (PET/CT) in mice with glucose-6-phosphate isomerase (G6PI)-induced arthritis for quantification of pathological bone metabolism. METHODS: F-fluoride was injected into mice before disease onset and at various time points of progressing experimental arthritis. Radioisotope accumulation in joints in the fore- and hindpaws was analyzed by PET measurements. For validation of bone metabolism quantified by 18?F-fluoride PET, bone surface parameters of high-resolution ?CT measurements were used. RESULTS: Before clinical arthritis onset, no distinct accumulation of 18?F-fluoride was detectable in the fore- and hindlimbs of mice immunized with G6PI. In the course of experimental autoimmune disease, 18?F-fluoride bone uptake was increased at sites of enhanced bone metabolism caused by pathophysiological processes of autoimmune disease. Moreover, 18?F-fluoride signaling at different stages of G6PI-induced arthritis was significantly correlated with the degree of bone destruction. CT enabled identification of exact localization of 18?F-fluoride signaling in bone and soft tissue. CONCLUSIONS: The results of this study suggest that small-animal PET/CT using 18?F-fluoride as a tracer is a feasible method for quantitative assessment of pathophysiological bone metabolism in experimental arthritis. Furthermore, the possibility to perform repeated noninvasive measurements in vivo allows longitudinal study of therapeutical intervention monitoring.

SUBMITTER: Irmler IM

PROVIDER: S-EPMC4220085 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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18 F-Fluoride positron emission tomography/computed tomography for noninvasive in vivo quantification of pathophysiological bone metabolism in experimental murine arthritis.

Irmler Ingo M IM Gebhardt Peter P Hoffmann Bianca B Opfermann Thomas T Figge Marc-Thilo MT Saluz Hans P HP Kamradt Thomas T

Arthritis research & therapy 20140722 4

<h4>Introduction</h4>Evaluation of disease severity in experimental models of rheumatoid arthritis is inevitably associated with assessment of structural bone damage. A noninvasive imaging technology allowing objective quantification of pathophysiological alterations of bone structure in rodents could substantially extend the methods used to date in preclinical arthritis research for staging of autoimmune disease severity or efficacy of therapeutical intervention. Sodium 18 F-fluoride (18 F-NaF) ...[more]

PMID: 25053370

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Project description:BackgroundMicrocalcifications in atherosclerotic plaques are destabilizing, predict adverse cardiovascular events, and are associated with increased morbidity and mortality.18F-fluoride positron emission tomography (PET)/computed tomography (CT) imaging has demonstrated promise as a useful clinical diagnostic tool in identifying high-risk plaques; however, there is confusion as to the underlying mechanism of signal amplification seen in PET-positive, CT-negative image regions. This study tested the hypothesis that 18F-fluoride PET/CT can identify early microcalcifications.Methods18F-fluoride signal amplification derived from microcalcifications was validated against near-infrared fluorescence molecular imaging and histology using an in vitro 3-dimensional hydrogel collagen platform, ex vivo human specimens, and a mouse model of atherosclerosis.ResultsMicrocalcification size correlated inversely with collagen concentration. The 18F-fluoride ligand bound to microcalcifications formed by calcifying vascular smooth muscle cell derived extracellular vesicles in the in vitro 3-dimensional collagen system and exhibited an increasing signal with an increase in collagen concentration (0.25 mg/mL collagen -33.8×102±12.4×102 counts per minute; 0.5 mg/mL collagen -67.7×102±37.4×102 counts per minute; P=0.0014), suggesting amplification of the PET signal by smaller microcalcifications. We further incubated human atherosclerotic endarterectomy specimens with clinically relevant concentrations of 18F-fluoride. The 18F-fluoride ligand labeled microcalcifications in PET-positive, CT-negative regions of explanted human specimens as evidenced by 18F-fluoride PET/CT imaging, near-infrared fluorescence, and histological analysis. Additionally, the 18F-fluoride ligand identified micro and macrocalcifications in atherosclerotic aortas obtained from low-density lipoprotein receptor-deficient mice.ConclusionsOur results suggest that 18F-fluoride PET signal in PET-positive, CT-negative regions of human atherosclerotic plaques is the result of developing microcalcifications, and high surface area in regions of small microcalcifications may amplify PET signal.

Project description:ObjectiveTo determine the prevalence and correlates of subclinical myocardial inflammation in patients with rheumatoid arthritis (RA).MethodsRA patients (n = 119) without known cardiovascular disease underwent cardiac 18-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET-CT). Myocardial FDG uptake was assessed visually and measured quantitatively as the standardized uptake value (SUV). Multivariable linear regression was used to assess the associations of patient characteristics with myocardial SUVs. A subset of RA patients who had to escalate their disease-modifying antirheumatic drug (DMARD) therapy (n = 8) underwent a second FDG PET-CT scan after 6 months, to assess treatment-associated changes in myocardial FDG uptake.ResultsVisually assessed FDG uptake was observed in 46 (39%) of the 119 RA patients, and 21 patients (18%) had abnormal quantitatively assessed myocardial FDG uptake (i.e., mean of the mean SUV [SUVmean ] ≥3.10 units; defined as 2 SD above the value in a reference group of 27 non-RA subjects). The SUVmean was 31% higher in patients with a Clinical Disease Activity Index (CDAI) score of ≥10 (moderate-to-high disease activity) as compared with those with lower CDAI scores (low disease activity or remission) (P = 0.005), after adjustment for potential confounders. The adjusted SUVmean was 26% lower among those treated with a non-tumor necrosis factor-targeted biologic agent compared with those treated with conventional (nonbiologic) DMARDs (P = 0.029). In the longitudinal substudy, the myocardial SUVmean decreased from 4.50 units to 2.30 units over 6 months, which paralleled the decrease in the mean CDAI from a score of 23 to a score of 12.ConclusionSubclinical myocardial inflammation is frequent in patients with RA, is associated with RA disease activity, and may decrease with RA therapy. Future longitudinal studies will be required to assess whether reduction in myocardial inflammation will reduce heart failure risk in RA.

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18?F-Fluoride positron emission tomography/computed tomography for noninvasive in vivo quantification of pathophysiological bone metabolism in experimental murine arthritis.

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18 F-Fluoride positron emission tomography/computed tomography for noninvasive in vivo quantification of pathophysiological bone metabolism in experimental murine arthritis.

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