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A Novel Technique for Generating and Observing Chemiluminescence in a Biological Setting

Intraoperative imaging techniques have the potential to make surgical interventions safer and more effective; for these reasons, such techniques are ...

Memorial Sloan Kettering Cancer Center

Graduate Center of City University of New York

Fibroblast growth factor 23 (FGF23) is a hormone released primarily by osteocytes that regulates phosphate and vitamin D metabolism. Recent observational studies in humans suggest that circulating FGF23 is independently associated with cardiac hypertrophy and increased mortality, but it is unknown whether FGF23 can directly alter cardiac function. We found that FGF23 significantly increased cardiomyocyte cell size in vitro, the expression of gene markers of cardiac hypertrophy, and total protein content of cardiac muscle. In addition, FGFR1 and FGFR3 mRNA were the most abundantly expressed FGF receptors in cardiomyocytes, and the coreceptor α-klotho was expressed at very low levels. We tested an animal model of chronic kidney disease (Col4a3(-/-) mice) that has elevated serum FGF23. We found elevations in common hypertrophy gene markers in Col4a3(-/-) hearts compared with wild type but did not observe changes in wall thickness or cell size by week 10. However, the Col4a3(-/-) hearts did show reduced fractional shortening (-17%) and ejection fraction (-11%). Acute exposure of primary cardiomyocytes to FGF23 resulted in elevated intracellular Ca(2+) ([Ca(2+)](i); F/F(o) + 86%) which was blocked by verapamil pretreatment. FGF23 also increased ventricular muscle strip contractility (67%), which was inhibited by FGF receptor antagonism. We hypothesize that although FGF23 can acutely increase [Ca(2+)](i), chronically this may lead to decreases in contractile function or stimulate cardiac hypertrophy, as observed with other stress hormones. In conclusion, FGF23 is a novel bone/heart endocrine factor and may be an important mediator of cardiac Ca(2+) regulation and contractile function during chronic kidney disease.

FGF23 is a novel regulator of intracellular calcium and cardiac contractility in addition to cardiac hypertrophy.

The current study presents [(18)F]PARPi-FL as a bimodal fluorescent/positron emission tomography (PET) agent for PARP1 imaging.

Dual-Modality Optical/PET Imaging of PARP1 in Glioblastoma.

Fluorescent imaging agents are becoming evermore important in preclinical and clinical research. They do, however, suffer from poor tissue penetration, which makes optical fluorescence imaging incompatible with whole-body imaging techniques. The design of novel bimodal PET active and fluorescent tracers could therefore combine the benefits of optical imaging with radioactively labeled imaging probes. Herein, we report the synthesis and evaluation of a clickable (18)F-labeled fluorescent dye.

Development of a clickable bimodal fluorescent/PET probe for in vivo imaging.

The current study presents [(18)F]PARPi as imaging agent for PARP1 expression.

Non-invasive PET Imaging of PARP1 Expression in Glioblastoma Models.

Intraoperative imaging technologies recently entered the operating room, and their implementation is revolutionizing how physicians plan, monitor, and perform surgical interventions. In this work, we present a novel surgical imaging reporter system: intraoperative chemiluminescence imaging (ICI). To this end, we have leveraged the ability of a chemiluminescent metal complex to generate near-infrared light upon exposure to an aqueous solution of Ce(4+) in the presence of reducing tissue or blood components. An optical camera spatially resolves the resulting photon flux. We describe the construction and application of a prototype imaging setup, which achieves a detection limit as low as 6.9 pmol cm(-2) of the transition-metal-based ICI agent. As a proof of concept, we use ICI for the in vivo detection of our transition metal tracer following both systemic and subdermal injections. The very high signal-to-noise ratios make ICI an interesting candidate for the development of new intraoperative imaging technologies.

Near-Infrared Intraoperative Chemiluminescence Imaging.

Diffuse intrinsic pontine glioma (DIPG) is a childhood brainstem tumor with a universally poor prognosis. Here, we characterize on a positron emission tomography (PET) probe for imaging DIPG in vivo. In human histological tissues, the probes target, poly(ADP)ribose polymerase 1 (PARP1), was highly expressed in DIPG compared to normal brain. PET imaging allowed for the sensitive detection of DIPG in a genetically engineered mouse model (GEMM), and probe uptake correlated to histologically determined tumor infiltration. Imaging with the sister fluorescence agent revealed that uptake was confined to proliferating, PARP1 expressing cells. Comparison to other imaging technologies revealed remarkable accuracy of our biomarker approach. We subsequently demonstrated that serial imaging of DIPG in mouse models enables monitoring of tumor growth, as shown in modeling of tumor progression. Overall, this validated method for quantifying DIPG burden would serve useful in monitoring treatment response in early phase clinical trials.

Biomarker based PET Imaging of Diffuse Intrinsic Pontine Glioma in Mouse Models.

Ataxia telangiectasia and Rad3-related (ATR) threonine serine kinase is one of the key elements in orchestrating the DNA damage response (DDR). As such, inhibition of ATR can amplify the effects of chemo- and radiation-therapy, and several ATR inhibitors (ATRi) have already undergone clinical testing in cancer. For more accurate patient selection, monitoring and staging, real-time in vivo imaging of ATR could be invaluable; the development of appropriate imaging agents has remained a major challenge.

Brandon Carney

Department of Radiology

Memorial Sloan Kettering Cancer Center

A Novel Technique for Generating and Observing Chemiluminescence in a Biological Setting