Hyperpolarized Nano-NMR Platform for Quantification of Mass Limited Samples.

Metabolic flux analysis of live cells using NMR enables the study of cancer metabolism and response to treatment. However, conventional NMR platforms require often prohibitively high numbers of cells to achieve significant resolution. In this work, we present a double 1H/13C resonance NMR probe consisting of a solenoid coil with a less than 100 nL sensitive region. In-solution robustness is demonstrated through measurement of decaying hyperpolarized signals. A suspension of live cells and hyperpolarized (HP) [1-13C]pyruvate is loaded in the coil, and dynamic changes in pyruvate and lactate concentrations by fractions of femtomoles are detected from just 2000 live cells at a time, in seconds. Through an integrated microfluidic channel, the probe is used as high-throughput platform to perform nondestructive quantitative analysis of metabolic flux of different leukemia cell lines with sensitivity to detect on target treatment response. This approach platform provides an approach to study mass-limited samples and living cells with dramatically enhanced sensitivity in real time.

First in-human evaluation of [1-13C]pyruvate in D2O for hyperpolarized MRI of the brain: A safety and feasibility study.

PURPOSE: To investigate the safety and value of hyperpolarized (HP) MRI of [1-13C]pyruvate in healthy volunteers using deuterium oxide (D2O) as a solvent. METHODS: Healthy volunteers (n = 5), were injected with HP [1-13C]pyruvate dissolved in D2O and imaged with a metabolite-specific 3D dual-echo dynamic EPI sequence at 3T at one site (Site 1). Volunteers were monitored following the procedure to assess safety. Image characteristics, including SNR, were compared to data acquired in a separate cohort using water as a solvent (n = 5) at another site (Site 2). The apparent spin-lattice relaxation time (T1) of [1-13C]pyruvate was determined both in vitro and in vivo from a mono-exponential fit to the image intensity at each time point of our dynamic data. RESULTS: All volunteers completed the study safely and reported no adverse effects. The use of D2O increased the T1 of [1-13C]pyruvate from 66.5 ± 1.6 s to 92.1 ± 5.1 s in vitro, which resulted in an increase in signal by a factor of 1.46 ± 0.03 at the time of injection (90 s after dissolution). The use of D2O also increased the apparent relaxation time of [1-13C]pyruvate by a factor of 1.4 ± 0.2 in vivo. After adjusting for inter-site SNR differences, the use of D2O was shown to increase image SNR by a factor of 2.6 ± 0.2 in humans. CONCLUSIONS: HP [1-13C]pyruvate in D2O is safe for human imaging and provides an increase in T1 and SNR that may improve image quality.

Evidence of 13 C-lactate oxidation in the human brain from hyperpolarized 13 C-MRI.

PURPOSE: To test the hypothesis that lactate oxidation contributes to the 13 $$ {}^{13} $$ C-bicarbonate signal observed in the awake human brain using hyperpolarized 13 $$ {}^{13} $$ C MRI. METHODS: Healthy human volunteers (N = 6) were scanned twice using hyperpolarized 13 $$ {}^{13} $$ C-MRI, with increased radiofrequency saturation of 13 $$ {}^{13} $$ C-lactate on one set of scans. 13 $$ {}^{13} $$ C-lactate, 13 $$ {}^{13} $$ C-bicarbonate, and 13 $$ {}^{13} $$ C-pyruvate signals for 132 brain regions across each set of scans were compared using a clustered Wilcoxon signed-rank test. RESULTS: Increased 13 $$ {}^{13} $$ C-lactate radiofrequency saturation resulted in a significantly lower 13 $$ {}^{13} $$ C-bicarbonate signal (p = 0.04). These changes were observed across the majority of brain regions. CONCLUSION: Radiofrequency saturation of 13 $$ {}^{13} $$ C-lactate leads to a decrease in 13 $$ {}^{13} $$ C-bicarbonate signal, demonstrating that the 13 $$ {}^{13} $$ C-lactate generated from the injected 13 $$ {}^{13} $$ C-pyruvate is being converted back to 13 $$ {}^{13} $$ C-pyruvate and oxidized throughout the human brain.

Imaging Tumor Metabolism.

Molecular imaging-the mapping of molecular and cellular processes in vivo-has the unique capability to interrogate cancer metabolism in its spatial contexts. This work describes the usage of the two most developed modalities for imaging metabolism in vivo: positron emission tomography (PET) and magnetic resonance (MR). These techniques can be used to probe glycolysis, glutamine metabolism, anabolic metabolism, redox state, hypoxia, and extracellular acidification. This review aims to provide an overview of the strengths and limitations of currently available molecular imaging strategies.

Engineering focusing on cancer.

While cancer research and care have benefited from revolutionary advances in the ability to manipulate and study living systems, the field is limited by a lack of synergy to leverage the power of engineering approaches. Cancer engineering is an emerging subfield of biomedical engineering that unifies engineering and cancer biology to better understand, diagnose, and treat cancer. We highlight cancer engineering's unique challenges, the importance of creating dedicated centers and departments that enable translational collaboration, and educational approaches to arm a new generation of scientists with engineering expertise and a fundamental understanding of cancer biology to transform clinical cancer care.

New Horizons in Hyperpolarized 13C MRI.

Hyperpolarization techniques significantly enhance the sensitivity of magnetic resonance (MR) and thus present fascinating new directions for research and applications with in vivo MR imaging and spectroscopy (MRI/S). Hyperpolarized 13C MRI/S, in particular, enables real-time non-invasive assessment of metabolic processes and holds great promise for a diverse range of clinical applications spanning fields like oncology, neurology, and cardiology, with a potential for improving early diagnosis of disease, patient stratification, and therapy response assessment. Despite its potential, technical challenges remain for achieving clinical translation. This paper provides an overview of the discussions that took place at the international workshop "New Horizons in Hyperpolarized 13C MRI," in March 2023 at the Bavarian Academy of Sciences and Humanities, Munich, Germany. The workshop covered new developments, as well as future directions, in topics including polarization techniques (particularly focusing on parahydrogen-based methods), novel probes, considerations related to data acquisition and analysis, and emerging clinical applications in oncology and other fields.

Task Activation Results in Regional 13 C-Lactate Signal Increase in the Human Brain.

Hyperpolarized- 13 C magnetic resonance imaging (HP- 13 C MRI) was used to image changes in 13 C-lactate signal during a visual stimulus condition in comparison to an eyes-closed control condition. Whole-brain 13 C-pyruvate, 13 C-lactate and 13 C-bicarbonate production was imaged in healthy volunteers (N=6, ages 24-33) for the two conditions using two separate hyperpolarized 13 C-pyruvate injections. BOLD-fMRI scans were used to delineate regions of functional activation. 13 C-metabolite signal was normalized by 13 C-metabolite signal from the brainstem and the percentage change in 13 C-metabolite signal conditions was calculated. A one-way Wilcoxon signed-rank test showed a significant increase in 13 C-lactate in regions of activation when compared to the remainder of the brain ( p = 0.02, V = 21). No significant increase was observed in 13 C-pyruvate ( p = 0.11, V = 17) or 13 C-bicarbonate ( p = 0.95, V = 3) signal. The results show an increase in 13 C-lactate production in the activated region that is measurable with HP- 13 C MRI.

Imaging brain glucose metabolism in vivo reveals propionate as a major anaplerotic substrate in pyruvate dehydrogenase deficiency.

A vexing problem in mitochondrial medicine is our limited capacity to evaluate the extent of brain disease in vivo. This limitation has hindered our understanding of the mechanisms that underlie the imaging phenotype in the brain of patients with mitochondrial diseases and our capacity to identify new biomarkers and therapeutic targets. Using comprehensive imaging, we analyzed the metabolic network that drives the brain structural and metabolic features of a mouse model of pyruvate dehydrogenase deficiency (PDHD). As the disease progressed in this animal, in vivo brain glucose uptake and glycolysis increased. Propionate served as a major anaplerotic substrate, predominantly metabolized by glial cells. A combination of propionate and a ketogenic diet extended lifespan, improved neuropathology, and ameliorated motor deficits in these animals. Together, intermediary metabolism is quite distinct in the PDHD brain-it plays a key role in the imaging phenotype, and it may uncover new treatments for this condition.