RESUMO
Functional MRI (fMRI) and MRS (fMRS) can be used to noninvasively map cerebral activation and metabolism. Recently, hyperpolarized 13C spectroscopy and metabolic imaging have provided an alternative approach to assess metabolism. In this study, we combined 1H fMRI and hyperpolarized [1-13C]pyruvate MRS to compare cerebral blood oxygenation level-dependent (BOLD) response and real-time cerebral metabolism, as assessed with lactate and bicarbonate labelling, during nicotine stimulation. Simultaneous 1H fMRI (multislice gradient echo echo-planar imaging) and 13C spectroscopic (single slice pulse-acquire) data were collected in urethane-anaesthetized female Sprague-Dawley rats (n = 12) at 9.4 T. Animals received an intravenous (i.v.) injection of either nicotine (stimulus; 88 µg/kg, n = 7, or 300 µg/kg, n = 5) or 0.9% saline (matching volume), followed by hyperpolarized [1-13C]pyruvate injection 60 s later. Three hours later, a second injection was administered: the animals that had previously received saline were injected with nicotine and vice versa, both followed by another hyperpolarized [1-13C]pyruvate i.v. injection 60 s later. The low-dose (88 µg/kg) nicotine injection led to a 12% ± 4% (n = 7, t-test, p ~ 0.0006 (t-value -5.8, degrees of freedom 6), Wilcoxon p ~ 0.0078 (test statistic 0)) increase in BOLD signal. At the same time, an increase in 13C-bicarbonate signal was seen in four out of six animals. Bicarbonate-to-total carbon ratios were 0.010 ± 0.004 and 0.018 ± 0.010 (n = 6, t-test, p ~ 0.03 (t-value -2.3, degrees of freedom 5), Wilcoxon p ~ 0.08 (test statistic 3)) for saline and nicotine experiments, respectively. No increase in the lactate signal was seen; lactate-to-total carbon was 0.16 ± 0.02 after both injections. The high (300 µg/kg) nicotine dose (n = 5) caused highly variable BOLD and metabolic responses, possibly due to the apparent respiratory distress. Simultaneous detection of 1H fMRI and hyperpolarized 13C-MRS is feasible. A comparison of metabolic response between control and stimulated states showed differences in bicarbonate signal, implying that the hyperpolarization technique could offer complimentary information on brain activation.
Assuntos
Imageamento por Ressonância Magnética , Ácido Pirúvico , Ratos , Feminino , Animais , Imageamento por Ressonância Magnética/métodos , Ácido Pirúvico/metabolismo , Nicotina/farmacologia , Ratos Sprague-Dawley , Bicarbonatos/metabolismo , Isótopos de Carbono/metabolismo , Ácido Láctico/metabolismoRESUMO
The use of hyperpolarised 13 C pyruvate for nononcological neurological applications has not been widespread so far, possibly due to delivery issues limiting the visibility of metabolites. First proof-of-concept results have indicated that metabolism can be detected in human brain, and this may supersede the results obtained in preclinical settings. One major difference between the experimental setups is that preclinical MRI/MRS routinely uses anaesthesia, which alters both haemodynamics and metabolism. Here, we used hyperpolarised [1-13 C]pyruvate to compare brain metabolism in awake rats and under isoflurane, urethane or medetomidine anaesthesia. Spectroscopic [1-13 C]pyruvate time courses measured sequentially showed that pyruvate-to-bicarbonate and pyruvate-to-lactate labelling rates were lower in isoflurane animals than awake animals. An increased bicarbonate-to-lactate ratio was observed in the medetomidine group compared with other groups. The study shows that hyperpolarised [1-13 C]pyruvate experiments can be performed in awake rats, thus avoiding anaesthesia-related issues. The results suggest that haemodynamics probably dominate the observed pyruvate-to-metabolite labelling rates and area-under-time course ratios of referenced to pyruvate. On the other hand, the results obtained with medetomidine suggest that the ratios are also modulated by the underlying cerebral metabolism. However, the ratios between intracellular metabolites were unchanged in awake compared with isoflurane-anaesthetised rats.
Assuntos
Encéfalo/metabolismo , Isoflurano/farmacologia , Ácido Pirúvico/metabolismo , Anestesia , Animais , Isótopos de Carbono , Feminino , Ratos , Ratos Sprague-Dawley , Ratos Wistar , VigíliaRESUMO
Molecular exchange processes are ubiquitous in nature. Here, we introduce a method to analyze exchange processes by using low-cost, portable, single-sided NMR instruments. The inherent magnetic field inhomogeneity of the single-sided instruments is exploited to achieve diffusion contrast of exchange sites and spatial encoding of 2D data. This so-called ultrafast diffusion exchange spectroscopy method shortens the experiment time by two to four orders of magnitude. Furthermore, because full 2D data are measured in a single scan (in a fraction of a second), the sensitivity of the experiment can be improved by several orders of magnitude using so-called nuclear spin hyperpolarization methods (in this case, dissolution dynamic nuclear polarization). As the first demonstration of the feasibility of the method in various applications, we show that the method enables quantification of intra- and extracellular exchange of water in a yeast cell suspension.
Assuntos
Imageamento por Ressonância Magnética , Água , Difusão , Espectroscopia de Ressonância Magnética/métodos , Água/químicaRESUMO
Hyperpolarised [1-13 C]pyruvate MRI has shown promise in monitoring therapeutic efficacy in a number of cancers including glioma. In this study, we assessed the pyruvate response to the lentiviral suicide gene therapy of herpes simplex virus-1 thymidine kinase with the prodrug ganciclovir (HSV-TK/GCV) in C6 rat glioma and compared it with traditional MR therapy markers. Female Wistar rats were inoculated with 106 C6 glioma cells. Treated animals received intratumoural lentiviral HSV-TK gene transfers on days 7 and 8 followed by 2-week GCV therapy starting on day 10. Animals were repeatedly imaged during therapy using volumetric MRI, diffusion and relaxation mapping, as well as metabolic [1-13 C]pyruvate MRS imaging. Survival (measured as time before animals reached a humane endpoint and were euthanised) was assessed up to day 30 posttherapy. HSV-TK/GCV gene therapy lengthened the median survival time from 12 to 25 days. This was accompanied by an apparent tumour growth arrest, but no changes in diffusion or relaxation parameters in treated animals. The metabolic response was more evident in the case-by-case analysis than in the group-level analysis. Treated animals also showed a 37 ± 15% decrease (P < 0.05, n = 5) in lactate-to-pyruvate ratio between therapy weeks, whereas a 44 ± 18% increase (P < 0.05, n = 6) was observed in control animals. Hyperpolarised [1-13 C]pyruvate MRI can offer complementary metabolic information to traditional MR methods to give a more comprehensive picture of the slowly developing gene therapy response. This may benefit the detection of the successful therapy response in patients.
Assuntos
Isótopos de Carbono/química , Genes Transgênicos Suicidas , Terapia Genética , Glioma/genética , Glioma/terapia , Lentivirus/genética , Ácido Pirúvico/metabolismo , Animais , Linhagem Celular Tumoral , Sobrevivência Celular , Ganciclovir/uso terapêutico , Glioma/diagnóstico por imagem , Glioma/tratamento farmacológico , Humanos , Imageamento por Ressonância Magnética , Ratos Wistar , ÁguaRESUMO
Rapid cancer cell proliferation promotes the production of reducing equivalents, which counteract the effects of relatively high levels of reactive oxygen species. Reactive oxygen species levels increase in response to chemotherapy and cell death, whereas an increase in antioxidant capacity can confer resistance to chemotherapy and is associated with an aggressive tumor phenotype. The pentose phosphate pathway is a major site of NADPH production in the cell, which is used to maintain the main intracellular antioxidant, glutathione, in its reduced state. Previous studies have shown that the rate of hyperpolarized [1-13C]dehydroascorbic acid (DHA) reduction, which can be measured in vivo using non-invasive 13C magnetic resonance spectroscopic imaging, is increased in tumors and that this is correlated with the levels of reduced glutathione. We show here that the rate of hyperpolarized [1-13C]DHA reduction is increased in tumors that have been oxidatively prestressed by depleting the glutathione pool by buthionine sulfoximine treatment. This increase was associated with a corresponding increase in pentose phosphate pathway flux, assessed using 13C-labeled glucose, and an increase in glutaredoxin activity, which catalyzes the glutathione-dependent reduction of DHA. These results show that the rate of DHA reduction depends not only on the level of reduced glutathione, but also on the rate of NADPH production, contradicting the conclusions of some previous studies. Hyperpolarized [1-13C]DHA can be used, therefore, to assess the capacity of tumor cells to resist oxidative stress in vivo However, DHA administration resulted in transient respiratory arrest and cardiac depression, which may prevent translation to the clinic.
Assuntos
Ácido Desidroascórbico/metabolismo , NADP/metabolismo , Neoplasias/metabolismo , Estresse Oxidativo , Animais , Isótopos de Carbono , Linhagem Celular Tumoral , Humanos , Marcação por Isótopo , Espectroscopia de Ressonância Magnética , CamundongosRESUMO
The ability to track cells and their patterns of gene expression in living organisms can increase our understanding of tissue development and disease. Gene reporters for bioluminescence, fluorescence, radionuclide, and magnetic resonance imaging (MRI) have been described but these suffer variously from limited depth penetration, spatial resolution, and sensitivity. We describe here a gene reporter, based on the organic anion transporting protein Oatp1a1, which mediates uptake of a clinically approved, Gd(3+)-based, hepatotrophic contrast agent (gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid). Cells expressing the reporter showed readily reversible, intense, and positive contrast (up to 7.8-fold signal enhancement) in T1-weighted magnetic resonance images acquired in vivo. The maximum signal enhancement obtained so far is more than double that produced by MRI gene reporters described previously. Exchanging the Gd(3+) ion for the radionuclide, (111)In, also allowed detection by single-photon emission computed tomography, thus combining the spatial resolution of MRI with the sensitivity of radionuclide imaging.
Assuntos
Genes Reporter , Imageamento por Ressonância Magnética/métodos , Animais , Linhagem Celular Tumoral , Meios de Contraste/química , Feminino , Gadolínio/química , Gadolínio DTPA/química , Células HCT116 , Células HEK293 , Humanos , Aumento da Imagem/métodos , Íons , Células MCF-7 , Camundongos , Camundongos SCID , Microscopia de Fluorescência/métodos , Transplante de Neoplasias , Transportadores de Ânions Orgânicos/metabolismo , Tomografia Computadorizada de Emissão de Fóton Único/métodosRESUMO
OBJECTIVES: Pancreatic cancer (PCa) is treatable by surgery when detected at an early stage. Non-invasive imaging methods able to detect both established tumours and their precursor lesions are needed to select patients for surgery. We investigated here whether pancreatic preneoplasia could be detected prior to the development of invasive cancers in genetically engineered mouse models of PCa using metabolic imaging. DESIGN: The concentrations of alanine and lactate and the activities of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT) were measured in extracts prepared from the pancreas of animals at different stages of disease progression; from pancreatitis, through tissue with predominantly low-grade and then high-grade pancreatic intraepithelial neoplasia and then tumour. (13)C magnetic resonance spectroscopic imaging ((13)C-MRSI) was used to measure non-invasively changes in (13)C labelling of alanine and lactate with disease progression, following injection of hyperpolarised [1-(13)C]pyruvate. RESULTS: Progressive decreases in the alanine/lactate concentration ratio and ALT/LDH activity ratio with disease progression were accompanied by a corresponding decrease in the [1-(13)C]alanine/[1-(13)C]lactate signal ratio observed in (13)C-MRSI images of the pancreas. CONCLUSIONS: Metabolic imaging with hyperpolarised [1-(13)C]pyruvate enables detection and monitoring of the progression of PCa precursor lesions. Translation of this MRI technique to the clinic has the potential to improve the management of patients at high risk of developing PCa.
Assuntos
Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Carcinoma Ductal Pancreático/diagnóstico , Pâncreas/metabolismo , Neoplasias Pancreáticas/diagnóstico , Lesões Pré-Cancerosas/diagnóstico , Animais , Biomarcadores/metabolismo , Carcinoma Ductal Pancreático/metabolismo , Progressão da Doença , Camundongos , Camundongos Transgênicos , Pâncreas/patologia , Neoplasias Pancreáticas/metabolismo , Pancreatite/diagnóstico , Pancreatite/metabolismo , Lesões Pré-Cancerosas/metabolismo , Ácido PirúvicoRESUMO
PURPOSE: To assess the potential of an MRI gene reporter based on the ferritin receptor Timd2 (T-cell immunoglobulin and mucin domain containing protein 2), using T1- and T2-weighted imaging. METHODS: Pellets of cells that had been modified to express the Timd2 transgene, and incubated with either iron-loaded or manganese-loaded ferritin, were imaged using T1- and T2-weighted MRI. Mice were also implanted subcutaneously with Timd2-expressing cells and the resulting xenograft tissue imaged following intravenous injection of ferritin using T2-weighted imaging. RESULTS: Timd2-expressing cells, but not control cells, showed a large increase in both R2 and R1 in vitro following incubation with iron-loaded and manganese-loaded ferritin, respectively. Expression of Timd2 had no effect on cell viability or proliferation; however, manganese-loaded ferritin, but not iron-loaded ferritin, was toxic to Timd2-expressing cells. Timd2-expressing xenografts in vivo showed much smaller changes in R2 following injection of iron-loaded ferritin than the same cells incubated in vitro with iron-loaded ferritin. CONCLUSION: Timd2 has demonstrated potential as an MRI reporter gene, producing large increases in R2 and R1 with ferritin and manganese-loaded ferritin respectively in vitro, although more modest changes in R2 in vivo. Manganese-loaded apoferritin was not used in vivo due to the toxicity observed in vitro. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.
Assuntos
Genes Reporter/genética , Imageamento por Ressonância Magnética/métodos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Animais , Feminino , Ferritinas/administração & dosagem , Ferritinas/química , Ferritinas/metabolismo , Corantes Fluorescentes/administração & dosagem , Corantes Fluorescentes/química , Corantes Fluorescentes/metabolismo , Células HEK293 , Humanos , Proteínas de Membrana/química , Camundongos , Camundongos SCIDRESUMO
PURPOSE: Dissolution dynamic nuclear polarization can increase the sensitivity of the (13) C magnetic resonance spectroscopy experiment by at least four orders of magnitude and offers a novel approach to the development of MRI gene reporters based on enzymes that metabolize (13) C-labeled tracers. We describe here a gene reporter based on the enzyme pyruvate decarboxylase (EC 4.1.1.1), which catalyzes the decarboxylation of pyruvate to produce acetaldehyde and carbon dioxide. METHODS: Pyruvate decarboxylase from Zymomonas mobilis (zmPDC) and a mutant that lacked enzyme activity were expressed using an inducible promoter in human embryonic kidney (HEK293T) cells. Enzyme activity was measured in the cells and in xenografts derived from the cells using (13) C MRS measurements of the conversion of hyperpolarized [1-(13) C] pyruvate to H(13) CO3-. RESULTS: Induction of zmPDC expression in the cells and in the xenografts derived from them resulted in an approximately two-fold increase in the H(13) CO3-/[1-(13) C] pyruvate signal ratio following intravenous injection of hyperpolarized [1-(13) C] pyruvate. CONCLUSION: We have demonstrated the feasibility of using zmPDC as an in vivo reporter gene for use with hyperpolarized (13) C MRS. Magn Reson Med 76:391-401, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Assuntos
Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Imageamento por Ressonância Magnética/métodos , Imagem Molecular/métodos , Piruvato Descarboxilase/metabolismo , Ácido Pirúvico/farmacocinética , Proteínas Recombinantes/metabolismo , Zymomonas/enzimologia , Animais , Ativação Enzimática , Feminino , Genes Reporter/fisiologia , Células HEK293 , Humanos , Camundongos , Camundongos SCID , Proteínas Recombinantes/genética , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Distribuição Tecidual , Zymomonas/genéticaRESUMO
Imaging of the metabolism of hyperpolarized [1-(13) C]pyruvate has shown considerable promise in preclinical studies in oncology, particularly for the assessment of early treatment response. The repeatability of measurements of (13) C label exchange between pyruvate and lactate was determined in a murine lymphoma model in fasted and non-fasted animals. The fasted state showed lower intra-individual variability, although the [1-(13) C]lactate/[1-(13) C]pyruvate signal ratio was significantly greater in fasted than in non-fasted mice, which may be explained by the higher tumor lactate concentrations in fasted animals. These results indicate that the fasted state may be preferable for the measurement of (13) C label exchange between pyruvate and lactate, as it reduces the variability and therefore should make it easier to detect the effects of therapy. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.
Assuntos
Algoritmos , Biomarcadores Tumorais/metabolismo , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Jejum/metabolismo , Neoplasias Experimentais/metabolismo , Ácido Pirúvico/metabolismo , Processamento de Sinais Assistido por Computador , Animais , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Neoplasias Experimentais/patologia , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Glycosylation is a ubiquitous post-translational modification, present in over 50% of the proteins in the human genome, with important roles in cell-cell communication and migration. Interest in glycome profiling has increased with the realization that glycans can be used as biomarkers of many diseases, including cancer. We report here the first tomographic imaging of glycosylated tissues in live mice by using metabolic labeling and a gadolinium-based bioorthogonal MRI probe. Significant N-azidoacetylgalactosamine dependent T1 â contrast was observed inâ vivo two hours after probe administration. Tumor, kidney, and liver showed significant contrast, and several other tissues, including the pancreas, spleen, heart, and intestines, showed a very high contrast (>10-fold). This approach has the potential to enable the rapid and non-invasive magnetic resonance imaging of glycosylated tissues inâ vivo in preclinical models of disease.
Assuntos
Carboidratos/química , Imageamento por Ressonância Magnética/métodos , Animais , Gadolínio/farmacocinética , Glicosilação , Camundongos , Sondas Moleculares , Distribuição TecidualRESUMO
PURPOSE: Aldehyde dehydrogenase (ALDH2) is an emerging drug target for the treatment of heart disease, cocaine and alcohol dependence, and conditions caused by genetic polymorphisms in ALDH2. Noninvasive measurement of ALDH2 activity in vivo could inform the development of these drugs and accelerate their translation to the clinic. METHODS: [1-(13) C, U-(2) H5 ] ethanol was hyperpolarized using dynamic nuclear polarization, injected into mice and its oxidation in the liver monitored using (13) C MR spectroscopy and spectroscopic imaging. RESULTS: Oxidation of [1-(13) C, U-(2) H5 ] ethanol to [1-(13) C] acetate was observed. Saturation of the acetaldehyde resonance, which was below the level of detection in vivo, demonstrated that acetate was produced via acetaldehyde. Irreversible inhibition of ALDH2 activity with disulfiram resulted in a proportional decrease in the amplitude of the acetate resonance. CONCLUSION: (13) C magnetic resonance spectroscopy measurements of hyperpolarized [1-(13) C, U-(2) H5 ] ethanol oxidation allow real-time assessment of ALDH2 activity in liver in vivo.
Assuntos
Álcool Desidrogenase/metabolismo , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos , Etanol/metabolismo , Animais , Concentração Alcoólica no Sangue , Dissulfiram/farmacologia , Relação Dose-Resposta a Droga , Feminino , Fígado/efeitos dos fármacos , Fígado/enzimologia , Camundongos , Oxirredução/efeitos dos fármacos , Valor Preditivo dos TestesRESUMO
PURPOSE: To assess the potential of a gene reporter system, based on a urea transporter (UTB) and hyperpolarized [(13) C]urea. METHODS: Mice were implanted subcutaneously with either unmodified control cells or otherwise identical cells expressing UTB. After injection of hyperpolarized [(13) C]urea, a spin echo sequence was used to measure urea concentration, T1 , and diffusion in control and UTB-expressing tissue. RESULTS: The apparent diffusion coefficient of hyperpolarized urea was 21% lower in tissue expressing UTB, in comparison with control tissue (P < 0.05, 1-tailed t-test, n = 6 in each group). No difference in water apparent diffusion coefficient or cellularity between these tissues was found, indicating that they were otherwise similar in composition. CONCLUSION: Expression of UTB, by mediating cell uptake of urea, lowers the apparent diffusion coefficient of hyperpolarized (13) C urea in tissue and thus the transporter has the potential to be used as a magnetic resonance-based gene reporter in vivo. Magn Reson Med 73:1401-1406, 2015. © 2014 Wiley Periodicals, Inc.
Assuntos
Espectroscopia de Ressonância Magnética/métodos , Proteínas de Membrana Transportadoras/metabolismo , Ureia/farmacocinética , Animais , Isótopos de Carbono/farmacocinética , Células HEK293 , Humanos , Proteínas de Membrana Transportadoras/genética , Camundongos , Camundongos SCID , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Distribuição Tecidual , Transgenes/genética , Transportadores de UreiaRESUMO
PURPOSE: A resonance at â¼181 ppm in the (13) C spectra of tumors injected with hyperpolarized [U-(2) H, U-(13) C]glucose was assigned to 6-phosphogluconate (6PG), as in previous studies in yeast, whereas in breast cancer cells in vitro this resonance was assigned to 3-phosphoglycerate (3PG). These peak assignments were investigated here using measurements of 6PG and 3PG (13) C-labeling using liquid chromatography tandem mass spectrometry (LC-MS/MS) METHODS: Tumor-bearing mice were injected with (13) C6 glucose and the (13) C-labeled and total 6PG and 3PG concentrations measured. (13) C MR spectra of glucose-6-phosphate dehydrogenase deficient (zwf1Δ) and wild-type yeast were acquired following addition of hyperpolarized [U-(2) H, U-(13) C]glucose and again (13) C-labeled and total 6PG and 3PG were measured by LC-MS/MS RESULTS: Tumor (13) C-6PG was more abundant than (13) C-2PG/3PG and the resonance at â¼181 ppm matched more closely that of 6PG. (13) C MR spectra of wild-type and zwf1Δ yeast cells showed a resonance at â¼181 ppm after labeling with hyperpolarized [U-(2) H, U-(13) C]glucose, however, there was no 6PG in zwf1Δ cells. In the wild-type cells 3PG was approximately four-fold more abundant than 6PG CONCLUSION: The resonance at â¼181 ppm in (13) C MR spectra following injection of hyperpolarized [U-(2) H, U-(13) C]glucose originates predominantly from 6PG in EL4 tumors and 3PG in yeast cells.
Assuntos
Glucose/farmacocinética , Glicólise , Neoplasias Experimentais/metabolismo , Via de Pentose Fosfato , Urânio/farmacocinética , Animais , Linhagem Celular Tumoral , Feminino , Espectroscopia de Ressonância Magnética/métodos , Taxa de Depuração Metabólica , Camundongos , Camundongos Endogâmicos C57BL , Compostos Radiofarmacêuticos/farmacocinética , Reprodutibilidade dos Testes , Saccharomyces cerevisiae/metabolismo , Sensibilidade e EspecificidadeRESUMO
Acute kidney injury (AKI) is a common and important medical problem, affecting 10% of hospitalized patients, and it is associated with significant morbidity and mortality. The most frequent cause of AKI is acute tubular necrosis (ATN). Current imaging techniques and biomarkers do not allow ATN to be reliably differentiated from important differential diagnoses, such as acute glomerulonephritis (GN). We investigated whether (13)C magnetic resonance spectroscopic imaging (MRSI) might allow the noninvasive diagnosis of ATN. (13)C MRSI of hyperpolarized [1,4-(13)C(2)]fumarate and pyruvate was used in murine models of ATN and acute GN (NZM2410 mice with lupus nephritis). A significant increase in [1,4-(13)C(2)]malate signal was identified in the kidneys of mice with ATN early in the disease course before the onset of severe histological changes. No such increase in renal [1,4-(13)C(2)]malate was observed in mice with acute GN. The kidney [1-(13)C]pyruvate/[1-(13)C]lactate ratio showed substantial variability and was not significantly decreased in animals with ATN or increased in animals with GN. In conclusion, MRSI of hyperpolarized [1,4-(13)C(2)]fumarate allows the detection of early tubular necrosis and its distinction from glomerular inflammation in murine models. This technique may have the potential to identify a window of therapeutic opportunity in which emerging therapies might be applied to patients with ATN, reducing the need for acute dialysis with its attendant morbidity and cost.
Assuntos
Fumaratos , Necrose Tubular Aguda/diagnóstico , Imageamento por Ressonância Magnética/métodos , Animais , Isótopos de Carbono , Diagnóstico Precoce , Ácido Fólico , Humanos , Rim/anormalidades , Rim/patologia , Rim/fisiopatologia , Necrose Tubular Aguda/induzido quimicamente , Necrose Tubular Aguda/fisiopatologia , Cinética , Nefrite Lúpica/diagnóstico , Nefrite Lúpica/patologia , Malatos , Camundongos , Camundongos Endogâmicos C57BL , Ácido PirúvicoRESUMO
PURPOSE: The acquisition of ever increasing volumes of high resolution magnetic resonance imaging (MRI) data has created an urgent need to develop automated and objective image analysis algorithms that can assist in determining tumor margins, diagnosing tumor stage, and detecting treatment response. METHODS: We have shown previously that Minkowski functionals, which are precise morphological and structural descriptors of image heterogeneity, can be used to enhance the detection, in T1 -weighted images, of a targeted Gd(3+) -chelate-based contrast agent for detecting tumor cell death. We have used Minkowski functionals here to characterize heterogeneity in T2 -weighted images acquired before and after drug treatment, and obtained without contrast agent administration. RESULTS: We show that Minkowski functionals can be used to characterize the changes in image heterogeneity that accompany treatment of tumors with a vascular disrupting agent, combretastatin A4-phosphate, and with a cytotoxic drug, etoposide. CONCLUSIONS: Parameterizing changes in the heterogeneity of T2 -weighted images can be used to detect early responses of tumors to drug treatment, even when there is no change in tumor size. The approach provides a quantitative and therefore objective assessment of treatment response that could be used with other types of MR image and also with other imaging modalities.
Assuntos
Etoposídeo/uso terapêutico , Interpretação de Imagem Assistida por Computador/métodos , Linfoma/tratamento farmacológico , Linfoma/patologia , Imageamento por Ressonância Magnética/métodos , Estilbenos/uso terapêutico , Animais , Antineoplásicos/uso terapêutico , Linhagem Celular Tumoral , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Estadiamento de Neoplasias , Prognóstico , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Resultado do TratamentoRESUMO
Measurements of early tumor responses to therapy have been shown, in some cases, to predict treatment outcome. We show in lymphoma-bearing mice injected intravenously with hyperpolarized [1-(13)C]pyruvate that the lactate dehydrogenase-catalyzed flux of (13)C label between the carboxyl groups of pyruvate and lactate in the tumor can be measured using (13)C magnetic resonance spectroscopy and spectroscopic imaging, and that this flux is inhibited within 24 h of chemotherapy. The reduction in the measured flux after drug treatment and the induction of tumor cell death can be explained by loss of the coenzyme NAD(H) and decreases in concentrations of lactate and enzyme in the tumors. The technique could provide a new way to assess tumor responses to treatment in the clinic.
Assuntos
Linfoma/tratamento farmacológico , Linfoma/patologia , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Animais , Antineoplásicos Fitogênicos/administração & dosagem , Isótopos de Carbono/metabolismo , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Etoposídeo/administração & dosagem , Lactato Desidrogenases/metabolismo , Ácido Láctico/administração & dosagem , Ácido Láctico/metabolismo , Linfoma/enzimologia , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Camundongos , Transplante de Neoplasias , Ácido Pirúvico/administração & dosagem , Ácido Pirúvico/metabolismoRESUMO
As alterations in tissue pH underlie many pathological processes, the capability to image tissue pH in the clinic could offer new ways of detecting disease and response to treatment. Dynamic nuclear polarization is an emerging technique for substantially increasing the sensitivity of magnetic resonance imaging experiments. Here we show that tissue pH can be imaged in vivo from the ratio of the signal intensities of hyperpolarized bicarbonate (H(13)CO(3)(-)) and (13)CO(2) following intravenous injection of hyperpolarized H(13)CO(3)(-). The technique was demonstrated in a mouse tumour model, which showed that the average tumour interstitial pH was significantly lower than the surrounding tissue. Given that bicarbonate is an endogenous molecule that can be infused in relatively high concentrations into patients, we propose that this technique could be used clinically to image pathological processes that are associated with alterations in tissue pH, such as cancer, ischaemia and inflammation.
Assuntos
Bicarbonatos/metabolismo , Linfoma/diagnóstico , Linfoma/metabolismo , Imageamento por Ressonância Magnética/métodos , Equilíbrio Ácido-Base , Animais , Dióxido de Carbono/metabolismo , Isótopos de Carbono , Anidrases Carbônicas/metabolismo , Catálise , Concentração de Íons de Hidrogênio , Linfoma/patologia , Camundongos , Transplante de Neoplasias , Imagens de FantasmasRESUMO
PURPOSE: To assess the blood-tissue distribution of hyperpolarized (13) C-labeled molecules in vivo. METHODS: Spin-echo experiments with simultaneous acquisition of the free induction decay (FID) signal following the excitation pulse and the spin-echo signal, were used to monitor hyperpolarized [1-(13) C]lactate, [1-(13) C]pyruvate, and the perfusion marker, [(13) C]HP001, following their intravenous injection into tumor-bearing mice. Apparent T2 relaxation times and diffusion coefficients were also measured. RESULTS: An increasing tumor echo/FID ratio was observed for all three molecules, which could be explained by their extravasation into the tumor interstitial space, where T2 relaxation times were longer and diffusion coefficients smaller. Inhibition of the monocarboxylate transporter, which decreased by 40% the label exchange between pyruvate and lactate, reduced the increase in the echo/FID ratio for pyruvate and lactate, but not for HP001, demonstrating that some of the increase in the echo/FID ratio was due to cell uptake of lactate and pyruvate. The different relaxation and diffusion behavior of the intravascular and extravascular signals affected measurements of the apparent label exchange rate constants. CONCLUSION: Simultaneous collection of both FID and echo signals can provide information on cell uptake thus giving further insight into the kinetics of hyperpolarized (13) C label exchange. Care is needed when comparing exchange rate constants determined in spin-echo-based studies.
Assuntos
Ácido Láctico/farmacocinética , Linfoma/metabolismo , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Animais , Isótopos de Carbono/farmacocinética , Linhagem Celular Tumoral , Feminino , Linfoma/patologia , Taxa de Depuração Metabólica , Camundongos , Camundongos Endogâmicos C57BL , Compostos Radiofarmacêuticos/farmacocinética , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Marcadores de SpinRESUMO
Hyperpolarized NMR is a promising technique for non-invasive imaging of tissue metabolism in vivo. However, the pathways that can be studied are limited by the fast T1 decay of the nuclear spin order. In metabolites containing pairs of coupled nuclear spins-1/2, the spin order may be maintained by exploiting the non-magnetic singlet (spin-0) state of the pair. This may allow preservation of the hyperpolarization in vivo during transport to tissues of interest, such as tumors, or to detect slower metabolic reactions. We show here that in human blood and in a mouse in vivo at millitesla fields the (13)C singlet lifetime of [1,2-(13)C2]pyruvate was significantly longer than the (13)C T1, although it was shorter than the T1 at field strengths of several tesla. We also examine the singlet-derived NMR spectrum observed for hyperpolarized [1,2-(13)C2]lactate, originating from the metabolism of [1,2-(13)C2]pyruvate.