RESUMO
For glioblastoma (GBM), current therapeutic approaches focus on the combination of several therapies, each of them individually approved for GBM or other tumor types. Many efforts are made to decipher the best sequence of treatments that would ultimately promote the most efficient tumor response. There is therefore a strong interest in developing new clinical in vivo imaging procedures that can rapidly detect treatment efficacy and allow individual modulation of the treatment. In this preclinical study, we propose to evaluate tumor tissue changes under combined therapies, tumor vascular normalization under antiangiogenic treatment followed by radiotherapy, using a voxel-based clustering approach. This approach was applied to a rat model of glioma (F98). Six MRI parameters were mapped: apparent diffusion coefficient, vessel wall permeability, cerebral blood volume fraction, cerebral blood flow, tissue oxygen saturation and vessel size index. We compared the classical region of interest (ROI)-based analysis with a cluster-based analysis. Five clusters, defined by their MRI features, were sufficient to characterize tumor progression and tumor changes during treatments. These results suggest that the cluster-based analysis was as efficient as the ROI-based analysis to assess tumor physiological changes during treatment, but also gave additional information regarding the voxels impacted by treatments and their localization within the tumor. Overall, cluster-based analysis appears to be a powerful tool for subtle monitoring of tumor changes during combined therapies.
Assuntos
Inibidores da Angiogênese/uso terapêutico , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/radioterapia , Glioma/tratamento farmacológico , Animais , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Análise por Conglomerados , Modelos Animais de Doenças , Glioma/patologia , Imageamento por Ressonância Magnética , Masculino , Ratos Endogâmicos F344 , Sorafenibe/uso terapêuticoRESUMO
Twenty years ago, theoretical developments were initiated to model the behavior of the NMR transverse relaxation rates in presence of vessels. These developments enabled the MRI-based mapping of mean vessel diameter, microvascular density, and vessel size index with comparable results to those obtained by a pathologist. The transfer of these techniques to routine clinical use has been hindered by the unavailability of the required sequences, namely fast gradient-echo spin-echo sequences. Based on the increasing accessibility of such sequences on MRI scanners over recent years, we review the principles governing microvascular MRI, the validation studies, and the applications that have been tested worldwide by several teams. We also provide some recommendations on how to measure microvessel caliber and density with MRI.
Assuntos
Algoritmos , Densitometria/métodos , Interpretação de Imagem Assistida por Computador/métodos , Angiografia por Ressonância Magnética/métodos , Microvasos/anatomia & histologia , Humanos , Aumento da Imagem/métodos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The aim of this study was to determine the ability of multiparametric MRI to identify the early effects of individual treatment, during combined chemo-radiotherapy on brain tumours. Eighty male rats bearing 9L gliosarcomas were randomized into four groups: untreated, anti-angiogenic therapy (SORA group), microbeam radiation therapy (MRT group) and both treatments (MRT+SORA group). Multiparametric MRI (tumour volume, diffusion-weighted MR imaging (ADC), blood volume fraction (BVf), microvessel index (VSI), vessel wall integrity (AUC(P846)) and tissue oxygen saturation (StO2)) was performed 1 day before and 2, 5 and 8 days after treatment initiation. Unpaired t-tests and one-way ANOVA were used for statistical analyses. Each MR parameter measured in our protocol was revealed to be sensitive to tumour changes induced by any of the therapies used (individually or combined). When compared with untreated tumours, SORA induced a decrease in BVf, VSI, StO2 and AUC(P846), MRT generated an increase in ADC and AUC(P846) and combined therapies yielded mixed effects: an increase in ADC and AUC(P846) and a decrease in BVf, StO2 and AUC(P846). MRT and MRT+SORA significantly slowed tumour growth. Despite these two groups presenting with similar tumour sizes, the information yielded from MR multiparameter assessment indicated that, when used concomitantly, each therapy induced distinguishable and appreciable physiological changes in the tumour. Our results suggest that multiparametric MRI can monitor the effects of individual treatments, used concomitantly, on brain tumours. Such monitoring would be useful for the detection of tumour resistance to drug/radiotherapy in patients undergoing concomitant therapies.
Assuntos
Neoplasias Encefálicas/terapia , Imageamento por Ressonância Magnética/métodos , Inibidores da Angiogênese/uso terapêutico , Animais , Biomarcadores , Neoplasias Encefálicas/patologia , Masculino , Medicina de Precisão , Ratos , Ratos Endogâmicos F344RESUMO
BACKGROUND: Microvasculature plays a key role in stroke pathophysiology both during initial damage and extended neural repair. Moreover, angiogenesis processes seem to be a promising target for future neurorestorative therapies. However, dynamic changes of microvessels after stroke still remain unclear, and MRI follow-up could be interesting as an in vivo biomarker of these. METHODS: The aim of this study is to characterize the microvascular plasticity 25 days after ischemic stroke using both in vivo microvascular 7T-MRI (vascular permeability, cerebral blood volume (CBV), vessel size index (VSI), vascular density) and quantification of angiogenic factor expressions by RT-qPCR in a transient middle cerebral artery occlusion rat model. CBV and VSI (perfused vessel caliber) imaging was performed using a steady-state approach with a multi gradient-echo spin-echo sequence before and 2 min after intravenous (IV) injection of ultrasmall superparamagnetic iron particles. Vascular density (per mm2) was derived from the ratio [ΔR2/(ΔR2*)²/³]. Blood brain barrier leakage was assessed using T1W images before and after IV injection of Gd-DOTA. Additionally, microvessel immunohistology was done. RESULTS: 3 successive stages were observed: 1) 'Acute stage' from day 1 to day 3 post-stroke (D1-D3) characterized by high levels of angiopoietin-2 (Ang2), vascular endothelial growth factor receptor-2 (VEGFR-2) and endothelial NO synthase (eNOS) that may be associated with deleterious vascular permeability and vasodilation; 2) 'Transition stage' (D3-D7) that involves transforming the growth factors ß1 (TGFß1), Ang1, and tyrosine kinase with immunoglobulin-like and endothelial growth factor-like domains 1 (Tie1), stromal-derived factor-1 (SDF-1), chemokine receptor type 4 (CXCR-4); and 3) 'Subacute stage' (D7-D25) with high levels of Ang1, Ang2, VEGF, VEGFR-1 and TGFß1 leading to favorable stabilization and maturation of microvessels. In vivo MRI appeared in line with the angiogenic factors changes with a delay of at least 1 day. All MRI parameters varied over time, revealing the different aspects of the post-stroke microvascular plasticity. At D25, despite a normal CBV, MRI revealed a limited microvessel density, which is insufficient to support a good neural repair. CONCLUSIONS: Microvasculature MRI can provide imaging of different states of functional (perfused) microvessels after stroke. These results highlight that multiparametric MRI is useful to assess post-stroke angiogenesis, and could be used as a biomarker notably for neurorestorative therapy studies. Additionally, we identified that endogenous vessel maturation and stabilization occur during the 'subacute stage'. Thus, pro-angiogenic treatments, such as cell-based therapy, would be relevant during this subacute phase of stroke.
Assuntos
Imageamento por Ressonância Magnética , Microvasos/patologia , Acidente Vascular Cerebral/patologia , Animais , Barreira Hematoencefálica/patologia , Permeabilidade Capilar , Modelos Animais de Doenças , Infarto da Artéria Cerebral Média/patologia , Imageamento por Ressonância Magnética/métodos , Masculino , Ratos Sprague-Dawley , Acidente Vascular Cerebral/complicações , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
The aim of this study was to compare magnetic resonance imaging (MRI) and histological estimates of the mean vessel diameter (mVD), the vessel density (Density), and the vessel size index (VSI) obtained in the same tumor-bearing animals. Twenty-seven rats bearing intracranial glioma (C6 or RG2) were imaged by MRI. Changes in transverse relaxations (ΔR 2* and R(2)) were induced by the injection of an iron-based contrast agent and were mapped using a multi gradient-echo spin-echo sequence. Then, brain vascular network was studied ex vivo by histology. Three regions of interest were drawn in apparently normal tissue (neocortex and striatum) and in the tumor. In vivo mVD(MRI), Density(MRI), and VSI(MRI) were measured; ex vivo, mVD(histo), Density(histo), and VSI(histo) were quantified on the same animals. MRI and histology measurements differed by -15 to 26%. A positive correlation was found between MRI and histology for mVD, Density, and VSI counterparts (R(2) = 0.62, 0.50, 0.73, respectively; P < 0.001 in all cases). This study indicates that MRI and histology yields well correlated the estimates of mVD, Density, and VSI. VSI is the closest MRI estimate to histology. As Density and mVD or VSI provide complementary information, it is worth computing them to characterize angiogenesis beyond blood volume fraction.
Assuntos
Neoplasias Encefálicas/irrigação sanguínea , Encéfalo/irrigação sanguínea , Glioma/irrigação sanguínea , Imageamento por Ressonância Magnética , Animais , Meios de Contraste , Corpo Estriado/irrigação sanguínea , Técnicas Histológicas , Ferro/sangue , Masculino , Neocórtex/irrigação sanguínea , Transplante de Neoplasias , Ratos , Ratos Endogâmicos F344 , Ratos WistarRESUMO
PURPOSE: To analyze the contribution of the transverse relaxation parameter (T2), macroscopic field inhomogeneities (B0), and blood volume fraction (BVf) to blood oxygen level-dependent (BOLD)-based magnetic resonance (MR) measurements of blood oxygen saturation (SO2) obtained in a brain tumor model. MATERIALS AND METHODS: This study was approved by the local committee for animal care and use. Experiments were performed in accordance with permit 380 820 from the French Ministry of Agriculture. The 9L gliosarcoma cells were implanted in the brain of eight rats. Fifteen days later, 4.7-T MR examinations were performed to estimate T2*, T2, BVf, and T2*ΔB0corrected in the tumor and contralateral regions. MR estimates of SO2 were derived by combining T2, BVf, and T2*ΔB0corrected according to a recently described quantitative BOLD approach. Scatterplots and linear regression analysis were used to identify correlation between parameters. Paired Student t tests were used to compare the tumor region with the contralateral region. RESULTS: No significant correlations were found between T2* and any parameter in either tumor tissue or healthy tissue. T2* in the tumor and T2* in the uninvolved contralateral brain were the same (36 msec±4 [standard deviation] vs 36 msec±5, respectively), which might suggest similar oxygenation. Adding T2 information (98 msec±7 vs 68 msec±2, respectively) alone yields results that suggest apparent hypo-oxygenation of the tumor, while incorporating BVf (5.3%±0.6 vs 2.6%±0.3, respectively) alone yields results that suggest apparent hyperoxygenation. MR estimates of SO2 obtained with a complete quantitative BOLD analysis, although not correlated with T2* values, suggest normal oxygenation (68%±3 vs 65%±4, respectively). MR estimates of SO2 obtained in the contralateral tissue agree with previously reported values. CONCLUSION: Additional measurements, such as BVf, T2, and B0, are needed to obtain reliable information on oxygenation with BOLD MR imaging. The proposed quantitative BOLD approach, which includes these measurements, appears to be a promising tool with which to map tumor oxygenation.
Assuntos
Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/metabolismo , Glioblastoma/diagnóstico , Glioblastoma/metabolismo , Imageamento por Ressonância Magnética/métodos , Oximetria/métodos , Oxigênio/análise , Animais , Linhagem Celular Tumoral , Masculino , Ratos , Ratos Endogâmicos F344 , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
PURPOSE: To assess the reproducibility of the magnetic resonance (MR) estimate of blood oxygen saturation (sO(2)) in the rat brain, to evaluate the relationship between low MR estimate of sO(2) values and tissue hypoxia in a hypoxic and necrotic glioscarcoma model (9L gliosarcoma cells), and to evaluate the capability of the MR estimate of sO(2) parameter to help identify modifications induced by an antiangiogenic treatment (sorafenib) in 9L gliosarcoma tumors. MATERIALS AND METHODS: Experiments were performed with permits from the French Ministry of Agriculture. Forty-eight male rats bearing a 9L gliosarcoma were randomized in untreated and treated (sorafenib) groups. MR blood volume fraction and MR estimate of sO(2) parameters were estimated 1 day before and 1, 3, 5, and 8 days after the start of the treatment. The in vivo MR estimate of sO(2) measurement was correlated with the ex vivo hypoxia assessment by using pimonidazole staining. Paired and unpaired t tests, as well as parametric Pearson tests, were used for the statistical analyses. RESULTS: In healthy tissues, MR estimate of sO(2) measurements were comparable to literature values and were reproducible (mean across all animals, 68.0% ± 6.5 [standard deviation]). In untreated tumors, MR estimate of sO(2) and immunohistochemical analysis yielded correlated fractional hypoxic-necrotic areas (R(2) = 0.81). In tumors treated with antiangiogenic therapy, tumor MR estimate of sO(2) was decreased with respect to the healthy tissue (P< .001). CONCLUSION: Results of this study suggest that the MR estimate of sO(2) is a reproducible estimate that could be used as an in vivo probe of hypoxia in brain tumors and as a sensitive reporter of the hypoxic effects of antiangiogenic therapies.
Assuntos
Inibidores da Angiogênese/farmacologia , Benzenossulfonatos/farmacologia , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/metabolismo , Gliossarcoma/tratamento farmacológico , Gliossarcoma/metabolismo , Imageamento por Ressonância Magnética/métodos , Oxigênio/sangue , Piridinas/farmacologia , Análise de Variância , Animais , Dextranos/administração & dosagem , Hipóxia Encefálica/metabolismo , Processamento de Imagem Assistida por Computador , Imuno-Histoquímica , Modelos Lineares , Nanopartículas de Magnetita/administração & dosagem , Masculino , Niacinamida/análogos & derivados , Nitroimidazóis/administração & dosagem , Compostos de Fenilureia , Distribuição Aleatória , Ratos , Ratos Endogâmicos F344 , Reprodutibilidade dos Testes , SorafenibeRESUMO
Several MR methods have been proposed over the last decade to obtain quantitative estimates of the tissue blood oxygen saturation (StO2) using a quantification of the blood oxygen level dependent effect. These approaches are all based on mathematical models describing the time evolution of the MR signal in biological tissues in the presence of magnetic field inhomogeneities. Although the experimental results are very encouraging, possible biases induced by the model assumptions have not been extensively studied. In this study, a numerical approach was used to examine the influence on T(2)*, blood volume fraction, and StO2 estimates of possible confounding factors such as water diffusion, intravascular signal, and presence of arterial blood in the voxel. To evaluate the impact of the vessel geometry, straight cylinders and realistic data from two-photon microscopy for microvascular geometry were compared. Our results indicate that the models are sufficiently realistic, based on a good correlation between ground truth and MR estimates of StO2.
Assuntos
Espectroscopia de Ressonância Magnética/métodos , Modelos Cardiovasculares , Consumo de Oxigênio/fisiologia , Oxigênio/sangue , Animais , Simulação por Computador , Imageamento por Ressonância Magnética/métodos , Camundongos , Camundongos NusRESUMO
Vessel size index (VSI), a parameter related to the distribution of vessel diameters, may be estimated using two MRI approaches: (i) dynamic susceptibility contrast (DSC) MRI following the injection of a bolus of Gd-chelate. This technique is routinely applied in the clinic to assess intracranial tissue perfusion in patients; (ii) steady-state susceptibility contrast with USPIO contrast agents, which is considered here as the standard method. Such agents are not available for human yet and the steady-state approach is currently limited to animal studies. The aim is to compare VSI estimates obtained with these two approaches on rats bearing C6 glioma (n = 7). In a first session, VSI was estimated from two consecutive injections of Gd-Chelate (Gd(1) and Gd(2)). In a second session (4 hours later), VSI was estimated using USPIO. Our findings indicate that both approaches yield comparable VSI estimates both in contralateral (VSI{USPIO} = 7.5 ± 2.0 µm, VSI{Gd(1)} = 6.5 ± 0.7 µm) and in brain tumour tissues (VSI{USPIO} = 19.4 ± 7.1 µm, VSI{Gd(1)} = 16.6 ± 4.5 µm). We also observed that, in the presence of BBB leakage (as it occurs typically in brain tumours), applying a preload of Gd-chelate improves the VSI estimate with the DSC approach both in contralateral (VSI{Gd(2)} = 7.1 ± 0.4 µm) and in brain tumour tissues (VSI{Gd(2)} = 18.5 ± 4.3 µm) but is not mandatory. VSI estimates do not appear to be sensitive to T(1) changes related to Gd extravasation. These results suggest that robust VSI estimates may be obtained in patients at 3 T or higher magnetic fields with the DSC approach.
Assuntos
Vasos Sanguíneos/patologia , Neoplasias Encefálicas/irrigação sanguínea , Meios de Contraste , Dextranos , Gadolínio , Glioma/irrigação sanguínea , Imageamento por Ressonância Magnética/métodos , Nanopartículas de Magnetita , Animais , Linhagem Celular Tumoral , Difusão , Modelos Animais de Doenças , Humanos , Masculino , Transplante de Neoplasias , Tamanho do Órgão , Ratos , Ratos WistarRESUMO
Stroke, the leading cause of disability, lacks treatment beyond thrombolysis. The acute injection of human mesenchymal stem cells (hMSCs) provides a benefit which could be mediated by an enhancement of angiogenesis. A clinical autologous graft requires an hMSC culture delay incompatible with an acute administration. This study evaluates the cerebral microvascular changes after a delayed injection of hMSCs. At day 8 after middle cerebral artery occlusion (MCAo), two groups of rats received an intracerebral injection in the damaged brain of either 10 µL of cell suspension medium (MCAo-PBS, n = 4) or 4 × 105 hMSCs (MCAo-hMSC, n = 5). Two control groups of healthy rats underwent the same injection procedures in the right hemisphere (control-PBS, n = 6; control-hMSC, n = 5). The effect of hMSCs on the microvasculature was assessed by MRI using three parameters: apparent diffusion coefficient (ADC), cerebral blood volume (CBV) and vessel size index (VSI). At day 9, eight additional rats were euthanised for a histological study of the microvascular parameters (CBV, VSI and vascular fraction). No ADC difference was observed between MCAo groups. One day after intracerebral injection, hMSCs abolished the CBV increase observed in the lesion (MCAo-hMSC: 1.7 ± 0.1% versus MCAo-PBS: 2.2 ± 0.2%) and delayed the VSI increase (vasodilation) secondary to cerebral ischaemia. Histological analysis at day 9 confirmed that hMSCs modified the microvascular parameters (CBV, VSI and vascular fraction) in the lesion. No ADC, CBV or VSI differences were observed between control groups. At the stroke post-acute phase, hMSC intracerebral injection rapidly and transiently modifies the cerebral microvasculature. This microvascular effect can be monitored in vivo by MRI.
Assuntos
Cérebro/irrigação sanguínea , Cérebro/patologia , Imageamento por Ressonância Magnética , Transplante de Células-Tronco Mesenquimais , Células-Tronco Mesenquimais/citologia , Microvasos/patologia , Acidente Vascular Cerebral/terapia , Animais , Edema Encefálico/etiologia , Difusão , Humanos , Injeções Intraventriculares , Ratos , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/patologiaRESUMO
Blood oxygen saturation (SO(2)) is a promising parameter for the assessment of brain tissue viability in numerous pathologies. Quantitative blood oxygenation level-dependent (qBOLD)-like approaches allow the estimation of SO(2) by modelling the contribution of deoxyhaemoglobin to the MR signal decay. These methods require a high signal-to-noise ratio to obtain accurate maps through fitting procedures. In this article, we present a version of the qBOLD method at long TE taking into account separate estimates of T(2), total blood volume fraction (BV(f)) and magnetic field inhomogeneities. Our approach was applied to the brains of 13 healthy rats under normoxia, hyperoxia and hypoxia. MR estimates of local SO(2) (MR_LSO(2)) were compared with measurements obtained from blood gas analysis. A very good correlation (R(2) = 0.89) was found between brain MR_LSO(2) and sagittal sinus SO(2).
Assuntos
Encéfalo/metabolismo , Oxigênio/sangue , Animais , Volume Sanguíneo , Encéfalo/anatomia & histologia , Veia Femoral/metabolismo , Masculino , Ratos , Ratos WistarRESUMO
Early imaging or blood biomarkers of tumor response is needed to customize anti-tumor therapy on an individual basis. This study evaluates the sensitivity and relevance of five potential MRI biomarkers. Sixty nude rats were implanted with human glioma cells (U-87 MG) and randomized into three groups: one group received an anti-angiogenic treatment (Sorafenib), a second a cytotoxic drug [1,3-bis(2-chloroethyl)-1-nitrosourea, BCNU (Carmustine)] and a third no treatment. The tumor volume, apparent diffusion coefficient (ADC) of water, blood volume fraction (BVf), microvessel diameter (vessel size index, VSI) and vessel wall integrity (contrast enhancement, CE) were monitored before and during treatment. Sorafenib reduced tumor CE as early as 1 day after treatment onset. By 4 days after treatment onset, tumor BVf was reduced and tumor VSI was increased. By 14 days after treatment onset, ADC was increased and the tumor growth rate was reduced. With BCNU, ADC was increased and the tumor growth rate was reduced 14 days after treatment onset. Thus, the estimated MRI parameters were sensitive to treatment at different times after treatment onset and in a treatment-dependent manner. This study suggests that multiparametric MR monitoring could allow the assessment of new anti-tumor drugs and the optimization of combined therapies.
Assuntos
Inibidores da Angiogênese/uso terapêutico , Glioma/tratamento farmacológico , Glioma/patologia , Imageamento por Ressonância Magnética/métodos , Inibidores da Angiogênese/farmacologia , Animais , Benzenossulfonatos/farmacologia , Benzenossulfonatos/uso terapêutico , Volume Sanguíneo/efeitos dos fármacos , Carmustina/farmacologia , Carmustina/uso terapêutico , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Glioma/irrigação sanguínea , Humanos , Masculino , Microvasos/efeitos dos fármacos , Microvasos/patologia , Modelos Biológicos , Niacinamida/análogos & derivados , Compostos de Fenilureia , Piridinas/farmacologia , Piridinas/uso terapêutico , Ratos , Ratos Nus , Sorafenibe , Coloração e Rotulagem , Análise de SobrevidaRESUMO
Gliomas are the most common primary brain tumor affecting human adults and remain a therapeutic challenge because cells of origin are still unknown. Here, we investigated the cellular origin of low-grade gliomas in a rat model based on transplacental exposure to N-ethyl-N-nitrosourea (ENU). Longitudinal magnetic resonance imaging coupled to immunohistological and immunocytochemical analyses were used to further characterize low-grade rat gliomas at different stages of evolution. We showed that early low-grade gliomas have characteristics of oligodendroglioma-like tumors and exclusively contain NG2-expressing slow dividing precursor cells, which express early markers of oligodendroglial lineage. These tumor-derived precursors failed to fully differentiate into oligodendrocytes and exhibited multipotential abilities in vitro. Moreover, a few glioma NG2+ cells are resistant to radiotherapy and may be responsible for tumor recurrence, frequently observed in humans. Overall, these findings suggest that transformed multipotent NG2 glial precursor cell may be a potential cell of origin in the genesis of rat ENU-induced oligodendroglioma-like tumors. This work may open up new perspectives for understanding biology of human gliomas.
Assuntos
Antígenos/análise , Neoplasias Encefálicas/induzido quimicamente , Etilnitrosoureia/toxicidade , Células-Tronco Neoplásicas/patologia , Oligodendroglioma/induzido quimicamente , Proteoglicanas/análise , Animais , Neoplasias Encefálicas/patologia , Diferenciação Celular , Linhagem Celular Tumoral , Células-Tronco Neoplásicas/química , Oligodendroglioma/patologia , Ratos , Ratos Sprague-Dawley , Proteínas Ativadoras de ras GTPase/análiseRESUMO
PURPOSE: To evaluate the sequential injection of a low-molecular-weight (gadoterate meglumine [Gd-DOTA], 0.5 kDa) and a macromolecular (P846, 3.5 kDa) contrast media in monitoring the effect of antitumor therapies (antiangiogenic therapy and/or microbeam radiation therapy [MRT]) on healthy brain tissue and implanted tumors. MATERIALS AND METHODS: Animal use was compliant with official French guidelines and was assessed by the local Internal Evaluation Committee for Animal Welfare and Rights. Eighty male rats bearing 9L gliosarcoma were randomized into four groups: untreated, antiangiogenic (sorafenib) therapy, MRT, and both treatments. Magnetic resonance (MR) imaging was performed 1 day before and 1, 5, and 8 days after the start of the treatment. At all time points, vascular integrity to a macromolecular contrast medium (P846) and, 11 minutes 30 seconds later, to low-molecular-weight contrast medium (Gd-DOTA) was evaluated by using a dynamic contrast material-enhanced MR imaging approach. To quantify vessel wall integrity, areas under the signal intensity curves were computed for each contrast medium. Unpaired t tests and one-way analysis of variance were used for statistical analyses. RESULTS: Tumor vessels receiving antiangiogenic therapy became less permeable to the macromolecular contrast medium, but their permeability to the low-molecular-weight contrast medium remained unchanged. Healthy double-irradiated vessels became permeable to the low-molecular-weight contrast medium but not to the macromolecular contrast medium. CONCLUSION: Antiangiogenic therapy and MRT generate different effects on the extravasation of contrast medium in tumoral and healthy tissues. This study indicates that the use of a low-molecular-weight contrast medium and a macromolecular contrast medium provides complementary information and suggests that the use of two contrast media within the same MR imaging session is feasible.
Assuntos
Benzenossulfonatos/farmacologia , Barreira Hematoencefálica , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/radioterapia , Meios de Contraste/farmacocinética , Glioma/tratamento farmacológico , Glioma/radioterapia , Compostos Heterocíclicos/farmacocinética , Imageamento por Ressonância Magnética/métodos , Compostos Organometálicos/farmacocinética , Piridinas/farmacologia , Análise de Variância , Animais , Área Sob a Curva , Modelos Animais de Doenças , Substâncias Macromoleculares , Masculino , Neovascularização Patológica/tratamento farmacológico , Neovascularização Patológica/radioterapia , Niacinamida/análogos & derivados , Compostos de Fenilureia , Distribuição Aleatória , Ratos , SorafenibeRESUMO
The acidity of the tumor microenvironment aids tumor growth, and mechanisms causing it are targets for potential therapies. We have imaged extracellular pH (pHe) in C6 cell gliomas in rat brain using 1H magnetic resonance spectroscopy in vivo. We used a new probe molecule, ISUCA [(+/-)2-(imidazol-1-yl)succinic acid], and fast imaging techniques, with spiral acquisition in k-space. We obtained a map of metabolites [136 ms echo time (TE)] and then infused ISUCA in a femoral vein (25 mmol/kg body weight over 110 min) and obtained two consecutive images of pHe within the tumor (40 ms TE, each acquisition taking 25 min). pHe (where ISUCA was present) ranged from 6.5 to 7.5 in voxels of 0.75 microL and did not change detectably when [ISUCA] increased. Infusion of glucose (0.2 mmol/kg.min) decreased tumor pHe by, on average, 0.150 (SE, 0.007; P < 0.0001, 524 voxels in four rats) and increased the mean area of measurable lactate peaks by 54.4 +/- 3.4% (P < 0.0001, 287 voxels). However, voxel-by-voxel analysis showed that, both before and during glucose infusion, the distributions of lactate and extracellular acidity were very different. In tumor voxels where both could be measured, the glucose-induced increase in lactate showed no spatial correlation with the decrease in pHe. We suggest that, although glycolysis is the main source of protons, distributed sites of proton influx and efflux cause pHe to be acidic at sites remote from lactate production.
Assuntos
Glioma/metabolismo , Ácido Láctico/metabolismo , Ressonância Magnética Nuclear Biomolecular/métodos , Animais , Glucose/metabolismo , Glucose/farmacologia , Glicólise , Concentração de Íons de Hidrogênio , Masculino , Prótons , Ratos , Ratos Wistar , Succinatos/farmacologiaRESUMO
The aim of this work focuses on the description of the short-term response of a 9L brain tumor model and its vasculature to microbeam radiation therapy (MRT) using magnetic resonance imaging (MRI). Rat 9L gliosarcomas implanted in nude mice brains were irradiated by MRT 13 days after tumor inoculation using two orthogonal arrays of equally spaced 28 planar microbeams (25 microm width, 211 microm spacing and dose 500 Gy). At 1, 7 and 14 days after MRT, apparent diffusion coefficient, blood volume and vessel size index were mapped by MRI. Mean survival time after tumor inoculation increased significantly between MRT-treated and untreated groups (23 and 28 days respectively, log-rank test, p < 0.0001). A significant increase of apparent diffusion coefficient was observed 24 h after MRT in irradiated tumors versus non-irradiated ones. In the untreated group, both tumor size and vessel size index increased significantly (from 7.6 +/- 2.2 to 19.2 +/- 4.0 mm(2) and +23%, respectively) between the 14th and the 21st day after tumor cell inoculation. During the same period, in the MRT-treated group, no difference in tumor size was observed. The vessel size index measured in the MRT-treated group increased significantly (+26%) between 14 and 28 days of tumor growth. We did not observe the significant difference in blood volume between the MRT-treated and untreated groups. MRT slows 9L tumor growth in a mouse brain but MRI results suggest that the increase in survival time after our MRT approach may be rather due to a cytoreduction than to early direct effects of ionizing radiation on tumor vessels. These results suggest that MRT parameters need to be optimized to further damage tumor vessels.
Assuntos
Neoplasias Encefálicas/radioterapia , Gliossarcoma/radioterapia , Neovascularização Patológica/radioterapia , Radioterapia/métodos , Síncrotrons , Animais , Neoplasias Encefálicas/patologia , Gliossarcoma/patologia , Imageamento por Ressonância Magnética/métodos , Masculino , Camundongos , Camundongos Nus , Transplante de Neoplasias , Neovascularização Patológica/patologia , Radioterapia/instrumentação , Dosagem Radioterapêutica , Taxa de Sobrevida , Fatores de Tempo , Resultado do TratamentoRESUMO
Cerebral edema is one of the main acute complications arising after irradiation of brain tumors. Microbeam radiation therapy (MRT), an innovative experimental radiotherapy technique using spatially fractionated synchrotron x-rays, has been shown to spare radiosensitive tissues such as mammal brains. The aim of this study was to determine if cerebral edema occurs after MRT using diffusion-weighted MRI and microgravimetry. Prone Swiss nude mice's heads were positioned horizontally in the synchrotron x-ray beam and the upper part of the left hemisphere was irradiated in the antero-posterior direction by an array of 18 planar microbeams (25 mm wide, on-center spacing 211 mm, height 4 mm, entrance dose 312 Gy or 1000 Gy). An apparent diffusion coefficient (ADC) was measured at 7 T 1, 7, 14, 21 and 28 days after irradiation. Eventually, the cerebral water content (CWC) was determined by microgravimetry. The ADC and CWC in the irradiated (312 Gy or 1000 Gy) and in the contralateral non-irradiated hemispheres were not significantly different at all measurement times, with two exceptions: (1) a 9% ADC decrease (p < 0.05) was observed in the irradiated cortex 1 day after exposure to 312 Gy, (2) a 0.7% increase (p < 0.05) in the CWC was measured in the irradiated hemispheres 1 day after exposure to 1000 Gy. The results demonstrate the presence of a minor and transient cellular edema (ADC decrease) at 1 day after a 312 Gy exposure, without a significant CWC increase. One day after a 1000 Gy exposure, the CWC increased, while the ADC remained unchanged and may reflect the simultaneous presence of cellular and vasogenic edema. Both types of edema disappear within a week after microbeam exposure which may confirm the normal tissue sparing effect of MRT.
Assuntos
Edema Encefálico/complicações , Edema Encefálico/diagnóstico , Radioterapia/efeitos adversos , Radioterapia/métodos , Síncrotrons , Animais , Cérebro/metabolismo , Difusão , Feminino , Gravitação , Imageamento por Ressonância Magnética , Camundongos , Camundongos Nus , Dosagem Radioterapêutica , Sensibilidade e Especificidade , Fatores de Tempo , Água/metabolismoRESUMO
Knowledge of the blood volume per unit volume of brain tissue is important for understanding brain function in health and disease. We describe a direct method using two-photon laser scanning microscopy to obtain in vivo the local capillary blood volume in the cortex of anesthetized mouse. We infused fluorescent dyes in the circulating blood and imaged the blood vessels, including the capillaries, to a depth of 600 microm below the dura at the brain surface. Capillary cortical blood volume (CCBV) was calculated without any form recognition and segmentation, by normalizing the total fluorescence measured at each depth and integrating the collected intensities all over the stack. Theoretical justifications are presented and numerical simulations were performed to validate this method which was weakly sensitive to background noise. Then, CCBV had been estimated on seven healthy mice between 2%+/-0.3% and 2.4%+/-0.4%. We showed that this measure of CCBV is reproductible and that this method is highly sensitive to the explored zones in the cortex (vessel density and size). This method, which dispenses with form recognition, is rapid and would allow to study in vivo temporal and highly resolute spatial variations of CCBV under different conditions or stimulations.
Assuntos
Córtex Cerebral/anatomia & histologia , Córtex Cerebral/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Algoritmos , Animais , Volume Sanguíneo/fisiologia , Capilares/anatomia & histologia , Capilares/fisiologia , Simulação por Computador , Processamento de Imagem Assistida por Computador , Camundongos , Camundongos Nus , Microcirculação/fisiologia , Microscopia Confocal , Reprodutibilidade dos TestesRESUMO
Erythropoietin (Epo) is gaining interest in various neurological insults as a possible neuroprotective agent. We determined the effects of recombinant human Epo (rhEpo, 5000 IU per kg bw) on brain edema induced in rats by traumatic brain injury (TBI; impact-acceleration model; rhEpo administration 30 mins after injury). Magnetic resonance imaging (MRI) and a gravimetric technique were applied. In the MRI experiments, the apparent diffusion coefficient (ADC) and the tissue T(1) relaxation time were measured hourly in the neocortex and caudoputamen, during a 6 h time span after TBI. In the gravimetric experiments, brain water content (BWC) was determined in these two regions, 6 h after TBI. Apparent diffusion coefficient measurements showed that rhEpo decreased brain edema early and durably. Gravimetric measurements showed that rhEpo decreased BWC at H(6) in the neocortex as well as in the caudoputamen. No significant differences in ADC, in T(1), or in BWC were found between rhEpo treated-TBI rats and sham-operated rats. Our findings show that post-traumatic administration of rhEpo can significantly reduce the development of brain edema in a model of diffuse TBI. Further studies should be conducted to identify the biochemical mechanisms involved in these immediate effects and to assess the use of rhEpo as a possible therapy for post-traumatic brain edema.
Assuntos
Edema Encefálico/prevenção & controle , Lesões Encefálicas/tratamento farmacológico , Eritropoetina/uso terapêutico , Fármacos Neuroprotetores/uso terapêutico , Animais , Edema Encefálico/etiologia , Lesões Encefálicas/complicações , Humanos , Imageamento por Ressonância Magnética , Ratos , Ratos Wistar , Proteínas Recombinantes/uso terapêuticoRESUMO
This study evaluates the extravasation pathways of circulating macromolecules in a rat glioma model (RG2) which was observed by both magnetic resonance imaging using ultrasmall superparamagnetic iron oxide and electron microscopy. Although magnetic resonance imaging signal enhancement was observed as soon as 10 min after injection (9.4% 2 h after injection), electron microscopy showed that endothelial cells were still tightly sealed. However, circulating immunoglobulin G and ultrasmall superparamagnetic iron oxide were found in large membrane compartments of endothelial cells, in the basal lamina (7.4 ± 1.2 gold particles/µm2 in the tumor versus 0.38 ± 0.17 in healthy tissue, p = 1.4.10-5) and between tumoral cells. Altogether, this strongly suggests an active transport mediated by macropinocytosis. To challenge this transport mechanism, additional rats were treated with amiloride, an inhibitor of macropinocytosis, leading to a reduction of membrane protrusions (66%) and of macropinosomes. Amiloride however also opened tumoral tight junctions allowing a larger extravasation of ultrasmall superparamagnetic iron oxide (magnetic resonance imaging signal enhancement of 35.7% 2 h after injection). Altogether, these results suggest that ultrasmall superparamagnetic iron oxide and immunoglobulin G in the RG2 glioma model follow an active extravasation pathway mediated by a macropinocytosis process. Amiloride also appears as a potential strategy to facilitate the extravasation of chemotherapeutic drugs in glioma.