RESUMO
The effect of a human vascular endothelial growth factor antibody on the vasculature of human tumor grown in rat brain was studied. Using dynamic contrast-enhanced magnetic resonance imaging, the effects of intravenous bevacizumab (Avastin; 10 mg/kg) were examined before and at postadministration times of 1, 2, 4, 8, 12 and 24 h (N = 26; 4-5 per time point) in a rat model of orthotopic, U251 glioblastoma (GBM). The commonly estimated vascular parameters for an MR contrast agent were: (i) plasma distribution volume (vp ), (ii) forward volumetric transfer constant (Ktrans ) and (iii) reverse transfer constant (kep ). In addition, extracellular distribution volume (VD ) was estimated in the tumor (VD-tumor ), tumor edge (VD-edge ) and the mostly normal tumor periphery (VD-peri ), along with tumor blood flow (TBF), peri-tumoral hydraulic conductivity (K) and interstitial flow (Flux) and tumor interstitial fluid pressure (TIFP). Studied as % changes from baseline, the 2-h post-treatment time point began showing significant decreases in vp , VD-tumor, VD-edge and VD-peri , as well as K, with these changes persisting at 4 and 8 h in vp , K, VD-tumor, -edge and -peri (t-tests; p < 0.05-0.01). Decreases in Ktrans were observed at the 2- and 4-h time points (p < 0.05), while interstitial volume fraction (ve ; = Ktrans /kep ) showed a significant decrease only at the 2-h time point (p < 0.05). Sustained decreases in Flux were observed from 2 to 24 h (p < 0.01) while TBF and TIFP showed delayed responses, increases in the former at 12 and 24 h and a decrease in the latter only at 12 h. These imaging biomarkers of tumor vascular kinetics describe the short-term temporal changes in physical spaces and fluid flows in a model of GBM after Avastin administration.
Assuntos
Bevacizumab/uso terapêutico , Glioma/irrigação sanguínea , Glioma/tratamento farmacológico , Animais , Bevacizumab/farmacologia , Linhagem Celular Tumoral , Feminino , Glioma/diagnóstico por imagem , Humanos , Cinética , Imageamento por Ressonância Magnética , Modelos Biológicos , Ratos , Distribuição TecidualRESUMO
PURPOSE: This study demonstrates a DCE-MRI estimate of tumor interstitial fluid pressure (TIFP) and hydraulic conductivity in a rat model of glioblastoma, with validation against an invasive wick-in-needle (WIN) technique. An elevated TIFP is considered a mark of aggressiveness, and a decreased TIFP a predictor of response to therapy. METHODS: The DCE-MRI studies were conducted in 36 athymic rats (controls and posttreatment animals) with implanted U251 cerebral tumors, and with TIFP measured using a WIN method. Using a model selection paradigm and a novel application of Patlak and Logan plots to DCE-MRI data, the MRI parameters required for estimating TIFP noninvasively were estimated. Two models, a fluid-mechanical model and a multivariate empirical model, were used for estimating TIFP, as verified against WIN-TIFP. RESULTS: Using DCE-MRI, the mean estimated hydraulic conductivity (MRI-K) in U251 tumors was (2.3 ± 3.1) × 10-5 (mm2 /mmHg-s) in control studies. Significant positive correlations were found between WIN-TIFP and MRI-TIFP in both mechanical and empirical models. For instance, in the control group of the fluid-mechanical model, MRI-TIFP was a strong predictor of WIN-TIFP (R2 = 0.76, p < .0001). A similar result was found in the bevacizumab-treated group of the empirical model (R2 = 0.93, p = .014). CONCLUSION: This research suggests that MRI dynamic studies contain enough information to noninvasively estimate TIFP in this, and possibly other, tumor models, and thus might be used to assess tumor aggressiveness and response to therapy.
Assuntos
Neoplasias Encefálicas , Meios de Contraste/química , Líquido Extracelular , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Animais , Fenômenos Biomecânicos/fisiologia , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/fisiopatologia , Meios de Contraste/metabolismo , Modelos Animais de Doenças , Líquido Extracelular/diagnóstico por imagem , Líquido Extracelular/fisiologia , Feminino , Camundongos Nus , RatosRESUMO
MRI estimates of extracellular volume and tumor exudate flux in peritumoral tissue are demonstrated in an experimental model of cerebral tumor. Peritumoral extracellular volume predicted the tumor exudate flux. Eighteen RNU athymic rats were inoculated intracerebrally with U251MG tumor cells and studied with dynamic contrast enhanced MRI (DCE-MRI) approximately 18 days post implantation. Using a model selection paradigm and a novel application of Patlak and Logan plots to DCE-MRI data, the distribution volume (i.e. tissue porosity) in the leaky rim of the tumor and that in the tissue external to the rim (the outer rim) were estimated, as was the tumor exudate flow from the inner rim of the tumor through the outer rim. Distribution volume in the outer rim was approximately half that of the inner adjacent region (p < 1 × 10(-4)). The distribution volume of the outer ring was significantly correlated (R(2) = 0.9) with tumor exudate flow from the inner rim. Thus, peritumoral extracellular volume predicted the rate of tumor exudate flux. One explanation for these data is that perfusion, i.e. the delivery of blood to the tumor, was regulated by the compression of the mostly normal tissue of the tumor rim, and that the tumor exudate flow was limited by tumor perfusion.
Assuntos
Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/fisiopatologia , Encéfalo/patologia , Exsudatos e Transudatos/citologia , Exsudatos e Transudatos/metabolismo , Imageamento por Ressonância Magnética/métodos , Animais , Encéfalo/fisiopatologia , Neoplasias Encefálicas/complicações , Força Compressiva , Simulação por Computador , Interpretação de Imagem Assistida por Computador/métodos , Modelos Biológicos , Ratos , Ratos Nus , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estresse MecânicoRESUMO
PURPOSE: To test the hypothesis that a noninvasive dynamic contrast enhanced MRI (DCE-MRI) derived interstitial volume fraction (ve ) and/or distribution volume (VD ) were correlated with tumor cellularity in cerebral tumor. METHODS: T1 -weighted DCE-MRI studies were performed in 18 athymic rats implanted with U251 xenografts. After DCE-MRI, sectioned brain tissues were stained with Hematoxylin and Eosin for cell counting. Using a Standard Model analysis and Logan graphical plot, DCE-MRI image sets during and after the injection of a gadolinium contrast agent were used to estimate the parameters plasma volume (vp ), forward transfer constant (K(trans) ), ve , and VD . RESULTS: Parameter values in regions where the standard model was selected as the best model were: (mean ± S.D.): vp = (0.81 ± 0.40)%, K(trans) = (2.09 ± 0.65) × 10(-2) min(-1) , ve = (6.65 ± 1.86)%, and VD = (7.21 ± 1.98)%. The Logan-estimated VD was strongly correlated with the standard model's vp + ve (r = 0.91, P < 0.001). The parameters, ve and/or VD , were significantly correlated with tumor cellularity (r ≥ -0.75, P < 0.001 for both). CONCLUSION: These data suggest that tumor cellularity can be estimated noninvasively by DCE-MRI, thus supporting its utility in assessing tumor pathophysiology.
Assuntos
Neoplasias Encefálicas/patologia , Glioma/patologia , Imageamento por Ressonância Magnética/métodos , Algoritmos , Animais , Meios de Contraste , Modelos Animais de Doenças , Imagem Ecoplanar , Gadolínio DTPA , Xenoenxertos , Ratos , Ratos NusRESUMO
The distribution of dynamic contrast-enhanced MRI (DCE-MRI) parametric estimates in a rat U251 glioma model was analyzed. Using Magnevist as contrast agent (CA), 17 nude rats implanted with U251 cerebral glioma were studied by DCE-MRI twice in a 24 h interval. A data-driven analysis selected one of three models to estimate either (1) plasma volume (vp), (2) vp and forward volume transfer constant (K(trans)) or (3) vp, K(trans) and interstitial volume fraction (ve), constituting Models 1, 2 and 3, respectively. CA distribution volume (VD) was estimated in Model 3 regions by Logan plots. Regions of interest (ROIs) were selected by model. In the Model 3 ROI, descriptors of parameter distributions--mean, median, variance and skewness--were calculated and compared between the two time points for repeatability. All distributions of parametric estimates in Model 3 ROIs were positively skewed. Test-retest differences between population summaries for any parameter were not significant (p ≥ 0.10; Wilcoxon signed-rank and paired t tests). These and similar measures of parametric distribution and test-retest variance from other tumor models can be used to inform the choice of biomarkers that best summarize tumor status and treatment effects.
Assuntos
Neoplasias Encefálicas/química , Meios de Contraste/farmacocinética , Gadolínio DTPA/farmacocinética , Glioblastoma/química , Imageamento por Ressonância Magnética/métodos , Modelos Biológicos , Neuroimagem/métodos , Animais , Biomarcadores Tumorais , Neoplasias Encefálicas/irrigação sanguínea , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Glioblastoma/irrigação sanguínea , Glioblastoma/patologia , Xenoenxertos , Humanos , Transplante de Neoplasias , Plasma , Prótons , Ratos , Ratos Nus , Estatísticas não Paramétricas , Distribuição TecidualRESUMO
The apparent forward transfer constant, K transa, for albumin was measured in 9L cerebral tumors in 15 rats. An MRI study using gadolinium-labeled bovine serum albumin was followed by terminal quantitative autoradiography (QAR) using radioiodinated serum albumin. Look-Locker MRI estimates of T(1) followed gadolinium-labeled bovine serum albumin blood and tissue concentration. QAR and MRI maps of K transa were coregistered, a region of interest (ROI) that included the tumor and its surround was selected, and the two estimates of K transa from the ROI on QAR and MRI maps were compared by either mean per animal ROI or on pixel-by-pixel data using a generalized estimating equation. An ROI analysis showed a moderate correlation between the two measures (r = 0.57, P = 0.026); pixel-by-pixel generalized estimating equation analysis concurred (r = 0.54, P < 0.0001). The estimates of QAR with MRI of last time points (e.g., 25 min) showed a moderate correlation (ROI r = 0.55, P < 0.035; generalized estimating equation r = 0.58, P < 0.0001). Differences between the QAR and MRI estimates of K transa did not differ from zero, but the MRI 25-min estimate was significantly lower than the QAR estimate. Thus, noninvasive MRI estimates of vascular permeability can serve as a surrogate for QAR measures.
Assuntos
Albuminas/metabolismo , Autorradiografia/métodos , Neoplasias Encefálicas/metabolismo , Glioblastoma/metabolismo , Imageamento por Ressonância Magnética , Animais , Permeabilidade Capilar/fisiologia , Modelos Teóricos , Neoplasias Experimentais/metabolismo , Ratos , Ratos Endogâmicos F344 , Soroalbumina Radioiodada/metabolismoRESUMO
We employed lentivirus-based doublecortin (DCX), as a glioma suppressor gene therapy in an intracranial glioma tumor xenograft model in nude rats. Single DCX-expressing lentivirus was directly administered into the tumor on day 8 after U87 tumor cell implantation. DCX treatment significantly reduced U87 glioma tumor volume (approximately 60%) on day 14 after DCX lentivirus injection and significantly improved median survival of tumor-bearing nude rats. DCX synthesis induced neuronal markers MAP2, TUJ1, and PSA-NCAM and the glial marker glial fibrillary acidic protein (GFAP) in the implanted U87 glioma tumors. DCX synthesis induced GFAP that colocalized with tubulin in the mitotic stage, inhibited cleavage furrow during cytokinesis, and blocked mitosis in glioma cells. DCX lentivirus infection did not induce apoptosis but significantly inhibited expression of the proliferation marker Ki-67 and the blood vessel marker von-Willebrand factor (vWF). U87 and other glioma cells except for brain tumor stem cells (BTSCs) do not express neuronal markers or both neuronal and glial markers. DCX-synthesizing glioma cells express a phenotype of antiangiogenic BTSC-like cells with terminal differentiation that causes remission of glioma cells by blocking mitosis via a novel DCX/GFAP pathway. Direct local delivery of lentivirus-based DCX gene therapy is a potential differentiation-based therapeutic approach for the treatment of glioma.
Assuntos
Neoplasias Encefálicas/terapia , Terapia Genética/métodos , Glioma/terapia , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/uso terapêutico , Neuropeptídeos/genética , Neuropeptídeos/uso terapêutico , Animais , Astrócitos/patologia , Astrócitos/fisiologia , Encéfalo/patologia , Encéfalo/fisiopatologia , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/fisiopatologia , Linhagem Celular Tumoral , Citocinese/fisiologia , Proteínas do Domínio Duplacortina , Proteína Duplacortina , Vetores Genéticos , Proteína Glial Fibrilar Ácida/metabolismo , Glioma/patologia , Glioma/fisiopatologia , Lentivirus/genética , Transplante de Neoplasias , Neovascularização Patológica/patologia , Neovascularização Patológica/fisiopatologia , Neovascularização Patológica/terapia , Neurônios/patologia , Neurônios/fisiologia , Ratos , Ratos Nus , Resultado do TratamentoRESUMO
Using magnetic resonance imaging (MRI) protocols of T(2)-, T(2)*-, diffusion- and susceptibility-weighted imaging (T2WI, T2*WI, DWI, and SWI, respectively) with a 7T system, we tested the hypothesis that treatment of embolic stroke with erythropoietin (EPO) initiated at 24 hr and administered daily for 7 days after stroke onset has benefit in repairing ischemic cerebral tissue. Adult Wistar rats were subjected to embolic stroke by means of middle cerebral artery occlusion (MCAO) and were randomly assigned to a treatment (n = 11) or a control (n = 11) group. The treated group was given EPO intraperitoneally at a dose of 5,000 IU/kg daily for 7 days starting 24 hr after MCAO. Controls were given an equal volume of saline. MRI was performed at 24 hr and then weekly for 6 weeks. MRI and histological measurements were compared between groups. Serial T2WI demonstrated that expansion of the ipsilateral ventricle was significantly reduced in the EPO-treated rats. The volume ratio of ipsilateral parenchymal tissue relative to the contralateral hemisphere was significantly increased after EPO treatment compared with control animals, indicating that EPO significantly reduces atrophy of the ipsilateral hemisphere, although no significant differences in ischemic lesion volume were observed between the two groups. Angiogenesis and white matter remodeling were significantly increased and occurred earlier in EPO-treated animals than in the controls, as evident from T2*WI and diffusion anisotropy maps, respectively. These data indicate that EPO treatment initiated 24 hr poststroke promotes angiogenesis and axonal remodeling in the ischemic boundary, which may potentially reduce atrophy of the ipsilateral hemisphere.
Assuntos
Eritropoetina/uso terapêutico , Embolia Intracraniana/tratamento farmacológico , Imageamento por Ressonância Magnética/métodos , Fármacos Neuroprotetores/farmacologia , Acidente Vascular Cerebral/tratamento farmacológico , Animais , Atrofia , Modelos Animais de Doenças , Eritropoetina/farmacologia , Embolia Intracraniana/etiologia , Embolia Intracraniana/patologia , Masculino , Degeneração Neural/tratamento farmacológico , Degeneração Neural/etiologia , Degeneração Neural/patologia , Fármacos Neuroprotetores/uso terapêutico , Distribuição Aleatória , Ratos , Ratos Wistar , Proteínas Recombinantes , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/patologiaRESUMO
BACKGROUND AND PURPOSE: The objectives of the present study were to: (1) noninvasively identify white matter reorganization and monitor its progress within 6 weeks after the onset of stroke; and (2) quantitatively investigate the effect of recombinant human erythropoietin treatment on this structural change using in vivo measurement of diffusion anisotropy. METHODS: Male Wistar rats were subjected to middle cerebral artery occlusion and treated with recombinant human erythropoietin intraperitoneally at a dose of 5000 U/kg of body weight (n=11) or the same volume of saline (n=7) daily for 7 days starting 24 hours after middle cerebral artery occlusion. MRI measurements of T2- and diffusion-weighted images and cerebral blood flow were performed and neurological severity score was assessed at 1 day and weekly for 6 weeks after middle cerebral artery occlusion. Luxol fast blue and Bielschowsky staining were used to demonstrate myelin and axons, respectively. RESULTS: White matter reorganization occurred along the ischemic lesion boundary after stroke. The region of white matter reorganization seen on the tissue slice coincided with the elevated area on the fractional anisotropy map, which can be accurately identified. The increase in elevated fractional anisotropy pixels corresponded with progress of white matter reorganization and was associated with improvement of neurological function. Treatment with recombinant human erythropoietin after stroke significantly enhanced white matter reorganization, restored local cerebral blood flow, and expedited functional recovery. CONCLUSIONS: White matter reorganization can be detected by fractional anisotropy. Elevated fractional anisotropy pixels may be a good MRI index to stage white matter remodeling and predict functional outcome.
Assuntos
Encéfalo/patologia , Imagem de Difusão por Ressonância Magnética , Eritropoetina/uso terapêutico , Ataque Isquêmico Transitório/tratamento farmacológico , Ataque Isquêmico Transitório/patologia , Animais , Anisotropia , Axônios/patologia , Histocitoquímica , Humanos , Processamento de Imagem Assistida por Computador , Infarto da Artéria Cerebral Média/tratamento farmacológico , Infarto da Artéria Cerebral Média/patologia , Masculino , Bainha de Mielina/patologia , Ratos , Ratos Wistar , Proteínas Recombinantes , Recuperação de Função FisiológicaRESUMO
BACKGROUND AND PURPOSE: This study uses T(2)* weighted imaging (T2*WI) to measure the temporal evolution of cerebral angiogenesis in rats subjected to embolic stroke up to 6 weeks after stroke onset with or without sildenafil treatment. Method- Male Wistar rats were subjected to embolic stroke and treated with saline (n=10) or with sildenafil (n=11), with treatment initiated at 24 hours and continued daily for 7 days after onset of ischemia. T2*WI measurements were performed at 24 hours after embolization and weekly up to 6 weeks using a 7-Tesla system. Histological measurements were obtained at 6 weeks after MRI scans. RESULTS: Using T2*WI, cerebral angiogenesis was detected starting from 4 weeks and from 2 weeks after onset of embolic stroke in saline and sildenafil treated rats, respectively. Significant differences in the temporal and spatial features of angiogenesis after embolic stroke up to 6 weeks after onset of stroke were found between saline and sildenafil treated rats and were identified with T2*WI. MRI permeability parameter, K(i), complementarily detected angiogenesis after ischemia in embolic stroke rats. Sildenafil treatment of stroke rats significantly enhanced the angiogenesis, as confirmed histologically. CONCLUSIONS: T2*WI can quantitatively measure the temporal evolution of angiogenesis in rats subjected to embolic stroke. Compared to control rats, sildenafil treatment significantly increased angiogenesis in treated animals up to 6 weeks after stroke.
Assuntos
Artérias Cerebrais/efeitos dos fármacos , Embolia Intracraniana/tratamento farmacológico , Neovascularização Fisiológica/efeitos dos fármacos , Piperazinas/farmacologia , Acidente Vascular Cerebral/tratamento farmacológico , Sulfonas/farmacologia , Animais , Encéfalo/irrigação sanguínea , Encéfalo/efeitos dos fármacos , Mapeamento Encefálico/métodos , Artérias Cerebrais/anatomia & histologia , Imagem de Difusão por Ressonância Magnética/métodos , Modelos Animais de Doenças , Embolia Intracraniana/patologia , Embolia Intracraniana/fisiopatologia , Masculino , Microcirculação/anatomia & histologia , Microcirculação/efeitos dos fármacos , Piperazinas/uso terapêutico , Valor Preditivo dos Testes , Purinas/farmacologia , Purinas/uso terapêutico , Ratos , Ratos Wistar , Recuperação de Função Fisiológica/efeitos dos fármacos , Citrato de Sildenafila , Acidente Vascular Cerebral/patologia , Acidente Vascular Cerebral/fisiopatologia , Sulfonas/uso terapêutico , Fatores de Tempo , Resultado do Tratamento , Vasodilatadores/farmacologia , Vasodilatadores/uso terapêuticoRESUMO
To dynamically investigate the long-term response of an ischemic lesion in rat brain to the administration of sildenafil, male Wistar rats subjected to embolic stroke were treated with sildenafil (n=11) or saline (n=10) at a dose of 10 mg/kg administered subcutaneously 24-h after stroke and daily for an additional 6 days. Magnetic resonance images were acquired and functional performance was measured in all animals at 1 day, 2 days and weekly for 6 weeks post-stroke. All rats were sacrificed 6 weeks after stroke and endothelial barrier antigen immunostaining was employed for morphological analysis and quantification of cerebral vessels. Map-ISODATA was computed from T(1), T(2) and T(1sat) maps. ISODATA derived tissue signatures characterize the degree of ischemic injury. Based on the map-ISODATA calculated at 6 weeks, the ischemic lesion for each animal was divided into two specific regions, the ischemic boundary and ischemic core. The temporal profiles of cerebral blood flow (CBF) and tissue signature were retrospectively tracked in these two regions and were compared with histological evaluation and functional outcome. After 1 week of sildenafil treatment, the ischemic lesion exhibited two significantly different regions, with higher CBF level and correspondingly, lower tissue signature value in the boundary region than in the core region. Sildenafil treatment did not significantly reduce the lesion size, but did enhance angiogenesis. Functional performance was significantly increased after sildenafil treatment compared with the control group. Administration of sildenafil to rats with embolic stroke enhances angiogenesis and selectively increases the CBF level in the ischemic boundary, and improves neurological functional recovery compared to saline-treated rats.
Assuntos
Isquemia Encefálica/tratamento farmacológico , Circulação Cerebrovascular/efeitos dos fármacos , Embolia e Trombose Intracraniana/tratamento farmacológico , Neovascularização Fisiológica/efeitos dos fármacos , Piperazinas/farmacologia , Acidente Vascular Cerebral/tratamento farmacológico , Sulfonas/farmacologia , Animais , Antígenos de Superfície/efeitos dos fármacos , Antígenos de Superfície/metabolismo , Isquemia Encefálica/diagnóstico , Isquemia Encefálica/fisiopatologia , Artérias Cerebrais/efeitos dos fármacos , Artérias Cerebrais/metabolismo , Artérias Cerebrais/fisiopatologia , Circulação Cerebrovascular/fisiologia , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Embolia e Trombose Intracraniana/diagnóstico , Embolia e Trombose Intracraniana/fisiopatologia , Imageamento por Ressonância Magnética , Masculino , Neovascularização Fisiológica/fisiologia , Piperazinas/uso terapêutico , Purinas/farmacologia , Purinas/uso terapêutico , Ratos , Ratos Wistar , Recuperação de Função Fisiológica/efeitos dos fármacos , Recuperação de Função Fisiológica/fisiologia , Citrato de Sildenafila , Acidente Vascular Cerebral/diagnóstico , Acidente Vascular Cerebral/fisiopatologia , Sulfonas/uso terapêutico , Resultado do Tratamento , Vasodilatadores/farmacologia , Vasodilatadores/uso terapêuticoRESUMO
PURPOSE: The objective was to study temporal changes in tumor vascular physiological indices in a period of 24h in a 9L gliosarcoma rat model. METHODS: Fischer-344 rats (N=14) were orthotopically implanted with 9L cells. At 2weeks post-implantation, they were imaged twice in a 24h interval using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Data-driven model-selection-based analysis was used to segment tumor regions with varying vascular permeability characteristics. The region with the maximum number of estimable parameters of vascular kinetics was chosen for comparison across the two time points. It provided estimates of three parameters for an MR contrast agent (MRCA): i) plasma volume (vp), ii) forward volumetric transfer constant (Ktrans) and interstitial volume fraction (ve, ratio of Ktrans to reverse transfer constant, kep). In addition, MRCA extracellular distribution volume (VD) was estimated in the tumor and its borders, along with tumor blood flow (TBF) and peritumoral MRCA flux. Descriptors of parametric distributions were compared between the two times. Tumor extent was examined by hematoxylin and eosin (H&E) staining. Picrosirus red staining of secreted collagen was performed as an additional index for 9L cells. RESULTS: Test-retest differences between population summaries for any parameter were not significant (paired t and Wilcoxon signed rank tests). Bland-Altman plots showed no apparent trends between the differences and averages of the test-retest measures for all indices. The intraclass correlation coefficients showed moderate to almost perfect reproducibility for all of the parameters, except vp. H&E staining showed tumor infiltration in parenchyma, perivascular space and white matter tracts. Collagen staining was observed along the outer edges of main tumor mass. CONCLUSION: The data suggest the relative stability of these MR indices of tumor microenvironment over a 24h duration in this gliosarcoma model.
Assuntos
Neoplasias Encefálicas/irrigação sanguínea , Neoplasias Encefálicas/diagnóstico por imagem , Gliossarcoma/irrigação sanguínea , Gliossarcoma/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Animais , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Meios de Contraste , Modelos Animais de Doenças , Aumento da Imagem/métodos , Masculino , Ratos , Ratos Endogâmicos F344 , Reprodutibilidade dos Testes , TempoRESUMO
In this study we used magnetic resonance imaging (MRI) biomarkers to monitor the acute temporal changes in tumor vascular physiology with the aim of identifying the vascular signatures that predict response to combined anti-angiogenic and radiation treatments. Forty-three athymic rats implanted with orthotopic U-251 glioma cells were studied for approximately 21 days after implantation. Two MRI studies were performed on each animal, pre- and post-treatment, to measure tumor vascular parameters. Two animal groups received treatment comprised of Cilengitide, an anti-angiogenic agent and radiation. The first group received a subcurative regimen of Cilengitide 1 h before irradiation, while the second group received a curative regimen of Cilengitide 8 h before irradiation. Cilengitide was given as a single dose (4 mg/kg; intraperitoneal) after the pretreatment MRI study and before receiving a 20 Gy radiation dose. After irradiation, the post-treatment MRI study was performed at selected time points: 2, 4, 8 and 12 h (n = ≥5 per time point). Significant changes in vascular parameters were observed at early time points after combined treatments in both treatment groups (1 and 8 h). The temporal changes in vascular parameters in the first group (treated 1 h before exposure) resembled a previously reported pattern associated with radiation exposure alone. Conversely, in the second group (treated 8 h before exposure), all vascular parameters showed an initial response at 2-4 h postirradiation, followed by an apparent lack of response at later time points. The signature time point to define the "synergy" of Cilengitide and radiation was 4 h postirradiation. For example, 4 h after combined treatments using a 1 h separation (which followed the subcurative regimen), tumor blood flow was significantly decreased, nearly 50% below baseline (P = 0.007), whereas 4 h after combined treatments using an 8 h separation (which followed the curative regimen), tumor blood flow was only 10% less than baseline. Comparison between the first and second groups further revealed that most other vascular parameters were maximally different 4 h after combined treatments. In conclusion, the data are consistent with the assertion that the delivery of radiation at the vascular normalization time window of Cilengitide improves radiation treatment outcome. The different vascular responses after the different delivery times of combined treatments in light of the known tumor responses under similar conditions would indicate that timing has a crucial influence on treatment outcome and long-term survival. Tracking acute changes in tumor physiology after monotherapy or combined treatments appears to aid in identifying the beneficial timing for administration, and perhaps has predictive value. Therefore, judicial timing of treatments may result in optimal treatment response.
Assuntos
Inibidores da Angiogênese/farmacologia , Glioblastoma/diagnóstico por imagem , Glioblastoma/terapia , Imageamento por Ressonância Magnética , Venenos de Serpentes/farmacologia , Inibidores da Angiogênese/uso terapêutico , Animais , Apoptose/efeitos dos fármacos , Apoptose/efeitos da radiação , Linhagem Celular Tumoral , Terapia Combinada , Glioblastoma/irrigação sanguínea , Glioblastoma/patologia , Humanos , Ratos , Venenos de Serpentes/uso terapêutico , Fatores de TempoRESUMO
Vasculature in and around the cerebral tumor exhibits a wide range of permeabilities, from normal capillaries with essentially no blood-brain barrier (BBB) leakage to a tumor vasculature that freely passes even such large molecules as albumin. In measuring BBB permeability by magnetic resonance imaging (MRI), various contrast agents, sampling intervals, and contrast distribution models can be selected, each with its effect on the measurement's outcome. Using Gadomer, a large paramagnetic contrast agent, and MRI measures of T(1) over a 25-min period, BBB permeability was estimated in 15 Fischer rats with day-16 9L cerebral gliomas. Three vascular models were developed: (1) impermeable (normal BBB); (2) moderate influx (leakage without efflux); and (3) fast leakage with bidirectional exchange. For data analysis, these form nested models. Model 1 estimates only vascular plasma volume, v(D), Model 2 (the Patlak graphical approach) v(D) and the influx transfer constant K(i). Model 3 estimates v(D), K(i), and the reverse transfer constant, k(b), through which the extravascular distribution space, v(e), is calculated. For this contrast agent and experimental duration, Model 3 proved the best model, yielding the following central tumor means (+/-s.d.; n = 15): v(D) = 0.07 +/- 0.03 for K(i) = 0.0105 +/- 0.005 min(-1) and v(e) = 0.10 +/- 0.04. Model 2 K(i) estimates were approximately 30% of Model 3, but highly correlated (r = 0.80, P < 0.0003). Sizable inhomogeneity in v(D), K(i), and k(b) appeared within each tumor. We conclude that employing nested models enables accurate assessment of transfer constants among areas where BBB permeability, contrast agent distribution volumes, and signal-to-noise vary.
Assuntos
Neoplasias Encefálicas/diagnóstico , Permeabilidade Capilar , Modelos Animais de Doenças , Gadolínio , Glioma/diagnóstico , Imageamento por Ressonância Magnética , Animais , Neoplasias Encefálicas/irrigação sanguínea , Glioma/irrigação sanguínea , Masculino , Ratos , Ratos Endogâmicos F344 , Sensibilidade e EspecificidadeRESUMO
A macromolecular magnetic resonance contrast agent (MMCA) was prepared by linking bovine serum albumin (BSA) to gadolinium (Gd) via a chelating agent, diethylenetriaminepentaacetic acid (DTPA). Colorimetric testing with 2,7-bis(o-arsenophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (arsenazo III) was performed to check for the appearance of free gadolinium during preparation and to quantify the Gd content in the final product. The complex was purified by dialysis, concentrated by lyophilyzation and characterized by magnetic resonance (MR) proton relaxation times. The resultant product had a molecular weight of about 90 kDa, Gd:BSA ratio of 14:1, and T1 and T2 relaxation times of 128.3 and 48.9 ms, respectively, at a field strength of 7Tesla (T) and at 20% concentration. Contrast enhancement of Gadomer-17 (a dendritic MMCA) and Gd-linked to BSA (Gd-BSA) was sequentially evaluated in a rat brain gliosarcoma model (n = 5) by MR imaging (MRI). Following intravenous injection, the blood concentration of Gadomer-17 fell rapidly, whereas that of Gd-BSA was almost constant for the duration of imaging. The areas of enhancement of both MMCAs were comparable. The spatial distribution of Gd-BSA showed good agreement with Evans blue-tagged albumin. Treatment with dexamethasone decreased Gd-BSA enhancement in the tumor. These results suggest that the arsenazo III method is applicable in preparing Gd-BSA to image brain tumors and their response to treatment. This simple method may also be useful for preparing other gadolinium-linked MMCAs.
Assuntos
Arsenazo III/química , Meios de Contraste/síntese química , Gadolínio/análise , Imageamento por Ressonância Magnética , Soroalbumina Bovina/química , Animais , Neoplasias Encefálicas/diagnóstico por imagem , Meios de Contraste/química , Eletroforese em Gel de Poliacrilamida , Imunofluorescência , Gadolínio/química , Gliossarcoma/diagnóstico por imagem , Masculino , Cintilografia , Ratos , Ratos Endogâmicos F344RESUMO
To test the hypothesis that combination treatment of embolic stroke with rtPA and statins improves the efficacy of thrombolytic therapy in rats. Rats subjected to embolic MCA occlusion (MCAo) were randomized into control (n = 10) and treatment (n = 9) groups. Four hours after MCAo, a combination of rtPA and atorvastatin (treatment) or saline (control) was administered. MRI measurements were performed on all animals at 2 h, 24 h and 48 h after MCAo. The patency of cerebral microvessels was examined using fluorescent microscopy. MRI images showed complete blockage of the right MCA and a reduction of CBF in the territory supplied by the MCA 2 h after MCAo for all animals. By 48 h after stroke, MRI showed that the decreased lesion size, elevated CBF and increased incidence of recanalization were found in treated rats compared with the control rats. The combination treatment significantly increased microvascular patency (16.3 +/- 5.5% vs. 12.4 +/- 3.5%, of field-of-view) and reduced the infarct volume (23.1 +/- 9.6% vs. 38.8 +/- 13.3%, of hemisphere). These data demonstrate that the co-administration of rtPA and atorvastatin 4 h after ischemia is efficacious and is reflected by the MRI indices of recanalization of the MCA, reduction of secondary microvascular perfusion deficits and reduction of the ischemic lesion.
Assuntos
Anticolesterolemiantes/uso terapêutico , Ácidos Heptanoicos/uso terapêutico , Embolia Intracraniana/tratamento farmacológico , Embolia Intracraniana/patologia , Ativadores de Plasminogênio/uso terapêutico , Pirróis/uso terapêutico , Acidente Vascular Cerebral/tratamento farmacológico , Acidente Vascular Cerebral/patologia , Animais , Atorvastatina , Isquemia Encefálica/patologia , Circulação Cerebrovascular , Interpretação Estatística de Dados , Embolia Intracraniana/complicações , Angiografia por Ressonância Magnética , Imageamento por Ressonância Magnética , Masculino , Microcirculação/efeitos dos fármacos , Microscopia de Fluorescência , Ratos , Ratos Wistar , Proteínas Recombinantes/uso terapêutico , Acidente Vascular Cerebral/etiologiaRESUMO
The purpose of this study was to characterize changes in tumor vascular parameters hours after a single radiation exposure in an orthotopic brain tumor model. U-251 human brain tumors were established intracerebrally in rat brains, and tumor blood flow, forward volume transfer constant (K(trans)) and interstitial volume fraction (v(e)) were measured using magnetic resonance imaging (MRI). Tumors were exposure to a single stereotactic radiation treatment of 20 Gy. Vascular parameters were assessed one additional time between 2 and 24 h after irradiation. After the second MRI session, brain tissue histology was examined for gross changes and apoptosis. In separate studies, cerebral blood flow was measured in nonimplanted controls before radiation exposure and 2 and 24 h after 20 Gy irradiation, and in implanted rats before radiation exposure and at 2 and 24 h after 6 Gy irradiation. Significant changes were observed in tumor-bearing rat brains in the hours after 20 Gy irradiation. Two hours after 20 Gy irradiation, tumor blood flow decreased nearly 80% and ve decreased by 30%. At 4 h, the K(trans) increased by 30% over preirradiation values. Extensive vacuolization and an increase in apoptosis were evident histologically in rats imaged 2 h after irradiation. Between 8 and 12 h after irradiation, all vascular parameters including blood flow returned to near preirradiation values. One day after irradiation, tumor blood flow was elevated 40% over preirradiation values, and other vascular parameters, including K(trans) and ve, were 20-40% below preirradiation values. In contrast, changes in vascular parameters observed in the normal brain 2 or 24 h after 20 Gy irradiation were not significantly different from preirradiation values. Also, tumor blood flow appeared to be unchanged at 2 h after 6 Gy irradiation, with a small increase observed at 24 h, unlike the tumor blood flow changes after 20 Gy irradiation. Large and significant changes in vascular parameters were observed hours after 20 Gy irradiation using noninvasive MRI techniques. It is hypothesized that cellular swelling hours after a high dose of radiation, coinciding with vacuolization, led to a decrease in tumor blood flow and v(e). Four hours after radiation exposure, K(trans) increased in concert with an increase in tumor blood flow. Vascular permeability normalized, 24 h after 20 Gy irradiation, as characterized by a decrease in K(trans). Vascular parameters did not change significantly in the normal brain after 20 Gy irradiation or in the tumor-bearing brain after 6 Gy irradiation.
Assuntos
Circulação Sanguínea/efeitos da radiação , Glioma/fisiopatologia , Imageamento por Ressonância Magnética , Animais , Apoptose/efeitos da radiação , Linhagem Celular Tumoral , Transformação Celular Neoplásica , Relação Dose-Resposta à Radiação , Glioma/patologia , Humanos , Ratos , Fatores de TempoRESUMO
Increased efficacy of radiotherapy (RT) 4-8 h after Cilengitide treatment has been reported. We hypothesized that the effects of Cilengitide on tumor transvascular transfer parameters might underlie, and thus predict, this potentiation. Athymic rats with orthotopic U251 glioma were studied at ~21 days after implantation using dynamic contrast-enhanced (DCE)-MRI. Vascular parameters, viz: plasma volume fraction (v(p)), forward volume transfer constant (K(trans)) and interstitial volume fraction (v(e)) of a contrast agent, were determined in tumor vasculature once before, and again in cohorts 2, 4, 8, 12 and 24 h after Cilengitide administration (4 mg/kg; N = 31; 6-7 per cohort). Perfusion-fixed brain sections were stained for von Willebrand factor to visualize vascular segments. A comparison of pre- and post-treatment parameters showed that the differences between MR indices before and after Cilengitide treatment pivoted around the 8 h time point, with 2 and 4 h groups showing increases, 12 and 24 h groups showing decreases, and values at the 8 h time point close to the baseline. The vascular parameter differences between group of 2 and 4 h and group of 12 and 24 h were significant for K(trans) (p = 0.0001 and v(e) (p = 0,0271). Vascular staining showed little variation with time after Cilengitide. The vascular normalization occurring 8 h after Cilengitide treatment coincided with similar previous reports of increased treatment efficacy when RT followed Cilengitide by 8 h. Pharmacological normalization of vasculature has the potential to increase sensitivity to RT. Evaluating acute temporal responses of tumor vasculature to putative anti-angiogenic drugs may help in optimizing their combination with other treatment modalities.
Assuntos
Vasos Sanguíneos/efeitos dos fármacos , Vasos Sanguíneos/fisiopatologia , Glioma/irrigação sanguínea , Glioma/tratamento farmacológico , Venenos de Serpentes/farmacologia , Análise de Variância , Animais , Permeabilidade Capilar/efeitos dos fármacos , Quimioterapia Adjuvante , Glioma/radioterapia , Imuno-Histoquímica , Imageamento por Ressonância Magnética , Ratos , Ratos Nus , Fatores de Tempo , Fator de von WillebrandRESUMO
We tested the hypotheses that administration routes affect the migration and distribution of grafted neural progenitor cells (NPCs) in the ischemic brain and that the ischemic lesion plays a role in mediating the grafting process. Male Wistar rats (n=41) were subjected to 2-h middle cerebral artery occlusion (MCAo), followed 1 day later by administration of magnetically labeled NPCs. Rats with MCAo were assigned to one of three treatment groups targeted for cell transplantation intra-arterially (IA), intracisternally (IC), or intravenously (IV). MRI measurements consisting of T2-weighted imaging and three-dimensional (3D) gradient echo imaging were performed 24 h after MCAo, 4 h after cell injection, and once a day for 4 days. Prussian blue staining was used to identify the labeled cells, 3D MRI to detect cell migration and distribution, and T2 map to assess lesion volumes. Intra-arterial (IA) administration showed significantly increased migration, a far more diffuse distribution pattern, and a larger number of transplanted NPCs in the target brain than IC or IV administration. However, high mortality with IA delivery (IA: 41%; IC: 17%; IV: 8%) poses a serious concern for using this route of administration. Animals with smaller lesions at the time of transplantation have fewer grafted cells in the parenchyma.
Assuntos
Isquemia Encefálica/patologia , Isquemia Encefálica/terapia , Movimento Celular/fisiologia , Neurônios/transplante , Transplante de Células-Tronco/métodos , Animais , Isquemia Encefálica/mortalidade , Cisterna Magna , Processamento de Imagem Assistida por Computador , Injeções , Injeções Intra-Arteriais , Injeções Intravenosas , Imageamento por Ressonância Magnética , Masculino , Ratos , Ratos Wistar , Transplante de Células-Tronco/mortalidade , Fixação de TecidosRESUMO
PURPOSE: To demonstrate in the rat 9L cerebral tumor model that repeated MRI measurements can quantitate acute changes in the blood-brain distribution of Gadomer after dexamethasone administration. MATERIALS AND METHODS: A total of 16 Fischer 344 rats were studied at 7T, 15 days after cerebral implantation of a 9L tumor. MRI procedures employed a T-One by Multiple Read Out Pulses (TOMROP) sequence to estimate R(1) (R(1) = 1/T(1)) at 145-second intervals before and after administration of Gadomer (Bayer), a macromolecular contrast agent (CA). Two baseline studies preceded Gadomer administration and 10 subsequent R(1) maps tracked CA concentration in blood and brain for 25 minutes. Thereafter, either dexamethasone (N = 10) or normal saline (N = 6) was administered intravenously. A total of 90 minutes later a second series of 12 TOMROP measurements of Gadomer distribution was performed. The influx constant, K(1), plasma distribution volume, v(D), backflux constant, k(b), and interstitial space, v(e), were determined, and the test-retest differences of each of four vascular parameters were calculated. RESULTS: Dexamethasone decreased K(1) approximately 60% (P = 0.02), lowered k(b) and v(D) (P = 0.03 and P < 0.01, respectively), and marginally but insignificantly decreased v(e). CONCLUSION: This noninvasive MRI technique can detect drug effects on blood-brain transfer constants of CAs within two hours of administration.