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Liu Z, Zhu Y, Zhang L, Jiang W, Liu Y, Tang Q, Cai X, Li J, Wang L, Tao C, Yin X, Li X, Hou S, Jiang D, Liu K, Zhou X, Zhang H, Liu M, Fan C, Tian Y. Structural and functional imaging of brains. Sci China Chem 2022; 66:324-366. [PMID: 36536633 PMCID: PMC9753096 DOI: 10.1007/s11426-022-1408-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 09/28/2022] [Indexed: 12/23/2022]
Abstract
Analyzing the complex structures and functions of brain is the key issue to understanding the physiological and pathological processes. Although neuronal morphology and local distribution of neurons/blood vessels in the brain have been known, the subcellular structures of cells remain challenging, especially in the live brain. In addition, the complicated brain functions involve numerous functional molecules, but the concentrations, distributions and interactions of these molecules in the brain are still poorly understood. In this review, frontier techniques available for multiscale structure imaging from organelles to the whole brain are first overviewed, including magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), serial-section electron microscopy (ssEM), light microscopy (LM) and synchrotron-based X-ray microscopy (XRM). Specially, XRM for three-dimensional (3D) imaging of large-scale brain tissue with high resolution and fast imaging speed is highlighted. Additionally, the development of elegant methods for acquisition of brain functions from electrical/chemical signals in the brain is outlined. In particular, the new electrophysiology technologies for neural recordings at the single-neuron level and in the brain are also summarized. We also focus on the construction of electrochemical probes based on dual-recognition strategy and surface/interface chemistry for determination of chemical species in the brain with high selectivity and long-term stability, as well as electrochemophysiological microarray for simultaneously recording of electrochemical and electrophysiological signals in the brain. Moreover, the recent development of brain MRI probes with high contrast-to-noise ratio (CNR) and sensitivity based on hyperpolarized techniques and multi-nuclear chemistry is introduced. Furthermore, multiple optical probes and instruments, especially the optophysiological Raman probes and fiber Raman photometry, for imaging and biosensing in live brain are emphasized. Finally, a brief perspective on existing challenges and further research development is provided.
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Affiliation(s)
- Zhichao Liu
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241 China
| | - Ying Zhu
- Interdisciplinary Research Center, Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 201210 China
| | - Liming Zhang
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241 China
| | - Weiping Jiang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Chinese Academy of Sciences, Wuhan National Laboratory for Optoelectronics, Wuhan, 430071 China
| | - Yawei Liu
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022 China
| | - Qiaowei Tang
- Interdisciplinary Research Center, Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 201210 China
| | - Xiaoqing Cai
- Interdisciplinary Research Center, Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 201210 China
| | - Jiang Li
- Interdisciplinary Research Center, Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 201210 China
| | - Lihua Wang
- Interdisciplinary Research Center, Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 201210 China
| | - Changlu Tao
- Interdisciplinary Center for Brain Information, Brain Cognition and Brain Disease Institute, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Faculty of Life and Health Sciences, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | | | - Xiaowei Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240 China
| | - Shangguo Hou
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, 518055 China
| | - Dawei Jiang
- Department of Nuclear Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022 China
| | - Kai Liu
- Department of Chemistry, Tsinghua University, Beijing, 100084 China
| | - Xin Zhou
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Chinese Academy of Sciences, Wuhan National Laboratory for Optoelectronics, Wuhan, 430071 China
| | - Hongjie Zhang
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022 China
- Department of Chemistry, Tsinghua University, Beijing, 100084 China
| | - Maili Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Chinese Academy of Sciences, Wuhan National Laboratory for Optoelectronics, Wuhan, 430071 China
| | - Chunhai Fan
- School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Institute of Translational Medicine, Shanghai Jiao Tong University, Shanghai, 200240 China
| | - Yang Tian
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241 China
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Li Y, Gao S, Jiang H, Ayat N, Laney V, Nicolescu C, Sun W, Tweedle MF, Lu ZR. Evaluation of Physicochemical Properties, Pharmacokinetics, Biodistribution, Toxicity, and Contrast-Enhanced Cancer MRI of a Cancer-Targeting Contrast Agent, MT218. Invest Radiol 2022; 57:639-654. [PMID: 35703463 PMCID: PMC9444296 DOI: 10.1097/rli.0000000000000881] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 03/12/2022] [Indexed: 01/03/2023]
Abstract
OBJECTIVES Preclinical assessments were performed according to the US Food and Drug Administration guidelines to determine the physicochemical properties, pharmacokinetics, clearance, safety, and tumor-specific magnetic resonance (MR) imaging of MT218, a peptidic gadolinium-based MR imaging agent targeting to extradomain B fibronectin for MR molecular imaging of aggressive tumors. MATERIALS AND METHODS Relaxivity, chelation stability, binding affinity, safety-related target profiling, and effects on CYP450 enzymes and transporters were evaluated in vitro. Magnetic resonance imaging was performed with rats bearing prostate cancer xenografts, immunocompetent mice bearing murine pancreatic cancer allografts, and mice bearing lung cancer xenografts at different doses of MT218. Pharmacological effects on cardiovascular, respiratory, and central nervous systems were determined in rats and conscious beagle dogs. Pharmacokinetics were tested in rats and dogs. Biodistribution and excretion were studied in rats. Single and repeated dosing toxicity was evaluated in rats and dogs. In vitro and in vivo genotoxicity, in vitro hemolysis, and anaphylactic reactivity were also performed. RESULTS At 1.4 T, the r1 and r2 relaxivities of MT218 were 5.43 and 7.40 mM -1 s -1 in pure water, 6.58 and 8.87 mM -1 s -1 in phosphate-buffered saline, and 6.54 and 8.70 mM -1 s -1 in aqueous solution of human serum albumin, respectively. The binding affinity of MT218 to extradomain B fragment is 3.45 μM. MT218 exhibited no dissociation of the Gd(III) chelates under physiological conditions. The peptide degradation half-life ( t1/2 ) of MT218 was 1.63, 5.85, and 2.63 hours in rat, dog, and human plasma, respectively. It had little effect on CYP450 enzymes and transporters. MT218 produced up to 7-fold increase of contrast-to-noise ratios in the extradomain B fibronectin-rich tumors with a dose of 0.04 mmol/kg for at least 30 minutes. MT218 had little pharmacological effect on central nervous, cardiovascular, or respiratory systems. MT218 had a mean plasma elimination half-life ( t1/2 ) of 0.31 and 0.89 hours in rats and dogs at 0.1 mmol/kg, respectively. No detectable Gd deposition was observed in the brain at 6 hours postinjection of MT218 at 0.1 mmol/kg in rats. MT218 was not mutagenic and had no mortality or morbidity in the rats or dogs up to 1.39 and 0.70 mmol/kg/d, respectively. The no observed adverse effect level of MT218 in Sprague-Dawley rats was 1.39 mmol/kg for single dosing and 0.46 mmol/kg/d for repeated dosing. The no observed adverse effect level in dogs was 0.07 mmol/kg/d. MT218 exhibited no genotoxicity, hemolysis, and anaphylactic reactivity. CONCLUSION The preclinical assessments showed that the targeted contrast agent MT218 has high r1 and r2 relaxivities, satisfactory physicochemical properties, pharmacokinetic, and safety profiles and produces effective tumor enhancement in multiple cancer types in rats and mice at reduced doses.
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Affiliation(s)
- Yajuan Li
- From the Molecular Theranostics, LLC, Cleveland
| | - Songqi Gao
- From the Molecular Theranostics, LLC, Cleveland
| | | | - Nadia Ayat
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland
| | - Victoria Laney
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland
| | - Calin Nicolescu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland
| | - Wenyu Sun
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland
| | - Michael F. Tweedle
- Wright Center of Innovation, Department of Radiology, the Ohio State University, Columbus
| | - Zheng-Rong Lu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH
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Abstract
Molecular magnetic resonance (MR) imaging utilizes molecular probes to provide added biochemical or cellular information to what can already be achieved with anatomical and functional MR imaging. This review provides an overview of molecular MR and focuses specifically on molecular MR contrast agents that provide contrast by shortening the T1 time. We describe the requirements for a successful molecular MR contrast agent and the challenges for clinical translation. The review highlights work from the last 5 years and places an emphasis on new contrast agents that have been validated in multiple preclinical models. Applications of molecular MR include imaging of inflammation, fibrosis, fibrogenesis, thromboembolic disease, and cancers. Molecular MR is positioned to move beyond detection of disease to the quantitative staging of disease and measurement of treatment response.
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Affiliation(s)
| | | | - Peter Caravan
- The Institute for Innovation in Imaging, A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA
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Molecular Magnetic Resonance Imaging of Fibrin Deposition in the Liver as an Indicator of Tissue Injury and Inflammation. Invest Radiol 2020; 55:209-216. [PMID: 31895219 DOI: 10.1097/rli.0000000000000631] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RATIONALE AND OBJECTIVES Liver inflammation is associated with nonalcoholic steatohepatitis and other pathologies, but noninvasive methods to assess liver inflammation are limited. Inflammation causes endothelial disruption and leakage of plasma proteins into the interstitial space and can result in extravascular coagulation with fibrin deposition. Here we assess the feasibility of using the established fibrin-specific magnetic resonance probe EP-2104R for the noninvasive imaging of fibrin as a marker of liver inflammation. METHODS Weekly 100 mg/kg diethylnitrosamine (DEN) dosing was used to generate liver fibrosis in male rats; control animals received vehicle. Magnetic resonance imaging at 1.5 T with EP-2104R, a matched non-fibrin-binding control linear peptide, or the collagen-specific probe EP-3533 was performed at 1 day or 7 days after the last DEN administration. Imaging data were compared with quantitative histological measures of fibrosis and inflammation. RESULTS After 4 or 5 DEN administrations, the liver becomes moderately fibrotic, and fibrosis is the same if the animal is killed 1 day (Ishak score, 3.62 ± 0.31) or 7 days (Ishak score, 3.82 ± 0.25) after the last DEN dose, but inflammation is significantly higher at 1 day compared with 7 days after the last DEN dose (histological activity index from 0-4, 3.54 ± 0.14 vs 1.61 ± 0.16, respectively; P < 0.0001). Peak EP-2104R signal enhancement was significantly higher in animals imaged at 1 day post-DEN compared with 7 days post-DEN or control rats (29.0% ± 3.2% vs 22.4% ± 2.0% vs 17.0% ± 0.2%, respectively; P = 0.017). Signal enhancement with EP-2104R was significantly higher than control linear peptide at 1 day post-DEN but not at 7 days post-DEN indicating specific fibrin binding during the inflammatory phase. Collagen molecular magnetic resonance with EP-3533 showed equivalent T1 change when imaging rats 1 day or 7 days post-DEN, consistent with equivalent fibrosis. CONCLUSIONS EP-2104R can specifically detect fibrin associated with inflammation in a rat model of liver inflammation and fibrosis.
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Advocating the Development of Next-Generation High-Relaxivity Gadolinium Chelates for Clinical Magnetic Resonance. Invest Radiol 2019; 53:381-389. [PMID: 29462023 DOI: 10.1097/rli.0000000000000454] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The question of improved relaxivity, and potential efficacy therein, for a next-generation of magnetic resonance gadolinium chelates with extracellular distribution and renal excretion, which could also be viewed from the perspective of dose, is addressed on the basis of historical development, animal experimentation, and human trials. There was no systematic evaluation that preceded the choice of 0.1 mmol/kg as the standard dose for human imaging with the gadolinium chelates. In part, this dose was chosen owing to bloodwork abnormalities seen in phase I and phase II studies. Animal investigations and early clinical trials demonstrated improved lesion detectability at higher doses in the brain, liver, and heart. By designing an agent with substantially improved relaxivity, higher enhancement equivalent to that provided with the conventional gadolinium agents at high dose could be achieved, translating to improved diagnosis and, thus, clinical care. Implicit in the development of such high-relaxivity agents would be stability equivalent to or exceeding that of the currently approved macrocyclic agents, given current concern regarding dechelation and gadolinium deposition in the brain, skin, and bone with the linear agents that were initially approved. Development of such next-generation agents with a substantial improvement in relaxivity, in comparison with the current group of approved agents, with a 2-fold increase likely achievable, could lead to improved lesion enhancement, characterization, diagnosis, and, thus, clinical efficacy.
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Starmans LWE, van Mourik T, Rossin R, Verel I, Nicolay K, Grüll H. Noninvasive Visualization of Tumoral Fibrin Deposition Using a Peptidic Fibrin-Binding Single Photon Emission Computed Tomography Tracer. Mol Pharm 2015; 12:1921-8. [DOI: 10.1021/mp500673u] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Lucas W. E. Starmans
- Department
of Biomedical Engineering, Eindhoven University of Technology, High Tech
Campus 11, 5656 AE, Eindhoven, The Netherlands
| | - Tiemen van Mourik
- Department
of Biomedical Engineering, Eindhoven University of Technology, High Tech
Campus 11, 5656 AE, Eindhoven, The Netherlands
| | - Raffaella Rossin
- Oncology Solutions,
Philips Research, High Tech Campus
11, 5656 AE, Eindhoven, The Netherlands
| | - Iris Verel
- Oncology Solutions,
Philips Research, High Tech Campus
11, 5656 AE, Eindhoven, The Netherlands
| | - Klaas Nicolay
- Department
of Biomedical Engineering, Eindhoven University of Technology, High Tech
Campus 11, 5656 AE, Eindhoven, The Netherlands
| | - Holger Grüll
- Department
of Biomedical Engineering, Eindhoven University of Technology, High Tech
Campus 11, 5656 AE, Eindhoven, The Netherlands
- Oncology Solutions,
Philips Research, High Tech Campus
11, 5656 AE, Eindhoven, The Netherlands
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Chaabane L, Tei L, Miragoli L, Lattuada L, von Wronski M, Uggeri F, Lorusso V, Aime S. In Vivo MR Imaging of Fibrin in a Neuroblastoma Tumor Model by Means of a Targeting Gd-Containing Peptide. Mol Imaging Biol 2015; 17:819-28. [DOI: 10.1007/s11307-015-0846-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Morelli JN, Gerdes CM, Schmitt P, Ai T, Saettele MR, Runge VM, Attenberger UI. Technical considerations in MR angiography: An image-based guide. J Magn Reson Imaging 2013; 37:1326-41. [DOI: 10.1002/jmri.24174] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 03/20/2013] [Indexed: 11/09/2022] Open
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Molecular MRI of liver fibrosis by a peptide-targeted contrast agent in an experimental mouse model. Invest Radiol 2013. [PMID: 23192162 DOI: 10.1097/rli.0b013e3182749c0b] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVES Cyclic decapeptide CGLIIQKNEC (CLT1) has been demonstrated to target fibronectin-fibrin complexes in the extracellular matrix of different tumors and tissue lesions. Although liver fibrosis is characterized by an increased amount of extracellular matrix consisting of fibril-forming collagens and matrix glycoconjugates such as fibronectin, we aimed to investigate the feasibility of detecting and characterizing liver fibrosis using CLT1 peptide-targeted nanoglobular contrast agent (Gd-P) with dynamic contrast-enhanced magnetic resonance imaging in an experimental mouse model of liver fibrosis at 7 T. MATERIALS AND METHODS Gd-P, control peptide KAREC conjugated nanoglobular contrast agent (Gd-CP), and control nontargeting nanoglobular contrast agent (Gd-C) were synthesized. Male adult C57BL/6N mice (22-25 g; N = 54) were prepared and were divided into fibrosis (n = 36) and normal (n = 18) groups. Liver fibrosis was induced in the fibrosis group through subcutaneous injection of 1:3 mixture of carbon tetrachloride (CCl(4)) in olive oil at a dose of 4 μL/g of body weight twice a week for 8 weeks. Dynamic contrast-enhanced MRI was performed in all animals. Dynamic contrast-enhanced magnetic resonance imaging was analyzed to yield postinjection ΔR(1)(t) maps for quantitative measurements. Histological analysis was also performed. RESULTS Differential enhancements were observed and characterized between the normal and fibrotic livers using Gd-P at 0.03 mmol/kg, when compared with nontargeted controls (Gd-CP and Gd-C). For Gd-P injection, both the peak and steady-state ΔR(1) of the normal livers were significantly lower than those after 4 and 8 weeks of CCl(4) dosing. Liver fibrogenesis with increased amount of fibronectin in the extracellular space in insulted livers were confirmed by histological observations. CONCLUSIONS These results indicated that dynamic contrast-enhanced magnetic resonance imaging with CLT1 peptide-targeted nanoglobular contrast agent can detect and stage liver fibrosis by probing the accumulation of fibronectin in fibrotic livers.
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A historical overview of magnetic resonance imaging, focusing on technological innovations. Invest Radiol 2013; 47:725-41. [PMID: 23070095 DOI: 10.1097/rli.0b013e318272d29f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Magnetic resonance imaging (MRI) has now been used clinically for more than 30 years. Today, MRI serves as the primary diagnostic modality for many clinical problems. In this article, historical developments in the field of MRI will be discussed with a focus on technological innovations. Topics include the initial discoveries in nuclear magnetic resonance that allowed for the advent of MRI as well as the development of whole-body, high field strength, and open MRI systems. Dedicated imaging coils, basic pulse sequences, contrast-enhanced, and functional imaging techniques will also be discussed in a historical context. This article describes important technological innovations in the field of MRI, together with their clinical applicability today, providing critical insights into future developments.
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Abstract
RATIONALE AND OBJECTIVES Fibrin deposition has been indicated within the stroma of a majority of solid tumors. Here we assess the feasibility of using the established fibrin-specific probe EP-2104R for noninvasive imaging of fibrin in the context of breast cancer. METHODS EP-2104R, untargeted gadopentetate dimeglumine (Gd-DTPA), and a newly synthesized nonfibrin binding control linear peptide (CLP) were compared using steady-state and dynamic contrast-enhanced magnetic resonance imaging in a breast cancer xenograft mouse model at 9.4 T. RESULTS EP-2104R transiently enhanced both tumor core and tumor periphery, but only the enhancement in the tumor periphery persisted even 90 minutes after EP-2104R administration. However, untargeted Gd-DTPA and CLP are not retained in the tumor periphery. The half-life of EP-2104R in the tumor periphery (103 ± 18 minutes) is significantly longer (P < 0.05) than that of either Gd-DTPA (29.6 ± 2.4 minutes) or CLP (42.4 ± 1.5 minutes), but the rate of clearance is similar for all the 3 probes from the tumor core. The presence of high concentrations of fibrin in the tumor periphery was corroborated using immunohistochemistry with a fibrin-specific antibody. CONCLUSIONS The persistent enhancement observed in the tumor periphery with EP-2104R is likely a result of its fibrin-specific binding rather than its size and demonstrates the feasibility of EP-2104R for molecular imaging of fibrin in tumor stroma.
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In vivo characterization of changing blood-tumor barrier permeability in a mouse model of breast cancer metastasis: a complementary magnetic resonance imaging approach. Invest Radiol 2012; 46:718-25. [PMID: 21788908 DOI: 10.1097/rli.0b013e318226c427] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
OBJECTIVES The current lack of efficacy for any chemo- or molecular therapeutic in the treatment of brain metastases is thought to be due, in part, to the heterogeneous permeability of the blood-brain-barrier (BBB). Little is known about how heterogeneous permeability develops, or how it varies among individual metastases. Understanding the BBB's role in metastasis will be crucial to the development of new, more effective therapies. In this article, we developed the first magnetic resonance imaging-based strategy to detect and measure the volumes of BBB permeable and nonpermeable metastases and studied the development of altered BBB permeability in metastases in vivo, over time in a mouse model of breast cancer metastasis to the brain. MATERIALS AND METHODS Animals bearing human experimental brain metastases of breast cancer (231-BR cells) were imaged, using 3-dimensional balanced steady-state free precession to visualize total metastases, and contrast-enhanced T1-weighted spin echo with gadopentetic acid (Gd-DTPA) to visualize which of these displayed contrast enhancement, as Gd-DTPA leakage is indicative of altered BBB permeability. RESULTS Metastases detected 20 days after injection showed no Gd-DTPA enhancement. At day 25, 6.1% ± 6.3% (mean ± standard deviation) of metastases enhanced, and by day 30, 28.1% ± 14.2% enhanced (P < 0.05). Enhancing metastases (mid: 0.14 ± 0.18 mm, late: 0.24 ± 0.32 mm) had larger volumes than nonenhancing (mid: 0.04 ± 0.04 mm, late: 0.09 ± 0.09 mm, P < 0.05); however, there was no significant difference between the growth rates of the 2. CONCLUSIONS A significant number of brain metastases were uniformly nonpermeable, which highlights the need for developing treatment strategies that can overcome the permeability of the BBB. The model developed herein can provide the basis for in vivo evaluation of both BBB permeable and nonpermeable metastases response to therapy.
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