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Little PV, Arnberg F, Jussing E, Lu L, Ingemann Jensen A, Mitsios N, Mulder J, Tran TA, Holmin S. The cellular basis of increased PET hypoxia tracer uptake in focal cerebral ischemia with comparison between [ 18F]FMISO and [ 64Cu]CuATSM. J Cereb Blood Flow Metab 2021; 41:617-629. [PMID: 32423333 PMCID: PMC7922752 DOI: 10.1177/0271678x20923857] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PET hypoxia imaging can assess tissue viability in acute ischemic stroke (AIS). [18F]FMISO is an established tracer but requires substantial accumulation time, limiting its use in hyperacute AIS. [64Cu]CuATSM requires less accumulation time and has shown promise as a hypoxia tracer. We compared these tracers in a M2-occlusion model (M2CAO) with preserved collateral blood flow. Rats underwent M2CAO and [18F]FMISO (n = 12) or [64Cu]CuATSM (n = 6) examinations. [64Cu]CuATSM animals were also examined with MRI. Pimonidazole was used as a surrogate for [18F]FMISO in an immunofluorescence analysis employed to profile levels of hypoxia in neurons (NeuN) and astrocytes (GFAP). There was increased [18F]FMISO uptake in the M2CAO cortex. No increase in [64Cu]CuATSM activity was found. The pimonidazole intensity of neurons and astrocytes was increased in hypoxic regions. The pimonidazole intensity ratio was higher in neurons than in astrocytes. In the majority of animals, immunofluorescence revealed a loss of astrocytes within the core of regions with increased pimonidazole uptake. We conclude that [18F]FMISO is superior to [64Cu]CuATSM in detecting hypoxia in AIS, consistent with an earlier study. [18F]FMISO may provide efficient diagnostic imaging beyond the hyperacute phase. Results do not provide encouragement for the use of [64Cu]CuATSM in experimental AIS.
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Affiliation(s)
- Philip V Little
- The Department of Clinical Neuroscience, Karolinska Institutet, Stockholm Sweden.,The Department of Neuroradiology, BioClinicum, Karolinska University Hospital, Stockholm, Sweden
| | - Fabian Arnberg
- The Department of Clinical Neuroscience, Karolinska Institutet, Stockholm Sweden.,The Department of Neuroradiology, BioClinicum, Karolinska University Hospital, Stockholm, Sweden
| | - Emma Jussing
- The Department of Clinical Neuroscience, Karolinska Institutet, Stockholm Sweden.,The Department of Radiopharmacy, Karolinska University Hospital, Stockholm, Sweden.,The Department of Oncology and Pathology, Karolinska Institutet, Stockholm Sweden
| | - Li Lu
- The Department of Clinical Neuroscience, Karolinska Institutet, Stockholm Sweden.,The Department of Radiopharmacy, Karolinska University Hospital, Stockholm, Sweden.,The Department of Oncology and Pathology, Karolinska Institutet, Stockholm Sweden
| | | | - Nicholas Mitsios
- The Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Jan Mulder
- The Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Thuy A Tran
- The Department of Clinical Neuroscience, Karolinska Institutet, Stockholm Sweden.,The Department of Radiopharmacy, Karolinska University Hospital, Stockholm, Sweden.,The Department of Oncology and Pathology, Karolinska Institutet, Stockholm Sweden
| | - Staffan Holmin
- The Department of Clinical Neuroscience, Karolinska Institutet, Stockholm Sweden.,The Department of Neuroradiology, BioClinicum, Karolinska University Hospital, Stockholm, Sweden
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Assessing the Effects of Cytoprotectants on Selective Neuronal Loss, Sensorimotor Deficit and Microglial Activation after Temporary Middle Cerebral Occlusion. Brain Sci 2019; 9:brainsci9100287. [PMID: 31652564 PMCID: PMC6827002 DOI: 10.3390/brainsci9100287] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/18/2019] [Accepted: 10/20/2019] [Indexed: 01/21/2023] Open
Abstract
Although early reperfusion after stroke salvages the still-viable ischemic tissue, peri-infarct selective neuronal loss (SNL) can cause sensorimotor deficits (SMD). We designed a longitudinal protocol to assess the effects of cytoprotectants on SMD, microglial activation (MA) and SNL, and specifically tested whether the KCa3.1-blocker TRAM-34 would prevent SNL. Spontaneously hypertensive rats underwent 15 min middle-cerebral artery occlusion and were randomized into control or treatment group, which received TRAM-34 intraperitoneally for 4 weeks starting 12 h after reperfusion. SMD was assessed longitudinally using the sticky-label test. MA was quantified at day 14 using in vivo [11C]-PK111195 positron emission tomography (PET), and again across the same regions-of-interest template by immunofluorescence together with SNL at day 28. SMD recovered significantly faster in the treated group (p = 0.004). On PET, MA was present in 5/6 rats in each group, with no significant between-group difference. On immunofluorescence, both SNL and MA were present in 5/6 control rats and 4/6 TRAM-34 rats, with a non-significantly lower degree of MA but a significantly (p = 0.009) lower degree of SNL in the treated group. These findings document the utility of our longitudinal protocol and suggest that TRAM-34 reduces SNL and hastens behavioural recovery without marked MA blocking at the assessed time-points.
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The Roles of Hypoxia Imaging Using 18F-Fluoromisonidazole Positron Emission Tomography in Glioma Treatment. J Clin Med 2019; 8:jcm8081088. [PMID: 31344848 PMCID: PMC6723061 DOI: 10.3390/jcm8081088] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 07/16/2019] [Accepted: 07/22/2019] [Indexed: 12/14/2022] Open
Abstract
Glioma is the most common malignant brain tumor. Hypoxia is closely related to the malignancy of gliomas, and positron emission tomography (PET) can noninvasively visualize the degree and the expansion of hypoxia. Currently, 18F-fluoromisonidazole (FMISO) is the most common radiotracer for hypoxia imaging. The clinical usefulness of FMISO PET has been established; it can distinguish glioblastomas from lower-grade gliomas and can predict the microenvironment of a tumor, including necrosis, vascularization, and permeability. FMISO PET provides prognostic information, including survival and treatment response information. Because hypoxia decreases a tumor’s sensitivity to radiation therapy, dose escalation to an FMISO-positive volume is an attractive strategy. Although this idea is not new, an insufficient amount of evidence has been obtained regarding this concept. New tracers for hypoxia imaging such as 18F-DiFA are being tested. In the future, hypoxia imaging will play an important role in glioma management.
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