MR-Bildgebung eines experimentellen Schlaganfallmodells beim Schaf

Zusammenfassung

Ziel: Untersuchung der zerebrovaskulären Anatomie und Pathologie des Schafes unter Beachtung verschiedener Varianten der Gefäßversorgung mittels MRA und MR-morphologische Charakterisierung unterschiedlicher Infarktmuster bei einem neuen Großtiermodell der fokalen Ischämie. Material und Methoden: Bei 9 von 13 Merinoschafen wurden operativ Hauptäste der Arteria cerebri media permanent verschlossen. Insgesamt wurden 23 MRT-Untersuchungen an 10 Schafen vor und 2 - 46 Tage nach Ischämie durchgeführt mittels T1-, T2-, T2*- und Diffusionswichtung sowie TOF-MR-Angiographien. Die Volumina der Infarkte wurden bestimmt und Gefäßanatomie und Verschlusstyp dargestellt. Von 3 Schafen wurden Ausgusspräparate der hirnversorgenden Gefäße angefertigt. Ergebnisse: Die TOF-MRA stellt die Gefäßanatomie inklusive anatomischer Variationen und den Verschlusstyp dar. Schafe mit Gefäßverschluss zeigten abhängig von der Anzahl der erhaltenen Mediaäste (0; 1; 2) hochsignifikant (p < 0,001) unterschiedliche Läsionsvolumina (21 ± 5,7; 13; 1,7 ± 1,3 ml). Bei den scheinoperierten Tieren fanden sich nur kleine Kontusionszonen. Schlussfolgerung: Zum ersten Mal wurden fokale zerebrale Ischämien beim Schaf erzeugt und mittels MRT dargestellt. Die TOF-MRA eignet sich trotz des vorgeschalteten Rete mirabile zur Darstellung von Anatomie, Varianten und Verschlusstyp der Hirngefäße des Schafes in Übereinstimmung mit den Ausgusspräparaten. Somit ist die MRT mit TOF-MRA als nichtinvasives Monitoring des Schlaganfalls beim Schaf geeignet.

Abstract

Purpose: With respect to the specific characteristic of rete mirabile epidurale rostrale in sheep, the aim of this study was to investigate the use of time of flight (TOF) magnetic resonance angiography (MRA) to observe vascular anatomy and to validate MCA occlusion in a new model of experimental focal cerebral ischemia by permanent middle cerebral artery (MCA) occlusion in sheep (designed to study stroke therapy using autologous stem cells from umbilical cord blood). Furthermore, we wanted to assess the extent and natural time course of ischemic focal brain injury in sheep using functional and morphological magnetic resonance imaging (MRI). Materials and Method: 13 Merino sheep were examined. In 4 of the animals all, in 5 sheep 1 or 2 MCA branches were occluded and in 1 one case touched (sham operation). 4 controls did not undergo a surgical procedure. 23 MRI sessions were performed in 10 sheep. These sessions included T1, T2, T2* sequences, diffusion-weighted imaging (DWI) and TOF MRA before and 2 - 46 days after the onset of stroke using a 1.5T clinical MR scanner. Corrosion casts of the cerebral arteries of 3 sheep were prepared and compared to MRA. Results: The MRA visualized the vessel anatomy or occlusion distal to the rete mirabile. Anatomical variants concerning the variant origin of the MCA and inconstant arteria choroidea rostralis and communicans rostralis were revealed. Sheep with occluded left MCA showed space occupying lesions with a drop in ADC values. Depending on the number of preserved MCA branches (0; 1; 2), highly significant (p < 0.001) differences in lesion size (21 ± 5.7; 13; 1.7 ± 1.3 ml) could be found. No indication of ischemia but minimal contusion damage was observed in the sham operated animal. Conclusions: In our study focal cerebral ischemia was generated in sheep and examined using MRI for the first time. Depending on the occlusion type, the model produced a reproducible lesion size. TOF-MRA proved to be able to clearly depict the anatomy, variants and occlusion type of cerebral arteries in sheep in a manner comparable to that of corrosion casts despite the upstream rete mirabile. MRI with MRA is a useful tool for assessing the extent of brain injury and the type of MCA occlusion and is therefore suitable for non-invasive monitoring of lesion development upon stroke.

Key words

ischemia/infarction - brain - MR angiography - MR imaging - animals - stem cells

Literatur

• 1 Furlan A, Higashida R, Wechsler L. et al . Intra-arterial prourokinase for acute ischemic stroke. The PROACT II study: a randomized controlled trial. Prolyse in Acute Cerebral Thromboembolism.  JAMA. 1999;  282 2003-2011
• 2 Hacke W, Kaste M, Fieschi C. et al . Randomised double-blind placebo-controlled trial of thrombolytic therapy with intravenous alteplase in acute ischemic stroke (ECASS II). Second European-Australasian Acute Stroke Study Investigators.  Lancet. 1998;  352 1245-1251
• 3 Taguchi A, Soma T, Tanaka H. et al . Administration of CD34 + cells after stroke enhances neurogenesis via angiogenesis in a mouse model.  J Clin Invest. 2004;  114 330-338
• 4 Kurozumi K, Nakamura K, Tamiya T. et al . Mesenchymal stem cells that produce neurotrophic factors reduce ischemic damage in the rat middle cerebral artery occlusion model.  Mol Ther. 2005;  11 96-104
• 5 Khamas W A, Ghoshal N G, Bal H S. Histomorphologic structure of the carotid rete-cavernous sinus complex and its functional importance in sheep (Ovis aries).  Am J Vet Res. 1984;  45 156-158
• 6 Burbridge B, Matte G, Remedios A. Complex intracranial arterial anatomy in swine is unsuitable for cerebral infarction projects.  Can Assoc Radiol J. 2004;  55 326-329
• 7 Lametschwandtner A, Lametschwandtner U, Weiger T. Scanning electron microscopy of vascular corrosion casts - technique and applications. Updated review.  Scanning Microsc. 1990;  4 889-940
• 8 Rosamond W D, Folsom A R, Chambless L E. et al . Stroke incidence and survival among middle-aged adults: 9-year follow-up of the Atherosclerosis Risk in Communities (ARIC) cohort.  Stroke. 1999;  30 736-743
• 9 Nelson P T, Kondziolka D, Wechsler L. et al . Clonal human (hNT) neuron grafts for stroke therapy: neuropathology in a patient 27 months after implantation.  Am J Pathol. 2002;  160 1201-1206
• 10 Kelly S, Bliss T M, Shah A K. et al . Transplanted human fetal neural stem cells survive, migrate, and differentiate in ischemic rat cerebral cortex.  Proc Natl Acad Sci USA. 2004;  101 11 839-11 844
• 11 Hoyte L, Kaur J, Buchan A M. Lost in translation: taking neuroprotection from animal models to clinical trials.  Exp Neurol. 2004;  188 200-204
• 12 Richard Green A, Odergren T, Ashwood T. Animal models of stroke: do they have value for discovering neuroprotective agents?.  Trends Pharmacol Sci. 2003;  24 402-408
• 13 Feuerstein G Z, Wang X. Animal models of stroke.  Mol Med Today. 2000;  6 133-135
• 14 Rohl L, Sakoh M, Simonsen C Z. et al . Time evolution of cerebral perfusion and apparent diffusion coefficient measured by magnetic resonance imaging in a porcine stroke model.  J Magn Reson Imaging. 2002;  15 123-129
• 15 Ritzl A, Meisel S, Wittsack H J. et al . Development of brain infarct volume as assessed by magnetic resonance imaging (MRI): follow-up of diffusion-weighted MRI lesions.  J Magn Reson Imaging. 2004;  20 201-207
• 16 Kino T, Fuwa I, Kitano I. et al . Carotid rete mirabile presenting subarachnoid haemorrhage. Report Of two cases.  Acta Neurochir (Wien). 1999;  141 1183-1186
• 17 Karasawa J, Touho H, Ohnishi H. et al . Rete mirabile in humans-case report.  Neurol Med Chir (Tokyo). 1997;  37 188-192
• 18 Laughlin M H. Cerebral, coronary, and renal blood flows during hemorrhagic hypotension in anesthetized miniature swine.  Adv Shock Res. 1983;  9 189-201
• 19 Gerriets T, Stolz E, Walberer M. et al . Complications and pitfalls in rat stroke models for middle cerebral artery occlusion: a comparison between the suture and the macrosphere model using magnetic resonance angiography.  Stroke. 2004;  35 2372-2377
• 20 Noguchi Y, Nishio S, Kawauchi M. et al . A new method of inducing selective brain hypothermia with saline perfusion into the subdural space: effects on transient cerebral ischemia in cats.  Acta Med Okayama. 2002;  56 279-286
• 21 Kazemi M, Silva M D, Li F. et al . Investigation of techniques to quantify in vivo lesion volume based on comparison of water apparent diffusion coefficient (ADC) maps with histology in focal cerebral ischemia of rats.  Magn Reson Imaging. 2004;  22 653-659
• 22 Baird A E, Benfield A, Schlaug G. et al . Enlargement of human cerebral ischemic lesion volumes measured by diffusion-weighted magnetic resonance imaging.  Ann Neurol. 1997;  41 581-589
• 23 Hofmeijer J, Veldhuis W B, Schepers J. et al . The time course of ischemic damage and cerebral perfusion in a rat model of space-occupying cerebral infarction.  Brain Res. 2004;  1013 74-82
• 24 Gerriets T, Stolz E, Walberer M. et al . Noninvasive quantification of brain edema and the space-occupying effect in rat stroke models using magnetic resonance imaging.  Stroke. 2004;  35 566-571
• 25 Loubinoux I, Volk A, Borredon J. et al . Spreading of vasogenic edema and cytotoxic edema assessed by quantitative diffusion and T2 magnetic resonance imaging.  Stroke. 1997;  28 419-426
• 26 Schroeter M, Franke C, Stoll G. et al . Dynamic changes of magnetic resonance imaging abnormalities in relation to inflammation and glial responses after photothrombotic cerebral infarction in the rat brain.  Acta Neuropathol (Berl). 2001;  101 114-122
• 27 Hartmann M, Junkers R, Herold-Mende C. et al . Pseudonormalisierung diffusionsgewichteter Aufnahmen: Magnetresonanztomografische Untersuchungen im Tiermodel (C6-Gliom).  Fortschr Röntgenstr. 2005;  177 114-118
• 28 Jablonski R, Wiland C. Variation of the Arteries of the base of the Brain in Sheep.  Folia Morphol (Warsz). 1973;  32 339-347
• 29 Kapoor K, Kak V K, Singh B. Morphology and comparative anatomy of circulus arteriosus cerebri in mammals.  Anat Histol Embryol. 2003;  32 347-355
• 30 Gillilan L A. Blood supply to Brains of ungulates with and without a rete mirabile caroticum.  J Comp Neurol. 1974;  153 275-290