Detection of secondary neurodegeneration after subarachnoid hemorrhage in the rat using the PET tracer cis-4-[18F]fluoro-D-proline and functional MRI, and investigation of the neuroprotective effect of argon

• Applicants: Professor Dr. Mark Coburn; Professor Nadim Jon Shah, Ph.D.
• Subject Area: Anaesthesiology ; Nuclear Medicine, Radiotherapy, Radiobiology
• Term: from 2018 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 412303240

• Final Report Year: 2025

Final Report Abstract

This project aimed to improve the understanding of subarachnoid hemorrhage (SAH) using animal models, with a particular focus on establishing imaging methods for detecting secondary neurodegenerative damage. Additionally, a rat model of traumatic brain injury (TBI) was used for longitudinal monitoring of secondary lesions by means of small animal imaging. Initially, the SAH model in rats was re-established and technically refined in Aachen. It became clear that both the surgical technique and the choice of rat strain were critical to success: switching from the supplier Janvier to Charles River significantly improved SAH induction, as anatomical differences in the cervical vessels significantly affected the model's reproducibility. An unexpected finding was the frequent occurrence of additional bleeding types (e.g., subdural hematomas) and ischemic lesions, which complicated data interpretation. However, this reflects the clinical reality, where SAH in humans rarely presents in isolation. Another major methodological challenge was the placement of intracranial pressure (ICP) and cerebral blood flow (CBF) probes, which themselves induced brain damage and led to strong signals in autoradiography using the tracer cisF18DPro. A modified surgical technique (i.e., more precise drilling with cooling) successfully reduced these artifacts. This refinement allowed for artifactfree tracer distribution and the detection of genuine neurodegenerative regions, including the hippocampus, striatum, and thalamus. A key finding was that cisF18DPro is more sensitive to early tissue damage than FDG. The study also revealed that even minor surgical interventions can induce substantial changes, which was evident even in SHAM animals. This emphasizes the importance of rigorous control groups and is an important consideration for preclinical modeling. In parallel, a TBI model using controlled cortical impact (CCI) was established at the Forschungszentrum Jülich. Here, too, cisF18DPro reliably detected secondary neurodegeneration, both ex vivo and in longitudinal PET/MRI studies. The combination of cisF18DPro-PET and T2-weighted MRI enabled a spatially and temporally detailed visualization of primary and secondary brain lesions. A correlation was observed between the extent of the primary lesion and the magnitude of secondary damage in the thalamus and hippocampus. In addition, changes in metabolite levels and water content in affected brain regions indicated progressive neurodegenerative processes, the analysis of which is still ongoing. This study provides significant contributions to the optimization of experimental models in SAH and TBI research. The tracer cisF18DPro proved particularly suitable for detecting subtle brain damage. The findings highlight the importance of technical precision, standardized models, and critical evaluation of experimental artifacts for both preclinical imaging and animal welfare.

Publications

• Post-stroke treatment with argon attenuated brain injury, reduced brain inflammation and enhanced M2 microglia/macrophage polarization: a randomized controlled animal study. Critical Care, 23(1).
  Liu, Jingjin; Nolte, Kay; Brook, Gary; Liebenstund, Lisa; Weinandy, Agnieszka; Höllig, Anke; Veldeman, Michael; Willuweit, Antje; Langen, Karl-Josef; Rossaint, Rolf & Coburn, Mark
  
• An in vivo multimodal feasibility study in a rat brain tumour model using flexible multinuclear MR and PET systems. EJNMMI Physics, 7(1).
  Choi, Chang-Hoon; Stegmayr, Carina; Shymanskaya, Aliaksandra; Worthoff, Wieland A.; da Silva, Nuno A.; Felder, Jörg; Langen, Karl-Josef & Shah, N. Jon
  
• Investigation of Cerebral O-(2-[18F]Fluoroethyl)-L-Tyrosine Uptake in Rat Epilepsy Models. Molecular Imaging and Biology, 22(5), 1255-1265.
  Stegmayr, Carina; Surges, Rainer; Choi, Chang-Hoon; Burda, Nicole; Stoffels, Gabriele; Filß, Christian; Willuweit, Antje; Neumaier, Bernd; Heinzel, Alexander; Shah, N. Jon; Mottaghy, Felix M. & Langen, Karl-Josef
  
• Predicting experimental success: a retrospective case-control study using the rat intraluminal thread model of stroke. Disease Models & Mechanisms, 13(12).
  Liebenstund, Lisa; Coburn, Mark; Fitzner, Christina; Willuweit, Antje; Langen, Karl-Josef; Liu, Jingjin; Veldeman, Michael & Höllig, Anke
  
• Die Wirkung der Sexualsteroide Dehydroepiandosteron, Estradiol und Progesteron nach Glukose-Sauerstoff-Deprivation im murinen Modell der organotypischen Schnittkultur des Hippocampus. Doctoral thesis, RWTH Aachen University
  Lisa Liebenstund
  
• Noble gases and neuroprotection: summary of current evidence. Current Opinion in Anaesthesiology, 34(5), 603-606.
  Höllig, Anke & Coburn, Mark
  
• Spatiotemporal characterisation of ischaemic lesions in transient stroke animal models using diffusion free water elimination and mapping MRI with echo time dependence. NeuroImage, 244, 118605.
  Farrher, Ezequiel; Chiang, Chia-Wen; Cho, Kuan-Hung; Grinberg, Farida; Buschbeck, Richard P.; Chen, Ming-Jye; Wu, Kuo-Jen; Wang, Yun; Huang, Sheng-Min; Abbas, Zaheer; Choi, Chang-Hoon; Shah, N. Jon & Kuo, Li-Wei
  
• Post-stroke treatment with argon preserved neurons and attenuated microglia/macrophage activation long-termly in a rat model of transient middle cerebral artery occlusion (tMCAO). Scientific Reports, 12(1).
  Liu, Jingjin; Veldeman, Michael; Höllig, Anke; Nolte, Kay; Liebenstund, Lisa; Willuweit, Antje; Langen, Karl-Josef; Rossaint, Rolf & Coburn, Mark
  
• A multimodal imaging approach for the detection of secondary neurodegeneration in a traumatic brain injury (TBI) model in rats using the PET tracer cis‑4‑[18F]‑fluoro‑d‑proline (cis‑F‑d‑proline) and new quantitative MR methods. Posterabstract of the 18th European Molecular Imaging Meeting-EMIM 2023
  Carina Balduin, Michael Schöneck, Carina Stegmayr, Lisa Liebenstund, Jörg Felder, Wieland A. Worthoff, Chang-Hoon Choi, Ezequiel Farrher, Ana-Maria Oros- Peusquens, Dennis C. Thomas, Fabian Küppers, Bernd Neumaier, N. Jon Shah, Karl-Josef Langen & Antje Willuweit
  
• In Vivo Measurement of Rat Brain Water Content at 9.4 T MR Using Super‐Resolution Reconstruction: Validation With Ex Vivo Experiments. Journal of Magnetic Resonance Imaging, 60(1), 161-172.
  Thomas, Dennis C.; Oros‐Peusquens, Ana‐Maria; Schöneck, Michael; Willuweit, Antje; Abbas, Zaheer; Zimmermann, Markus; Felder, Jörg; Celik, Avdo & Shah, Nadim Joni