Impaired glymphatic system in secondary degeneration areas after ischemic stroke in rats

J Stroke Cerebrovasc Dis. 2020 Jul;29(7):104828. doi: 10.1016/j.jstrokecerebrovasdis.2020.104828. Epub 2020 May 11.

Abstract

Background: Pathomechanism of secondary degeneration in remote regions after ischemic stroke has not been totally clarified. Contrast-enhanced MRI with injecting Gd-DTPA in cisterna magna (CM) is regarded as an efficient method to measure glymphatic system function in brain. Our research aimed at evaluating glymphatic system changes in secondary degeneration areas by contrast-enhanced MRI.

Methods: Ischemic stroke was induced by left middle cerebral artery occlusion (MCAO) model. A total of 12 Sprague-Dawley rats were randomly divided into three groups: control group with sham operations (n=4), the group of acute phase (1 day after MCAO) (n=4), and the group of subacute phase (7 days after MCAO) (n=4). Contrast-enhanced MRI was performed in 1days or 7days after operations respectively. All rats received an intrathecal injection of Gd-DTPA (2μl/min, totally 20μl) and high-resolution 3D T1-weighted MRI for 6 h. The time course of the signal-to-noise ratio (SNR) in substantia Nigra (SN) and ventral thalamic nucleus (VTN) was evaluated between two hemispheres in all rats.

Results: In control group without ischemia, time-to-peak of SNR in SN was earlier than that in VTN. There were no differences of SNR between two hemispheres after intrathecal Gd-DTPA administration. In the group of acute phase, MRI revealed similar time course and time-to-peak of SNR between ipsilateral and contralateral VTN, while a tendency of higher SNR in ipsilateral SN than contralateral SN at 4h, 5h, 6h after Gd-DTPA injection. And time-to-peak of SNR was similar in bilateral SN. In the group of subacute phase, time-to-peak of SNR was similar in bilateral VTN, while longer in ipsilateral SN compared with contralateral side. In addition, SNR in T1WI in ipsilateral was significantly higher than SNR in contralateral SN and VTN at 5h (VTN, P= 0.003; SN, P=0.004) and 6h (VTN, P=0.015; SN, P=0.006) after Gd-DTPA injection.

Conclusion: Glymphatic system was impaired in ipsilateral SN and VTN after ischemic stroke, which may contribute to neural degeneration.

Keywords: Glymphatic system; Ischemic stroke; MRI; Secondary degeneration.

MeSH terms

  • Animals
  • Contrast Media / administration & dosage*
  • Disease Models, Animal
  • Gadolinium DTPA / administration & dosage*
  • Glymphatic System / diagnostic imaging*
  • Glymphatic System / pathology
  • Glymphatic System / physiopathology
  • Infarction, Middle Cerebral Artery / diagnostic imaging*
  • Infarction, Middle Cerebral Artery / pathology
  • Infarction, Middle Cerebral Artery / physiopathology
  • Magnetic Resonance Imaging*
  • Male
  • Nerve Degeneration*
  • Predictive Value of Tests
  • Rats, Sprague-Dawley
  • Signal-To-Noise Ratio
  • Substantia Nigra / diagnostic imaging*
  • Substantia Nigra / pathology
  • Substantia Nigra / physiopathology
  • Time Factors
  • Ventral Thalamic Nuclei / diagnostic imaging*
  • Ventral Thalamic Nuclei / pathology
  • Ventral Thalamic Nuclei / physiopathology

Substances

  • Contrast Media
  • Gadolinium DTPA