Novel rat middle cerebral artery occlusion model: Trans-femoral artery approach combined with preservation of the external carotid artery

Optimisation of a Mouse Model of Cerebral Ischemia-Reperfusion to Address Issues of Survival and Model Reproducibility and Consistency

Middle cerebral artery occlusion (MCAO) induced brain ischemia-reperfusion model in Mice is essential for understanding the pathology of stroke and investigating potential treatments, in which a variety of methods may be employed to block the middle cerebral artery (MCA), the most common being through the insertion of a monofilament; however, in vivo ischemia-reperfusion models are associated, particularly in mice, with high variability in lesion volume and high mortality. We aimed to optimise a mouse model of cerebral ischemia-reperfusion, addressing issues of mouse survival, model reproducibility, and consistency. The model was optimised in two ways: first, insert the monofilament directly through the internal carotid artery rather than through the external or common carotid artery, and second, by extending the length of the silicone coating on the monofilament, the length of the silicone coating enables embolization of the beginning of the middle cerebral artery, as well as the anterior cerebral artery and part of the posterior communicating artery. Results: We assessed various parameters, including blood flow changes in the middle cerebral artery, stability of the infarct area, correlation between infarct volume percentages and neurological deficit scores, mortality, weight changes, and wellbeing. We found that optimisation of the surgical procedure may improve mouse wellbeing and reduce mortality, through reduced weight loss and decrease the variability. In conclusion, we suggest that the optimisation of the model is superior for the study of both short and long-term outcomes of ischemic stroke. These results have considerable implications on stroke model selection for researchers.

Transfemoral Approach to Induce Transient Middle Cerebral Artery Occlusion in Rats: The Use of Commercially Available Endovascular Wires

BACKGROUND

Animal models of stroke play a crucial role in determining the pathophysiology of stroke progression and assessment of any new therapeutic approaches. Transient middle cerebral artery occlusion (tMCAo) in rodent models are the most common site-specific type of ischemia because of their relevance to the clinical setting. Compared with the intraluminal filament technique for inducing tMCAo, the transfemoral approach using endovascular wires is relatively a new technique METHODS: Here we present the use of commercially available wires used for neuro-endovascular surgical procedures to induce tMCAo in rats via a transfemoral approach. We used male Wistar rats in four groups to assess the effect of occlusion time (1 vs. 2 hours) and the wire type (PT2 TM 0.014″ vs. TransendTM EX, 0.014″, Boston Scientific, MA, USA). Infarct volume, edema, neurological deficits, and pro-inflammatory/anti-inflammatory blood biomarkers were used as outcome measures.

RESULTS

We observed a significant effect of the wire type on the infarct volume (p value = 0.0096) where infarcts were slightly larger in the PT2 wiregroups. However, the occlusion time had no significant effect on infarct volume, even though the interaction between wire-type * occlusion-time was significant (p value = 0.024). Also, the amount of edema and blood pro-inflammatory/anti-inflammatory biomarkers were not statistically different among the wire-type and occlusion-time groups.

CONCLUSIONS

The choice of appropriate endovascular wire should probably be the focus of the study design instead of the occlusion time when planning an experiment. The transfemoral approach using endovascular wires for inducing tMCAo in rats provides a more consistent outcome with fewer complications compared with suture filament models.

Focal middle cerebral artery ischemia in rats via a transfemoral approach using a custom designed microwire

OBJECTIVES

The aim of this study was to develop a reliable and repeatable method of inducing focal middle cerebral artery occlusion (MCAo) in rats without ligation of the external carotid artery (ECA), while reducing the risk of subarachnoid hemorrhage.

METHODS

We prototyped microwires with different diameters (0.0120 inch, 0.0115 inch, 0.0110 inch), materials, and construction methods (coil-on-core, extruded polymer jacket-on-core). Under fluoroscopic guidance and using femoral artery access, the microwires were navigated into the internal carotid artery of male Wistar rats (n=50, weight 376±64 g) to induce MCAo for 1 or 2 h. We performed neurological assessments at baseline, and at 3, 24, 72, and 168 h after MCAo. MRI measurements were performed on a 9.4 T scanner at 1 and 7 days post-injury.

RESULTS

The 0.0115 inch microwire with polymer jacket-on-core provided the most successful outcome. At 1 and 7 days post-injury, we observed similar infarction volumes for 1 and 2 h MCAo in the MRI study. Infarcted lesion volumes in both MCAo groups were significantly reduced at 7 days compared with 1 day post-injury. The trend in longitudinal changes for the scores of different neurological assessments was confirmed to be significant after the injury, but both groups showed a similar trend of neurological deficits over the course of the study.

CONCLUSIONS

We have developed a reliable and repeatable MCAo method in rats, allowing for precise occlusion of the MCA under direct fluoroscopic visualization without alteration of the cerebral hemodynamics associated with ECA ligation. The custom designed microwire can also be sized for targeted focal ischemia in larger animals.

A model of rat embolic cerebral infarction with a quantifiable, autologous arterial blood clot

We developed a novel model of a rat embolic cerebral infarction with a quantifiable autologous arterial blood clot. The left femoral artery had 0.15 ml of blood withdrawn and mixed with 10 units of thrombin in 50 μl saline. After 30 min, the clot was suctioned into a 4-French polyvinyl chloride tube. A 24-gage catheter was inserted up through the internal carotid artery via the external carotid artery stump. The 1-cm clot, at a volume of 7.2 mm3, was pushed and inserted into the internal carotid artery via the catheter. After withdrawing the catheter, the ICA blood flow recovered. We checked neurological status after 24 h (neurological free was 15, and worst was 1) and measured the infarction volume by the TTC method. Twelve rats were examined, and five sham-operated rats were included. Two rats were not able to achieve an 80% reduction in CBF. One rat died due to cerebral infarction. The success rate in producing infarction was 83%. The total infarction volume was 368.5 mm3±61.2 se. Median neurological score was 6. Hemorrhagic transformation was not detected. Sham-operated rats revealed no infarction and no neurological deficit. The volume of infarction correlated significantly with the neurological score. We conclude that this embolic stroke model is useful in producing a human, severe cardioembolic cerebral infarction.