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Updated: Apr 28, 2026
Author Spotlight: Assessing Ischemic Stroke Damage Through Middle Cerebral Artery Occlusion Model
Published on: August 11, 2023
Rat middle cerebral artery occlusion is not a suitable model for the study of stroke-induced spontaneous infections
Mireia Campos-Martorell1, , Mar Hernández-Guillamón1
1Neurovascular Research Laboratory, Institut de Recerca Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
Background:
Infections related to stroke-induced immunodepression are an important complication causing a high rate of death in patients. Several experimental studies in mouse stroke models have described this process but it has never been tested in other species such as rats.
Methods:
Our study focused on the appearance of secondary systemic and pulmonary infections in ischemic rats, comparing with sham and naive animals. For that purpose, male Wistar rats were subjected to embolic middle cerebral artery occlusion (eMCAO) or to transient MCAO (tMCAO) inserting a nylon filament. Forty-eight hours after ischemia, blood and lung samples were evaluated.
Results:
In eMCAO set, ischemic rats showed a significant decrease in blood-peripheral lymphocytes (naive = 58.8±18.1%, ischemic = 22.9±16.4%) together with an increase in polymorphonuclears (PMNs) (naive = 29.2±14.7%, ischemic = 71.7±19.5%), while no change in monocytes was observed. The increase in PMNs counts was positively correlated with worse neurological outcome 48 hours after eMCAO (r = 0.55, p = 0.043). However, sham animals showed similar changes in peripheral leukocytes as those seen in ischemic rats (lymphocytes: 40.1±19.7%; PMNs: 51.7±19.2%). Analysis of bacteriological lung growth showed clear differences between naive (0±0 CFU/mL; log10) and both sham (3.9±2.5 CFU/mL; log10) and ischemic (4.3±2.9 CFU/mL; log10) groups. Additionally, naive animals presented non-pathological lung histology, while both sham and ischemic showed congestion, edema or hemorrhage. Concordant results were found in the second set of animals submitted to a tMCAO.
Conclusions:
Inflammatory and infection changes in Wistar rats subjected to MCAO models may be attributed not only to the brain ischemic injury but to the surgical aggression and/or anaesthetic stress. Consequently, we suggest that stroke-induced immunodepression in ischemic experimental models should be interpreted with caution in further experimental and translational studies, at least in rat stroke models that entail cervicotomy and cranial trepanation.
Insights
Stroke-induced immunosuppression in rats may be influenced by surgical factors, not just brain injury. Researchers caution that these findings in rat models should be interpreted carefully in future studies.
Area of Science:
- Neuroscience
- Immunology
- Infectious Diseases
Background:
- Stroke-induced immunosuppression is a significant cause of mortality.
- Previous studies on this phenomenon were limited to mouse models.
- This study investigates immunosuppression in rat stroke models.
Purpose of the Study:
- To evaluate secondary systemic and pulmonary infections in rats following ischemic stroke.
- To compare immune responses in ischemic rats with sham-operated and naive controls.
- To determine the influence of surgical procedures on immune status in rat stroke models.
Main Methods:
- Male Wistar rats underwent embolic middle cerebral artery occlusion (eMCAO) or transient MCAO (tMCAO).
- Blood and lung samples were analyzed 48 hours post-ischemia.
- Leukocyte counts, peripheral lymphocyte levels, and lung bacteriological growth were assessed.
Main Results:
- Ischemic rats exhibited decreased lymphocytes and increased polymorphonuclears (PMNs).
- Sham-operated rats showed similar leukocyte changes, suggesting surgical influence.
- Both sham and ischemic groups presented lung pathology and increased bacterial growth compared to naive controls.
Conclusions:
- Inflammatory and infection changes in rat stroke models may result from surgical stress, not solely ischemic injury.
- Findings suggest caution in interpreting stroke-induced immunosuppression in rat models involving cervicotomy and cranial trepanation.
- Results emphasize the need for careful consideration of confounding factors in translational stroke research.
