Abstract: BACKGROUND: Distal middle cerebral artery occlusion in mice leads to secondary demyelinating lesions. In the acute phase, the progression of demyelinating injury is closely related to the inflammatory response of microglia. Microglia possess phagocytic functions and clear degraded myelin debris through relevant mechanisms post-injury, thereby repairing the microenvironment of the damaged area.
OBJECTIVE: To establish a mouse model of ischemic stroke using electrocoagulation and investigate demyelination, inflammatory responses, and related mechanisms.
METHODS: Kunming mice were randomly divided into a sham operation group and an electrocoagulation group. The electrocoagulation group was further subdivided into 12-hour, 1-day, 3-day, 5-day, and 7-day subgroups, with nine mice in each group. Using the sham group as the control, motor and memory abilities were compared via Bederson scoring and Y-maze tests. 2,3,5-Triphenyl tetrazolium chloride staining was used to observe the infarct area, while Luxol fast blue staining was employed to detect the degree of myelin loss in the cerebral cortex. Immunofluorescence staining was performed to detect the expression of myelin basic protein, degraded myelin basic protein, ionized calcium-binding adapter molecule 1, Janus kinase 2 (JAK2), and signal transducer and activator of transcription 3 (STAT3). Western blot was used to measure JAK2 and STAT3 protein expression, and ELISA was conducted to quantify levels of interleukin-6, tumor necrosis factor-α, interleukin-1β, interferon-γ, and interleukin-10. These experiments were employed to analyze the mechanisms of myelin injury and inflammatory responses in the model mice.
RESULTS AND CONCLUSION: The ischemic stroke model was successfully established in mice using electrocoagulation. Compared with the sham group, the following results were observed: (1) Mice in the electrocoagulation subgroups exhibited varying degrees of motor dysfunction, with significant differences in total distance traveled within the same time frame. (2) At 1 day of electrocoagulation, the ischemic area identified by 2,3,5-triphenyl tetrazolium chloride staining (P < 0.001) and the demyelinated area in the cerebral cortex detected by Luxol fast blue staining (P < 0.001) reached their maximum extent. (3) Immunofluorescence staining showed that myelin basic protein significantly decreased at 1 day of electrocoagulation (P < 0.05), degraded myelin basic protein significantly increased at 1 day of electrocoagulation (P < 0.001), ionized calcium-binding adapter molecule 1 significantly increased at 3-5 days of electrocoagulation (P < 0.001), JAK2 significantly increased at 1 day of electrocoagulation (P < 0.01), and STAT3 significantly increased at 1-3 days of electrocoagulation (P < 0.01). (4) ELISA results indicated that inflammatory factor levels significantly increased after electrocoagulation. (5) Western blot results revealed significantly elevated protein expression of JAK2 and STAT3 in the electrocoagulation group. These findings indicate that electrocoagulation induces central nervous system demyelination, impairs motor and memory functions, triggers cerebral inflammatory responses, and activates the JAK2-STAT3 pathway, which may be involved in microglial phagocytosis of myelin debris.

Key words: demyelination, ischemic stroke, microglia, neuroinflammation, Janus kinase 2-signal transducer and activator of transcription 3, phagocytosis