Dynamically visualizing the effects of rTMS on GCPII repair after ischemic stroke by [68Ga]Ga-PSMA-11 PET/CT.

BACKGROUND: Glutamate excitotoxicity driven by pathological upregulation of glutamate carboxypeptidase II (GCPII) and consequent depletion of neuroprotective metabotropic glutamate receptor 3 (mGluR3) constitutes a critical cascade underlying post-ischemic neuronal injury. Repetitive transcranial magnetic stimulation (rTMS) benefits post-stroke rehabilitation and modulates glutamatergic neurotransmission, but the underlying molecular mechanisms remain incompletely understood. OBJECTIVE: To evaluate [68Ga]Ga-PSMA-11 PET/CT for quantifying GCPII expression dynamics after ischemic stroke, and to determine whether high-frequency rTMS confers neuroprotection by modulating the GCPII/mGluR3 axis. METHODS: Primary rat astrocytes underwent oxygen-glucose deprivation/reperfusion (OGD/R) and 20 Hz rTMS in vitro. GCPII expression and [68Ga]Ga-PSMA-11 uptake were assessed by immunofluorescence and gamma counting. A rat model of middle cerebral artery occlusion (MCAO) was established, and longitudinal microPET/CT was performed in sham-operated controls (day 0) and in MCAO animals on days 3, 7, 14, and 21 post-surgery. GCPII and mGluR3 expression was validated by immunohistochemistry and Western blotting. Neurological recovery in the modeled rats was assessed by the modified Neurological Severity Score (mNSS) and rotarod test. RESULTS: OGD/R upregulated GCPII and [68Ga]Ga-PSMA-11 uptake in astrocytes, attenuated by rTMS (p < 0.01). In MCAO rats, ipsilateral PET signal peaked on day 7, correlating positively with GCPII (R2 = 0.9101, 0.7717) and inversely with mGluR3 (R2 = 0.7982). rTMS improved mNSS and rotarod performance, reduced ipsilateral PET signal (p < 0.0001), and restored mGluR3 expression. CONCLUSIONS: [68Ga]Ga-PSMA-11 PET/CT enables longitudinal in vivo GCPII mapping after ischemic stroke. High-frequency rTMS may promote recovery by suppressing GCPII overexpression and restoring mGluR3 neuroprotection, identifying a novel molecular mechanism underlying rTMS efficacy.