Total saponins of Trillium tschonoskii Maxim. mitigate locomotor deficits associated with cerebral ischemia by facilitating microglial phenotype switching through the Jagged1/Notch1/Hes5 signaling pathway.

Trillium tschonoskii Maxim. (TTM) is a traditional Chinese medicinal herb historically employed to enhance functional recovery in patients with cerebrovascular disorders, particularly during post-stroke rehabilitation. Despite its documented therapeutic benefits, the underlying molecular mechanisms by which TTM mitigated ischemic injury remain poorly understood. This study aimed to elucidate the neuroprotective effects of the saponins of T. tschonoskii (TSTT) on post-ischemic neural recovery and to investigate the specific signaling pathways involved in microglial polarization. A permanent middle cerebral artery occlusion (pMCAO) rat model and LPS/IFN-γ-stimulated BV2 microglia were established for in vivo and in vitro evaluations, respectively. Neural recovery was assessed using multimodal MRI, CatWalk gait analysis, and H&E/LFB staining. The modulation of microglial polarization and the Jagged1/Notch1/Hes5 signaling axis were analyzed via immunofluorescence and western blotting. TSTT treatment significantly attenuated ventricular atrophy (0.4-fold, P < 0.01) and increased neuronal survival (1.9-fold, P < 0.01) in the ipsilateral somatosensory cortex. Myelination and axonal integrity were preserved, as evidenced by increased LFB integrated optical density (IOD) and fractional anisotropy (FA) values. Mechanistically, TSTT suppressed pro-inflammatory M1 state (downregulating iNOS, CD86, and CD16) while promoting the M2 anti-inflammatory phenotype (upregulating CD206, Arg-1, and IL-10) both in vivo and in vitro. These effects were associated with the downregulation of Jagged1, Notch1, and Hes5. Furthermore, co-treatment with DAPT (γ-secretase inhibitor) did not demonstrate a synergistic or additive effect, suggesting that TSTT's M2-promoting effect was likely mediated through the same Notch-dependent signaling axis. These findings illustrated that TSTT alleviated cerebral ischemic injury by modulating microglial switching from the M1 to M2 phenotype via inhibition of the Jagged1/Notch1/Hes5 axis. This study provided a mechanistic foundation for the clinical application of TSTT in stroke rehabilitation.