SPP1-mediated microglial synaptic engulfment modulates the glial-vascular unit: Mechanistic insights into electroacupuncture for ischemic stroke.

BACKGROUND

This study aimed to investigate the protective effect of electroacupuncture (EA) on the glial-vascular unit (GVU) in ischemic stroke (IS) by regulating microglial synaptic phagocytosis through secreted phosphoprotein 1 (SPP1).

METHODS

This study involved basic and clinical aspects. Clinically, our research used EA and non-EA groups to investigate the effect of EA on the functional improvement of patients with IS. Basic research involved a mouse model and the following experimental groupings: middle cerebral artery occlusion reperfusion (MCAO/R) NC group, MCAO/R shSpp1 group, MCAO/R EA group, and MCAO/R shSpp1 EA group. In the MCAO/R shSpp1 and MCAO/R shSpp1 EA groups, AAV-shSpp1 was injected stereotactically into the ipsilateral temporoparietal cortex (3 μL per mouse). Thirty days later, a mouse model of MCAO/R was constructed for the four groups, including the MCAO/R NC group, and the MCAO/R EA group. After 24 h, the MCAO/R EA group and the MCAO/R shSpp1 EA group underwent EA treatment for two weeks. Following behavioral tests, Super-Resolution Vascular Imaging, and Laser Speckle Contrast Imaging, brain tissues were collected for immunofluorescence, TUNEL staining, transmission electron microscopy (TEM), Quantitative Real-Time PCR (RT-qPCR) and western blotting analysis.

RESULTS

Analysis revealed that EA and Spp1 knockdown restored synaptic structure and synaptic protein expression levels, reduced microglial phagocytic events, improved blood-brain barrier integrity, reduced infarct volume, and improved behavioral performance (P<0.5). When EA was combined with Spp1 knockdown, there was no further improvement in any parameter, thus identifying a ceiling effect and suggesting that SPP1 represented the terminal rate-limiting node in the EA protective chain.

CONCLUSION

The downregulation of SPP1 replicated the multicellular protective phenotype of EA, establishing SSP1 as a necessary downstream molecule for EA-induced effects and providing a theoretical and experimental basis for the modernization of acupuncture and a multimodal stroke rehabilitation strategy centered on SPP1 that is both interventional and monitorable.