Fig. 3

sEVs Distribution and function in spatial learning and memory function of APP/PS1 mice after injection. A–C Live mice were imaged using an in vivo imaging system 24 h after DiR-labeled sEVs were injected. A control group (only DiR without sEVs) was established to exclude the false-positive staining caused by the dye. A, B Imaging of the backside and the ventral side, respectively. C The indicated organs were harvested and imaged with the in vivo imaging system. D The sEVs were labeled with the fluorescence dye CellMask (red) and injected via the tail vein in the mice. Brain slices were produced and subjected to the immunostaining of the neuron marker NeuN (green) and visualized. The control group mice were injected with CellMask only without sEVs. N = 3. E–H APP/PS1 mice were injected with Ctrl sEVs (APP/PS1-Ctrl sEV group), glutamate sEVs (APP/PS1-Glutamate sEV group) or GABA sEVs (APP/PS1-GABA sEV group) through tail vein at the same time every other day. The dosage of sEVs was 1.0 × 10¹⁰ particles/g body weight (p/g). In addition, C57BL/6 wild-type (C57 group) and AD model group with an equivalent volume of PBS injection (APP/PS1-PBS group) were included as the negative and positive controls, respectively. After 40 days, spatial learning and memory were evaluated based on the MWM performance (N = 12/group). During Days 1–5, the time that elapsed until the mice reached the platform was noted. * represents p < 0.05, ** represents p < 0.01 compared with APP/PS1-Ctrl sEV Group (E). For latency to escape, Kaplan–Meier survival analysis with the Mantel-Cox log-rank test was employed to account for the non-normal distribution of latencies resulting from the 60-s maximum trial duration (F). On Day 6, the number of times that the animals swam over the platform location (G) and the pathways that elapsed were evaluated (H). The green circle represents the platform, and the red curve shows the swimming path of the mice. Data are represented as the mean ± SEM, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001