AR model and MSCs-Exo treatment
BALB/c mice were sensitized with ovalbumin (OVA) (Sigma-Aldrich, A5503) and aluminum hydroxide gel (Thermo Scientific, 77161) to establish the AR model. At 4 weeks of age, the mice were randomly divided into the control group, the AR group, and the MSCs-Exo treatment group. AR mice were given an intraperitoneal injection of 100 μg OVA in 100 μl PBS combined with 100 μl aluminum hydroxide gel on days 1, 5, and 10 and were treated intranasally with 20 μl 10% OVA in PBS per nostril every day from day 15 to 21. Mice in the control group were given an intraperitoneal injection of 100 μl PBS combined with 100 μl aluminum hydroxide gel, and they were treated intranasally with 20 μl PBS per nostril every day. Mice in the MSCs-Exo treatment group were given an intraperitoneal injection of 20 μg of OVA in 100 μl PBS combined with 100 μl aluminum hydroxide gel on days 1, 5, and 10; were treated intranasally with 20 μl 10% OVA in PBS per nostril every day from day 15 to 21; and were treated intranasally with 20 μl MSCs-Exo at different concentrations per nostril every day. Administration was performed using a 10-μL pipette with no anesthetics.