Fig. 3

MSC-derived EVs reduce 10 Gy WBI-induced epithelial apoptosis and surge their proliferation. Nude mice received 10 Gy WBI. a Schema of the experimental protocol. Irradiated mice were then randomly assigned to three different groups. The first group received one intravenous injection of 200 μg MSC-derived EVs 6 h after WBI and were then sacrificed 24 h post-irradiation. The second group received two injections of 200 μg each of MSC-derived EVs 6 h and 24 h after WBI and were then sacrificed 48 h post-irradiation. The third group received three injections of 200 μg each of MSC-derived EVs 6 h, 24 h, and 48 h after WBI and were then sacrificed 72 h post-irradiation. The fourth, fifth, and seventh groups received 5.10⁶ MSC 6 h after WBI and were then sacrificed 6 h, 24 h, or 72 h post-irradiation, respectively. b–e Crypt cell apoptosis (b) and proliferation (d) were respectively assessed by TUNEL assay and KI67 immunostaining performed on small intestinal sections. Representative pictures from non-irradiated mice (b (a), d (a)), mice subjected to 10 Gy WBI and treated with PBS (b (b), d (b)), mice subjected to 10 Gy WBI and treated with MSC (b (c), d (c)), and mice subjected to 10 Gy WBI and treated by MSC-derived EVs (b (d), d (d)). Arrows show cells with the highest positive staining. Quantification of c crypt cell apoptosis and d crypt cell proliferation in non-irradiated NUDE mice (12 and 24 animals, respectively), 24 h, 48 h, or 72 h after 10 Gy WBI with PBS treatment (5 and 4 mice at 24 h, 6 and 5 mice at 48 h, and 6 and 17 mice at 72 h, respectively); 24 h, 48 h, or 72 h after 10 Gy WBI with 5.10⁶ MSC treatment (6 and 4 mice at 24 h, 6 and 4 mice at 48 h, and 3 and 3 mice at 72 h, respectively); or 24 h, 48 h, or 72 h after 10 Gy WBI with MSC-derived EVs (7 and 6 mice at 24 h, 6 and 5 mice at 48 h, and 6 and 7 mice at 72 h, respectively). Each value represents the average of 30 independent measurements per crypt and is expressed as a percentage of the non-irradiated value, N = 1. ***p ≤ 0.0001 compared with the non-irradiated group; ^$p ≤ 0.05, ^$$$p ≤ 0.0001 in comparison between the 10-Gy WBI group treated with MSC-derived EVs and the 10-Gy WBI group treated with PBS; ^#p < 0.05, ^###p < 0.0001 in comparison between the 10-Gy WBI group treated with MSC-derived EVs and the 10-Gy WBI group treated with MSC