Col-EVs treatment alleviated apoptosis in vivo and in vitro. a Immunohistochemical staining of cleaved caspase-3 at day3 after AKI. Scale bar, 50 μm. b Quantification of cleaved caspase-3+ staining area in each group. Data were represented as mean ± SEM (n = 5; *P < 0.05 vs. sham; #P < 0.05 vs. PBS; $P < 0.05 vs. Col). c Representative immunofluorescence images of γ-H2AX (red) expression in HK-2 cells. Scale bar, 50 μm. d Quantification of γ-H2AX+ cells in each group. Data were represented as mean ± SEM. *P < 0.05 vs. control; #P < 0.05 vs. PBS; $P < 0.05 vs. Col.