Bioactivity of mesenchymal stem/stromal cell (MSC) extracellular vesicles (EVs) released from 3D-printed GelMA hydrogels. Human umbilical vein endothelial cells (HUVECs) were treated with growth media only (EGM; positive control), basal media only (EBM; negative control), and 100 μg/ml of pooled EVs collected between Hour 1 and Hour 24 from the indicated constructs. GelMA only controls were included. (A, B) Results of EVs released from GelMA hydrogels crosslinked with 0.1% LAP. (C, D) Results of EVs released from GelMA hydrogels crosslinked with 0.2% LAP. An additional control of unmodified MSC EVs was included. Representative images for each group and timepoint are displayed with the gap area outlined. Statistical significance was calculated using one-way ANOVA with Holm–Sidak’s test (*p < .05, **p < .01, ***p < .001, ****p < .0001) (n = 3)