Effect of allogeneic serum on the morphological changes and PDT of canine MSCs. (A) Experimental design shows that canine MSCs were categorized into three groups based on passage number: early passage (passage 3), mid-passage (passage 7), and late passage (passage 10). Canine MSCs were initially cultured in a medium containing 10% FBS. During the adaptation phase from passage 0 to passage 3, the percentage of canine serum was gradually increased from 0% to 10%. (B) Canine MSCs cultured in FBS medium and allogeneic serum medium were observed under the phase-contrast microscope (×40), size bar = 200 μm. (C) The PDT of canine MSCs was measured for both FBS and allogeneic serum groups. Symbols are presented as mean ± SEM. The significance of differences was determined using the student t-test. ***p < 0.001 versus the allogeneic serum group.