Randomization and masking
All eligible subjects (n = 42) were randomly assigned into two groups (1:1 ratio) to either the intervention group, who were to receive NA-UC-MSCs (n = 21), or the placebo group, who were administered with NaCl (n = 21). Randomization was performed using blocks (block size = 4), and subjects were assigned to both groups with randomization software (sealedenvelope.com) by an independent statistician. The trial was prepared by a third party with no responsibility for patient care and data collection. All subjects, investigators, and treating physicians were blinded.