Isolation and Characterization of SCAP

Isolation and culture of SCAP were according to the previous study [1 (link)]. SCAP were isolated from the apical papilla tissue of the developing tooth root apex of extracted human impacted lower third molars of healthy donors as described in Additional file 2: Supplementary Methods. Attached colony-forming cells on plastic culture flasks were expanded. The growth medium consisted of 15% fetal bovine serum (FBS; Equitech-Bio, Kerrville, TX), 100 μM l-ascorbic acid 2-phosphate (Wako Pure Chemicals, Osaka, Japan), 2 mM l-glutamine (Nacalai Tesque, Kyoto, Japan), and premixed antibiotics containing 100 U/ml penicillin and 100 μg/ml streptomycin (Nacalai Tesque) in minimum essential medium Eagle alpha modification (αMEM; Thermo Fisher Scientific, Waltham, MA). The passage 3 (P3) cells were analyzed for determining the characterization as MSCs and SCAP according to previous reports [1 (link), 24 (link)] and were used for further experiments.