Figure 1.

Dental pulp stem cells reside near blood vessels and are endowed with self-renewal. (A) Confocal microscopy of human dental pulp. Green color depicts dental pulp stem cells as indicated by aldehyde dehydrogenase 1 (ALDH1) staining, and red color depicts endothelial cells as indicated by CD31 staining. (B) Frequency distribution of the distance of between ALDH1^high (stem) cells and CD31⁺ blood vessels (n = 173 perivascular niches). (C) Frequency distribution of the distance between Bmi-1^high (self-renewing) cells and CD31⁺ blood vessels (n = 92 perivascular niches). (D) Phase contrast microscopy of secondary orospheres (dental pulp stem cells [DPSCs] or stem cells from human exfoliated deciduous teeth [SHED]) cultured in ultralow-attachment conditions with either Dulbecco’s modified Eagle medium/Nutrient Mixture F-12 (DMEM/F12) or Sphere Media (SM; DMEM/F12 supplemented with 10 ng/mL epidermal growth factor [EGF], 10 ng/mL basic fibroblast growth factor [bFGF], 2% fetal bovine serum [FBS]) for 7 d. (E) Graph depicting the number of secondary orospheres generated by DPSCs or SHED cultured with DMEM/F12 or SM in ultralow-attachment plates (10⁵ cells/well) after 7 d. (F) Western blots for Bmi-1 expression in DPSCs or SHED cultured in DMEM/F12 (standard culture conditions), SM (standard culture conditions), or SM (ultralow-attachment conditions) for 7 d. Bmi-1 band density was normalized to respective GAPDH lanes. (G) Phase contrast microscopy of DPSC secondary orospheres cultured in SM or SM containing 10 µM PTC-209 (Bmi-1 inhibitor). (H) Graph depicting the number of secondary orospheres generated by DPSCs or SHED cultured in SM containing 0, 0.1, 1, or 10 µM PTC-209 for 7 d. *P < 0.05.