Objectives: Isolate, characterize and assess ABSC undifferentiated status by expression of OCT4 and NANOG; mitogenic potential by cell growth and MTT assay; and osteogenic capability by RUNX2 expression and Alizarin red stain. Hypothesis: Undifferentiated ABSC are present in the surrounding periodontal apparatus and demonstrate capabilities to remain undifferentiated or differentiate into bone-like tissues.
Methods: ABSC were isolated from alveolar bone surrounding extracted third molars. Cells were sorted using STRO-1 antibody. Human bone marrow stem cells (BMSC) were used as controls. Cells were counted at 1-4 days, MTT assay was performed. Cells were induced for 7, 14, 21 and 28 days using osteogenic differentiation media. RNA was isolated at each time point, qRT-PCR was performed for NANOG, OCT4 and RUNX2. Mineralization was confirmed using Alizarin red.
Results: STRO-1+ ABSC accounted for 3.6% of the population, substantiating the presence of undifferentiated cells at the alveolus. Cell growth at 1 and 2 days showed cells doubled in numbers. Compared to AB+ cells, decreased amount of cell numbers were found in AB- and BMSC. Analyses for mitochondrial activity corroborated these findings. Undifferentiated status was confirmed by the presence of OCT4 and NANOG (transcriptional factors related to cell undifferentiation). A 5-fold increase in OCT4 and a 3-fold increase in NANOG confirmed these findings. ABSC showed peak expression of RUNX2 at 14 days, comparable to BMSC. Alizarin red stain demonstrated complete mineralization in all groups.
Conclusions: ABSC are a viable alternative for bone regeneration, available in unlimited amounts with minimally invasive procedures. Compared with BMSC, ABSC have a higher rate of proliferation and comparable differentiation. Therefore, ABSC can be used for regeneration of the craniofacial complex.
Keywords: Bone, Osteoblasts/osteoclasts, Periodontics, Regeneration and Stem cells