Alveolar Bone Stem Cells: An Isolation, Characterization, and Differentiation Approach

Alveolar bone plays an important role in dental support and periodontal health.  We isolated and characterized alveolar bone stem cells (ABSC), which represent an ideal resource for therapy.

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.