Hypoxia promotes growth of stem cells in dental follicle cell populations.

Adult stem cells (ASC) have been found in many tissues and are of great therapeutic potential due to their capability of differentiation. However, ASC comprise only a small fraction of the tissues. In order to use ASC for therapeutic purposes, it is important to obtain relatively pure stem cells in large quantities. Current methods for stem cell purification are mainly based on marker-dependent cell sorting techniques, which have various technical difficulties. In this study, we have attempted to develop novel conditions to favor the growth of the dental follicle stem cells (DFSC) such that the resultant cell populations are enriched in stem cells. Specifically, a heterogeneous dental follicle cell (H-DFC) population containing stem cells and homogenous non-stem cell dental follicle cell population were cultured at 1% or 5% hypoxic conditions. Only the heterogeneous population could increase proliferation in the hypoxic condition whereas the homogenous DFC did not change their proliferation rate. In addition, when the resultant cells from the heterogonous population were subjected to differentiation, they appeared to have a higher capacity of adipogenesis and osteogenesis as compared to the controls grown in the normal atmosphere (normoxic condition). These hypoxia-treated cells also express higher levels of some stem cell markers. Together, these data suggest that stem cells are enriched by culturing the heterogeneous cell populations in a reduced O(2) condition.