The presence of heterogeneous cell populations in dental pulp may count for the considerable variation in the outcome of in vitro and in vivo experiments. Here, we intended to determine whether a minor cell sub-population of high proliferation and odontogenic potential existed among a larger compartment of perhaps more committed progenitors. In this study, the STRO-1 antigen, defining a mesenchymal stem cell or progenitor subpopulation, was used for separating rat dental pulp cells with fluorescence-activated cell sorting (FACS). Subsequently, the STRO-1 positive cells were tested for their ability to differentiate towards an odontoblast-like phenotype. Three cell populations (STRO-1 positive, STRO-1 negative, and non-sorted cells) were cultured in odontogenic medium containing dexamethasone and beta-glycerophosphate. Cultures were analyzed by light- and scanning electron microscopy (SEM), and assessed for proliferation, ALP activity, and calcium content. Results showed that the STRO-1 positive cell population was able to differentiate into the odontoblast phenotype, similar to the non-sorted population. The negative cells however showed a fibroblast-like phenotype. SEM and real-time PCR confirmed such results. In conclusion, the STRO-1 selection proved applicable for rat-derived material, to obtain a cell population which is more homogeneous. This positive cell fraction was capable of differentiating into the odontogenic pathway, whereas the negative fraction was not. However, the effect was not always advantageous, when compared to non-sorted cells. 2007 John Wiley & Sons, Ltd
