Dental pulp tissue contains dental pulp stem cells (DPSCs). Dental pulp cells (also known as dental pulp-derived mesenchymal stem cells) are capable of differentiating into multilineage cells including neuron-like cells. The aim of this study was to examine the capability of DPSCs to differentiate into neuron-like cells without using any reagents or growth factors. DPSCs were isolated from teeth extracted from 6- to 8-week-old mice and maintained in complete medium. The cells from the fourth passage were induced to differentiate by culturing in medium without serum or growth factors. RT-PCR molecular analysis showed characteristics of Cd146+, Cd166+, and Cd31？ in DPSCs, indicating that these cells are mesenchymal stem cells rather than hematopoietic stem cells. After 5 days of neuronal differentiation, the cells showed neuron-like morphological changes and expressed MAP2 protein. The activation of Nestin was observed at low level prior to differentiation and increased after 5 days of culture in differentiation medium, whereas Tub3 was activated only after 5 days of neuronal differentiation. The proliferation of the differentiated cells decreased in comparison to that of the control cells. Dental pulp stem cells are induced to differentiate into neuron-like cells when cultured in serum- and growth factor-free medium. 1. Introduction Dental pulp tissue contains many types of cells including committed cells (e.g., endothelial cells) and uncommitted cells (i.e., DPSCs). DPSCs are of mesenchymal stem cells (MSCs) [1]. In mice, the majority of MSCs were isolated from bone marrow [2] and peripheral blood [3, 4]. These MSCs can be characterized by the expression of specific gene markers such as CD44, CD73, CD90, CD105, CD117, and CD166 [5, 6]. DPSCs are capable of differentiating into multilineage cells [7–9] including neuron-like cells [10]. Neuron-like cells differentiated from MSCs derived from bone marrow cells [11–13] and brain [14]. However, MSCs derived from dental pulp, that is, DPSCs, are also capable of differentiating into neuron-like cells [10]. The characteristics of MSCs from bone marrow are similar to those cells derived from dental pulp [11]. Both types of MSCs express Cd44, Cd106, Cd146, and Cd166 [15–17]. Many factors are involved in neuronal differentiation including nestin [18], tubulin3 (Tub3) [19], and MAP2 [20]. Nestin is involved in the radial growth of axons during neuronal differentiation in vertebrate cells [19, 21]. Therefore, Nestin is known as a neural marker and its presence can be considered as a criterion for the ability to
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