Immunomic Screening of Cell Surface Molecules on Undifferentiated Human Dental Pulp Stem Cells

Human adult dental pulp tissue is a source of adult stem cells that have a potential to differentiate into various tissues, although the primary cell suspensions cultured from pulp tissue are mixtures of both stem cell and nonstem cell populations with heterogeneous phenotypes and various differentiation efficiencies. Therefore, cell surface protein markers on dental pulp stem cells are critical for detection and purification of stem cell populations. Yet, little is known about the cell surface molecules that are specifically associated with the undifferentiated and progenitor state of human adult dental pulp stem cells (hDPSCs). Presently, cell surface proteins expressed on hDPSCs were assessed by screening surface molecules specifically expressed on dentinogenic progenitors. Using a decoy immunization strategy, a set of monoclonal antibodies (MAbs) was generated against undifferentiated pulp progenitor cells. Forty-five hybridomas produced MAbs that interacted weakly, if at all, to differentiated pulp cells. Of these, 19 MAbs (18 IgG, 1 IgM) recognized surface molecules on undifferentiated hDPSCs. By multicolor flow cytometric analysis, 40%-60% of newly identified MAb-positive cells were demonstrated to be positive for the CD44 and CD90 mesenchymal markers. When MAb-positive cells were sorted from the heterogeneous pulp cell suspension, mineralization efficiency was increased three to five times compared with MAb-negative cells. The results suggest that the decoy immunization is an efficient method for isolation of MAbs against dentinogenic progenitors. These MAbs will be helpful for identification and enrichment of hDPSCs for efficient dentin regeneration.