206 GENERATION OF HUMAN INDUCED PLURIPOTENT STEM CELLS FROM DENTAL PULP-DERIVED MESENCHYMAL STEM CELLS

Abstract

Induced pluripotent stem (iPS) cells are somatic cells that have been reprogrammed to a pluripotent state and a great source for regenerative medicine. Several types of human somatic and adult stem cells have been reprogrammed into iPS cells, including mesenchymal stem cells (MSC). Recently, human dental pulp has been considered as a valuable alternative source of MSC (hDP-MSC) with excellent proliferation capacity and multilineage differentiation potential. In this study, our objective was to establish iPS cells from hDP-MSC and evaluate the expression of transcriptional factors and in vitro differentiation potential into mesenchymal lineages. The hMSC were isolated from the dental pulp of male donor (∼18 years old) were cultured in advanced-DMEM supplemented with 10% fetal bovine serum at 37°C, 5% CO₂ in a humidified atmosphere. The hDP-MSC at passage 3 were analysed for the expression of MSC-specific surface markers (CD44 and CD90) using flow cytometry and transcriptional factors (Oct4, Nanog and Sox2) by immunofluorescence staining and reverse transcription-polymerase chain reaction (RT-PCR). Differentiation into adipocytes and osteocytes of hDP-MSC was carried out under specific conditions for 2 and 4 weeks, respectively and assessed by cytochemical staining (Oil red O, von Kossa and Alizarin Red S, respectively). iPS cells were generated from hDP-MSC at passage 3 by using pMXs retroviral vector (Addgene, Cambridge, MA, USA) containing cDNA of c-Myc, Klf4, Nanog and Sox2. The iPS cells were evaluated for alkaline phosphatase (AP) activity, expression of human embryonic stem cells (hESC) markers (Rex1, Nanog, Oct4, SSEA-1 and TRA-160) by immunostaining. Isolated hDP-MSC expressed surface markers, such as CD44 and CD90 (86% and 93%, respectively) by flow cytometry and positively stained for transcriptional factors (Oct4, Nanog and Sox2) by immunofluorescence. Further, the cells were capable of differentiating in vitro into adipocytes and osteocytes as demonstrated by Oil red O and von Kossa and Alizarin red S staining, respectively. The iPS cells generated from hDP-MSC were positive for AP staining and clearly expressed the markers specific to hESC, including Rex1, Nanog, Oct4, SSEA-1 and TRA-160. In conclusion, hMSC derived from dental pulp could be successfully reprogrammed into iPS cells by retroviral vector systems and the generated iPS cells shared the similar characteristics of hESC. Therefore, hDP-MSC might be an ideal alternative cell source to derive autologous iPS cells for therapeutic applications.

This work was supported by Grant No. 2007031034040 from Bio-organ and Grant No. 200908FHT010204005 from Biogreen21.