Differentiation of BMMSCs into odontoblast-like cells induced by natural dentine matrix

OBJECTIVE: To assess the odontogenic potential of bone marrow mesenchymal stem cells (BMMSCs) to differentiate into odontoblast-like cells under the morphogenetic influence of dentine matrix as a possible basis for new stem cell-mediated therapeutic approaches to pulp diseases. DESIGN: BMMSCs were harvested from the whole bone marrow and cells at passages 3-5 were used for subsequent experiments. For in vitro studies, 1×10(4) cells were seeded on the surface of dentine slabs and co-cultured for 2 weeks in 24-well plates, then fixed, decalcified, embedded in paraffin and serial sections were processed for analyses. Haematoxylin-eosin (HE) staining was used for the morphological analysis of BMMSCs on the dentine slabs. The protein expression of dentine sialoprotein (DSP) in co-cultured BMMSCs was detected by immunohistochemical (IHC) staining. For in vivo studies, 5×10(6) cells were collected as cell pellets, seeded onto dentine slices and transplanted into renal capsules for 6 weeks. Histological analyses of harvested tissues were performed as described for the in vitro studies. Total RNA and protein were extracted from harvested tissues and Dspp/DSP expression was investigated by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively. RESULTS: After 2 weeks of co-culture with dentine slabs, BMMSCs demonstrated good viability in terms of morphological appearance and some showed polarization and extension of their cytoplasmic processes into dentine tubules with DSP expression. In vivo study demonstrated similar morphological changes and DSP expression in cells adjacent to dentine. RT-PCR and Western blot also demonstrated that the expression of Dspp/DSP in the co-cultured BMMSCs groups was higher than in the control groups. CONCLUSION: Dentine matrix can signal morphogenic induction of differentiation of BMMSCs into odontoblast-like cells in vivo and in vitro.