ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effects of specific RNA interference (RNAi) to Notch ligand Delta1 on proliferation and differentiation of human dental pulp stem cells (DPSC).</p><p><b>METHODS</b>DPSC were infected by lentivirus vectors carrying Delta1-RNAi. DPSC were divided into three groups, DPSC/Delta1-RNAi group, DPSC/wt group and DPSC/vector group as control. Cell counting kit-8 (CCK-8) assay and flow cytometry were used to evaluate the proliferation of DPSC. Expression of proliferating cell nuclear antigen (PCNA) was examined with immunohistochemical staining. All groups were cultured in an odonto-inductive medium and were observed under microscope. The number of mineralization nodules was counted after Alizarin red staining. Alkaline phosphatase (ALP) activity and the expression of dentin sialophosphoprotein (DSPP) were detected by ALP activity assay and Western blotting.</p><p><b>RESULTS</b>Compared with DPSC/wt or DPSC/vector separately, proliferating rate and S-cycle of DPSC/Delta1-RNAi was significantly lower. The S phase and proliferation index (PI) decreased markedly from 22.32 ± 2.35 and 33.68 ± 4.19 (DPSC/Delta1-RNAi) to 5.44 ± 0.91 and 16.00 ± 6.07 (DPSC/wt). The PCNA staining of DPSC/Delta1-RNAi was evidently weaker. DPSC/Delta1-RNAi group had more calcified cell nodules than the other two control groups, and ALP activity and DSPP expression of DPSC/Delta1-RNAi group increased markedly.</p><p><b>CONCLUSIONS</b>Delta1-RNAi induced by the lentivirus vectors may inhibit DPSC proliferation and differentiation. Notch-Delta signal pathway plays an important role in self-renewal and differentiation.</p>