To investigate the role of miRNA-633 in targeting the regulation of bone morphogenetic protein (BMP) and Smad protein pathways in promoting the proliferation and differentiation of dental pulp stem cells into dentin.

Human dental pulp stem cells were randomly divided into control, ov-miRNA-633, NC, anti-miRNA-633 and cotransfection groups. The ov-miRNA-633 and control groups were transfected with miRNA-633 overexpression vector and corresponding control blank vector, respectively. The anti-miRNA-633 and NC groups were transfected with miRNA-633 knockout vector and corresponding control blank vector, respectively. The cotransfection group was transfected with miRNA-633 overexpression vector + shRNA-N-Cadherin. Cell proliferation was detected by CCK-8 method. The expression levels of N-Cadherin were detected by real-time polymerase chain reaction. The expression levels of phosphorylated Smad 1/5/8 (p-Smad 1/5/8) were detected by Western blotting.

The optical density values on the 7^th day of the control, ov-miRNA-633, NC, anti-miRNA-633 and cotransfection groups were 1.65±0.05, 1.79±0.08, 1.55±0.05, 1.19±0.08 and 1.76±0.07; the relative expression levels of N-Cadherin mRNA were 1.09±0.03, 0.63±0.03, 1.06±0.04, 1.31±0.09 and 0.46±0.06; the relative expression levels of p-Smad 1/5/8 protein were 0.79±0.05, 1.28±0.08, 0.80±0.09, 0.62±0.06 and 1.09±0.18, respectively. The differences of above indexes were statistically significant between the ov miRNA-633 group and the control group (P<0.05, P<0.01). And the differences of above indexes were statistically significant between the cotransfection group and the anti miRNA-633 group (all P<0.05).

miRNA-633 could promote the proliferation and differentiation of dental pulp stem cells into dentin by inhibiting N-cadherin expression, activating the BMPs/Smad pathway.