牙髓细胞(DPCs)具有强大的成牙本质和成骨等定向分化潜能，促进DPCs分化为牙髓牙本质复合体是牙髓生物学中最具有挑战性、且更贴近临床应用的课题。我们在前期研究中采用microRNAs芯片筛选组织矿化液诱导DPCs成牙本质向分化过程中特异表达的microRNAs，发现miR-135b在DPCs成牙本质向分化中显著低表达；应用生物信息学预测发现Smad5/Smad4为miR-135b可能的靶基因，并且miR-135b能下调Smad5/Smad4蛋白和mRNA的表达。Smad5/Smad4为骨形成蛋白(BMPs)/Smads信号通路重要的信号转导分子。因此，本项目拟进一步从细胞和分子水平证实miR-135b靶向调控Smad5/Smad4基因，并探讨这一事件对牙髓细胞成牙本质向分化的重要性和意义。本研究可能发现新的牙髓细胞成牙本质向分化的机制，为牙髓损伤修复的临床转化提供新的思路和方法。

Dental pulp cells (DPCs) have powerful potentiality of odontogenic and osteogenic differentiation. That is an important challenge and clinical application, promoting DPCs to differentiate into dentin pulp complex in pulp biology. In our preliminary study, miRNA microarray was used to examine the overall similarities and differences in miRNA expression profiles between differentiated DPCs and controls. We found miR-135b was markedly downregulated in DPCs of odontoblast differentiation. We predicted that Smad5/Smad4 may be the target genes of miR-135b by bioinformatics. Moreover, miR-135b can down regulate the expression of Smad5/Smad4 protein and mRNA. Significantly, Smad5 and Smad4 are important signal transduction molecules in bone morphogenetic protein (BMPs)/Smads signaling pathway. Therefore, we will confirm that miR-135b targeting Smad5/Smad4 genes in cell and molecular levels on the basis of preliminary research, and explore the importance and significance of this event for DPCs differentiating into odontoblasts. This study may find a new mechanism of odontoblast differentiation of dental pulp cells, which will provide the new ideas and methods for clinical transformation of dental pulp injury repair.