TIF1γ在BMP-2诱导牙髓细胞分化中的作用及机制

Bone morphogenetic protein can induce the ondontoblastic differentiation of dental pulp cells through the Smads pathway. Most researchers considered that Smad4 played a central role in TGF-β/BMP-Smads pathways as a essential partner of all RSmads and a mediator of many TGF-β/BMP effects. Nevertheless, latest research finds that TIF1γ is involved in the processes of controlling cells differentiation through selectively binding receptor-phosphorylated RSmads in competition with Smad4 in the TGF-β-Smads pathway. Previous study from our Research Group found that Smad1/5 combined with Smad4 to mediate the BMP-Smads signal transduction and promote the odontoblastic differentiation of human dental pulp cells, but whether TIF1γ is involved in controlling dental pulp cells differentiation is still unclear.Our Research Group in the preliminary experiment observes that dental pulp cell expresses TIF1γ, and the expression of TIF1γ will increase after pulp cell is stimulated by BMP-2,and TIF1γ can combine with Smad1. Then our Research Group infers that TIF1γ is involved in controling the process of BMP-2 inducing the differentiation of dental pulp cells. Through controlling TIF1γ expression and observing their effects in dental pulp cell differentiation, the research aims to specify the role of TIF1γ in BMP-2 inducing dental pulp cell differentiation. The research further explores what signal molecule along with TIF1γ mediates BMP-2 signal transduction, clarifies the potential mechanism of TIF1γ in BMP-Smads signal transduction and thus provides theoretical basis for indepth research on the reparative response mechanism of dental pulp cells.

BMP可通过Smads通路诱导牙髓细胞分化。Smad4被认为是TGF-β/BMP-Smads通路中唯一能与R-Smads结合的信号分子，新近研究发现TGF-β-Smads通路中 TIF1γ能与Smad4竞争结合上游R-Smads，调控细胞分化。课题组前期研究表明Smad1/5可与Smad4结合介导BMP-Smads信号传递促进牙髓细胞分化，但TIF1γ是否在此通路中参与调控牙髓细胞分化尚未清楚。本课题组预实验发现：BMP-2刺激后牙髓细胞中TIF1γ表达升高；TIF1γ低表达可下调牙髓细胞成牙本质向分化标记物，推测TIF1γ参与调控BMP-2诱导牙髓细胞分化。本研究拟通过构建分子载体、细胞转染、免疫共沉淀等技术，明确TIF1γ在BMP-2诱导牙髓细胞分化中的作用；阐明TIF1γ与Smad1/5作用机理；探讨TIF1γ在BMP-Smads通路中的分子机制，为研究牙髓修复反应调控机制提供新思路

TGF-β/BMP-Smads通路可调控间充质细胞的分化。Smad4被认为是TGF-β/BMP-Smads通路中唯一能与R-Smads结合的信号分子，新近研究发现TGF-β-Smads通路中 TIF1γ能与Smad4竞争结合上游R-Smads，调控细胞分化。课题组前期研究表明Smad1/5可与Smad4结合介导BMP-Smads信号传递促进牙髓细胞分化，但TIF1γ是否在此通路中参与调控成骨细胞分化尚未清楚。据此，本研究详尽阐明了TIF 1γ在成骨细胞增殖及成骨向分化中的重要作用及机制。本研究利用小鼠间充质干细胞系C3H10T1/2和成骨前体细胞系MC3T3-E1，首先通过检测碱性磷酸酶（ALP）的mRNA表达水平、成骨特异性转录因子（Runx2）和骨钙素（OCN）的蛋白水平，阐明了TIF 1γ可调控成骨细胞的分化。其次，本研究对TIF 1γ调控成骨向分化的机制进行了进一步的探索，研究发现TIF 1γ可通过结合Smad1/5，并调控促使Smad1/5磷酸化的基因，来调节pSmad1/5的表达水平，从而调控成骨向分化。最后，该课题研究了TIF 1γ对成骨细胞增殖的影响，发现了敲低TIF 1γ可抑制成骨细胞向S-G2-M期发展，从而明显抑制成骨细胞的生长。综上，本研究结果系统阐述了TIF 1γ在成骨细胞成骨向分化及增殖中的重要作用，并阐明了TIF 1γ可通过TGF-β/BMP通路调控成骨向分化；同时通过调控细胞周期来影响成骨细胞的增殖。这为深入研究骨组织的损伤修复提供了新的理论依据，并为其治疗提供了新的靶点。