Notch1信号通路介导的短链NELL-1诱导人牙囊干细胞成骨作用的研究

Dental follicle stem cell (DFSC), one kind of ectomesenchymal stem cells, has gained increasing attention in periodontal tissue engineering research. However, the wide biomedical application of DFSC for research has several limitations, including difficult large-scale reproduction in vitro and unclear mechanism of multi-differentiation capacities. The recent findings indicated that one kind of short isoform NELL-1 can effectively stimulate proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSC). In addition, short isoform NELL-1 can upregulate the expression of HEY1 in BMMSC. The recent studies also showed short isoform NELL-1 significantly increased the activity of alkaline phosphatase in human dental follicle stem cells (HDFSC) and Notch1 signaling was involved in regulation of HDFSC proliferation and differentiation. Based on these evidences, it has been proposed that short isoform NELL-1 can induce the proliferation and osteogenic differentiation of HDFSC through Notch1 signaling pathway. To confirm this hypothesis, the present study will first examine the role of short isoform NELL-1 in stimulating HDFSC proliferation and osteogenic differentiation in vivo and in vitro. Then, the effect of Notch1 signaling pathway inhibition on short isoform NELL-1-induced HDFSC proliferation and osteogenic differentiation is analyzed. Finally, the mechanism of Notch1 signaling involved in short isoform NELL-1-induced osteogenesis is investigated. The outcomes of this study are important for extending the utility of short isoform NELL-1 in bone regeneration and DFSC in periodontal tissue engineering research.

牙囊干细胞（DFSC）是一种外胚间充质干细胞，在牙周组织工程研究中受到广泛关注，但DFSC体外扩增困难及分化机制不明确限制了其在牙周组织工程研究中的应用。近期发现短链NELL-1能有效诱导骨髓间充质干细胞增殖及成骨分化，且能上调HEY1基因表达；短链NELL-1能显著增加人牙囊干细胞（HDFSC）碱性磷酸酶活性；Notch1信号通路参与HDFSC增殖、分化的调控。据此，我们推断短链NELL-1能通过Notch1信号通路诱导DFSC增殖与成骨分化。为验证假说，本项目拟首先从体内体外两方面研究短链NELL-1在HDFSC增殖、成骨分化中的作用，然后分析Notch1信号通路抑制对短链NELL-1诱导HDFSC增殖、成骨分化的影响，最后探讨Notch1信号通路介导短链NELL-1诱导成骨作用的机制。本研究对推动短链NELL-1在骨再生方面的应用及DFSC在牙周组织工程研究中的应用均具有重要意义。

牙囊干细胞（DFSC）是一种外胚间充质干细胞，在牙周组织工程研究中受到广泛关注，但DFSC体外扩增困难及多向分化机制不明确限制了其在牙周组织工程研究中的应用。研究发现NELL-1是一种具有较强成骨活性的生长因子，在治疗各类骨组织缺损与骨再生方面具有广阔而良好的应用前景。但以往有关NELL-1成骨作用的研究多集中于全长NELL-1，对短链NELL-1的成骨作用鲜见报道。. 本研究以全长NELL-1、BMP2为对照，采用细胞外干预及细胞内过表达两种方式，通过一系列体内体外实验证明短链NELL-1能有效促进DFSC增殖及成骨分化。短链NELL-1促进成骨作用虽然弱于BMP2，但强于全长NELL-1。研究同时发现，BMP2促进DFSC成脂的能力明显强于短链NELL-1和全长NELL-1。这表明短链NELL-1比全长NELL-1具有更高效的骨诱导作用，短链NELL-1骨诱导活性较BMP2更具有特异性。. 在此基础上，本研究通过一系列体内体外实验发现Notch1信号抑制后，短链NELL-1促进DFSC增殖及成骨分化的作用被削弱。本研究进一步发现，短链NELL-1能与Notch1受体结合，促进ICN1转运进入细胞核并与DNA结合蛋白CSL结合，并上调Notch1信号通路下游靶基因HES1、HEY1转录水平。这表明Notch1信号通路介导短链NELL-1诱导成骨作用。. 本研究首次从组织、细胞、分子水平深层次地解析短链NELL-1在DFSC增殖、成骨分化中的作用及机制，研究结果对推动短链NELL-1在骨再生方面的应用及DFSC在牙周组织工程研究中的应用均具有重要意义。