骨关节炎软骨损伤难以修复是因为缺乏对软骨细胞生物学特性及分化机理的深入研究。我们前期研究发现Notch受体激活可使细胞周期抑制基因p57高表达，软骨细胞分裂停滞而分化成熟，且Runxl在软骨成熟中表达降低。文献报道Runx1对维持细胞增殖成熟及细胞周期调控发挥重要作用；其中Ser48、Ser303、Ser424丝氨酸残基磷酸化可导致Runx1功能丧失。目前尚无Notch-Runx1信号轴及Runx1 S48/S303/S424靶点在软骨分化成熟中的研究报道。据此我们合理假设：Notch受体激活后以Ser48、Ser303、Ser424为靶点抑制下游Runx1表达使软骨细胞分裂停滞而分化成熟。本课题拟从软骨细胞增殖与分化平衡这个新视点及从分子、细胞、组织和动物水平等多层次明确Notch-Runx1信号轴在软骨成熟中的作用及机制；为软骨损伤修复及软骨组织工程构建提供新的理论和新的靶点。

The reason why it is difficult to repair cartilage injury in osteoarthritis is due to the lack of chondrocyte biological characteristics and in-depth study of differentiation mechanism. Previously We found that Notch intracellular segment, NICD, can increase the expression of cell cycle inhibitive gene p57, leading to chondrocyte maturation instead of proliferation. Moreover, we also found that the expressive level of Runxl in cartilage maturation decreased. According to literatures, Runx1 plays an important role in maintaining cell proliferation and cell cycle regulation by promoting cells transition from G1 phase to S phase. The phosphorylation of Ser48, Ser303 and Ser424 serines can lead to disfunction of Runx1. Nevertheless, there are no relative reports about Notch-Runx1 signal axis and regulatory target of Runx1 S48 / S303 / S424 in cartilage differentiation and maturation so far. Therefore, it is reasonable to assume that by targetting Ser48, Ser303 and Ser424 of Runx1, activing Notch receptor could inhibit the expression of its potential downstream gene Runx1 to stagnate division and promote maturation of chondrocytes. This study was expected to clarify the role of Notch-Runx1 signal axis in cartilage maturation from molecular, cellular, tissue and animal levels simultaneously, and to explore the specific target of Runx1 expressive regulation as well, revealing that Notch regulate cartilage maturation by phosphorylational modifing of Runx1 in Ser48, Ser303, Ser424. This study will explore the biomolecular mechanism from a new perspective of the balance between proliferation and differentiation of chondrocytes, contributing to providing a new theory and target for researches about repire of osteoarthritis and cartilage injury, and cartilage tissue engineering.