PBXIP1调控β-catenin蛋白表达在儿童骺板损伤修复过程中的作用及其机制研究

Bone bridges during the repair of growth plate injury could destroy normal growth function of limbs in children. Our previous study showed that knockout of PBXIP1 could reduce the expression of β-catenin protein and bone bridges and improve the deformity of limbs. However, the action mechanisms were not clear. We hypothesis that PBXIP1 could reduce the β-catenin protein to control the formation of bone bridges during the growth plate injury. In order to confirm the scientific hypothesis, we will explore the correlation and zone of action between the PBXIP1 and β-catenin protein during the formation of bone bridges in mice with knockout of PBXIP1 of growth plate injury. Then, we will explore molecular mechanism and regulatory signaling network in PBXIP1 in regulating β-catenin protein and Wnt signaling pathway. At last, we expect the biological function and molecular mechanism of PBXIP1 in regulating β-catenin protein in repair of growth plate injury and the formation of bone bridges. The achievements in scientific research could provide the new thinking and theory evidence in explore regulating PBXIP1 in the repair of growth plate injury and the formation of bone bridges, and the new orientation of screen the treatment target in clinical in order to control the formation of bone bridges.

儿童骺板损伤修复过程中出现异常骨桥组织，将严重影响患儿肢体正常生长功能。课题组前期研究在PBXIP1基因敲除小鼠模型中发现：骺板损伤处β-catenin蛋白表达水平明显下调，骨桥组织减少而且肢体畸形得到改善，但其具体机制并不清楚。我们推测“PBXIP1有可能通过降低β-catenin蛋白表达，抑制骺板损伤处骨桥组织的形成”。为证实上述科学假设，本课题组拟在PBXIP1基因敲除小鼠骺板损伤模型中，首先探讨PBXIP1与β-catenin蛋白在骨桥形成中相互关系及作用区域；随后重点探讨PBXIP1调控β-catenin及Wnt信号通路表达的分子机制以及涉及的调控信号网路；最终，阐明PBXIP1调控β-catenin蛋白参与骺板损伤后骨桥形成的生物学功能及作用机制。相关研究成果将为研究骺板损伤修复、骨桥形成的分子生物学机制提供新的思路和理论依据，同时为临床治疗靶点筛选，抑制骨桥形成提供新的方向。

儿童骺板损伤修复过程中出现异常骨桥组织，将严重影响患儿肢体正常生长功能。研究骺板损伤后分子机制及信号调控网络，对于修复骺板损伤、抑制骨桥形成具有重要意义。课题组首先发现PBXIP1和β-catenin蛋白在骺板损伤后均呈现明显高表现状态，体内实验显示PBXIP1在骺板损伤后上调β-catenin蛋白表达，而且，基因敲除小鼠骺板损伤模型中，IL-1β，PDGF-B，IGF-1，FGF-2，TGF-β1，TNF-α，PKD及VEGFR1表达均下调；其次，内源性PBXIP1与β-catenin蛋白在骺板细胞中相互作用，抑制PBXIP1表达能够明显下调β-catenin的蛋白水平，而且Wnt/β-catenin信号通路下游基因Survivin和CyclinD1的表达水平明显低于对照组（P<0.001）；PBXIP1通过泛素-蛋白酶体途径改变β-catenin蛋白水平，同时调控β-catenin结合的转录因子Axin、APC、GSK3 和CK1α发挥生物学功能；最后，PBXIP1基因敲除小鼠骺板骺板损伤模型中，术后第4周出现轻度成角畸形程度，随着时间延长，肢体成角畸形程度逐渐增加，但其畸形程度均明显小于野生组（P<0.001）；组织学显示实验组中可见类似软骨细胞外基质样结构，甲苯胺蓝及Ⅱ型胶原免疫组织化学染色呈阳性。直到术后第16周，实验组仍残留的骺板软骨样结构；而野生组在术后第4周可见大量骨小梁及纤维组织浸润，第12周时骺板组织趋于闭合。课题组首次通过PBXIP1调控β-catenin蛋白表达修复骺板损伤，为抑制骨桥形成、减少肢体畸形提供新的思路和方向。