Wnt/β-catenin信号通路在钛颗粒诱导成骨细胞性骨形成减少中的作用及机制

Aseptic loosening, one of the most common complications following total joint arthroplasty, is a kind of complicated disease associated with multi-factors. The condition is characterized by an area of osteolysis found at the bone-prosthesis interface. Periprosthetic osteolysis is initiated by an aseptic inflammatory response to phagocytosis of implant wear particles, resulting in decreased proliferation and differentiation of osteoblast precursors into mature osteoblasts and activated osteoclasts. Progressive osteolysis can lead to loss of fixation, eventually requiring revision surgery. Wnt proteins are a family of 19 secreted glycoproteins that regulate many aspects of cell proliferation, differentiation, function, and death. Wnt signals typically involve the canonical Wnt/β-catenin pathway, the Wnt/Ca2+ pathway, and the Wnt/polarity pathway. Among those, the canonical Wnt/β-catenin pathway, which activates the transcription factors T cell factor and lymphoid enhancer factor through β-catenin activity, appears to be particularly important for bone biology. We have demonstrated that nuclear accumulation of β-catenin immunoreactivity was markedly decreased in Ti particle-induced osteoblast cells, determined by colocalisation with the nuclear stain DAPI. Meanwhile, we also demonstrated that, Dickkopf 1, a special inhibitor of Wnt/β-catenin signaling, is highly expressed in the osteolytic tissue induced by titanium particles. Accordingly, we hypothesize that Wnt/β-catenin signaling pathway was blocked in the area of bone-prosthesis interface during aseptic loosening, subsequently impeded the proliferation and differentiation of osteoblast, and then makes osteolysis seriously. In this study, we decided to investigate the effect of Wnt/β-catenin signaling in the process of osteolysis in a murine calvarial osteolysis model. Furthermore, we also investigate the role of Wnt/β-catenin signaling in osteoblast proliferation and differentiation reduced by wear particles. In this study we performed a detailed analysis of the expression of Wnt/β-catenin signaling components induced by titanium particles in vivo and in vitro, and then determined the effects of Wnt/β-catenin signaling on osteoclast activation during the osteoblast-osteoclast cooperation. The purpose of this study was to clarify the relationship between Wnt/β-catenin signaling and osteoblast bone formation reduced by wear particles in the local area of loosening prosthesis-bone interface, and provide a promising therapeutic target for treating or preventing of aseptic loosening.

假体无菌性松动（AL）是多因素作用的复杂病变，其中松动假体-骨界面处磨损颗粒引起的骨形成减少是其显著特征之一。已知Wnt/β-catenin通路是调控细胞生长、发育和分化的关键通路。课题组预研结果证实：Ti颗粒处理后，β-catenin在成骨细胞（OB）核内分布减少；且Wnt通路抑制因子DKK1在骨溶解局部高表达。据此，本项目提出假说：磨损颗粒通过阻断Wnt通路，抑制OB增殖与分化，导致骨形成减少，加剧AL的发生。为了验证该假说，本项目利用细胞和小鼠颅骨骨溶解模型拟研究：（1）Wnt通路关键因子表达变化及其对骨溶解的影响；（2）Ti对OB Wnt通路和细胞增殖、凋亡和分化的影响及机制；（3）Ti干预Wnt通路调控破骨细胞成熟的机制；（4）激活或抑制Wnt通路对Ti诱导骨溶解的影响及机制。期望通过本项目研究，进一步阐明Wnt通路与磨损颗粒诱导骨形成减少的关系，为AL的防治提供新思路和新靶点。

成骨细胞骨形成能力减弱是磨损颗粒诱导假体周围骨溶解的主要原因，Wnt/β-catenin是调控成骨细胞功能的重要信号通路；因此，磨损颗粒可能通过Wnt/β-catenin信号通路影响成骨细胞的功能，从而引起骨溶解。我们的研究结果发现：磨损颗粒明显活化成骨细胞GSK-3β，抑制Wnt/β-catenin信号通路活性；靶向干预Wnt/GSK-3β/β-catenin信号通路抑制磨损颗粒引起的骨溶解；GSK-3β的小分子抑制剂调控成骨细胞抑制磨损颗粒诱导的破骨细胞活化；GSK-3β的抑制剂通过调控NF-κB信号通路抑制RANKL诱导的破骨细胞活化。上述结果首次表明磨损颗粒依赖GSK-3β/Wnt/β-catenin信号通路，抑制成骨细胞性骨形成，导致假体周围骨溶解，为以GSK-3β/β-catenin为靶点治疗假体无菌性松动提供了理论支持。