Fetuin-A介导异位骨化及其相关骨质流失的机制研究

异位骨化（HO）是指正常骨骼系统外的骨形成。然而，HO与骨结构功能障碍之间的联系尚不清楚。申请人近期研究表明损伤诱导的HO模型小鼠与HO病人皆出现骨流失。RNA-seq和免疫荧光染色结果提示胎球蛋白Fetuin-A (FetA) 在HO早期的巨噬细胞中富集，但在正常骨中表达显著减少，且与免疫抑制相关基因被同时富集。免疫检查点蛋白决定免疫抑制并调控破骨细胞增殖。因此提出假设FetA通过调控免疫检查点蛋白失衡，从而介导巨噬、破骨细胞功能异常，最终促进HO及其相关骨流失的形成。为了验证该假设，本课题将在HO小鼠模型、巨噬细胞和破骨细胞模型中，利用化学干预以及基因操纵技术来探究免疫检查点蛋白在巨噬细胞极化和破骨细胞活化中的作用及分子机制；研究FetA调控免疫检查点蛋白的机制；探究异常极化的巨噬细胞来源关键细胞因子促进HO的机制。该研究为HO形成中的骨免疫相互作用提供新的见解，为HO治疗提供新思路。

Heterotopic ossification (HO) is the abnormal formation of bone in extraskeletal sites. However, the mechanisms linking HO pathogenesis with bone structure dysfunction remain unclear. Our recent data have shown that mice harboring injury-induced HO exhibit bone loss similar to the presentation in HO patients. RNA-seq and immunofluorescence staining revealed Fetuin-A (FetA), as an inhibitor of calcification, was detected frequently in macrophages of HO lesion, but rarely in HO-adjacent normal bone. RNA-seq analysis reveals that FetA and immunosuppressive genes are simultaneously enriched in the early stage of HO. Inhibitory immune checkpoint proteins (ICP) determine immunosuppression and promote HO formation. Co-stimulatory ICP promotes osteoclast activation. Therefore, we speculate that FetA promotes HO and associated bone loss by dysregulating ICP in immune cells. To test this hypothesis, we will first identify the role and molecular mechanism of ICP driving abnormal function of macrophages and osteoclasts using chemical intervention and gene manipulation techniques in HO mouse model and primary macrophages and osteoclasts. Next, we will investigate the detailed molecular mechanism of FetA in ICP regulation and test the potential of identified targets in HO treatment. Finally, we will explore the mechanism that altered macrophages polarization promotes osteogenic differentiation of MSCs. Collectively, our findings provide new insights into the osteoimmunological interactions during HO formation and suggest FetA as a potential therapeutic target for the treatment of HO.