A dual MMP9/MMP14 Axis Regulates Osteoclast Bone Resorptive Function

双MMP9/MMP14轴对破骨细胞骨吸收功能的调节 摘要 破骨细胞(OC)活性过高可导致多种骨骼疾病，包括骨质疏松症 类风湿性关节炎到肿瘤引起的骨溶解。尽管开发了几种抗吸收药物 在治疗方面，它们的姑息作用往往是有限的，或者伴随着不想要的副作用。在这方面， 组织蛋白酶K作为胶原酶的关键作用已成为治疗干预的靶点。 降解I型胶原，这是骨细胞外基质的主要蛋白质成分。有趣的是， 然而，OCs也表达基质金属蛋白酶，其在OC骨吸收活动中的作用仍然存在。 很大程度上是不确定的。在这里，我们使用无偏转录组筛选以及体外实验来鉴定 MMP9和MMP14是OCS表达的两种主要的MMPs。但是，在生成Mmp9-/-或 髓系特异性CSF1R-Cre/Mmp14f/f OCS，初步研究表明这两种蛋白水解酶在 骨吸收。出乎意料的是，我们发现CSF1R-CRE/Mmp14f/f/Mmp9-/-双敲出式OCS显示主要 体内和体外的骨吸收缺陷。在努力定义联合的 OC功能对MMP9和MMP14的要求--野生型与双基因敲除OC的初步分析 基因表达发现碳水化合物代谢、锌指结合和 线粒体。这些发现使我们假设并证实，MMP9和MMP14共同发挥着关键作用 在调控锌指转录抑制因子ZEB1调节OC激活的代谢途径中的作用 与MMPs介导骨胶原溶解作用的能力相结合。因此，我们建议i)表征 MMP9/MMP14在体内外调控破骨细胞功能和骨吸收中的协同作用 利用髓系和OC特异性条件性基因敲除小鼠，II)鉴定新的MMP9/MMP14-ZEB1轴 在调节体外和体内的能量代谢和破骨细胞活性方面，以及iii)确定了 MMP9/MMP14协同依赖的ZEB1上游Galectin-3膜晶格的蛋白降解 骨I型胶原溶解在调节破骨细胞骨吸收功能中的作用。独特的蛋白质分解和代谢 这一建议中概述的信号通路应该为OC介导的骨重建提供新的见解，并且 推进改进治疗策略的研究，旨在防止病理性骨丢失。

A dual MMP9/MMP14 Axis Regulates Osteoclast Bone Resorptive Function Abstract Excessive osteoclast (OC) activity is responsible for a wide range of bone diseases, ranging from osteoporosis and rheumatoid arthritis to tumor-induced osteolysis. Despite the development of several anti-resorptive therapeutics, their palliative effects are often limited or accompanied by unwanted side effects. In this regard, cathepsin K has been targeted for therapeutic intervention given its key role as a collagenolytic enzyme capable of degrading type I collagen, the dominant protein component of the bone extracellular matrix. Interestingly, however, OCs also express matrix metalloproteinases whose function in OC bone-resorptive activity remains largely undefined. Herein, we utilized unbiased transcriptome screening as wells as ex vivo assays to identify MMP9 and MMP14 as the two dominant MMPs expressed by OCs. However, after generating Mmp9-/- or myeloid-specific Csf1r-Cre/Mmp14f/f OCs, preliminary studies suggest that neither proteinase plays a key role in bone resorption. Unexpectedly, we find that Csf1r-Cre/Mmp14f/f/Mmp9-/- double knockout OCs display major defects in bone resorption in vitro and in vivo. In an effort to define the mechanisms underlying a combined requirement for MMP9 and MMP14 in OC function, preliminary analysis of wild-type versus double knockout OC gene expression identified unexpected alterations in carbohydrate metabolism, zinc finger binding and mitochondrion. These findings led us to posit and confirm that working together, MMP9 and MMP14 play a critical role in regulating a zinc finger transcription repressor Zeb1-arbitrated metabolic pathway to govern OC activation in tandem with the ability of the MMPs to mediate bone collagenolytic effects. Thus, we propose to i) characterize the cooperative role of MMP9/MMP14 in controlling osteoclast function and bone resorption in vitro and in vivo, utilizing both myeloid- and OC-specific conditional knockout mice, ii) identify a novel MMP9/MMP14-Zeb1 axis in regulating energy metabolism and osteoclast activity in vitro and in vivo, and iii) Define the dual roles of the MMP9/MMP14 co-dependent proteolysis of galectin-3 membrane lattice as upstream of Zeb1, in parallel with bone type I collagenolysis in regulating osteoclast bone-resorptive function. The unique proteolytic and metabolic signaling route outlined in this proposal should provide new insights into OC-mediated bone remodeling, and advance the search for improved therapeutic strategies designed to prevent pathologic bone loss.