PDK1调控破骨细胞在骨质疏松症发病中的分子机制研究

One case of osteoporotic fracture occurs every three seconds worldwide. Osteoclasts play an important role in the pathogenesis of osteoporosis. Our previous study indicated that as the expression of PDK1 gene progressively increased with the differentiation of osteoclasts, and osteoclast differentiation could be inhibited by silenced PDK1 gene. Furthermore, mice model of conditional PDK1 gene knockout in osteoclasts constructed, we found that bone mass increased and osteoclasts decreased simultaneously in PDK1 flox/flox CtsK-cre mice compared with wild-type. Inhibition of PDK1 could down-regulate the phosphorylation of P65 protein and AKT protein. Therefore, we hypothesized that PDK1 regulates osteoclast differentiation and bone metabolism by targeting NF-κB and AKT signaling pathways. We considered applying Ctsk-cre and RANK-cre mediated conditional PDK1 knockout mice. The mechanism of differentiation of osteoclasts regulated by PDK1 was studied from several aspects such as animals, cells and molecular mechanisms, and the effect of silenced PDK1 in the pathogenesis of osteoporosis was studied with the application of small-molecule PDK1 inhibitors. Through the progression of this study, it is expected to provide a new target for the clinical treatment of osteoporosis.

全球每三秒发生一例骨质疏松性骨折。破骨细胞在骨质疏松症发病中发挥重要作用。我们前期研究表明，PDK1随着破骨细胞的分化表达渐进式增加，沉默PDK1可抑制破骨细胞分化，进一步构建破骨细胞内PDK1条件性基因敲除小鼠，发现PDK1 flox/flox Ctsk-cre小鼠较野生型骨量增高、破骨细胞减少，抑制PDK1能下调P65蛋白及AKT蛋白磷酸化表达。因此，我们假说PDK1通过靶向NF-κB及AKT信号通路调控破骨细胞的分化及骨代谢平衡。为此，我们将结合Ctsk-cre和RANK-cre介导的PDK1条件性基因敲除小鼠，从动物、细胞、分子机制等多个层面研究PDK1调控破骨细胞的分化机制，并结合PDK1小分子抑制剂，研究沉默PDK1在骨质疏松症发病中的效应。通过本研究的开展，有望为临床治疗骨质疏松症提供新的靶点。

骨质疏松症是一种以骨量低下、骨微结构破坏，导致骨脆性增加、易发生骨折为特征的系统性、全身性代谢性骨病。骨质疏松症的发生发展与破骨细胞、成骨细胞、骨细胞的功能息息相关。破骨细胞的骨吸收功能和成骨细胞的骨形成功能相互协调，并接受骨细胞的调控，维持人体的骨代谢平衡。本课题组前期研究发现PDK1通过调控Akt/mTOR/NF-κB信号通路在破骨细胞分化及骨代谢中发挥重要功能。为此，我们构建了PDK1flox/floxCtsK-cre和PDK1flox/floxOCN-cre小鼠，分别在破骨细胞和成骨细胞中敲除PDK1基因，从细胞、基因、蛋白质、动物等多层次水平上明确了PDK1对破骨细胞和成骨细胞分化及功能的调控机制。研究结果表明，PDK1基因通过AKT-GSK3β-NFATC1和PI3K/AKT/GSK3β信号通路对破骨细胞和成骨细胞分化及功能起调控作用，说明了PDK1有成为治疗骨质疏松症和病理性骨病的药物靶点的潜力，这为进一步了解骨代谢疾病和治疗骨质疏松疾病提供了研究基础和实验基础。