铁调控MATN3影响绝经后女性骨形成的分子机制研究

Recent studies have suggested that the pathogenesis of postmenopausal osteoporosis is closely related to iron accumulation in bone tissue. Our previous study revealed that iron intervention could inhibit the mineralization of osteoblasts and the formation of bone trabeculae while causing bone iron accumulation in mice. Based on proteomics of human bone tissue, our team had screened out the extracellular matrix Matrilin-3 (MATN3), which is associated with both bone mineral density and bone iron content. Our preliminary results showed that MATN3 was expressed in osteoblast, and iron treatment not only increased ROS levels, but also enhanced MATN3 expression. Therefore, we constructed osteoblastic-specific Matn3 conditional knock-out mouse model, in which bone formation was enhanced and bone trabeculae were increased. In this project, we intend to use the above-mentioned mouse model, at animal, cell and molecular levels, to clarify the regulation of iron on Matn3 and the resulting changes in bone formation and bone mass, as well as the role of ROS in this process. It is expected to provide a new target for the prevention and treatment of postmenopausal osteoporosis by confirming the scientific hypothesis that iron affects postmenopausal women's bone formation through regulating MATN3.

近年研究发现，绝经后骨质疏松症发病机制与骨组织铁蓄积密切相关。申请人前期研究发现：铁剂干预造成小鼠骨铁蓄积的同时，抑制了成骨细胞矿化功能及小鼠骨小梁的形成。本项目基于人体骨组织标本，采用蛋白质谱技术筛选出了与骨密度及骨铁含量均具有相关性的细胞外基质蛋白MATN3。预实验提示：MATN3在成骨细胞中表达，铁剂干预促进成骨细胞活性氧ROS产生的同时，还增强了MATN3表达。为此，我们构建了成骨细胞Matn3基因条件性敲除小鼠模型，发现该小鼠骨形成能力增强，骨小梁增多。本项目中，我们拟利用上述小鼠模型，在动物、细胞、分子三个水平，阐明铁对MATN3的调控作用以及由此引起骨形成及骨量变化，并揭示ROS在其中的作用。最终拟证实铁通过调控MATN3影响绝经女性骨形成的科学假说，以期望为绝经后骨质疏松症的防治提供新的靶点。

近年来的研究发现铁蓄积是骨质疏松症的一个独立危险因素，但是其具体分子机制尚不清楚。本项目前期基于人体骨组织标本，采用蛋白质谱技术筛选出了与骨密度及骨铁含量均具有相关性的细胞外基质蛋白MATN3。本项目采用MATN3条件性敲除小鼠为实验对象，从动物、细胞及分子水平研究铁对MATN3的调控作用以及由此引起骨形成及骨量变化。我们的研究发现：（1）铁离子干预可降低成骨细胞表达MATN3，并抑制成骨细胞矿化及成骨特异性基因的表达。（2）在经铁离子干预的成骨细胞中加入MATN3重组蛋白后，成骨细胞的矿化功能得到明显恢复。（3）MATN3可以与BMP4结合，影响下游成骨特异性蛋白的表达。（4）给予MATN3条件性敲除小鼠（MATN3-/-）以及野生型小鼠腹腔注射铁剂后，骨量均明显下降，但MATN3-/-小鼠骨量下降更为明显。（5）对铁剂干预的野生型小鼠进行尾静脉MATN3重组蛋白注射后，可以部分恢复小鼠骨量。以上结果提示，铁蓄积可以通过降低MATN3的表达，影响MATN3与BMP4的结合，导致小鼠骨量丢失，而补充MATN3可以部分逆转铁蓄积对骨量的不良影响。