核因子IA通过调节破骨细胞分化影响骨稳态和骨量的作用及其机制研究

前期体外研究发现核因子IA（NFIA）通过抑制经典Wnt信号通路而减弱骨髓基质干细胞成骨分化并促进成脂分化。构建了成骨细胞及骨细胞条件性Nfia基因敲入鼠，其生物表型主要表现为长骨干骺端松质骨小梁数量显著增加而破骨细胞减少，但其成骨细胞Rankl/Opg比值不下降，提示NFIA除了调节成骨细胞分化外，以不依赖RANKL方式调控破骨细胞分化而影响机体骨稳态和骨量。本项目将继续完善模型鼠表型研究，从整体和组织学水平，结合体外细胞生物学及分子生物学实验，观察NFIA对破骨细胞分化和骨量、骨稳态的影响，观察骨细胞Nfia基因敲入是否有助于阻止小鼠发生骨丢失。在此基础上，运用RNA-seq和ChIP-seq技术结合生物信息学分析，筛选并鉴定NFIA下游靶基因，通过体外、体内实验阐释靶基因调节破骨细胞分化而影响小鼠骨稳态和骨量的作用及有关机制。本研究将深化对骨稳态机制的认识，为骨质疏松防治提供新思路。

In our preliminary work, we found that the transcription factor nuclear factor I-A (NFIA) inhibited osteogenic differentiation and promoted adipogenic differentiation of bone marrow stromal progenitor cells in vitro by inhibiting the canonical Wnt pathway. We made osteoblast- and osteocyte-specific gene knock-in mice which mainly showed that in the proximal metaphysis of long bones the trabecular bone mass dramatically increased and osteoclast numbers significantly decreased. Moreover, the NFIA overexpression in osteoblasts did not decrease the ratio of RANKL to OPG. These data suggest that in addition to regulating the differentiation of osteoblasts, NFIA also affects the bone mass and homeostasis by regulating osteoclast differentiation in a RANKL-independent manner. In the proposed study, we will continue to analyze the phenotypes of the knock-in mice and further investigate the effects of NFIA on osteoclast differentiation, bone mass, bone microstructure and bone homeostasis from the overall and histological levels, combined with in vitro cell biology and molecular biology experiments. We will also study if the Nfia knock-in in osteocytes helps to block the development of osteoporosis in mice. By using high-throughput RNA-Seq and ChIP-seq technology combined with bioinformatics analysis, we will screen and identify the downstream target genes of NFIA potentially responsible for the regulation of osteoclast differentiation. Then, through in vitro and in vivo experiments, we will validate the role of the potential target gene(s) in regulating osteoclast differentiation and bone mass and homeostasis in mice. The implementation of this project will provide novel insights into the mechanisms of osteoclast development and bone homeostasis, and implicate potential novel approach for bone loss recovery.