FoxO3a在绝经后铁蓄积导致骨代谢异常中的作用机制研究

In recent years, studies have shown that postmenopausal osteoporosis occur not only due to estrogen deficiency, but also owing to the accumulation of body iron content during perimenopausal and menopausal period. There are some reports which have confirmed the efficacy of some way to reduce the body iron content in preventing and treating postmenopausal osteoporosis. However, the concrete mechanism of iron accumulation induced abnormal bone metabolism is still unclear, FoxO3a activated by oxidative stress induced by iron accumulation may play an important role.. In this project, the wildtype and FoxO3a knockout mice are used for study, osteoblasts and osteoclasts are obtained from these mice by primary culture and co-cultured together. Both the mice and the cell coculture are treated with ferric ammonium citrate. We observe the crucial role of FoxO3a in iron accumulation induced abnormal bone metabolism through detecting a series of markers. These markers include iron metabolism markers (such as serum iron, serum ferritin), oxidative stress markers (such as SOD, MDA), FoxO3a markers, canonical Wnt/β-catenin signaling pathway markers (such as serum β-catenin), OPG/RANKL/RANK system markers (such as serum RANKL and OPG), bone metabolism markers (such as ALP, CTX) and bone mineral density.. This study may provide the new evidence to explain the abnormal bone metabolism induced by iron accumulation, and thus explore the therapeutical way based on the findings.

近年来的研究表明，绝经后骨质疏松症的发生不仅与绝经后雌激素缺乏有关，而且与绝经后体内铁含量蓄积有关。目前已有一些报道证实某些降低体内铁含量的方法具有防治绝经后骨质疏松症的疗效。然而，铁蓄积对骨代谢的影响机制尚不明确，现有研究提示铁蓄积通过氧化应激激活叉形头转录因子O亚型3a（FoxO3a），进而抑制经典Wnt信号通路可能在其中发挥重要的作用。本项目以小鼠和细胞为研究对象（分wild type和FoxO3a knockout组），以枸橼酸铁铵为干预手段，通过检测铁代谢指标、氧化应激指标、FoxO3a指标、Wnt/β-catenin信号通路指标、OPG/RANKL/RANK系统指标、骨代谢指标及骨密度，观察FoxO3a在铁蓄积导致骨代谢异常中的关键作用，旨在探讨绝经后骨质疏松症新的病因机制。

项目的背景：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。..主要研究内容：本研究以铁调素敲除小鼠为实验对象，铁调素敲除小鼠是研究铁蓄积导致骨质疏松症的理想模型，因为本项目组前期研究已经报道铁调素敲除小鼠体内存在铁蓄积和骨量丢失情况（Shen, G. S. et al. Hepcidin1 knockout mice display defects in bone microarchitecture and changes of bone formation markers. Calcif Tissue Int 94, 632-639 (2014).）。本项目的具体研究内容：1、确认6月龄铁调素敲除雄性小鼠的骨量丢失情况；2、明确铁调素敲除小鼠的骨量丢失是否与成骨细胞分化有关；3、明确铁调素敲除小鼠的骨量丢失是否与破骨细胞分化有关；4、铁调素敲除对小鼠骨组织中FOXO3a以及经典Wnt/β-catenin信号通路的影响；5、铁调素敲除小鼠给予FOXO3a抑制剂干预后骨量的改变。..主要研究结果：1、与野生型小鼠相比，6月龄铁调素敲除雄性小鼠的骨量明显丢失；2、铁调素敲除小鼠的骨量丢失与成骨细胞分化有关；3、铁调素敲除小鼠的骨量丢失与破骨细胞分化无关；4、铁调素敲除小鼠和野生型小鼠骨组织内b-catenin表达水平无明显差异，但是铁调素敲除小鼠骨组织内更多的b-catenin与FOXO3a结合，而不与TCF/LEF因子结合，干扰了经典Wnt/b-catenin通路影响骨形成；5、FOXO3a抑制剂干预可改善铁调素敲除引起的骨密度降低。..关键数据及其科学意义：1、该研究发现铁调素敲除小鼠骨组织内更多的b-catenin与FOXO3a结合，而不与经典Wnt/b-catenin通路中的TCF/LEF因子结合，干扰了经典Wnt/b-catenin通路进而影响骨形成，该研究结果解释了铁蓄积导致骨质疏松症的分子机理。2、通过FOXO3a-RNAi尾静脉注射干预铁调素敲除小鼠，可改善铁调素敲除引起的骨量丢失，该研究结果为将来铁蓄积导致骨质疏松症的防治提供了一种潜在的治疗方法。