铝骨病大鼠骨形成抑制的Wnt/β-catenin信号转导机制

Aluminum (Al) toxicity is an increasingly hotspot of international research in nowadays.Our previous research confirmed that Al inhibited osteogenesis in rats, but it is not known at which stage of osteogenesis the inhibition incurs, neither the signal transmission mechanism involved in this inhibitory process. We hypothesize that Al-related bone diseases cause inhibition and regulatory disorder of osteogenesis in rats. The research aims to explore the Wnt/β-catenin signal transmission mechanism in the process of inhibited osteogenesis in rats subject to Al-related bone diseases. We will study the effects of sub-chronic Al exposure on each of the four stages of osteogenesis, ie, proliferation, differentiation, mineralisation and apoptosis, as well as on regulatory mechanisms using advanced technologies in modern toxicology, molecular biology and cytobiology. Two models, both in vivo (rats subject to aluminum-related bone diseases) and in vitro (culturing osteocytes) will be applied to investigate dynamic changes of the key markers for each stage of osteogenesis, calcium regulating hormones, the local regulatory factors, changes of the key molecules in the Wnt/β-catenin signal pathway as well as the genes in the down stream of the pathway,and bone density.The correlation between these indexes and Al-related bone diseases will be analysed to develope early diagnostic tools for these diseases. The results will provide a theoretic base for revealing the pathogenesis of Al-related bone diseases and detoxification of Al.

铝毒危害是现今国际研究的热点，申请者前期研究表明,铝抑制大鼠骨形成，但究竟抑制骨形成过程的某个阶段还是某几个阶段及对骨形成调控的细胞信号转导机制尚不清楚。本研究以铝骨病大鼠骨形成抑制及其调控紊乱为理论假说，从骨形成四个阶段（即增殖、分化、矿化和凋亡）及其整体调控（全身调节、局部调节及Wnt/β-catenin信号通路）两个环节作为研究切入点，利用现代毒理学、分子生物学和细胞生物学等研究手段，拟通过铝骨病大鼠在体实验和体外大鼠成骨细胞培养实验，动态观测大鼠的骨密度，骨形成四个阶段主要标志物，钙调激素，骨局部调节因子，信号转导系统Wnt/β-catenin中关键因子及下游靶基因的变化，分析其与铝骨病的相关性，获得铝骨病的早期诊断指标，阐明铝抑制骨形成的Wnt/β-catenin信号转导机制，为揭示铝骨病的发病机理和铝骨毒性危害的解除提供理论与实验依据。

铝具有骨毒性，可抑制骨形成。成骨细胞（OB）是骨形成的重要功能细胞，OB在骨形成过程中要经历细胞增殖、分化、矿化和凋亡四个阶段。OB的骨形成过程受骨相关激素、骨形成因子及信号转导的精细调控才能完成。细胞信号转导是骨形成调控系统的核心，骨组织局部调节因子、骨相关激素需通过信号通路传递到转录效应因子，控制OB不同阶段特异基因的表达，从而控制骨形成过程。Wnt/β-catenin信号通路是骨形成调控系统的核心，与骨组织发育及骨量调节等多个病理生理过程有关，但其在铝抑制骨形成中的调控作用尚不清楚。本研究从骨形成四个阶段及其整体调控（全身调节、局部调节及Wnt/β-catenin信号通路）两个环节作为研究切入点，通过铝骨病大鼠在体实验和体外大鼠OB染铝实验，动态观测大鼠的骨密度，骨形成四个阶段主要标志物，钙调激素，骨局部调节因子，信号转导系统Wnt/β-catenin中关键因子及下游靶基因的变化，获得了如下开创性研究成果：（1）BGP mRNA表达自染铝30d开始显著低于对照组，而ALP、Col I和BMD分别在60d和120d才显著低于对照组，说明BGP mRNA水平降低可作为铝骨病的早期诊断指标。（2）染铝可抑制大鼠钙调激素（PTH、CT、和1,25-(OH)2-D3）的分泌和局部调控因子（TGF-β1、IGF-1、Runx-2）的表达。（3）体内外的实验均证明，染铝可抑制Wnt/β-catenin信号通路中关键因子的转导，降低下游靶基因Runx-2的转录活性，抑制 I型胶原、BGP、ALP、OPN等骨形成相关蛋白的转录和表达，上调凋亡相关基因Caspase-3、Bax和p53的表达，说明铝暴露可通过抑制Wnt/β-catenin信号通路抑制骨形成，导致骨质疏松。研究结果为揭示铝骨病的发病机理和铝骨毒性的解除奠定了理论依据。