基于铅的骨血转化模式探讨不同年龄段铅中毒儿童治疗的差异性

Childhood lead poisoning still happens frequently in China （10%-20%） or in other countries. Recent evidence has demonstrated that childhood lead exposure is likely a risk factor for adult chronic disease, such as neurodegenerative disease and hypertension. Therefore, it's very important to improve the treatment of childhood lead poisoning. Currently, blood lead is considered as the only basis of chelation therapy of lead-poisoned children. Based on literature review, the lead kinetic model (mainly bone-blood turnover model) had a great influence on the distribution of lead within the body and lead-induced health damage, and that model was also suggested to be probably age-dependent during childhood. According to our clinic records on 172 moderate lead-poisoned children, we found that lead-poisoned children of different ages needed different periods of chelation treatment, which implied that different patterns of lead bone-blood turnover model may really exist among children of different ages, and that might correlate with different neurodevelopmental deficits and different treatment efficacy. However, no answers could be found to this specific and important question in current literature. Therefore, our study aims to analyze the impacts of lead bone-blood turnover model on treatment efficacy in lead-poisoned children of different ages and the related mechanisms, and to further explore the possibility of differentiation treatment for lead-poisoned children of different ages. Our proposed study will include: (1) Clinical research: 90 moderate lead-poisoned children of different ages (divided into 3 groups based on the age) and 90 age- and gender-matched healthy controls will be recruited in our lead clinic, among which, lead-poisoned children will be chelation treated in hospital, and a series of evaluation will be conducted when new recruitment and will be repeated when children with lead-poisoning complete chelation, so as to investigate their lead levels (questionnaire inquiry, assessments of blood and bone lead), bone metabolisms and neurodevelopmental deficits (using event-related potential) before and after therapies. (2) Animal studies: we plan to establish the rat models of developmental lead poisoning during different stages of development, and rats with lead poisoning will then be divided into subgroups based on the periods of chelation treatment. Before and after treatment, blood and bone lead, serum trace elements, and bone lead metabolism related hormone and protein expression will be detected. After that, bone histomorphometry, examinations of electron microscopy and long-term potentiation on hippocampus will be performed on lead-poisoned and chelation treated rats to analyze the impact of lead poisoning and lead removal on the morphology and function of bones and hippocampus. By comprehensively analyzing the data from clinical and animal studies, we believe that our research will offer new understanding of the role of age in treatment of childhood lead poisoning from the perspective of lead bone-blood turnover model.

我国儿童铅中毒发生率达10％-20％，严重损害儿童健康。目前驱铅治疗方案都将血铅作为治疗的唯一依据。可我们临床发现初始血铅接近但年龄不同的患儿驱铅疗效有差异。铅骨血转换模式影响铅在骨骼和血液间分布，研究提示它可能与骨代谢相关，而儿童年龄不同骨代谢率有差异，因此我们假设铅骨血转换模式与儿童年龄相关。驱铅治疗影响铅骨血转换，因此我们假设铅骨血转换模式是不同年龄铅中毒儿童疗效差异的原因之一。国际上尚无此类研究。 本团队拟利用儿童铅中毒的诊治优势、病儿资源和研究基础，进行（1）建立不同年龄中度铅中毒儿童的病例-对照及患儿驱铅前后的自身对照研究，采用XRF仪、Elisa、ERP等比较骨铅、骨代谢和钙铁代谢、脑功能损伤等指标的差异；（2）通过动物实验验证上述结果并离体检测幼鼠骨骼和海马的形态功能变化。来分析铅骨血转换模式对不同年龄铅中毒儿童驱铅疗效的影响及机制，希望为完善细化儿童铅中毒治疗方案提供依据。

背景：铅仍是威胁儿童健康不可忽略的环境因素。不同年龄儿童的铅吸收率和骨代谢水平可能有差异，因此分析发育期不同阶段铅中毒对儿童铅骨血转化模式影响的差异，不同年龄段儿童的铅骨血转换模式在常规驱铅治疗后的变化规律是否相同，由此是否影响驱铅疗效具有重要意义。.内容及结果：1、临床部分：在儿科门诊招募铅超标及对照组儿童，共招募0-16岁儿童284例。测定儿童的血铅和微量元素、评估在体骨铅水平、检测铅中毒患儿的污染源、血清骨代谢标志物和骨转换调节因素、评估神经行为等。对中度铅中毒儿童驱铅治疗。比较每个驱铅疗程末血铅和骨铅变化。发现婴幼儿的骨代谢水平相对较高，血铅骨铅相关性更强。铅暴露儿童中婴幼儿的血铅骨铅水平最高。首个驱铅疗程后年龄与血铅骨铅下降值呈曲线关系。年龄小于6岁时，年龄增加后血铅骨铅下降幅度减少，但差别无统计学意义，6岁后变化不大。驱铅后血清骨代谢水平改变，年龄越小，改变越明显，但无统计学意义。高血铅和骨铅儿童冲动-多动的风险增高，高骨铅儿童对立违抗的风险增高。2. 动物实验部分：①构建婴儿期、儿童期、青春期三个发育阶段幼鼠的铅中毒模型，给予一和两个疗程的驱铅治疗，并匹配对照组。检测各组幼鼠血铅、微量元素、密质骨和松质骨骨铅水平、血清和骨的骨代谢标志物、骨血转换调节因素的mRNA和蛋白水平、海马神经元标志物的mRNA和蛋白的表达、海马神经元超微结构、电生理变化等。Micro CT观察骨三维立体结构。发现铅暴露后，骨密度、骨小梁数目和厚度减少，骨小梁间隙增加。驱铅后骨形态有逆转。驱铅一疗程后婴儿期组的血铅骨铅驱除率均最高。铅暴露后OC、RUNX2、CTX的表达降低，PTH和PINP升高，治疗后有逆转。铅暴露后海马神经元超微结构损伤及神经元标志物表达下调。.结论及意义：婴幼儿是铅中毒的易感人群，发育期铅暴露及相应的驱铅治疗引起儿童骨代谢和骨形态的变化，婴幼儿比更大龄儿童首疗程的驱铅效果相对更好。骨铅水平是儿童多动、冲动、尤其是对立违抗的影响因素。