A model of kidney stone disease using D. melanogaster

描述（由申请人提供）：症状性肾结石可能是严重疼痛、感染和发病率的重要来源，影响高达12%的美国人，每年产生超过20亿美元的医疗费用。肾结石形成的过程仍然知之甚少，由于缺乏良好的肾结石形成模型，在制定预防结石发生或复发的医疗或饮食干预措施方面进展有限。在黑腹果蝇中，马氏小管的功能相当于人类的卷曲小管，将离子和其他溶质从苍蝇的循环系统转运到排泄系统。此外，在苍蝇排泄系统中发现的一些基因在人类排泄系统中起保守作用。蝇小管产生含有钙、磷和其他与有机基质结合的离子的结晶结晶。这些结块似乎是由小的球形结构形成的，这些结构与兰德尔斑块（人类肾脏早期结石形成的中心）中所见的纳米颗粒（球粒）惊人地相似。我们发现这些苍蝇石含有黄嘌呤和一种二磷酸盐结合物质，可能是羟基磷灰石和钙，这是早期人类石头的主要成分。我们还发现，抑制黑腹龙黄嘌呤脱氢酶（XDH）导致高蛋白饮食中结块的积累增加，这可以通过抑制维生素D受体同源物来挽救。值得注意的是，这些基因和高蛋白饮食与人类结石疾病有关。考虑到黑腹果蝇和人类在小管生理、排泄系统基因的保护、结石形成特征方面的相似性，以及在果蝇中强大的遗传工具的可用性，我们假设黑腹果蝇可以作为一个有意义的模型来提高对肾结石疾病的理解，并确定新的治疗方法。本研究的目的是：(1)XDH敲除蝇早期结石形成和小管生理特征；(2)确定果蝇早期结石形成的遗传和药理学调控。将黑胃蝇蝇作为研究肾结石的转化模型的意义在于，它将为更好地了解人类肾结石形成的机制和发现肾结石疾病的新治疗方法提供机会。该建议具有创新性，因为应用无脊椎动物转化模型的特点是寿命短，维护成本相对较低，可以实现大规模筛选遗传和药理学操作，以开发肾结石治疗方法。

DESCRIPTION (provided by applicant): Symptomatic kidney stones can be a significant source of severe pain, infection, and morbidity, affecting up to 12% of Americans and generating more than $2 billion in healthcare costs annually. The process of kidney stone formation remains poorly understood and there has been limited progress in developing medical or dietary interventions to prevent the occurrence or recurrence of stones due to paucity of good models for kidney stone formation. In Drosophila melanogaster (D. melanogaster), the Malpighian tubule is the functional equivalent of the human convoluted tubule and transports ions and other solutes from the fly circulatory system into the excretory system. Furthermore, a number of genes found in the fly excretory system play a conserved role in the human excretory system. The fly tubule produces crystalline concretions containing calcium, phosphorus, and other ions combined with an organic matrix. These concretions appear to be formed from small spherical structures that bear a striking resemblance to the nanoparticles (spherites) seen in Randall plaques, the nidus of early stone formation in human kidneys. We show that these fly stones contain xanthine and a bisphosphonate-binding substance, presumably hydroxyapatite and calcium, the primary component of early human stones. We have also found that inhibition of xanthine dehydrogenase (XDH) in D. melanogaster leads to increased accumulation of concretions on a high protein diet which can be rescued by inhibition of a Vitamin D receptor ortholog. Notably these genes and a high protein diet have been implicated in human stone disease. Given the similarities in tubule physiology, conservation of genes in the excretory system, and characteristics of stone formation between D. melanogaster and humans, and the availability of powerful genetic tools in the fly, we hypothesize that D. melanogaster can be utilized as a meaningful model to improve understanding of kidney stone disease and to identify novel therapeutics. The aims of the proposed study are: (1) Characterization of early stone formation and tubule physiology in the XDH knockdown fly; and (2) identification of genetic and pharmacologic manipulations that modulate early fly stone formation, The significance of developing D. melanogaster as a translational model for studying nephrolithiasis is that it would provide an opportunity to better understand the mechanism of human kidney stone formation and to discover novel therapeutics for kidney stone disease. This proposal is innovative because of the application of an invertebrate translational model characterized by a short lifespan and relatively low cost of maintenance, to achieve large scale screening of genetic and pharmacological manipulations for developing therapeutics for nephrolithiasis. PUBLIC HEALTH RELEVANCE: While kidney stone disease is a significant source of medical cost and morbidity in the United States, minimal advancement in the areas of medical treatment and prevention has been made in the last several decades. Given the similarity in various aspects of stone formation and renal physiology between flies and humans, this proposal aims to develop a novel animal model for kidney stone disease using D. melanogaster. Such a model holds significant promise for better understanding of the pathophysiologic mechanisms underlying early stone formation as well as for the discovery of novel therapeutics for renal stone disease.