Pathogenesis-Driven Therapeutic Development for Pulmonary Alveolar Microlithiasis

 描述(申请人提供)：肺泡微石症(PAM)是一种罕见的常染色体隐性遗传性肺疾病，与肺泡室内聚积的磷酸钙微结石有关。这种疾病在早期通常没有症状，但到了中年，超过一半的患者会进展到呼吸衰竭和死亡。2006年，遗传分析发现PAM是由于SLC34A2基因突变失活所致，SLC34A2基因编码在肺泡II型细胞上表达的关键磷酸转运蛋白Npt2b。我们的工作假设是，由于Npt2b功能丧失而导致的肺泡积聚导致磷酸钙晶体形成，肺部炎症，肺表面活性物质代谢和功能受损，以及肺纤维化。我们已经创建了PAM的小鼠模型，通过上皮特异性删除Npt2b，这已被证明是对人类情况的非常真实的模拟。动物出现大量的微结石形成，几乎影响到每个肺泡，弥漫性放射学混浊，受限的肺生理，意外的肺泡磷脂沉积，泡沫巨噬细胞浸润和炎症，以及轻度的肺纤维化。我们在这个项目中的目标是通过完成三个紧密结合的目标，在彻底了解疾病发病机制的基础上，制定治疗PAM的策略。在第一个目标中，我们将研究微结石的形成机制，包括结石的分子组成，微结石积累的动力学，以及维持磷酸盐稳态的转运蛋白的光谱、细胞定位、定向和功能。在第二个目标中，我们将研究磷酸盐代谢在肺泡动态平衡中的作用，包括磷脂沉积和纤维化的机制。在第三个目标中，我们将使用Npt2b-/-小鼠作为平台来试验基于发病机制的治疗，包括遗传纠正、钙离子螯合、抑制磷酸钙晶体形成、 以及通过其他转运蛋白刺激替代肺泡磷酸盐输出。这些特定目标的成功完成将提供在PAM患者身上进行临床试验所需的临床前数据。

 DESCRIPTION (provided by applicant): Pulmonary alveolar microlithiasis (PAM) is rare, autosomal recessive lung disorder associated with accumulation of calcium phosphate microliths in the alveolar compartment. The disease is often asymptomatic in early life, but progresses to respiratory failure and death in more than half of patients by middle age. In 2006, PAM was revealed by genetic analyses to be due to inactivating mutations in SLC34A2, a gene which encodes a key phosphate transporter expressed on alveolar type II cells called Npt2b. Our working hypothesis is that accumulation of alveolar due to loss of Npt2b function leads to calcium phosphate crystal formation, pulmonary inflammation, impaired surfactant metabolism and function, and pulmonary fibrosis. We have created a mouse model of PAM, by epithelium specific deletion of Npt2b, which has proven to be a remarkably authentic mimic of the human condition. The animals develop abundant microlith formation affecting nearly every alveolus, diffuse radiographic opacification, restrictive pulmonary physiology, an unexpected alveolar phospholipidosis, foamy macrophage infiltration and inflammation, and modest pulmonary fibrosis. Our goal in this project is to develop strategies for treatment of PAM, based on a thorough understanding of disease pathogenesis, through the completion of three tightly integrated aims. In the first aim we will examine the mechanisms of microlith formation, including the molecular composition of the stone, kinetics of microlith accumulation, and the spectrum, cellular localization, orientation and function of transporters that maintain phosphate homeostasis. In the second aim, we will examine the role of phosphate metabolism in alveolar homeostasis, including mechanisms responsible for phospholipidosis and fibrosis. In the third aim, we will use the Npt2b-/- mouse as a platform to trial pathogenesis-based therapies, including genetic correction, calcium chelation, inhibition of calcium phosphate crystal formation, and stimulation of alternative alveolar phosphate export via other transporters. Successful completion of these specific aims will provide the preclinical data needed to conduct a clinical trial in individuals with PAM.