Developing MRI contrast agents to detect progression in renal disease as a consequence of acidema

有机酸血症是一类先天代谢障碍，它扰乱氨基酸代谢和 导致血液、尿液和其他生物材料中可检测到的有机酸异常积累。而当 个别罕见，总体而言，这些疾病对儿童的健康有重大影响。慢性肾脏 疾病(CKD)是几种有机酸血症的主要特征，患者需要常规监测 肾功能管理他们的治疗。甲基丙二酸血症(MMA)是一种有机酸血症，具有 甲基丙二酰辅酶A变位酶(Mut)突变引起的频率为1/50,000至1/100,000 可预见地演变为CKD。事实上，慢性肾脏病是在以下情况下发生的MMA患者的中位发病年龄为6.5岁 发生肾功能不全的风险很高。不幸的是，目前监测肾脏健康的方法 对于MMA患者来说，包括血肌酐和血氮尿素的测定是不可靠的。一个 另一种策略是使用MRI造影剂来获取肾脏的功能信息。这 提案涉及使用耐受性良好的有机化合物，这些化合物通过 化学交换饱和转移(CEST)。这一机制的一个吸引人的特点是它使 制作反映试剂周围环境的pH图，这可能特别有用 对于肾脏，控制身体酸碱平衡的器官。我们将设计CEST pH传感器 它可以通过pH和血流灌注的变化来监测CKD的进展，并将提供可靠的 肾脏整体健康状况的指标。在目标1中，我们将合成一系列咪唑-4，5-二甲酰胺 探头以提供pH敏感的MRI对比度。质子交换率和由此产生的CEST对比将是 作为缓冲溶液中pH的函数进行量化，以确定这些化合物的体外性能。我们还将 使用C57BL/6对照优化我们的pH和灌注成像方案并表征药代动力学 老鼠。在目标2中，我们将评估目标1中我们最好的试剂对检测肾脏范围的敏感性。 在C57BL/6Mut-/-；TgINS-Alb-Mut小鼠模型中的疾病，并验证使用 ISUCA。C57BL/6Mut-/-；TgINS-Alb-Mut小鼠表现为慢性肾小管间质肾炎， 肾小球滤过率(GFR)，通过将小鼠置于高蛋白(HP)饮食2个月来启动。 在目标3中，我们将在六组小鼠身上测试我们最好的传感器，其中三组用柠檬酸钠处理。 通过饮食补充，另有三人在饮食中添加辅酶Q10维生素E。这个 小组还将包括三个不同的时间，以应对高蛋白挑战，这会导致肾脏损伤。我们 预计我们的新试剂和成像方案可以提供CKD的早期检测，而不需要 侵入性肾活检。这在标准监控方法不适用的情况下尤为关键 可行的，如MMA。

Organic acidemias are a class of inborn metabolic disorders which disrupt amino acid metabolism and lead to abnormal accumulation of organic acids detectable in blood, urine and other biomaterials. While individually rare, collectively these disorders have a significant impact on children’s health. Chronic Kidney Disease (CKD) is a cardinal feature of several organic acidemias, and patients require routine monitoring of kidney function to manage their treatment. Methylmalonic Acidemia (MMA) is an organic acidemia with a frequency of 1/50,000 to 1/100,000 caused by mutations in methylmalonyl-CoA mutase (Mut) with a predictable evolution to CKD. In fact, CKD is developed at a median onset age of 6.5 y in MMA patients who are at high risk of developing renal insufficiency. Unfortunately, current methods for monitoring renal health which include measuring blood creatinine and blood nitrogen urea are not reliable for MMA patients. An alternative strategy is to administer MRI contrast agents to acquire functional information on the kidneys. This proposal involves administering well tolerated, organic compounds which create MRI contrast through Chemical Exchange Saturation Transfer (CEST). An attractive feature of this mechanism is that it enables production of pH maps which reflect the environment surrounding the agents and might be particularly useful for the kidneys, organs which control the acid-base balance of the body. We will design CEST pH sensors which can monitor progression towards CKD through changes in pH and perfusion, and will provide a reliable indicator of the overall health of the kidneys. In Aim 1, we will synthesize a set of imidazole-4,5-dicarboxyamide probes to provide pH sensitive MRI contrast. The proton exchange rates and resulting CEST contrast will be quantified as a function of pH in buffered solutions to determine the performance of these in vitro. We will also optimize our pH and perfusion imaging protocol and characterize the pharmacokinetics using C57BL/6 control mice. In Aim 2, we will evaluate the sensitivity of our best agents from Aim 1 for detecting the extent of renal disease in the C57BL/6 Mut-/-;TgINS-Alb-Mut mouse model of MMA and validate the pH measurements using ISUCA. C57BL/6 Mut-/-;TgINS-Alb-Mut mice manifest chronic tubulointerstitial nephritis and a decreased glomerular filtration rate (GFR) which is initiated by placing the mice on a high protein (HP) diet for 2 months. In Aim 3, we will test our best sensor on six groups of mice with three groups treated with sodium citrate through diet supplementation and three more with CoQ10 + Vitamin E supplemented into their diets. The groups will also include three different timings for the high protein challenge which induces kidney injury. We expect our new agents and imaging protocols could provide an earlier detection of CKD without need of invasive kidney biopsy. This is particularly critical in conditions where standard monitoring methods are not feasible, such as MMA.