Assessing Mitochondrial Metabolism using 31P Magnetic Resonance Fingerprinting

描述（由申请人提供）：在美国，缺血-再灌注（IR）损伤诱导的心肌细胞死亡是发病率和死亡率的主要原因。越来越多的证据表明，非特异性线粒体内膜传导通道（线粒体通透性转换孔（mPTP））的开放是IR损伤的关键因素。mPTP开放的一个效应是质子穿过线粒体内膜的泄漏，其使线粒体氧化与ATP合成解偶联并加剧预先存在的ATP缺乏。药理学抑制mPTP是急性缺血事件中心脏保护的有前途的策略。然而，缺乏有效的非侵入性方法来研究体内线粒体功能限制了对IR损伤机制的理解，以及新疗法的开发。磷-31（31 P）磁共振波谱（MRS）是解决这一需求的有吸引力的方法。31 P磁化转移光谱（MT-MRS）长期以来一直被提议作为测量体内ATP合成速率的手段。结合31 P MT-MRS与氧耗率的测量可以评估线粒体偶联。然而，目前的31 P MT-MRS方法需要过长的成像时间来准确测量ATP合成速率。另一方面，磁共振指纹（MRF）方法的最新发展为磁共振数据采集提供了一个全新的框架，允许同时测量几个组织特性，包括弛豫时间，在高速。MT-MRS中的化学交换通量的测量与MR成像中的弛豫时间的测量高度类似。因此，本提案的总体目标是开发和验证快速新颖的31 P磁共振光谱指纹（MRSF）技术，以定量测量ATP合成速率。该项目有两个具体目标。目标1有三个部分：通过计算机模拟开发31 P MRSF方法，在体模实验中实施所开发的方法，并在不同工作负荷下的灌注心脏中验证31 P MRSF方法与已建立的31 P MT-MRS方法。在目的2中，将在大鼠整体IR损伤模型中进一步评估所开发的31 P MRSF方法的效用，其中存在和不存在mPTP的药理学抑制。这些拟议的实验的结果将有助于阐明mPTP抑制诱导的心脏保护IR的机制。此外，成功的方法开发将铺平道路，为临床可行的和相关的诊断，以及纵向研究的代谢紊乱的频谱。

DESCRIPTION (provided by applicant): Myocardial cell death induced by ischemia-reperfusion (IR) injury is a major cause of morbidity and mortality in the US. Mounting evidence suggests that the opening of a nonspecific inner mitochondrial membrane conductance channel, the mitochondrial Permeability Transition Pore (mPTP), is a key factor of IR injury. One effect of mPTP opening is the leakage of protons across the inner mitochondrial membrane, which uncouples mitochondrial oxidation from ATP synthesis and exacerbates the preexisting ATP deficit. Pharmacological inhibition of mPTP is a promising strategy for cardio protection in acute ischemic events. However, the lack of effective noninvasive methods to study mitochondrial function in vivo limits the understanding of IR injury mechanisms, as well as the development of novel therapeutics. Phosphorus-31 (31P) Magnetic Resonance Spectroscopy (MRS) is an attractive method to address this need. 31P Magnetization Transfer spectroscopy (MT-MRS) has long been proposed as a means of measuring ATP synthesis rates in vivo. Combination of 31P MT-MRS with the measurement of oxygen consumption rates allows the assessment of mitochondrial coupling. However, current 31P MT-MRS methods require prohibitively long imaging time to accurately measure ATP synthesis rates. On the other hand, recent development of Magnetic Resonance Fingerprinting (MRF) method provides a completely new framework for Magnetic Resonance data acquisition that allows simultaneous measurement of several tissue properties, including relaxation times, at high speed. The measurement of chemical exchange flux in MT-MRS is highly analogous to the measurement of relaxation times in MR imaging. Therefore, the overall objective of this proposal is to develop and validate fast novel 31P Magnetic Resonance Spectroscopy Fingerprinting (MRSF) technique to quantitatively measure ATP synthesis rate. This project has two specific aims. Aim 1 has three parts: developing 31P MRSF methods by computer simulation, implementing the developed methods in phantom experiments, and validating 31P MRSF methods against established 31P MT-MRS methods in perfused hearts under varying workloads. In Aim 2, the utility of the developed 31P MRSF method will be further assessed in a rat model of global IR injury, with and without pharmacological inhibition of mPTP. The results of these proposed experiments will help elucidate the mechanisms of mPTP inhibition induced cardio protection in IR. Furthermore, successful method development will pave the way for clinically feasible and relevant diagnostics as well as longitudinal studies of a spectrum of metabolic disorders.