CEST/FLEX MRI for the Detection of the Host Immune Response to CNS Grafts

描述（由申请人提供）：使用脑内移植物治疗神经系统疾病的临床试验数量不断增加。然而，一旦移植物沉积在脑内，患者的免疫应答以及该应答对移植物功能的可能影响是未知的。神经炎症的成像，例如在多发性硬化症中使用MRI，是基于增加的相对水含量（水肿）和/或血脑屏障（BBB）破坏的测量。细胞移植物内的炎症，由于小尺寸，高细胞性，以及受注射针影响的BBB，不能通过相同的方法监测。在我们对啮齿类动物细胞移植的广泛经验中，我们观察到个体动物之间免疫细胞的移植物浸润存在很大差异，并且患者中可能发生类似的差异。这可以解释患者之间结果的显著差异，包括在少数患者中观察到的意想不到的严重副作用，这使患者和临床研究人员感到沮丧。因此，本提案的目的是开发新的、临床上适用的方法来非侵入性地检测细胞移植物的免疫细胞浸润。我们已经建立了一个实验平台，非常适合实现这一建议的目标。免疫缺陷的rag 2-/-小鼠，其特征在于对所有类型的细胞移植物的绝对耐受性，将B用作实验性免疫活性宿主的参考.将通过非侵入性生物发光成像重复评价脑内移植物活力。使用髓鞘形成障碍的颤抖小鼠（rag 2-/-和野生型）作为移植受体将使得能够对由于免疫细胞浸润而损害的移植物功能进行行为评估，并且还将使得能够使用针对MBP的免疫组织化学对移植物分化进行死后评估。我们的初步研究表明，移植到免疫活性宿主的细胞的存活率是高度依赖于植入部位。我们将采用两个拒绝倾向和拒绝抵抗的目标网站，以验证所提出的适用性， 无创排异监测读数。我们假设免疫细胞浸润导致局部微环境的改变。因此，我们将采用新的MRI技术，如CEST，这已被公认为一个强大的工具，用于非侵入性采集的分子信息在活组织中，和FLEX，这是互补的，并增加了有关快速交换质子的信息。我们将使用这些技术检测移植排斥反应的分子特征，并监测免疫抑制对移植物浸润的影响，包括行为结果和移植物分化和免疫细胞浸润的死后分析。在成功完成这一提议后，我们预计我们将建立一种有效的方法来评估对移植细胞的免疫反应，目的是将这种技术进一步转化为脑内移植患者的诊断工具。

DESCRIPTION (provided by applicant): There have been an increased number of clinical trials with the use of intracerebral grafts for the treatment of neurological disorders. However, once the graft is deposited intracerebrally, the patient's immune response and the possible influence of that response on graft functionality is unknown. Imaging of neuroinflammation, such as with MRI in multiple sclerosis, is based on increased relative water content (edema) and/or measurements of a blood brain barrier (BBB) breach. Inflammation within cellular grafts, due to the small size, high cellularity, and the BBB that is affected by the injection needle, cannot be monitored by the same methods. In our extensive experience with cell transplantation in rodents, we have observed a great variability of graft infiltration by immune cells between individual animals, and a similar variability likely occurs in patients. This could explain the striking difference in outcomes between patients, including the unexpected severe side effects observed in a few patients, which frustrates both patients and clinical researchers. Thus, the aim of this proposal is to develop novel, clinically applicable approaches to the non-invasive detection of immune cell infiltration of the cellular graft. We have already established an experimental platform that is ideally suited to address the aims of this proposal. The immune deficient rag2-/- mice, characterized by absolute tolerance to all types of cellular grafts, will b employed as a reference for experimental, immune- competent hosts. Graft viability within the brain will be repeatedly evaluated by non-invasive bioluminescent imaging. The use of dysmyelinating shiverer mice (both rag2-/- and wild-type) as transplant recipients will enable the behavioral assessment of compromised graft functionality due to infiltration of immune cells, and will also enable post mortem assessment of graft differentiation using immunohistochemistry against MBP. Our preliminary studies have demonstrated that the survival of cells grafted into immunocompetent hosts is highly dependent on the implantation site. We will employ both rejection-prone and rejection-resistant target sites, to validate the applicability of the proposed non-invasive rejection monitoring readouts. We hypothesize that immune cell infiltration results in an alteration of the local microenvironment. Thus, we will employ novel MRI techniques, such as CEST, which has been recognized as a powerful tool for the non-invasive acquisition of molecular information in living tissues, and FLEX, which is complementary and adds information about rapidly exchanging protons. We will use these techniques for the detection of the molecular signature of graft rejection and to monitor the effects of immunosuppression on graft infiltration with regard to behavioral outcomes and post mortem analysis of graft differentiation and infiltration by immune cells. Upon the successful completion of this proposal, we anticipate that we will have established an efficient method by which to evaluate the immune response against transplanted cells, with the intention to translate this technique further as a diagnostic tool for patients with intracerebral grafts.