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越来越多。然而，一旦移植物沉积在脑内，患者的免疫反应以及这种反应对移植物功能的可能影响是未知的。神经炎症的成像，如多发性硬化症的MRI，是基于相对含水量增加（水肿）和/或血脑屏障（BBB）破坏的测量。细胞移植物内的炎症，由于体积小，细胞密度高，并且血脑屏障受注射针的影响，无法用相同的方法监测。在我们对啮齿动物细胞移植的广泛经验中，我们观察到免疫细胞在个体动物之间移植物浸润的巨大差异，并且在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，这让患者和临床研究人员都感到沮丧。因此，本建议的目的是开发新的，临床适用的方法来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，非常适合实现这一提议的目标。免疫缺陷的rag2-/-小鼠对所有类型的细胞移植物具有绝对的耐受性，将被用作实验中免疫能力强的宿主的参考。移植物在大脑内的生存能力将通过非侵入性生物发光成像反复评估。使用髓鞘异常震颤小鼠（包括rag2-/-型和野生型）作为移植受体，可以对免疫细胞浸润导致的移植物功能受损进行行为评估，也可以使用免疫组织化学方法对MBP进行死后移植物分化评估。我们的初步研究表明，细胞移植到具有免疫能力的宿主的存活高度依赖于植入部位。我们将采用易排斥和抗排斥的目标位点，以验证所提出的适用性

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.