Trimodal Vitality Imaging of Neural Progenitor Cells in the Spinal Cord

摘要 脊髓疾病和病症如脊髓损伤（SCI）和肌萎缩性侧索硬化（ALS）是常见的。 使人衰弱，往往导致丧失行动能力和降低受影响者的生活质量。一个有希望 治疗包括将神经祖细胞（NPC）移植到脊髓中， 具有神经保护作用。然而，大多数基于NPC的疗法在进入临床试验后失败， 由于没有一种方法来监测注射的细胞和活力，定位注射的NPC仅限于死后 组织学跟踪和评估移植细胞活力的能力对于理解 无论失败是技术性的还是生物性的，例如注射的细胞是否被输送到 保持在正确的位置或存活移植。我们建议发展多模态对比 试剂和临床超声和光声（US/PA）成像系统，用于图像引导的经- 种植细胞和纵向监测。与临床磁共振成像（MRI）一起， US/PA成像可以允许细胞的术前、术中和术后可视化。MRI和US成像 在临床上已经建立了良好的模式，PA可以很容易地与现有的临床US成像集成 系统.我们假设，可视化注射的神经前体细胞的位置和活力， 通过用造影剂标记NPC将允许更好地理解移植细胞的行为 以及改善基于细胞的疗法的转化。两种造影剂将被开发：光磁纳米造影剂， 粒子，这将允许光声和MRI跟踪，和基于染料的凋亡报告，这将 在凋亡活性上提供光声对比。这些将被传递到神经原细胞的胞质溶胶中， 生殖细胞并评估标记效率和毒性。一旦优化，以不同比例标记的NPC 将活体与死体的比例注射到大鼠的脊髓中，以评估区分活体与死体的可行性。 体内细胞注射后，将使用三模式US/PA/MR成像纵向监测NPC。后 为了验证造影剂在体内的性能，将开发临床US/PA成像系统， 演示实时图像引导输送、US/PA/MRI纵向跟踪和PA可行性评估， 标记的细胞。在手术过程中和手术后的每一个点监测移植细胞的能力将 允许更准确地递送细胞，并且可以阐明注射的NPC的常见问题和行为 可以改善治疗效果此外，如果成功，将验证两种造影剂 和US/PA作为跟踪和监测基于细胞的治疗以改善临床转化的有价值的工具。

ABSTRACT Spinal cord diseases and disorders such as spinal cord injury (SCI) and amyotrophic lateral sclerosis (ALS) are debilitating, often resulting in loss of mobility and decreased quality of life for those affected. One promising treatment involves the transplantation of neural progenitor cells (NPC) into the spinal cord, which has been shown to have neuroprotective properties. However, most NPC-based therapies fail after reaching clinical trials, and without a method to monitor the injected cells and viability, locating injected NPCs is limited to postmortem histology. The ability to track and assess the viability of transplanted cells could be crucial in understanding whether the failure is technical or biological in nature, such as whether the injected cells were delivered to and remain at the correct location or survived transplantation. We propose the development of multi-modal contrast agents and a clinical ultrasound and photoacoustic (US/PA) imaging system for image guided delivery of trans- planted cells and longitudinal monitoring. Together with clinical magnetic resonance imaging (MRI), the use of US/PA imaging can allow for pre-, intra- and post-operative visualization of the cells. The MRI and US imaging modalities are well established in the clinic, and PA can be easily integrated with existing clinical US imaging systems. We hypothesize that visualizing the location and viability of injected neural progenitor cells obtained through the labeling of NPCs with contrast agents will allow for better understanding of transplanted cell behavior and improved translation of cell based therapies. Two contrast agents will be developed: photo-magnetic nano- particles, which will allow for photoacoustic and MRI tracking, and a dye-based apoptosis reporter, which will provide photoacoustic contrast upon apoptotic activity. These will be delivered to the cytosol of the neural pro- genitor cells and assessed for labeling efficiency and toxicity. Once optimized, labeled NPCs in different ratios of live to dead will be injected into the spinal cords of rats to assess the feasibility of distinguishing live and dead cells in vivo. After injection, the NPCs will be monitored longitudinally using trimodal US/PA/MR imaging. After validating the performance of the contrast agents in vivo, a clinical US/PA imaging system will be developed to demonstrate real-time image guided-delivery, US/PA/MRI longitudinal tracking, and PA viability assessment of the labeled cells. The ability to monitor the transplanted cells at every point during and after the procedure will allow for more accurate delivery of the cells and could elucidate common issues and behaviors of injected NPCs that could lead to therapeutic improvements. Furthermore, if successful, it will validate both the contrast agents and US/PA as a valuable tool for tracking and monitoring cell-based therapies to improve clinical translation.