Ultrasound-guided photoacoustic imaging and tracking of stem cells in the spinal cord

摘要 干细胞，包括间充质干细胞(MSCs)，已被证明是一种令人兴奋和有前途的治疗方法。 用于治疗许多脊髓疾病和障碍，如脊髓损伤(SCI) 肌萎缩侧索硬化症(ALS)。临床前研究的积极结果导致了翻译的增加。 干细胞疗法的发展。然而，在达到临床试验时，许多干细胞疗法都失败了。在寻找 答案是，临床医生和研究人员缺少关键信息；细胞一旦被植入，其命运如何。 因此，临床上迫切需要一种能够准确实时引导的技术。 定量干细胞向靶区输送的优势，干细胞定位的非侵入性纵向体内跟踪- 在分娩后一段时间内对干细胞活性进行评估。这个项目基于一个假设，即 用光声成像造影剂和光声凋亡可以有效地标记干细胞 分别用于可视化细胞定位和确定其生存能力的传感器；以及超声波引导的光声- TIC(USPA)成像系统和方法可用于纵向、定量和非侵入性跟踪。 双标记干细胞及其在体内的去向。 本研究计划的总体目标是开发一种新的细胞标记系统和相应的USPA 成像方法，允许实时图像引导，以精确和准确地注射干细胞，以及 纵向追踪干细胞在脊髓中的活体位置和活性。首先，对PA敏感 将开发一种追踪器，它将允许实时反馈干细胞在 在注射后立即，以及在手术后跟踪移植细胞随时间的位置。 其次，将开发一种检测细胞凋亡的PA传感器。该传感器将在细胞中提供独特的PA信号， 正在进行细胞凋亡，使我们能够确定细胞的生存能力。同时使用PA跟踪器和 双标记干细胞的凋亡传感器对于实时成像引导细胞递送和跟踪至关重要 体内纵向可存活和可凋亡的细胞。USPA成像双标记细胞将提供极高的价值- 干细胞在体内去向的可靠信息，可用于完善和推进干细胞领域 脊髓移植。如果成功，这项工作将为活体实时术中奠定基础 然后对脊髓内的移植细胞进行纵向USPA成像-这是两者都需要的技术 科学家和临床医生。

ABSTRACT Stem cells, including mesenchymal stem cells (MSCs) have proven to be an exciting and promising thera- peutic for the treatment of numerous diseases and disorders of the spinal cord, such as spinal cord injury (SCI) and amyotrophic lateral sclerosis (ALS). Positive results in preclinical studies have led to an increase in transla- tion of stem cell therapies. However, upon reaching clinical trials, many stem cell therapeutics fail. In search for answers, the clinicians and researchers are missing critical information; the fate of the cells once implanted. Therefore, there is a definite and urgent clinical need for a technique that is capable of accurate real-time guid- ance of quantitative stem cell delivery to target areas, noninvasive longitudinal in vivo tracking of stem cell loca- tion, and assessment of stem cell viability over time after the delivery. This project is based on a hypothesis that stem cells can be effectively labeled with a photoacoustic imaging contrast agent and a photoacoustic apoptosis sensor to visualize cell localization and ascertain their viability, respectively; and ultrasound-guided photoacous- tic (USPA) imaging system and approach can be developed for longitudinal, quantitative, and noninvasive track- ing of double-labeled stem cells and their fate in vivo. The overall goal of this research program is to develop a novel cell labeling system and corresponding USPA imaging approach allowing real time image guidance for precise and accurate injection of the stem cells, and longitudinal tracking both the location and viability of stem cells in vivo in the spinal cord. First, a PA sensitive tracker will be developed, which will allow for real time feedback on the location of the stem cells during and immediately after injection, as well as post-operative tracking the location of the transplanted cells over time. Second, a PA sensor of apoptosis will be developed. This sensor will provide a unique PA signal in cells which are undergoing apoptosis, allowing us to ascertain the cells viability. The combination of both PA tracker and apoptotic sensor to double label stem cells is critical for real time imaged guided delivery of cells, and tracking viable and apoptotic cells longitudinally in vivo. The USPA imaging double-labeled cells will provide highly valu- able information of the fate of stem cells in vivo, which can be used to refine and advance the field of stem cell transplantation in the spinal cord. If successful, this work will lay foundation for in vivo real-time intra-operative and then longitudinal USPA imaging of transplanted cells within the spinal cord – the technology needed by both scientists and clinicians.