Leahy Martin, Thompson Kerry, Zafar Haroon, Alexandrov Sergey, Foley Mark, O'Flatharta Cathal, Dockery Peter
Tissue Optics & Microcirculation Imaging Group, School of Physics, National University of Ireland (NUI), Galway, Ireland.
Chair of Applied Physics, National University of Ireland (NUI), Galway, Ireland.
Stem Cell Res Ther. 2016 Apr 19;7(1):57. doi: 10.1186/s13287-016-0315-2.
In vivo imaging is a platform technology with the power to put function in its natural structural context. With the drive to translate stem cell therapies into pre-clinical and clinical trials, early selection of the right imaging techniques is paramount to success. There are many instances in regenerative medicine where the biological, biochemical, and biomechanical mechanisms behind the proposed function of stem cell therapies can be elucidated by appropriate imaging. Imaging techniques can be divided according to whether labels are used and as to whether the imaging can be done in vivo. In vivo human imaging places additional restrictions on the imaging tools that can be used. Microscopies and nanoscopies, especially those requiring fluorescent markers, have made an extraordinary impact on discovery at the molecular and cellular level, but due to their very limited ability to focus in the scattering tissues encountered for in vivo applications they are largely confined to superficial imaging applications in research laboratories. Nanoscopy, which has tremendous benefits in resolution, is limited to the near-field (e.g. near-field scanning optical microscope (NSNOM)) or to very high light intensity (e.g. stimulated emission depletion (STED)) or to slow stochastic events (photo-activated localization microscopy (PALM) and stochastic optical reconstruction microscopy (STORM)). In all cases, nanoscopy is limited to very superficial applications. Imaging depth may be increased using multiphoton or coherence gating tricks. Scattering dominates the limitation on imaging depth in most tissues and this can be mitigated by the application of optical clearing techniques that can impose mild (e.g. topical application of glycerol) or severe (e.g. CLARITY) changes to the tissue to be imaged. Progression of therapies through to clinical trials requires some thought as to the imaging and sensing modalities that should be used. Smoother progression is facilitated by the use of comparable imaging modalities throughout the discovery and trial phases, giving label-free techniques an advantage wherever they can be used, although this is seldom considered in the early stages. In this paper, we will explore the techniques that have found success in aiding discovery in stem cell therapies and try to predict the likely technologies best suited to translation and future directions.
体内成像技术是一种平台技术，能够将功能置于其天然的结构背景中。随着将干细胞疗法转化为临床前和临床试验的需求不断增加，早期选择合适的成像技术对于成功至关重要。在再生医学中有许多实例表明，通过适当的成像可以阐明干细胞疗法所提议功能背后的生物学、生物化学和生物力学机制。成像技术可以根据是否使用标记以及是否可以在体内进行成像来划分。体内人体成像对可使用的成像工具施加了额外的限制。显微镜和纳米显微镜，尤其是那些需要荧光标记的，在分子和细胞水平的发现中产生了非凡的影响，但由于它们聚焦于体内应用中遇到的散射组织的能力非常有限，它们主要局限于研究实验室中的浅表成像应用。纳米显微镜在分辨率方面有巨大优势，但仅限于近场（例如近场扫描光学显微镜（NSNOM））或非常高的光强度（例如受激发射损耗（STED））或缓慢的随机事件（光激活定位显微镜（PALM）和随机光学重建显微镜（STORM））。在所有情况下，纳米显微镜都仅限于非常浅表的应用。使用多光子或相干选通技巧可以增加成像深度。在大多数组织中，散射是成像深度的主要限制因素，这可以通过应用光学清除技术来缓解，这些技术可以对要成像的组织施加轻微（例如局部应用甘油）或严重（例如CLARITY）的变化。将疗法推进到临床试验需要对应该使用的成像和传感方式进行一些思考。在整个发现和试验阶段使用可比的成像方式有助于实现更顺利的进展，在可以使用无标记技术的任何地方都赋予它们优势，尽管在早期阶段很少考虑这一点。在本文中，我们将探索在辅助干细胞疗法发现方面取得成功的技术，并尝试预测最适合转化和未来方向的可能技术。
