Wallace H. Coulter Department of Biomedical Engineering, George W. Woodruff School of Mechanical Engineering, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology Atlanta, GA, USA.
Front Physiol. 2013 Aug 15;4:215. doi: 10.3389/fphys.2013.00215. eCollection 2013.
Near-infrared (NIR) imaging has emerged as a novel imaging modality for assessing lymphatic function in vivo. While the technique has provided quantitative data previously unavailable, questions remain in regards to the spatiotemporal capabilities of the approach. We address three of the more important issues here using the rodent tail, one of the most widely utilized in vivo model systems in the lymphatic literature. Specifically we demonstrate (1) the transient vs. steady state response of lymphatics to tracer injection, (2) the functional characteristics of multiple collecting vessels draining the same tissue space in parallel, and (3) the long-term consequences of fluorescent tracers on lymphatic function to repeated functional measurements.
Rat tails were imaged with NIR and metrics of function were calculated for both collecting vessels that drain the tail. A nitric oxide donor cream (GTNO) was applied to the tail. Additionally, two different NIR dyes, indocyanine green (ICG) and LI-COR IRDye 800CW PEG, were utilized for function imaging at the time of initial injection and at 1, 2, and 4 week follow-up time points after which both draining lymph nodes were harvested.
Significant differences were found between the two collecting vessels such that the vessel first showing fluorescence (dominant) produced enhanced functional metrics compared to the second vessel (non-dominant). GTNO significantly reduced lymphatic function in the non-dominant vessel compared to the dominant. ICG remained visible in the tail for 2 weeks after injection and was accompanied by significant losses in lymphatic function and enlarged draining lymph nodes. The Licor tracer also remained visible for 2 weeks. However, the dye produced significantly lower effects on lymphatic function than ICG, and lymph nodes were not enlarged at any time point, suggesting that this may be a more appropriate contrast agent for longitudinal lymphatic imaging.
近红外（NIR）成像是一种用于评估体内淋巴功能的新型成像方式。虽然该技术以前所未有的方式提供了定量数据，但在该方法的时空能力方面仍存在一些问题。我们使用最广泛应用于淋巴文献中的体内模型系统之一——鼠尾，来解决这里的三个更重要的问题。具体来说，我们证明了（1）淋巴管对示踪剂注射的瞬态与稳态反应，（2）同时引流同一组织空间的多个收集管的功能特征，以及（3）荧光示踪剂对淋巴功能的长期影响对重复功能测量。
用 NIR 对鼠尾进行成像，并计算用于引流鼠尾的两条收集管的功能指标。在鼠尾上涂抹一氧化氮供体乳膏（GTNO）。此外，两种不同的近红外染料，吲哚菁绿（ICG）和 LI-COR IRDye 800CW PEG，在初始注射时以及注射后 1、2 和 4 周的随访时间点用于功能成像，然后收获两个引流淋巴结。
两条收集管之间存在显著差异，首先显示荧光（优势）的血管产生的功能指标明显高于第二条血管（非优势）。与优势相比，GTNO 显著降低了非优势血管的淋巴功能。ICG 在注射后 2 周仍在尾部可见，并伴有明显的淋巴功能丧失和引流淋巴结肿大。利科追踪剂也在 2 周内可见。然而，与 ICG 相比，该染料对淋巴功能的影响要小得多，而且淋巴结在任何时间点都没有肿大，这表明它可能是一种更适合纵向淋巴成像的造影剂。
