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C Ross Ethier, Eric Snider, Kelsey Kubelick, Heechul Yoon, Stanislav Emelianov; Visualizing stem cell delivery to trabecular meshwork using ultrasound/photoacoustic imaging with nanoparticles. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3497.
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© ARVO (1962-2015); The Authors (2016-present)
Due to reduced trabecular meshwork (TM) cellularity in glaucoma, stem cells offer potential therapeutic benefits if delivery and engraftment into TM occurs. Here, we utilize ultrasound and photoacoustic (US/PA) imaging to track nanoparticle-tagged adipose-derived mesenchymal stem cells (adMSCs) during delivery into the anterior segment and to the TM.
adMSCs (Lonza) were labeled with 20nm diameter gold nanospheres (AuNS) and fluorescently tagged (CFSE) for histology. Labeled adMSCs were injected into the anterior chamber of whole enucleated porcine eyes or into an anterior segment porcine organ culture model while pressure was hydrostatically clamped at physiologic levels. Cell injections and delivery to the TM were monitored in real-time using US/PA (Vevo 2100/LAZR) imaging. Whole eyes and organ-cultured anterior segments were fixed 4 hours and 1 week (respectively) after adMSC injection for more detailed US/PA imaging and delivery confirmation by en face TM fluorescent micrographs.
US/PA imaging visualized key anatomical landmarks due to PA signal from pigmented tissue, e.g. iris and TM (Fig 1A). Following labeled-adMSC injection, cells were evident in the anterior segment (Fig 1B) and their movement could be tracked over time. The unique spectral signature of AuNS allowed unmixing of AuNS signal from that of pigmented tissues; after injection, cells were evident in the TM, iris and lens regions (Fig 2A-D). TM delivery of adMSCs was evident 4 hrs (Fig 2E) and 1 week post-injection (Fig 2F) from fluorescent micrographs.
US/PA imaging can track adMSC injection and subsequent delivery to the TM. Next steps will optimize adMSC injection protocol and labeling to increase TM engraftment and generate greater PA signal. Further, longitudinal US/PA imaging will confirm engraftment can be tracked for multiple weeks.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig 1: (A) representative US/PA image of porcine anterior globe with relevant anatomical landmarks identified, (B) US/PA image immediately following adMSC injection into anterior chamber.
Fig 2: PA images taken before (A, B) and 4 hours after (C, D) adMSC injection into porcine eyes. Signals from AuNS (A, C) and background (B, D) were spectrally unmixed. adMSC delivery was confirmed at 4 hours (E) and at 1 week (F) by fluorescence microscopy. Panels A-D are from the same eye but image plane in C,D is slightly different to A,B.
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