Abstract
Purpose:
Several approaches to treat blindness are being tested, ranging from virus-vector mediated optogenetic therapy (Busskamp et al 2010) to implantable chips to electrically stimulate surviving retinal neurons (Zrenner 2002). To further develop and improve these methods, in particular for translational aspects (clinical treatment of patients), it is desirable to examine the treatment success directly on human retina. Thus, our goal was to establish an in-vitro testing system for the evaluation of treatment approaches in human retina. This includes: (1) evaluating if post mortem human retina is suited for this purpose, in particular (2) a detailed characterization of ischemic influences on the retina and (3) the establishment of organotypic tissue culture conditions for the human retina.
Methods:
We systematically investigated the influence of duration of ischemia on the health status of post-mortem pig retina. Human retina was obtained from enucleations (ex-vivo) and cornea donations (post-mortem) from the University Eye Hospital of Tübingen. For both pig and human retina, the viability was assessed by electrophysiological recordings (MEA) and histologically. Furthermore, we set up a tissue culturing procedure to maintain the retina in healthy conditions.
Results:
Despite the current opinion that retinal ganglion cell death during ischemia begins after 2 hours, and is completed after 4 hours (Hayreh & Zimmerman 2005), we were able to record ganglion cell spiking activity in pig retina after up to 14 hours ischemia time. Ganglion cells of post mortem human retina, were still activity when the tissue was obtained 15, 25 (2x) and even 27.5 hours post mortem. In culture, ganglion cells of the 25h-old post mortem human retina maintained activity for at least 96 hours. Additionally, we were able to maintain light responsiveness in cultured retina (obtained ex vivo) for at least 48 (mouse), 72 (pig), and 24 (human) hours.
Conclusions:
Our results demonstrate that retinal ganglion cells can survive ischemia considerably longer than expected. With such tissue, we have successfully established culture conditions to maintain human retina in an active physiological state for several days, so that it remains accessible for testing treatment approaches. In addition, our results may be relevant for assessing the time frame within which the treatment of retinal central artery occlusions is indicated.
Keywords: 572 ischemia •
531 ganglion cells •
694 retinal culture