Effects of Glial Cell Line-derived Neurotrophic Factor on the Cultured Adult Full-thickness Porcine Retina

Background: The tissue culture system offers a possibility to study factors involved in neuronal survival which may be important in a transplantation paradigm. The use of adult tissue in this setting poses specific challenges since traditionally mature neurons survive poorly in vitro. In the current paper, we have explored effects of glial cell line-derived neurotrophic factor (GDNF) on cultures of adult porcine retina. Methods: Full-thickness retinal sheets were isolated from adult porcine eyes and were cultured for 5 or 10 days under standard culture conditions with or without GDNF added to the culture medium. The grafts were analyzed morphologically using hematoxylin and eosin staining, immunohistochemistry and transferase dUTP nick end labeling (TUNEL) labeling. Retinas derived from normal adult porcine eyes were used as controls. Results: After 5 d in vitro (DIV), cultures without GDNF showed dissolving retinal lamination while specimens cultured with GDNF displayed the normal laminated morphology. At 10 DIV, the untreated cultures had been reduced to a degenerated cell mass, while the GDNF-cultured specimens retained thin but distinguishable retinal layers. TUNEL labeling confirmed these results. Immunohistochemical labelings and outer nuclear layer thickness measurements showed an increased preservation of photoreceptors and horizontal cells in the GDNF-treated group. Conclusions: The procedure of culturing retina involves several steps causing severe traumatic effects on the tissue, such as ganglion cell axotomy, interruption of the blood flow as well as separation from the retinal pigment epithelium (RPE). In this paper, we have shown that addition of GDNF in the culture medium attenuates the effect of these steps, resulting in enhanced preservation of several retinal neuronal subtypes. The results may be of importance for research in retinal transplantation where storage time of the donor tissue prior to transplantation is a critical issue.