Abstract
Purpose: :
Explanted rat retinas show progressive photoreceptor degeneration that affects the inner retina, in particular the recoverin-expressing cone bipolar cells. Explantation is accompanied by activation of Müller- and microglial cells, as well as the retinal pigment epithelium (RPE). The purpose of this investigation was to detemine whether the presence of a feeder layer of human neural progenitor cells (HNPC) suppresses regressive and reactive changes in the rat explants.
Methods: :
The HNPC line was generated from forebrain tissue from one 9-week (postconception) embryo, and expanded as free-floating cell aggregates in DMEM-F12 medium with basic fibroblast growth factor, epidermal growth factor and leukemia inhibitory. Feeder layers of HNPCs were established two days after passage (mechanical dissociation), in DMEM-F12 medium with 10% fetal calf serum (FCS). Retinal explants were generated from postnatal day 11-13 rats. A single retina separated from the RPE was explanted onto a culture plate insert with the vitreal side oriented upwards, in DMEM/F12 medium and 10% FCS. The left retina was co-cultured with the feeder layer, and the corresponding right retina was grown in medium only as control. The effect of two cell concentrations of was studied, 2x105 and 1x104 cells, respectively, after 1 week in vitro.
Results: :
In control explants, immunohistochemical analysis showed extensive sprouting of rod photoreceptors axon terminals to the inner retina and a reduced density of recoverin-positive cone bipolar cells and their terminals in the inner plexiform layer. Indeed, both sprouting and cone bipolar cell degeneration were significantly lower in retinas cultured with a feeder layer compared to controls. Inner and outer nuclear layers were significantly thicker in retinas cultured with a feeder layer, which suggests an increased survival of photoreceptors and interneurons. Decreased activation and migration of microglia in the retinal layers was noted in explants grown in the presence of feeder layer cells.
Keywords: neuroprotection • retinal culture • photoreceptors