Abstract
Purpose::
Many studies have transplanted neural progenitor cells into damaged retinas to replace lost neurons. In these studies, the loss of vision has been attenuated although there have been few compelling examples of neuron-replacement. The transplanted cells in these studies have not been shown to directly contribute to host retinal circuitry. However, the data are convincing that retinal function is maintained to a greater extent when transplanted cells are present. Thus, the purpose of this study was to characterize the ability of chicken Retinal Progenitor Cells (RPCs) to promote neuronal survival.
Methods::
We utilized a co-culture system where a feeder layer of chicken RPCs from varying developmental stages was labeled with the nuclear dye Hoechst 33342. A donor layer of mature neurons was labeled with Dye Cycle Orange and plated on top of the feeder layer. This co-culture was maintained for varying lengths of time and immunolabeled to determine the number of surviving neurons. For transplantation studies, E4 RPCs were virally transfected with a GFP reporter (RCAS-eGFP). The RPCs were injected into the vitreous of postnatal birds one day after NMDA-induced retinal injury.
Results::
We found a five-fold increase in the survival of neurons when cultured with E4 RPCs than when cultured alone. Transplanted RPCs that integrated into the retina failed to express any markers of mature neurons. By contrast, we find evidence for neuronal differentiation when the RPCs remained in the vitreous as a colony.
Conclusions::
We conclude that RPCs promote the survival of mature neurons in culture. Additional studies have found that embryo-derived RPCs can integrate into the injured retina. We propose that RPCs could be transplanted to promote the survival of retinal neurons in diseased retinas.
Keywords: cell survival • retina • transplantation