Abstract
Abstract: :
Purpose: To test whether there are neural precursors in the non-pigmented epithelium (NPE) of the ciliary body of the chicken eye. The NPE is continuous with the neural retina and is derived from the neural tube during embryonic development. However, this tissue normally does not contain neurons and functions to produce components of the aqueous humor. Methods: We made intraocular injections of insulin, EGF or FGF2. Subsequently, we assayed for proliferation, by using BrdU-labeling, and neuronal markers, by using standard immunocytochemical techniques, in whole-mount preparations and sections of the ciliary body. Results: We found that these growth factors stimulate NPE cells to proliferate and differentiate into neurons. These growth factors had region-specific effects along the radial axis of the ciliary body, with insulin and EGF stimulating proliferation of NPE cells close to the retina, while FGF2 stimulated the proliferation of NPE cells further toward the lens. Similar region-specific effects were observed for accumulations of neurons in the NPE in response to injections of different growth factors. The neurons derived from NPE cells express neurofilament, ß3 tubulin, RA4, calretinin, Islet1, or Hu, and a few produced long axonal projections, several mm in length that extend across the ciliary body. Conclusions: Our results suggest that the NPE cells of the ciliary body have the capacity to generate retinal neurons. Some of the NPE cells may be a quiescent form of retinal stem cell.
Keywords: retinal development • ganglion cells • growth factors/growth factor receptors