Abstract
Purpose: :
To fully characterize the sphere forming cells arising from the adult ciliary epithelium.
Methods: :
Ciliary epithelia (CE) and spheres derived from ciliary epithelia were analyzed by TEM, real-time RT-PCR, dual beam electron microscopy (FIB) and immuno-fluorescence. Cultures of differentiated spheres were analyzed by immuno-fluorescence. Cell cycle analysis was done with the addition of 3H-thymidine. Adult retina, RPE, iris, and CE, as well as adult brain SVZ (sub-ventricular zone) and neurospheres derived from the adult SVZ, were used as controls.
Results: :
Data from our cell cycle labeling studies as well as dual beam FIB indicates that the proliferative cells maintain their differentiated ciliary phenotype. Cells in CE-derived spheres had junctional complexes such as tight junctions, similar to the CE from which they were derived. CE-derived spheres expressed genes that are found in the CE and few retinal markers. Differentiated cultures expressed genes of both the CE and the retina.
Conclusions: :
The cells that form spheres in vitro more closely resemble the cells of the ciliary epithelium than those of the retina. The data are more consistent with a transdifferentiation mechanism rather than a stem cell mechanism.
Keywords: ciliary body • differentiation • proliferation