Abstract
Abstract: :
Purpose: The vertebrate retina is highly ordered along both its dorsoventral (DV) and nasotemporal (NT) axes. However, it is not known whether this order is maintained in cultured embryonic and adult ciliary epithelium (CE)–derived retinal progenitor cells (RPCs). This study was conducted to investigate the DV and NT gradients in these cultured RPCs. Methods: The embryonic 18 (E18) Wister rat neural retina and adult ciliary epithelium (CE) were divided into the dorsonasal (DN), dorsotemporal (DT), ventronasal (VN), and ventrotemporal (VT) portions, and the cells from the four portions were separately cultured to enrich RPCs by a monolayer or a sphere culture system. Cells were plated at a density of 5x105 and 1 x 104 cells/ well in the monolayer culture and sphere culture, respectively. To assess the properties of growth, overall cell number in the monolayer culture was determined, and the number and diameter of the sphere colonies were examined in the sphere culture after 7 days. Expression of DV and NT markers including Vax2, Tbx5, Eph–A3, B3, ephrin–A2, B1 was examined in these cultured RPCs. Results: No differences were observed in the overall cell number of the cells in the monolayer culture. RT–PCR analysis revealed that the RPCs expressed all the DV and NT markers tested. The number and the diameter of the sphere colonies obtained from E18 DT, DN, VT and VN retinal cells were 1.3, 0.3, 10, 0.4 per well and 76, 73, 78 and 60 μm, respectively. The number and the diameter of the sphere colonies obtained from adult DT, DN, VT and VN CE cells were 31, 25, 31, 23 per well and 76, 73, 78 and 60 μm, respectively. Spheres from E18 retinal cells expressed all DT and NT markers tested whereas the CE–derived spheres expressed Eph and ephrins but did not express detectable levels of Vax2 and Tbx5. The DV and NT markers were expressed in the RPCs in a manner that was not graded along the DV and VT axes. Conclusions:There are relatively minor differences in the growth properties among the RPCs from the different regions within the retina, and the RPCs are not intrinsically limited to express marker genes of regional identity, suggesting that RPCs might not be regionally specified within the retina.
Keywords: retinal development • retinal culture • retina