Localization of BrdU–Labeled Cells in Retina and Iris–Ciliary Body During Development in Rat Eyes

Abstract

Abstract: : Purpose: To investigate the number and localization of possible stem and/or proliferating cells with DNA synthesis properties, bromodeoxiuridine (BrdU)–labeled cells were identified in iris–ciliary body and retina during developmental stages. Methods: Sprague–Dawley (SD) rats were treated with BrdU(5mg/100g body weight) intraperitoneally for 3 consecutive days at embryonal day 12 (E12), postnatal day 1 (P1), P7 and P14. Eyes were enucleated at P14, P28 and P56, and were subjected to immunohistochemistry for BrdU and cell type markers including nestin. Adult rats were also treated with BrdU. Results: In eyes with BrdU treatments on E12, BrdU–labeled cells were found in ganglion cell layer (GCL) at both central and peripheral retinas. In eyes with BrdU injection on P1, a large number of BrdU–labeled cells were noted in inner nuclear cell layer (INL) and outer nuclear cell layer (ONL) at central and peripheral retina. After then, BrdU–labeled cells were localized at peripheral retina (in INL and ONL), ciliary body and iris. In eyes with BrdU treatments on P14, BrdU–labeled cells were found only at ciliary body and iris, but no positive cells in retina. In adult eyes with BrdU treatments, only a very small number of BrdU–labeled cells were present at the surface regions of ciliary body and iris. No BrdU–labeled cells were present at central retina in eyes injected on P7, P14 and adult rats. There were no significant changes in the number and distribution of BrdU–labeled cells from P14 to P56 in eyes with BrdU injection on E12, P1, P7 and P14. Also, additional immunohistochemical studies showed some of BrdU–labeled cells localized on the surface of iris–ciliary body are immunoreactive to nestin, immature neural cell type marker. Conclusions: Our studies showed that proliferating (BrdU–labeled) cells are equivalent to differentiating cells during retinal development, and that some of the BrdU–labeled cells in adult eyes may be accordance with retinal stem cells.

Keywords: retinal development