A subpopulation of retinal pigment epithelial cells capable of in vivo regeneration identified by Bromo–2’–deoxyuridine incorporation.

Abstract

Abstract: : Purpose: To identify a possible subpopulation of the retinal pigment epithelium (RPE) capable of dividing in response to ‘submacular’ surgery with central RPE injury. Methods: 3 month old Danish Landrace pigs underwent a standard 3 port vitrectomy on the left eye and had either RPE a mechnically removed (n=6) or amnion membrane transplanted subretinally (n=5) or both (n=1). Dividing cells were identified by their incorporation of the thymidine analogue, (+)–5–Bromo–2’–deoxyuridine (5–BrdU) (Sigma–Aldrich, DK) injected intravenously at postoperative day 0 and day 1. Operated left eyes were collected and examined histologically at 2 (n=10), 5 (n=1) and 14 (n=1) day’s survival times. Right eyes were used as controls. The eyes were cut in sagittal sections. Immuno–histochemistry using an Anti–Bromodeoxyuridine antibody (Clone BU–33, Sigma–Aldrich, DK) was performed in order to identify cells that incorporated 5–BrdU. The RPE cell layer was divided into 4 concentric zones, and the number of 5–BrdU positive cells per lightmicroscopic field was counted. Results: Control eyes showed 1–2 5–BrdU positive RPE cells per field in each section. Operated eyes showed in contrast a very high number of 5–BrdU positive RPE cells. Dividing cells were found only in the equatorial regions, and predominantly in the areas near Ora Serrata. No reactive cells were found in proximity to the central surgical injury. Conclusions: Central RPE injury causes cell division in the equatorial RPE. Despite RPE is considered a stationary cell population, apparently there is an equatorial subpopulation of RPE cells that is capable of dividing in response to injury.

Keywords: retinal pigment epithelium • wound healing • transplantation