DENSITY-DEPENDENT GROWTH-REGULATION OF PIG RETINAL-PIGMENT EPITHELIAL-CELLS IN-VITRO

Background: Transplantation of the retinal pigment epithelium (RPE) in volves delivering donor RPE onto a bare area of host Bruch's membrane that is surrounded by a confluent monolayer of RPE. We investigated th e effects of different plating densities and the presence of an adjace nt confluent monolayer on the growth characteristics and final morphol ogy of pig RPE in vitro. Methods: In single-well experiments, porcine RPE were plated in 24-well plates at densities varying from 1 to 75 ce lls/mm(2). Triplicate plates were counted on the 3rd and 10th days aft er plating and at confluence. A multiwell chamber was built to allow c ells plated at different densities to be bathed with conditioned media from adjoining wells. Results: In single-well experiments, plating at low densities increased the time to reach confluence and resulted in fewer, larger and more fusiform RPE at confluence. In multiwell experi ments, the growth rate of cells plated at low density decreased as the amount of high-density medium increased in communicating wells and le d to smaller, rounder cells at confluence. The presence of low-density RPE in adjoining wells increased the growth rate of RPE plated at hig h density and produced fewer, larger and more fusiform cells at conflu ence. Newly plated RPE grew more slowly when confluent monolayers of R PE were present in adjoining wells. Conclusions: Plating density is a critical factor in determining the growth rate and the final morpholog y of RPE in tissue culture. The presence of a neighboring confluent mo nolayer of RPE inhibits the growth rate of newly plat ed RPE in vitro.