REGULATION OF PROLIFERATION AND PHOTORECEPTOR DIFFERENTIATION IN FETAL HUMAN RETINAL CELL-CULTURES

Purpose. To examine whether fetal human retinal cells can be maintaine d in vitro over long time periods and to determine whether exogenous g rowth factors can be used to generate large numbers of photoreceptors within these cultures. Methods. Fetal human retinas (6 to 13 weeks aft er conception) were dissected, dissociated, and plated into culture we lls. Specific growth Factors and steroid/thyroid hormones, which have been shown to influence retinal progenitor cell proliferation and diff erentiation in rats, were added to the culture medium to determine whe ther any of these factors had similar effects on human retinal cells. Results. Fetal human retinal cells survived and continued to prolifera te for up to 300 days in vitro. Under control conditions, 15 million c ells were generated from an initial plating of 100,000 cells; however, the addition of either epidermal growth factor or basic fibroblast gr owth factor stimulated proliferation and resulted in the generation of more than 100 million cells. A percentage of these cells was induced to differentiate as photoreceptors by adding either retinoic acid or t riiodo-thyronine to the culture medium. Conclusions. Fetal human retin al cells can be maintained and expanded in vitro, indicating that this technique may be useful for generating large numbers of retinal cells . The number and types of cells generated can be influenced by adding exogenous factors to the culture medium. The response of human retinal cells to growth factors and hormones is similar to the response of ro dent retinal cells to the same factors, suggesting that the effects of these factors are conserved across species.