A STUDY OF GROWTH-FACTOR RECEPTORS IN HUMAN LENS EPITHELIAL-CELLS ANDTHEIR RELATIONSHIP TO FIBER DIFFERENTIATION

Recent studies have demonstrated that several growth factors enhance f iber differentiation in cultured human lens epithelial (HLE) cells in early passages. However, these effects gradually decrease in cells of later passages. The purpose of this investigation is to test the hypot hesis that the decreasing effect of growth factors on fiber differenti ation in later passages may be due to a decrease or the inactivation o f growth factor receptors as a function of serial subcultures. Specime ns of HLE cells were obtained from infants. First through to fourth pa ssage cells were treated with 10 ng ml(-1) of epidermal growth factor, basic fibroblast growth factor or insulin-like growth factor-I. Fiber differentiation was determined from spontaneous lentoid formation by phase-contrast and transmission electron microscopy. Growth factor bin ding to the receptor on the cell surface was determined by transmissio n electron microscopy using the conjugates of colloidal gold and growt h factors, and the number of receptors on the cell surface were also q uantified by immunocytochemistry. Spontaneous lentoid formation was en hanced by all of the growth factors studied in the first passage. Howe ver, in the second and third passage only double layering of cells wit hout characteristic fiber differentiation was observed while in the fo urth passage, growth factors had no effect on differentiation. The num ber of growth factor bindings as well as the number of growth factor r eceptors gradually decreased with the number of passages. The loss of effect of growth factors on fiber differentiation with increasing numb er of passages correlated with the decrease in receptor number. (C) 19 96 Academic Press Limited