CHARACTERIZATION OF A RAT GLOMERULAR VISCERAL EPITHELIAL-CELL LINE

Cultures of glomerular epithelial cells (GEC) are currently used to id entify important cellular and molecular mechanisms involved in the pat hogenesis of renal diseases. However, there is still controversy in th e literature as to the visceral or parietal origin of cultured GEC. Ou r aim was to firmly establish the nature of a GEC cell line. The react ivity of cultured GEC was investigated with a large panel of mono- and polyclonal antibodies by using immunofluorescent techniques and compa red with literature data on the in vivo expression of these antigens o n podocytes. In addition, the podocyte specific 5A (podocalyxin), 13A and 27A (9-O-acetylated GD3) antigen expression was investigated in im mune-overlay experiments with isolated gangliosides and in immunopreci pitations with metabolically labelled cells. In general, immunoreactiv ities between cultured GEC and literature data on GEC in vivo expressi ons were similar. Important podocyte epitopes in vivo were expressed b y cultured GEC such as podocalyxin, gp330 and the 13A antigen. Culture d GEC however differed from their in vivo counterparts in their expres sion of keratin-18, their lack of expression of pp44 and no detectable immunohistological expression of the ganglioside 9-O-acetylated GD3. Interestingly, the podocyte-specific epitope 9-O-acetylated GD3 was de tected by the 27A antibodies in immune-overlays of isolated GEC gangli osides. Moreover, by using the 27A antibody, we were able to precipita te the podocyte-specific 103-kD protein from S-35-methionine metabolic ally labelled GEC. From our immunohistological data together with the detectability of the 27A antigen we conclude that the cell line we use very probably originates from glomerular visceral epithelial cells.