INCREASED EXPRESSION OF P21(SDI1) ADRENOCORTICAL-CELLS WHEN THEY ARE PLACED IN CULTURE

Expression of the cell cycle inhibitor p21(Sdi1/WAF1/Cip1) was investi gated in a differentiated cell type, the adrenocortical cell, at diffe rent stages of culture, from the preparation of cells from the adrenal gland to senescence after long-term growth. In bovine adrenocortical cells, expression of SDI1 was much higher in culture than in vivo. Ele vation of SDI1 mRNA, accompanied by elevation of the level of a protei n reacting with anti-p21(Sid1) antibodies, was observed as early as 3 h after the start of the tissue dissociation procedure used to prepare cells for culture. This level of expression was then maintained durin g plating and subsequent long-term growth in culture. Growth and quies cence in bovine adrenocortical cells can be modulated by inclusion or removal of FGF from the culture medium. In these cells SDI1 mRNA was n ot increased by long-term mitotic quiescence resulting from FGF depriv ation. In cultured fetal human adrenocortical cells, SDI1 mRNA was als o detected at all stages of the culture life span, including 2 days af ter isolation of cells from the adrenal gland and plating in culture. Midlife-span cells had higher SDI1 mRNA than senescent human fibroblas ts. Clones of human adrenocortical cells nearing senescence in culture had somewhat higher SDI1 mRNA than early passage cells. Thus, SDI1 ex pression in adrenocortical cells is not associated with mitotic quiesc ence either in vivo or in vitro, yet isolation of the cells and cultur ing them exerts a powerful inductive influence on its expression. (C) 1995 Academic Press, Inc.