HEPARIN-BINDING EPIDERMAL GROWTH FACTOR-LIKE GROWTH-FACTOR EXPRESSION IN CULTURED FETAL HUMAN VASCULAR SMOOTH-MUSCLE CELLS - INDUCTION OF MESSENGER-RNA LEVELS AND SECRETION OF ACTIVE MITOGEN

Heparin-binding EGF-like growth factor (HB-EGF) is a recently identified potent mitogen for smooth muscle cells (SMC). To explore whether SMC can also synthesize HB-EGF, cultured fetal human vascular SMC (FHVSMC) were analyzed for the production of HB-EGF mRNA and active growth factor. It was found that in FHVSMC, HB-EGF has the characteristics of an early response gene in that (i) the addition of fresh 10% fetal calf serum to serum-starved FHVSMC led to a rapid and transient rise in HB-EGF mRNA levels with a maximal induction of 12-14-fold occurring within 2-4 h, (ii) the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) also elevated HB-EGF mRNA levels rapidly and transiently with a maximal induction of 7-8-fold occurring at 2-4 h, and (iii) cyclohexamide at 40 mug/ml markedly increased basal, serum-, and TPA-induced HB-EGF mRNA levels. In addition, HB-EGF mRNA levels were increased 7-11-fold by addition of either HB-EGF itself, platelet-derived growth factor, or basic fibroblast growth factor, all potent SMC mitogens. Besides synthesizing HB-EGF mRNA, FHVSMC were found to release into conditioned medium a bioactive HB-EGF-like protein that cross-reacted with anti-HB-EGF antibody.