[Effect of platelet-derived growth factor PDGF on replication of cultivated bovine lens epithelial cells]

It has previously been reported that PDGF isoforms AB and BB induce an increase of cytosolic free calcium in cultured bovine lens epithelial cells in a dose-dependent manner. To evaluate the biological capacity of PDGF, we investigated the proliferative response of bovine lens epithelial cells to stimulation with PDGF-AA, -AB and -BB. Since various unspecific components of serum-containing media act as mitogenes and mask the effect of PDGF, serum-free culture conditions were a prerequisite for growth-factor-induced effects. Therefore, a basic medium (Waymouth's MB 752/1 with Ham F12 Nutrient Mixture 1:2, v/v; Gibco BRL) was supplemented with only 2 mM CaCl2, 10 micrograms/ml Transferrin, 10 micrograms/ml Thyroglobulin (both Sigma Chemie) and standard amounts of antibiotics. PDGF isoforms were obtained by separate expression of cloned genes in Escherichia coli, which has been previously described. Under these conditions the isoforms PDGF-AB and -BB caused an increase in proliferation in a dose-dependent manner. The maximum increase of the cell number was 21% for PDGF-AB with an EC5 of 5 ng/ml. PDGF-BB revealed a maximum increase of 33% with an EC5 of 1.5 ng/ml. PDGF-AA, when used in similar concentration was ineffective. These data show the involvement of PDGF isoforms AB and BB in the replicative action of BLEC.