A HEPARIN-BINDING FORM OF PLACENTA GROWTH-FACTOR (PLGF-2) IS EXPRESSED IN HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS AND IN PLACENTA

Placenta Growth Factor (PlGF) was recently discovered as a secreted gr owth factor for vascular endothelial cells and based on its homology t o vascular endothelial growth factor (VEGF), can be classified as a ne w member of this growth factor family. We have carried out polymerase chain amplification (PCR) of RNA from human umbilical vein endothelial cells and placenta tissue and discovered a second species of PlGF, Pl GF-2. PlGF-2 has a 21-amino acid insertion not present in PlGF-1 codin g for a highly basic region near the C-terminus. This is similar to VE GF189. Northern analysis has shown, that the PlGF gene is expressed on ly in a limited number of cell types and tissues, e.g. human umbilical vein endothelial cells (HUVE) and placenta. Infection of Sf158 insect cells with recombinant baculoviruses specific for the two forms showe d, that both, PlGF-1 and PlGF-2 are secreted efficiently into the supe rnatant and PlGF-2 can bind with high affinity to heparin. Both PlGF f orms had a similar mitog enic potency for bovine aortic endothelial ce lls. Binding studies with I-125-VEGF(165) demonstrate, that supernatan t of PlGF expressing insect cells can compete for receptor binding. Si milar to VEGF, PlGF can exist in different forms which are probably ge nerated by differential splicing. The occurrence of two molecular form s of this endothelial specific growth factor suggests different physio logical roles of the two forms during placental development and differ entiation.