Connective Tissue Growth Factor

Connective tissue growth factor (CTGF) is secreted by human umbilical vein endothelial cells and has a biological activity related to that of platelet-derived growth factor (PDGF). Human umbilical vein endothelial cells have been previously reported to secrete PDGF-related factors into the media. DiCorleto et at. reported that endothelial cells secrete factors that are chemotactic and mitogenic for connective tissue cells and around 30% of this activity was neutralized by antihuman PDGF antibodies (1). Collins et at. reported that human umbilical vein endothelial cells express both the A and B chain genes of PDGF (2, 3). Thus the mitoattractant activity found in human umbilical vein endothelial cells was thought to be due to PDGF gene products. However, the exact nature of this protein was uncertain. We tried to determine the properties of the PDGF-related molecules secreted by human umbilical vein endothelial cells and found a new peptide distinct from PDGF (4). Confluent human umbilical vein endothelial cells were incubated in serum free media for 6 and 48 hours. Then conditioned media was recovered and analyzed by Western blotting which was probed with anti-PDGF antibody. We detected 36-38kd molecules which were bigger than PDGF B chain dimers. Neither anti amino terminal A chain nor anticarboxy terminal B chain antibody picked up this band, indicating that this peptide does not contain PDGF A or B chain peptides. In reduced conditions, the band appeared at 38kd, indicating that this peptide is a monomer. We termed this protein CTGF. We purified CTGF from the conditioned media using an affinity column made with the anti-PDGF antibody and an Affigel 10 support. We performed chemotactic and mitogenic assays using NIH3T3 cells. These data show that CTGF has biological activities affecting these cells, as do PDGF isoforms.