Comparison of intracellular and extracellular mitogenic activity

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Endothelial cells secrete growth factors influencing cell proliferation.
• Endothelial cell-derived growth factor (ECDGF) is a known mitogen.
• The presence and nature of mitogenic activities within endothelial cell lysates require further characterization.

Purpose of the Study:

• To investigate the mitogenic activities present in endothelial cell lysates.
• To compare the properties of ECDGF with mitogenic activities found in cell lysates.
• To differentiate these mitogens from platelet-derived growth factor (PDGF).

Main Methods:

• In vitro culture of bovine aortic endothelial cells and other cell types.
• Preparation of cell lysates and isolation of secreted factors.
• Assays for mitogenic activity, including cell proliferation assays.
• Heat stability and trypsin sensitivity tests.
• Receptor competition assays to compare with PDGF.

Main Results:

• ECDGF, secreted by endothelial cells, is a mixture of heat-stable, trypsin-sensitive mitogens.
• Cell lysates from endothelial cells and other cell types contained significant mitogenic activity.
• Lysate mitogenic activities were heat-sensitive (56°C) and trypsin-resistant.
• Both ECDGF and lysate mitogens promoted cell proliferation.
• Lysate mitogens were distinguished from PDGF through receptor competition and other assays.

Conclusions:

• Endothelial cells contain and secrete distinct mitogenic factors.
• Cellular lysates harbor unique mitogenic activities with properties different from secreted ECDGF and PDGF.
• These findings suggest diverse intracellular and extracellular mitogenic signaling pathways in endothelial cells and related cell types.