Inhibition of endothelial cell growth by a factor isolated from cartilage

Abstract

An endothelial cell growth inhibitor (EGI), which affects proliferation of vascular endothelial cells, has been isolated from a 1 M guanidine hydrochloride extract of bovine cartilage by ion exchange chromatography on CM-Sephadex C-25. Two peaks of EGI activity were observed, both of which eluted in positions separate from a peak of trypsin inhibitory activity. Using bovine endothelial cells in culture, we have demonstrated that EGI is not cytotoxic, but rather affects the cell cycle. The average population doubling time increased from 24 h for cells grown in control media to 40 h when cells were grown in the presence of 2 μg EGI/ml of culture medium. The trypsin inhibitor isolated from cartilage had no effect on endothelial cell proliferation. As predicted by segmented regression analysis of the growth curves, we have shown that EGI remains active in the media for a period of 3 days. An appendix of the statistical treatment of the data by segmented regression analysis is presented.