Interspecific interaction of aortic endothelial and smooth muscle cells.

The proliferation stimulating or inhibitory effect of aortic endothelial cells on aortic smooth muscle cells and vice versa was studied in cell culture by using a newly developed co-cultivation technique. The effect was registered as the incorporation of labelled thymidine detected by liquid scintillation counting. The experiments were performed in intra and interspecific combinations, using bovine, pig or rat aortic cell cultures. The endothelial cells stimulated smooth muscle cell proliferation in a species specific way. In interspecies combinations either inhibition or no effect was observed. The smooth muscle cells usually had an inhibitory effect on the proliferation of endothelial cells except for the pig smooth muscle cells which had a stimulatory effect in both inter and intraspecies combinations. Co-cultivation of smooth muscle or endothelial cells with cells of the same type resulted mostly in inhibition or no effect in both intra and interspecies combinations. This phenomenon was particularly conspicuous with endothelial cells. The different stimulatory and inhibitory effects produced by these cells may play an important role in the regulation of neovascularization and in reendothelization of denuded intimal areas.