Alterations of tropoelastin biosynthesis by elastase damage to smooth muscle cell matrices

The effect of porcine pancreatic elastase (PPE)-induced proteolysis of the extracellular matrix on elastin biosynthesis in neonatal rat aortic smooth muscle cell cultures (NRSMC) was examined. The quantity of insoluble elastin remaining in the damaged cultures decreased with increasing amounts of enzyme used, however no significant cell damage was demonstrated. The accumulation of soluble elastin (tropoelastin) was examined in enzyme injured and control cultures by radiolabelling with [3H]-valine for 4 hours. The tropoelastin content of both the cell layer and media were less in injured cultures on the day of injury and up to one week later when compared to control cultures. In addition, experiments in which cultures were radiolabelled for 15 minutes demonstrated that the biosynthesis of tropoelastin was decreased in the enzyme treated cultures. Moreover, the incorporation of radiolabelled elastin into the insoluble matrix also decreased. Steady-state levels of elastin mRNA showed no differences between injured and control cultures, which suggested that elastin synthesis is affected at a translational or post-translational level.