uPA, uPAR and TGFβ₁ expression during early and late post myocardial infarction period in rat myocardium.

The expression patterns of transforming growth factor beta 1 (TGFβ₁), urokinase-type plasminogen activator (uPA) and uPA receptor (uPAR) were analysed after artery ligation-induced myocardial infarction (MI) in the rat myocardium. uPA and uPAR expressions were significantly increased both at transcriptional and protein level during early phase post MI period (uPA at 1 hour and uPAR at 24 hours post infarction). TGFβ1 mRNA expression profile revealed a significant increase of TGFβ1 expression from day 4 up to 8 weeks post infarction. These data suggest that the need for an increasing TGFβ₁ bioavailability during the post-infarction period in rat myocardium is achieved in the early post MI period by an increased expression of uPA/uPAR proteolytic system (indirect activation of latent TGFβ₁) and in the late post MI period by direct regulation of TGFβ₁ expression. It is therefore concluded that differential regulation of the TGFβ₁ bioavailability may be a crucial step of the repair mechanisms during the post MI infarction period in the rat myocardium.