The plasminogen-activating system in hepatic stellate cells

Area of Science:

• Cell Biology
• Biochemistry
• Liver Pathophysiology

Background:

• Hepatic stellate cells (HSCs) are central to liver fibrosis pathogenesis.
• HSCs contribute to extracellular matrix (ECM) production and matrix metalloproteinase (MMP) secretion.
• The plasminogen-activating system, involving urokinase plasminogen activator (uPA) and its inhibitor (PAI-1), regulates ECM degradation.

Purpose of the Study:

• To investigate the role of HSCs in plasmin generation.
• To assess the expression and activity of the plasminogen-activating system components in HSCs.
• To determine the effect of retinoic acid on HSCs' plasminogen-activating system.

Main Methods:

• Primary rat HSCs were cultured.
• Northern analysis was used to detect mRNA expression for PAI-1, uPA, and uPA receptor.
• Zymography and reverse zymography were employed to assess enzymatic activities.
• In vitro cultures were supplemented with plasminogen to measure plasmin generation.
• HSCs were treated with retinoic acid to evaluate its effects.

Main Results:

• HSCs express mRNA for PAI-1, uPA, and uPA receptor.
• Cell-surface-associated uPA activity and uPA/PAI-1 were detected in culture media.
• Net uPA activity peaked at 7 days, while PAI-1 remained elevated.
• HSCs actively generated plasmin in the presence of plasminogen.
• Retinoic acid treatment significantly increased uPA secretion (2.6-fold) without affecting PAI-1.

Conclusions:

• HSCs synthesize and secrete key components of the plasminogen-activating system.
• HSCs possess the capacity to generate plasmin, thereby regulating MMP activation.
• Increased uPA synthesis by retinoic acid in HSCs may play a role in matrix remodeling during stellate cell activation.