Substrate Stiffness-Driven Membrane Tension Modulates Vesicular Trafficking via Caveolin-1.

Area of Science:

• Cell Biology
• Biochemistry
• Gastroenterology

Background:

• Liver fibrosis involves excessive extracellular matrix (ECM) deposition and cross-linking, driven by hepatic stellate cells (HSCs).
• Dysregulated ECM remodeling and increased matrix stiffness in HSCs contribute to chronic liver disease, including cirrhosis and hepatocellular carcinoma.
• Tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) is crucial for ECM remodeling, but its post-translational regulation by mechanical cues in HSCs is not fully understood.

Purpose of the Study:

• To elucidate the mechanism by which mechanical stimuli regulate TIMP-1 expression at the post-translational level in HSCs.
• To identify the role of plasma membrane tension and associated signaling pathways in TIMP-1 secretion.
• To investigate the relevance of these findings in liver fibrosis models and clinical conditions like cirrhosis and hepatocellular carcinoma.

Main Methods:

• Investigated the impact of matrix stiffness on TIMP-1 protein and mRNA expression in HSCs.
• Utilized 3D fibrosis models with encapsulated HSCs in polypeptide hydrogels.
• Examined the involvement of the β1 integrin/RhoA axis, caveolin-1, and dynamin-2 in TIMP-1 secretion.
• Analyzed TIMP-1 and caveolin-1 expression in patient samples with cirrhosis and hepatocellular carcinoma.

Main Results:

• Matrix stiffness regulates plasma membrane tension, leading to elevated TIMP-1 exocytosis and secretion in HSCs.
• This stiffness-dependent secretion is mediated by the β1 integrin/RhoA axis and requires caveolin-1 and dynamin-2.
• Increased TIMP-1 and caveolin-1 expression was observed in cirrhosis and hepatocellular carcinoma, conditions associated with fibrosis.
• The observed effects were recapitulated in a 3D HSC-based fibrosis model.

Conclusions:

• Stiffness-dependent plasma membrane tension is a key regulator of TIMP-1 secretion and function in HSCs.
• The β1 integrin/RhoA, caveolin-1, and dynamin-2 pathways are critical for this mechanotransduction process.
• TIMP-1 and caveolin-1 upregulation in fibrotic liver diseases highlights their potential as therapeutic targets for modulating ECM remodeling.