Inhibition of profibrotic microRNA-21 affects platelets and their releasate

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiovascular Research

Background:

• Fibrosis is a significant cause of organ damage with limited therapeutic options.
• MicroRNA-21 (miR-21) is implicated in fibrogenesis, and miR-21 inhibitors are in clinical trials.

Purpose of the Study:

• To investigate the mechanisms by which miR-21 inhibition may reduce fibrosis.
• To explore the role of miR-21 in extracellular matrix (ECM) regulation and profibrotic factor secretion.

Main Methods:

• Proteomics analysis of murine cardiac fibroblasts and hearts from miR-21-null mice.
• Correlation analysis of plasma miR-21 levels with profibrotic factors in human samples (Bruneck Study).
• In vivo studies using antagomiR-21 to inhibit miR-21 and assessing platelet TGF-β1 release and Wiskott-Aldrich syndrome protein (WASP) as a direct miR-21 target.

Main Results:

• miR-21 inhibition showed limited direct effects on ECM protein secretion in cardiac fibroblasts or cardiac ECM composition in miR-21-null mice.
• Plasma miR-21 levels correlated with platelet-derived profibrotic factors, including TGF-β1.
• Pharmacological miR-21 inhibition reduced platelet release of TGF-β1, identifying WASP as a direct target.
• miR-21-null mice exhibited altered platelet, leukocyte, and megakaryocyte counts.

Conclusions:

• miR-21 inhibition may attenuate fibrosis through a previously unrecognized effect on platelet function.
• Reducing platelet TGF-β1 release via miR-21 inhibition is a potential therapeutic strategy for fibrotic diseases.