Absence of SPARC results in increased cardiac rupture and dysfunction after acute myocardial infarction

Area of Science:

• Cardiovascular Biology
• Extracellular Matrix Research
• Wound Healing Mechanisms

Background:

• The matricellular protein SPARC (secreted protein, acidic and rich in cysteine) plays a role in cell-matrix interactions and extracellular matrix (ECM) regulation.
• Its function in myocardial infarction (MI) healing and cardiac ECM maturation remains largely unexplored.

Purpose of the Study:

• To investigate the role of SPARC in infarct healing and ECM maturation following myocardial infarction (MI).
• To assess the therapeutic potential of SPARC in preventing cardiac dysfunction post-MI.

Main Methods:

• Utilized SPARC-null and wild-type (WT) mice models for MI.
• Administered adenoviral SPARC overexpression in WT mice.
• Conducted in vitro studies using cardiac fibroblasts with SPARC manipulation.
• Analyzed Smad2 phosphorylation pathways and transforming growth factor beta (TGF-β) signaling.

Main Results:

• SPARC deficiency in mice led to a fourfold increase in mortality post-MI, primarily due to cardiac rupture and failure.
• SPARC-null infarcts showed disorganized granulation tissue and immature collagenous ECM.
• Adenoviral SPARC overexpression in WT mice enhanced collagen maturation and prevented cardiac dilatation and dysfunction.
• SPARC influenced TGF-β-mediated Smad2 phosphorylation in cardiac fibroblasts and in vivo.

Conclusions:

• Local SPARC production is essential for maintaining cardiac ECM integrity after MI.
• SPARC demonstrates significant protective effects against cardiac rupture, dilatation, and dysfunction post-MI.
• SPARC represents a potential therapeutic target for improving outcomes after myocardial infarction.