Changes in extracellular collagen matrix alter myocardial systolic performance

Area of Science:

• Cardiovascular Biology
• Extracellular Matrix Research
• Cardiac Physiology

Background:

• The extracellular matrix, particularly fibrillar collagen, plays a critical role in cardiac structure and function.
• Understanding the specific contribution of collagen to myocardial mechanics is essential for comprehending heart disease.
• Previous research suggests collagen influences force transmission but direct evidence is limited.

Purpose of the Study:

• To investigate the impact of acute disruption of fibrillar collagen on myocardial systolic performance.
• To determine if collagen degradation affects cardiomyocyte contractility independently of overall heart muscle function.
• To test the hypothesis that fibrillar collagen is crucial for translating cardiomyocyte contraction into effective myocardial force.

Main Methods:

• Isolated papillary muscles from animal models were treated with plasmin to induce collagen degradation.
• Gelatin zymography, hydroxyproline assays, and scanning electron microscopy were used to confirm collagen degradation and matrix metalloproteinase activation.
• Myocardial systolic performance was assessed by measuring isotonic shortening extent and isometric developed tension.
• Cardiomyocyte contractility was evaluated by measuring shortening extent and velocity in isolated cells.

Main Results:

• Plasmin treatment led to significant collagen degradation and matrix metalloproteinase activation.
• Myocardial systolic performance decreased significantly, with reduced isotonic shortening extent and isometric developed tension.
• Isolated cardiomyocyte contractility (shortening extent and velocity) was not altered by plasmin treatment.
• A significant reduction in myocardial systolic performance was observed following acute collagen disruption.

Conclusions:

• Acute disruption of the fibrillar collagen network significantly impairs myocardial systolic performance.
• Fibrillar collagen is essential for the effective transduction of cardiomyocyte contraction into myocardial force.
• These findings highlight the mechanical role of the extracellular matrix in maintaining normal cardiac systolic function.
• The study supports the hypothesis that fibrillar collagen is vital for myocardial performance, independent of individual cardiomyocyte contractility.