Full-Field Analysis Indicates Late Reperfusion Therapy Broadens and Mechanically Smooths the Borderzone During...

Area of Science:

• Cardiovascular Research
• Biomedical Engineering
• Regenerative Medicine

Background:

• Late reperfusion therapy (LRT) reduces ventricular rupture post-myocardial infarction (MI), but underlying mechanisms are unknown.
• Understanding the biomechanical changes in the infarct borderzone is crucial for improving therapeutic strategies.

Purpose of the Study:

• To investigate how LRT affects the structural and mechanical properties of the left ventricle extracellular matrix (LV ECM) during the inflammatory healing phase post-MI.
• To compare the biomechanical differences in the infarct borderzone between LRT and permanent occlusion (PO) models.

Main Methods:

• Utilized laser micrometry, planar biaxial testing, and quantitative polarized light imaging (QPLI) in Sprague-Dawley rats.
• Assessed geometric, mechanical, and structural properties of LV ECM 1-day post-MI in PO, LRT, and sham groups.
• Analyzed infarct borderzone size, stiffness gradients, and collagen fiber alignment.

Main Results:

• LRT resulted in a significantly larger infarct borderzone (31.5 mm²) compared to PO (22.5 mm²).
• Infarct core and borderzone stiffness decreased post-MI, with LRT showing smoother stiffness gradients than PO.
• While collagen alignment decreased in infarct cores, LRT showed more gradual transitions in alignment throughout the LV ECM.

Conclusions:

• LRT modifies infarct borderzone biomechanics, creating a larger and more uniformly stiffened region.
• These findings support LRT's protective effects and suggest potential for therapies targeting spatial modulation of post-MI tissue mechanics.
• Further research can leverage these insights to enhance patient outcomes after myocardial infarction.