Polarized Light Microscopy for Quantitative Assessment of Sarcomere-Scale Structural Order in Cardiac Tissue

Polarization-resolved imaging provides a powerful, label-free means of visualizing anisotropic structural order in biological tissue, yet its quantitative exploitation remains limited in routine microscopy. Here, we present a polarization-resolved imaging approach based on polarized light microscopy (PLM) that enables automated, quantitative extraction of sarcomere-scale structural metrics from unstained cardiac tissue sections. Using experimental rat models of acute cardiorespiratory arrest as controlled test systems, we demonstrate that polarization-derived intensity profiles encode reproducible information on sarcomere length and band composition, with distinct patterns of structural compression observed across experimental conditions. Image-derived measurements were validated against conventional histological and immunohistochemical staining, highlighting the complementary value of polarization contrast for rapid, staining-free assessment of tissue anisotropy. Rather than addressing diagnostic specificity, this proof-of-concept study establishes PLM as a scalable quantitative imaging modality for polarization-resolved analysis of hierarchical structural order in biological tissue, with potential integration into multimodal imaging workflows in biomedical research.