Refractive Index-Corrected Light-Sheet Microscopy for Macro-View Cardiovascular Imaging

Light-sheet fluorescence microscopy (LSFM) enables rapid data acquisition with minimal phototoxicity, while optical clearing reduces light scattering by matching sample and imaging medium refractive indices (RIs). Emerging clearing methods extend from cells and organoids to entire organs and organisms, prompting macro-view LSFM microscopes with macro-objectives for low-magnification imaging of larger specimens at adequate resolution. In cardiovascular studies, multiple organs often require imaging, yet clearing protocols optimized for different organs alter the sample RIs inconsistently. Standard-size dipping objectives use correction collars for RI adaptation, but macro-objectives, owing to their large size and long working distances, are typically dry lenses lacking built-in RI correction. An RI-corrected (rc)-LSFM macro-view system addresses this limitation by accommodating a broad range of RI values. By integrating axial sweeping, multi-view imaging, and a closed quartz chamber, the rc-LSFM improves field of view (up to ≈8.8 mm), isotropy, spatial resolution (≈3 µm), and operational safety. It effectively visualizes microvascular networks in zebrafish embryos and post-natal mouse retina, traces the stem cell lineage of cardiomyocytes in mouse embryos, and reveals sympathetic nerve innervation in adult mouse aorta. The rc-LSFM macro-view system is compatible with various optical clearing protocols for multi-scale imaging with high isotropy and spatial resolution.