Calcein selectively binds to calcium-associated fibrillin-rich elastic fibers: A biochemical tool for visualizing...

This study evaluated calcein, a calcium-binding fluorescent dye, as a tool for visualizing elastic structures in connective tissue. Tissue samples from chicken and cow subcutaneous fascia and porcine auricular tissue were stained with calcein and examined by fluorescence microscopy. To assess specificity, the staining pattern was compared with established markers for elastic fibers and calcium deposits. In subcutaneous fascia, calcein labeled fibrous structures that overlapped with fibrillin-1-rich elastic fibers, and the signal disappeared after calcium removal or enzymatic degradation. In porcine auricular tissue, calcein strongly highlighted the outer layers of blood vessels, where elastic fibers are abundant. In contrast, the elastic cartilage region showed no calcein staining despite the presence of elastic fibers confirmed by Modified Verhoeff's staining; it was also negative for calcium deposition and fibrillin-1 immunolabeling. These results indicate that calcein selectively binds to calcium-associated elastic fibers and enables visualization of their structure in fascia. This method is rapid, reversible, and simple, though not applicable to all elastic tissues, making it a useful approach for studying elastic fiber organization in calcium-rich environments.