Identification of elastic fibers and lamellae in porcine pericardium and aorta by confocal, fluorescence and polarized light microscopy.

Pericardial connective tissue has been used to construct bioprostheses to repair various types of injuries, including aortic wall repairs. The arrangement and the distribution of elastic and collagen staple fibers are related directly to the biomechanical properties of the tissue and thus determine the choice tissue for the construction of bioprostheses. Although elastic fibers can be visualized using several histochemical methods, the specificity and mechanism of binding involved remain to be clarified. In this work, we compared the elastic net of the porcine pericardial matrix with that of the aortic wall using 1-anilino-8-naphthalene sulfonate (ANS) and dansyl chloride (DCl) as fluorescent probes and the permanganate-bisulfite-toluidine (PBT) method. Polarized light and fluorescence microscopy were simultaneously used to analyze the tissues. Some samples also were examined using confocal microscopy. Aorta and pericardium treated with ANS and DCl showed elastic fibers and lamellae with an intense blue fluorescence. When stained with the PBT method, the aortic elastic lamellae were clearly metachromatic and, under polarized light, they showed a greenish birefringence. DCl provided clearer fluorescent labelling of elastic fibers when examined using confocal microscopy.