Extracellular matrix of porcine pericardium: biochemistry and collagen architecture.

Pericardial tissue has been used to construct bioprostheses employed in the repair of different kinds of injuries, mostly cardiac. However, calcification and mechanical failure have been the main causes of the limited durability of cardiac bioprostheses constructed with bovine pericardium. In the course of this work, a study was conducted on porcine fibrous pericardium, its microscopic structure and biochemical nature. The general morphology and architecture of collagen were studied under conventional light and polarized light microscopy. The biochemical study of the pericardial matrix was conducted according to the following procedures: swelling test, hydroxyproline and collagen dosage, quantification of amino acids in soluble collagen, component extraction of the extracellular matrix of the right and left ventral regions of pericardium with different molarities of guanidine chloride, protein and glycosaminoglycan (GAG) dosage, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and total GAG analysis. Microscopic analysis showed collagen fibers arranged in multidirectionally oriented layers forming a closely knit web, with a larger number of fibers obliquely oriented, initiating at the lower central region toward the upper left lateral relative to the heart. No qualitative differences were found between proteins extracted from the right and left regions. Likewise, no differences were found between fresh and frozen material. Protein dosages from left frontal and right frontal pericardium regions showed no significant differences. The quantities of extracted GAGs were too small for detection by the method used. Enzymatic digestion and electrophoretic analysis showed that the GAG found is possibly dermatan sulfate. The proteoglycan showed a running standard very similar to the small proteoglycan decorin.

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.