tannins and Calcinosis

The lifetime of bioprosthetic heart valves (BHVs) is limited by the mechanical damage and calcification. The major components of BHVs are collagen and elastin. Collagen could be well protected by glutaraldehyde (GLUT) crosslinking, while elastin is not stabilized and has a high risk of degradation, which could lead to the calcification of BHVs. We aimed to develop methods for stabilizing elastin and decreasing calcification. We investigated the combined tannic acid (TA) or epigallocatechin gallate (EGCG) with ferric chloride to stabilize elastin and prevent calcification. We found that the amount of TA/EGCG bound to elastin was in a time-dependent pattern and this reaction showed better efficiency in acidic condition and ethanol-water mixed solvents. Moreover, Fe

Topics: Animals; Bioprosthesis; Calcinosis; Catechin; Chlorides; Collagen; Cross-Linking Reagents; Elastin; Ferric Compounds; Glutaral; Heart Valve Prosthesis; Male; Pericardium; Polyphenols; Protein Stability; Rats, Sprague-Dawley; Swine; Tannins; Tensile Strength

Bioprosthetic heart valves derived from glutaraldehyde (Glut)-fixed xenografts have been widely used to replace diseased cardiac valves. However, calcification and degeneration are common following their implantation. Inflammation is closely associated with calcification of Glut-fixed xenografts via macrophage infiltration. Tannic acid (TA) possesses anti-inflammatory effects. This study was designed to investigate the anti-calcification of TA treatment on the Glut-fixed bovine pericardium (BP) in a rat subdermal model.. Fresh BP was divided into two groups (10 in each group) and separately subjected to different fixation procedures as follows: (1) Glut group: fixation with 0.6% Glut alone; (2) Glut/TA group: fixation with 0.6% Glut and subsequent 0.3% TA. Then the BP samples were subdermally implanted in juvenile male Sprague-Dawley rats and explanted 21 days after implantation. Each explanted BP sample was divided into three parts for calcium content analysis, von Kossa's staining and immunohistochemical staining, and reverse transcription-polymerase chain reaction study.. The data from quantitative calcium analysis and von Kossa's staining showed that Glut-fixed BP developed significantly more calcification than Glut/TA-fixed BP ((90.3 +/- 32.5) mg/g dry weight vs (6.4 +/- 1.3) mg/g dry tissue, P < 0.01). Immunostaining demonstrated lower matrix metalloproteinase-9 and tenascin-C expression as well as macrophage infiltration into Glut/TA-fixed BP than in its Glut-fixed counterpart (P < 0.01 for all). Additionally, the reverse transcription-polymerase chain reaction study showed that higher levels of expression of matrix metalloproteinase-9 and tenascin-C mRNA occurred within Glut-fixed BP than within the Glut/TA-fixed ones (P < 0.01 for all).. TA exerts excellent anti-calcification effects on Glut-fixed BP via inhibiting macrophage infiltration and expression of matrix metalloproteinase-9 and tenascin-C.

Topics: Animals; Calcinosis; Cattle; Glutaral; Male; Matrix Metalloproteinase 9; Pericardium; Rats; Rats, Sprague-Dawley; Tannins; Tenascin; Tissue Fixation

Progressive degeneration and calcification of glutaraldehyde (Glut) fixed tissues used in cardiovascular surgery restrict their long-term clinical performance. This limited biological stability may be attributable to the inability of Glut to adequately protect certain tissue components such as elastin from enzymatic attack. The aim of our studies was to develop novel tissue-processing techniques targeted specifically at elastin stabilization by using tannic acid (TA), a plant polyphenol capable of protecting elastin from digestion by specific enzymes. In present studies we demonstrated that Glut does not adequately protect porcine aorta from elastase-mediated degradation in vitro. The addition of TA to the Glut fixation process increased the stability of Glut-fixed aorta to elastase digestion by 15-fold and also decreased calcification in the rat subdermal model by 66%. TA was found to be chemically compatible with Glut fixation and did not hinder collagen crosslinking as shown by minor changes in thermal denaturation temperatures, resistance to collagenase and mechanical properties. In vitro and in vivo studies also revealed that TA binding to aortic wall was stable over an extended period of time. TA-mediated elastin stabilization in Glut-fixed cardiovascular implants may significantly extend the clinical durability of these tissue replacements.

Topics: Animals; Aorta; Bioprosthesis; Calcinosis; Cattle; Drug Combinations; Elasticity; Elastin; Glutaral; Heart Valve Prosthesis; In Vitro Techniques; Male; Organ Preservation Solutions; Pancreatic Elastase; Rats; Rats, Sprague-Dawley; Tannins; Tensile Strength; Tissue Preservation

A lesion of pseudoxanthoma elasticum at a very early stage was studied by light microscopy and electron microscopy using both tannic acid fixation and the conventional method of fixation. The observations strongly indicated that the primary morphological event arose from alteration in the composition of normal native collagen fiber by way of so-called "elastotically degenerated collagen". Deposition of calcium salts did not appear to initiate degenerative changes in the involved fibers, but merely accompanied the abnormally increased elastic fiber as a secondary phenomenon.

Topics: Adult; Calcinosis; Collagen; Elastic Tissue; Histological Techniques; Humans; Hydrolyzable Tannins; Male; Microscopy, Electron; Pseudoxanthoma Elasticum; Staining and Labeling; Tannins