van Wachem P B, Brouwer L A, Zeeman R, Dijkstra P J, Feijen J, Hendriks M, Cahalan P T, van Luyn M J
University of Groningen, Medical Biology, Tissue Engineering, University Hospital, Entrance 25, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
J Biomed Mater Res. 2001 Jun 5;55(3):415-23. doi: 10.1002/1097-4636(20010605)55:3<415::aid-jbm1031>3.0.co;2-x.
Calcification limits the long-term durability of xenograft glutaraldehyde (GA)-crosslinked heart valves. Previously, a study in rats showed that epoxy-crosslinked heart valves reduced lymphocyte reactions to the same extent as the GA-crosslinked control and induced a similar foreign-body response and calcification reaction. The present study was aimed at reducing the occurrence of calcification of epoxy-crosslinked tissue. Two modifications were carried out and their influence on cellular reactions and the extent of calcification after 8 weeks' implantation in weanling rats was evaluated. First, epoxy-crosslinked valves were post-treated with two detergents to remove cellular elements, phospholipids and small soluble proteins, known to act as nucleation sites for calcification. The second approach was to study the effect of the impaired balance between negatively and positively charged amino acids by an additional crosslinking step with a dicarboxylic acid. The detergent treatment resulted in a washed-out appearance of especially the cusp tissue. With the dicarboxylic acid, both the cusps and the walls had a limited washed-out appearance. The wall also demonstrated some detachment of the subendothelium. After implantation, both detergent and dicarboxylic acid post-treatment histologically resulted in reduced calcification at the edges of cusps and walls. However, total amounts of calcification, measured by atomic emission spectroscopy, were not significantly reduced. Data concerning the presence of lymphocytes varied slightly, but were in the same range as the GA-crosslinked control, i.e., clearly reduced compared with a noncrosslinked control. It is concluded that both the double detergent and the dicarboxylic acid post-treatment of epoxy-crosslinked heart valve tissue do not represent a sound alternative in the fabrication of heart valve bioprostheses.
钙化限制了异种移植戊二醛（GA）交联心脏瓣膜的长期耐久性。此前，一项在大鼠身上进行的研究表明，环氧交联心脏瓣膜在减少淋巴细胞反应方面与GA交联对照组程度相同，并引发了类似的异物反应和钙化反应。本研究旨在减少环氧交联组织的钙化发生率。进行了两项改良，并评估了它们对细胞反应的影响以及在断奶大鼠体内植入8周后的钙化程度。首先，用两种去污剂对环氧交联瓣膜进行后处理，以去除细胞成分、磷脂和小的可溶性蛋白质，这些物质已知可作为钙化的成核位点。第二种方法是通过用二羧酸进行额外的交联步骤来研究带负电荷和正电荷氨基酸之间平衡受损的影响。去污剂处理导致尤其是瓣叶组织出现洗脱后的外观。使用二羧酸时，瓣叶和瓣壁都有有限的洗脱后外观。瓣壁还显示出一些内皮下层的分离。植入后，去污剂和二羧酸后处理在组织学上均导致瓣叶和瓣壁边缘的钙化减少。然而，通过原子发射光谱法测量的钙化总量并未显著降低。关于淋巴细胞存在的数据略有不同，但与GA交联对照组处于相同范围，即与未交联对照组相比明显减少。得出的结论是，环氧交联心脏瓣膜组织的双去污剂和二羧酸后处理在心脏瓣膜生物假体制造中都不是一种可靠的替代方法。
