Golomb G, Ezra V
School of Pharmacy, Hebrew University of Jerusalem, Israel.
J Biomed Mater Res. 1991 Jan;25(1):85-98. doi: 10.1002/jbm.820250107.
Calcification is the principal cause of the clinical failure of bioprosthetic heart valves (BHV). Calcification occurs through an interaction of host and implant factors, mainly younger age and glutaraldehyde pretreatment, respectively. The hypothesis of this work was that an impaired balance between positively and negatively charged amino acids, due to the reaction with Lys and Hyl tissue-collagen residues, expose affinity sites to Ca++. We further hypothesized that regardless of the cause(s) of BHV calcification, positive charge modification of the tissues will prevent their propensity to calcify. Modification of BHV tissue was obtained by covalently binding protamine sulfate, a polybasic peptide, via formaldehyde and subsequent glutaraldehyde tissue crosslinking. Protamine-bound tissue exhibited stability properties (shrinkage temperature and resistance to collagenase digestion) similar to BHV tissue. Protamine-treated tissue was less permeable to Ca++, and reduced staining was observed with positively charged dyes, indicating the presence of positively charged functional groups in the modified tissue. Significant prevention of calcification was exhibited by the p-bound tissue in comparison to BHV tissue, 30.9 and 109 micrograms/mg calcium, respectively, after 30 days of subdermal implants in rats. The modification procedure resulted in stable, covalent links of approximately 10% w/w protamine with undiminished anticalcification properties, even after 1 year storage. The results support our hypotheses, and orthotopical heart valve replacements are required in order to completely evaluate the treatment efficacy and biocompatibility.
钙化是生物人工心脏瓣膜（BHV）临床失效的主要原因。钙化通过宿主和植入物因素的相互作用发生，主要分别是年龄较小和戊二醛预处理。这项工作的假设是，由于与赖氨酸（Lys）和羟赖氨酸（Hyl）组织胶原蛋白残基反应，正负电荷氨基酸之间的平衡受损，从而使亲和位点暴露于钙离子（Ca++）。我们进一步假设，无论BHV钙化的原因是什么，组织的正电荷修饰将阻止其钙化倾向。通过经由甲醛共价结合硫酸鱼精蛋白（一种多碱性肽）并随后进行戊二醛组织交联来实现BHV组织的修饰。结合鱼精蛋白的组织表现出与BHV组织相似的稳定性特性（收缩温度和对胶原酶消化的抗性）。经鱼精蛋白处理的组织对Ca++的渗透性较低，并且用带正电荷的染料观察到染色减少，表明修饰后的组织中存在带正电荷的官能团。与BHV组织相比，结合鱼精蛋白的组织在大鼠皮下植入30天后分别显示出显著的钙化预防效果，钙含量分别为30.9和109微克/毫克。即使经过1年的储存，修饰过程也导致约10%（重量/重量）的鱼精蛋白形成稳定的共价连接，且抗钙化性能未降低。结果支持了我们的假设，并且需要进行原位心脏瓣膜置换以全面评估治疗效果和生物相容性。
