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Abstract: The lifespan of biological heart valve prostheses available in the market is limited due to structural alterations caused by calcium phosphate deposits formed from blood plasma in contact with the tissues. The objective of this work is to present a comparative methodology for the investigation of the formation of calcium phosphate deposits on bioprosthetic and tissue-engineered scaffolds in vitro and the influence of mechanical forces on tissue mineralization. Based on earlier investigations on biological mineralization at constant supersaturation, a circulatory loop simulating dynamic blood flow and physiological pressure conditions was developed. The system was appropriately adapted to evaluate the calcification potential of decellularized (DCV) and glutaraldehyde-fixed (GAV) porcine aortic valves. Results indicated that DCV calcified at higher, statistically nonsignificant, rates in comparison with GAV. This difference was attributed to the tissue surface modifications and cell debris leftovers from the decellularization process. Morphological analysis of the solids deposited after 20 h by scanning electron microscopy in combination with chemical microanalysis electron-dispersive spectroscopy identified the solid formed as octacalcium phosphate (Ca8(PO4)6H2·5H2O, OCP). OCP crystallites were preferentially deposited in high mechanical stress areas of the test tissues. Moreover, GAV tissues developed a significant transvalvular pressure gradient increase past 36 h with a calcium deposition distribution similar to the one found in explanted prostheses. In conclusion, the presented in vitro circulatory model serves as a valuable prescreening methodology for the investigation of the calcification process of bioprosthetic and tissue-engineered valves under physiological mechanical load.

希腊Dimosthenis Mavrilas等 | 准生理流动条件下人工生物脱细胞心脏瓣膜的体外钙化研究

本研究论文聚焦准生理流动条件下人工生物脱细胞心脏瓣膜的体外钙化研究。由于由血浆与组织接触形成的磷酸钙沉积物引起的结构改变，市面上可买到的生物心脏瓣膜假体的使用寿命受到了限制。此研究的目的是提出一种比较方法，用于研究体外生物假体和组织工程支架上磷酸钙沉积物的形成以及机械力对组织矿化的影响。基于前期对恒定过饱和下生物矿化的研究，开发了模拟动态血流和生理压力条件的循环回路。该系统适用于评估脱细胞（DCV）和戊二醛固定（GAV）的猪主动脉瓣的钙化潜力。结果表明，与GAV相比，DCV钙化率更高，但在统计学上无显著差异。这种差异归因于组织表面修饰和脱细胞过程中残留的细胞碎片。通过扫描电子显微镜结合化学微分析电子分散光谱对沉积20小时后的固体进行形态分析，确定形成的固体为磷酸八钙（Ca8(PO4)6H2·5H2O，OCP）。OCP晶体优先沉积在测试组织的高机械应力区域。此外，GAV组织在经过36小时后出现明显的跨瓣压力梯度增加，钙沉积分布与在外植假体中发现的钙沉积分布相似。总之，本文提出的体外循环模型可作为一种有价值的预筛查方法，用于研究在生理机械负荷下人工生物组织工程瓣膜的钙化过程。