According to guidelines, total ischemic time for homografts at processing must be kept short to avoid degeneration. Many homografts are discarded due to practical inability to finish all steps from procurement to cryopreservation within the time limit. Although, several studies have shown that homografts with prolonged ischemic time show adequate quality and performance. Twenty aortic and 12 pulmonary homografts were collected and biopsies were retrieved at preparation (day 0) and after 1, 2, 3, 4, 7, 14, 21, 28, and 60 days in antibiotic decontamination at 4 °C. Biopsies were prepared for light microscopy (LM) and transmission electron microscopy (TEM). Assessment generated scores for cells, elastin, and collagen. Relative differences between times were compared with Wilcoxon signed rank test. Bonferroni corrected p value of 0.0056 was considered significant. LM could only reveal decrease in cell count at 60 days in aortic homografts, no other differences was detected. TEM showed affected cell appearance in day 3 and day 4 and beyond for aortic and pulmonary homografts respectively. Elastin appearance was affected at day 60 for aortic and day 21 for pulmonary homografts. Collagen appearance was affected at day 28 for aortic homografts, with no significant differences in pulmonary homografts. Cell degeneration starts early after homograft procurement, but elastic and collagen fibers are more resistant to degeneration. Overall structure integrity as seen in LM was not affected at all, while TEM could reveal small degeneration signs in individual elastic fibers and collagen bundles at 21 and 28 days respectively.

根据指南，同种移植物在加工过程中的总缺血时间必须保持较短，以避免变性。由于实际上无法在时限内完成从采购到冷冻保存的所有步骤，许多同种移植物被丢弃。尽管如此，一些研究表明，缺血时间延长的同种移植物显示出足够的质量和性能。收集了 20 个同种主动脉和 12 个肺同种移植物，并在准备时（第 0 天）以及 4°C 抗生素净化后 1、2、3、4、7、14、21、28 和 60 天后检索活检。准备活检用于光学显微镜（LM）和透射电子显微镜（TEM）。评估产生细胞、弹性蛋白和胶原蛋白的分数。时间之间的相对差异与 Wilcoxon 符号秩检验进行比较。Bonferroni 校正的p值为 0.0056 被认为是显着的。LM 只能显示同种主动脉移植物在 60 天时细胞计数减少，没有检测到其他差异。TEM 显示主动脉和肺同种移植物分别在第 3 天和第 4 天及之后受影响的细胞外观。主动脉的弹性蛋白外观在第 60 天受到影响，肺同种移植物的弹性蛋白外观在第 21 天受到影响。第 28 天，同种主动脉移植物的胶原外观受到影响，同种肺移植物的胶原蛋白外观没有显着差异。细胞变性在同种移植物获得后很早就开始，但弹性纤维和胶原纤维更能抵抗变性。LM 中看到的整体结构完整性根本没有受到影响，而 TEM 可以分别在 21 天和 28 天时显示单个弹性纤维和胶原束的微小退化迹象。