Mechanical, structural and microbiological evaluation of stored by freezing human cadaveric iliac vessel grafts

This study aims to evaluate the mechanical, microbiological properties and structural integrity of the stored by freezing grafts, how long they can be stored in a standard freezer at -24°C after being decontaminated with cefazolin without using cryoprotectant solution, and whether the grafts are suitable for use or not after this treatment. In our study, 28 artery and 26 vein iliac vein grafts were taken from 28 different cadaveric donors between the ages of 20-89 between January 2018 and June 2021 were used..These grafts were grouped as fresh, 0-6 months, 6-12 months, 12-24 months and over 24 months old based on their storage time. Thawed grafts were cross-sectioned in a sterile environment and evaluated for the presence of growth. For histopathological evaluation, the samples were compared with the internal elastic lamina (IEL) integrity, tunica media thickness and morphological examination results under the light microscope. For the evaluation of endothelial morphology, the samples were examined under scanning electron microscope (SEM) and compared against the scoring system. For mechanical testing, the right and left common iliac vessels were anastomosed in vitro and anastomotic burst pressures were compared. The demographic data of the donors were similar among the groups. There was no difference between the burst pressure of the grafts based on the storage time. No graft contamination was observed in the microbiological analysis. There was no difference between the groups in the tunica media thickness of the vessels under light microscopy. While there was no difference in the IEL fragmentation of the arteries, it showed a significant increase in the samples over 24 months in reduplication. Edema, hyalinization, increase in connective tissue and areas of necrosis were observed in the tunica media. In the SEM examination, most of the grafts whose endothelial structure was stored before 12 months were observed to be grade 1 and grade 2, while the grafts stored for more than 12 months had grade 3, grade 4 and grade 5 appearances. With this storage procedure, grafts stored for more than 12 months can be problematic to use because significant degenerative changes in the endothelial structure have been detected. Key words: Vascular allografts, cryopreservation, organ transplantation.