The Impact of Prolonged Cold Ischemia in Different Protection Solutions on Vascular Remodelling in a Model of Murine Abdominal Aortic Transplantation

Objectives: Cold storage is a widely used principle of organ protection before transplantation. Different preservation solutions have been developed to protect the donor organ from cold ischemia damage that leads inevitably to ischemia/reperfusion injury after transplantation. Both in vascular and solid organ transplantation this injury leads to vascular remodelling with intimal thickening, functional loss of the vessels and late transplant failure. To address this clinically important issue we conducted a study testing the storage capability of different solutions after two weeks cold ischemia in a murine in vivo model of orthotopic aortic transplantation.

Methods: Aortic donor grafts were harvested from male Wistar rats and stored at 4°C for two weeks in NaCl (n = 25), Custodiol (n = 26) and TiProtec (n = 24). Thereafter stored donor grafts were transplanted into abdominal aorta of male Wistar rats (n = 75). Vessel grafts were collected after 8, 16 and 26 weeks and subjected to histological and immunohistochemical analysis (H&E, α-SMA, Ki67, Vimentin, Desmin and MMP-2) to assess vessel wall morphology including intimal hyperplasia, vascular smooth muscle cell (VSMC) migration and VSMC phenotype switch. The activity of the transcription factor nuclear factor-kappa B (NF-κB) was measured to evaluate the vascular inflammatory responses.

Results: Intimal hyperplasia was significantly lower in grafts stored in TiProtec^® compared with NaCl 8 and 26 weeks after transplantation. The presence of VSMC was markedly higher in the medial layer in grafts stored in TiProtec^®. In all groups level of Ki67-positive cell proliferation and the presence of MMP-2 were especially high in the adventitia and the neo-intima. The positivity for Desmin and Vimentin is reduced or almost absent in the media layer after 16 and 26 weeks except in grafts stored in TiProtec^®. NF-κB was up-regulated particularly after 16 and 26 weeks in grafts stored in Custodiol and TiProtec^®.

Conclusion: The above-mentioned findings represent a pronounced vascular remodelling process with enhanced VSMC migration and phenotypic switching after prolonged cold ischemia of rat aortic transplants in different protection solutions. Only storing in TiProtec^® could reduce intimal hyperplasia significantly and partially prevent the vascular remodelling process. This is clinically important regarding transplant survival and graft patency.