Long term results of rat aortic isografts transplantation after prolonged cold storage in TiProtec® preservation solution

Title: Long-term results of rat aortic isograft transplantation after prolonged cold storage in the vascular preservation solution TiProtec® Objectives: The need for biological arterial vessel replacement in case of infected alloplastic grafts and/or lack of autologous bypass grafts is still an unresolved problem in vascular and cardiac surgery. So far only alloplastic silver coated and/or antibiotic bonded grafts or human cryopreserved homografts are available. While alloplastic material has the risk of reinfection, homografts are not readily available and have the risk of graft degeneration. In situ autologous reconstruction depends on good quality autologous venous material, has great morbidity and the operation is time-consuming. Considering the lack of availability of vessel tissue, preservation of vascular grafts represents a crucial point. The new vascular preservation solution TiProtec® has shown superior in vitro results compared to commonly used storage solutions for a period of up to two weeks. On the other hand, there are only few reports about in vivo testing after only short storage times (2-8-h) but no reports about its prolonged storage capacity, which is especially important for banking and distribution of vascular grafts. In order to address this clinically important issue we conducted a study testing the storage capability of TiProtec® solution after two weeks cold ischemia in an in vivo model of orthotopic aortic transplantation in rats. Methods: Transplantation of abdominal aorta was performed in 16 weeks old male Wistar rats (n=75). Donor grafts were stored at 4°C for two weeks in TiProtec® (n=24), HTK (n=26) and NaCl (n=25) and transplanted thereafter in the abdominal position of age and size matched Wistar rat recipients after excising a segment of abdominal aorta thereby creating a vascularized pressurized aortic transplant. After 8, 16 and 26 weeks transplanted grafts were harvested and vascular function testing with respect to vascular tone development and relaxation was performed. Morphological analyses were conducted on paraffine-embeded graft sections. Results: Vessel tone development was very low in all groups. 26 weeks after transplantation grafts stored in TiProtec® showed a slightly better vessel tone development after challenge with KCL (100mM) and norepinephrine (3x10-6M). However, there was no significant difference compared to grafts stored in NaCl and HTK. Smooth muscle dilative function and endothelium-dependent relaxation were severely impaired in all groups. Intimal hyperplasia was significantly lower in grafts stored in TiProtec® compared to NaCl 8 and 26 weeks after transplantation. Conclusion: Long-term follow up after transplantation of rat aortic isografts stored for 2 weeks in TiProtec® revealed a significant reduction in intimal hyperplasia in TiProtec® stored grafts which is a clinically relevant endpoint for graft patency. Vascular reagibility to pharmacological stimuli was impaired in all groups during our study period owing most likely due to a negative effect of prolonged ischemia on vascular smooth muscle cell function. This is the first study on long-term vascularized and pressurized aortic grafts in a clinically relevant experimental setting.2019-03-2