NIV Congres

Background The superior long-term survival of kidneys from living donors (LD) compared to brain death (BD) or non heart beating (NHB) donors is now well established. The pathophysiology that leads to organ damage following BD is relatively well established. In contrast, experimental studies on the changes that occur in organs are sparse.The aim of this study therefore was to compare expression levels of genes indicative of inflammation, cytoprotection and injury at the time of explantation, after clinically relevant cold ischemia times and over a time-course during cold storage.

Material and methods Male Brown Norway rats were randomly assigned to a LD, BD or NHB group (n=7/group). LD rats, control group, were mechanically ventilated after 1 hour nephrectomy was performed. In the BD a frontolateral trepanation was made and a balloon catheter was introduced and inflated which led to BD. After 6 hours both kidneys were removed. In the NHB group cardiac arrest was induced by isoflurane overdose. The NHB period lasted 20 minutes before starting with retrieval of NHB donor kidneys. After explantation kidneys of all groups were flushed and stored (4°C) in UW solution. At 0, 2, 4, 6, 12, 18 and 24 hours they were collected and snap frozen in liquid nitrogen.

Results At explantation,mRNA levels of the inflammatory genes IL-1β, IL-6, TNF-α, MCP-1, TLR4, P-selectin and E-selectin were massively upregulated in kidneys from BD compared to LD. IL-1β, IL-6, P-selectin and E-selectin were, to a lesser extend, increased in NHB donors. HMGB1 showed no significant difference. This inflammation resulted in significant injury of the kidney, as shown by the 319-fold increase of the kidney injury marker Kim-1 in BD as compared to only 5.3-fold in NHB. The cytoprotective gene HO-1 and cell cycle control gene p21were strongly increased in BD. During an 18 hour cold storage period HO-1, HIF-1α, Bcl-2, Bax, VEGF, TLR4 and HMGB1 were analysed. At the end of the cold storage period gene expression levels reflected those at the time of explantation.

Conclusion Following BD a massive up-regulation of inflammatory, injury and cytoprotective genes in kidneys is present at the time of graft explantation. These expression levels do not change during cold preservation. In contrast, kidneys from NHB donors show only mild inflammation and injury. These results may explain why delayed graft function in NHB kidneys has not the deleterious effect on graft survival as it has in BD donors.