Targeting ischemia-reperfusion injury in kidney transplantation

For patients with end-stage renal disease, kidney transplantation represents an effective treatment option, providing substantial improvements in quality of life and cost-effectiveness. Although transplantation outcomes are generally favorable, there is potential for further improvement, particularly by reducing early damage to the transplanted kidney, which significantly impacts long-term graft survival. Considering ongoing organ shortages, and extended criteria for deceased donors, a better understanding of early post-transplant events, particularly ischemia-reperfusion injury (IRI), is important for optimizing patient outcomes.

This thesis explores different aspects of IRI, an unavoidable consequence of organ donation and transplantation, through several experimental and clinical approaches. The aim has been to increase our understanding of the mechanisms behind IRI in kidney transplantation and to evaluate different strategies to mitigate this condition.

Study I investigated the effects of a novel oxygenated organ preservation solution in a porcine model of kidney transplantation from brain-dead donors. The findings indicate that this oxygenated preservation solution may offer benefits over a standard, non-oxygenated preservation solution in reducing IRI. Given that IRI is a critical factor influencing graft function and survival, these results suggest that advancements in organ preservation techniques, such as oxygenation during cold storage, could improve outcomes in kidney transplantation.

Study II examined the early molecular response to IRI during living donor kidney transplantation, and whether remote ischemic preconditioning (RIPC) of the donors could modulate this response. The study was divided in three parts: First an analysis of early gene expression associated with IRI in living donor kidney transplantation, which revealed pronounced and significant alterations. Secondly, the study explored the effect of RIPC, to assess whether this intervention could modulate early gene expression associated with IRI, where no significant differences in gene expression were observed between treated and untreated groups. Finally, a comparative pathway analysis, including the kynurenine pathway (KYNA-P), was conducted to compare findings from previously published studies in animal models with the human data obtained in this study. This analysis indicated that some pathways activated in animals were not activated in human donors or healthy volunteers treated with RIPC. Although the RIPC protocol used in this study is commonly applied and has demonstrated effects in other settings, it did not yield detectable effects in our specific context, which focused on investigating early gene expression and measuring metabolites of the KYNA-P.

Study III, focused on comparing two experimental models of IRI, one conducted in vivo, and the other ex vivo. In a porcine model of donation after circulatory death followed by kidney transplantation, the effects of IRI on renal allograft gene expression and histopathology were analyzed and compared to those in an ex vivo precision-cut kidney slices (PCKS) cell culture model. No difference in gene expression was observed between models proving that our ex vivo model can be used to a certain extent instead of the kidney transplant model in vivo. The absence of circulating blood and immune cells in the ex vivo model limited its ability to fully replicate the in vivo response to IRI.

Study IV was a clinical phase 1b pharmaceutical trial involving eight recipients of kidneys from living donors, evaluating the pharmacokinetics and safety profile of the study drug, RMC-035, a modified form of the endogenous protein alpha-1- microglobulin, with potential protective effects against IRI. The results demonstrated dose-linearity, with the drug well tolerated by the participants and no significant differences from the typically favorable outcomes observed in standard living donor kidney transplantation. Deeper investigation is necessary to investigate RMC 035's potential protective effects on IRI.

In summary, this thesis explores several aspects of IRI in kidney transplantation, identifying the potential benefits of an oxygenated preservation solution, and illustrates the need to carefully evaluate new potentially protective interventions and pharmacological drugs. As also shown in this thesis, IRI experiments in ex vivo models can be informative and useful. Possibly, the thesis has also contributed to an increased understanding of IRI. However, continued studies on the mechanisms behind IRI and potential modalities to mitigate IRI, are needed.

List of scientific papers

I. Asif S, Sedigh A Nordstrom J*, Brandhorst H, Jorns C, Lorant T, Larsson E, Magnusson PU, Nowak G, Theisinger S, Hoeger S, Wennberg L, Korsgren O, Brandhorst D. Oxygen-charged HTK-F6H8 emulsion reduces ischemia-reperfusion injury in kidney from brain- dead pigs. Journal of Surgical Research. 2012 December;178(2):959-967. https://doi.org/10.1016/j.jss.2012.06.031 *2nd author

II. Nordström J*, Badia-I-Mompel P*, Witasp A, Schwarz A, Evenepoel P, Moor MB, Wennberg L, Saez-Rodriguez J, Wernerson A, Olauson H. Defining the molecular response to ischemia-reperfusion injury and remote ischemic preconditioning in human kidney transplantation. PLoS ONE 2024 October;19(10):e0311613. https://doi.org/10.1371/journal.pone.0311613 *Shared 1st author

III. Moor M*, Nordström J*, Burmakin M, Raki M, Al-Saad S, Nowak G, Wennberg L, Patrakka J, Olauson H. Comparative analysis of kidney transplantation modeled using precision-cut kidney slices and kidney transplantation in pigs. [Manuscript] *Shared 1st author

IV. Nordström J*, Wennberg L, Nowak G, Larsson T, Thuresson S, Reusch M. Assessing Pharmacokinetics and Safety of Therapeutic Alpha-1-Microglobulin in First-in-Human Kidney Transplantation: A Non-Comparative Open Label Multiple Dose Phase 1b Study. Transplantation Direct 2024 December;10(12):p e1727. https://doi.org/10.1097/TXD.0000000000001727 *1st author