What Happens When You Administer Mesenchymal Stromal Cells During Normalthermic Machine Perfusion of Porcine Kidneys: Possible and Helpful, or not?

K Rozenberg 1, L Knijff 1, J M Sierra Parraga 2, L Lo Faro 1, M J Hoogduijn 2, C 2, J Hunter 1, R Ploeg 1 Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom Department of Internal Medicine, Nephrology and Transplantation, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands BackgroundDonation after circulatory death kidneys are widely used to increase the donor pool, despite their inferior quality. Normothermic machine perfusion (NMP) could provide a platform to assess organ viability prior to transplantation and offers the unique opportunity for active interventions to an isolated organ. Mesenchymal stromal cells (MSC) have been shown to possess potent anti-inflammatory and regenerative properties ameliorating ischaemia reperfusion injury. However, the most common delivery route of MSC is intravenous infusion, which is associated with off-target distribution. We aimed to determine the dose of MSC needed to allow successful homing in donor kidneys during NMP without adversely affecting renal perfusion dynamics. MethodsPorcine slaughterhouse kidneys with 20 min warm ischaemia were retrieved and underwent 3h hypothermic machine perfusion followed by NMP for 7h. An oxygenated, autologous blood-based solution containing albumin, electrolytes and nutrients was used as perfusate. Following 1h of NMP, either a vehicle, 2 x 106, 10 x 106 or 50 x 106 labelled (Qdots) porcine adipose derived MSC (n=3 per group) were injected into the cannulated renal artery. Physiological recordings were taken regularly. Perfusate, urine and biopsies were obtained for biomarker analysis and to locate MSC. ResultsNo difference was found in average renal blood flow (p=0.668), renal resistance (p=0.828) and urine production (p=0.307) between all MSC groups compared to control. Damage markers LDH and AST increased during NMP and remained similar between groups (p=0.816 and p=0.312). Confocal microscopy demonstrated mainly glomerular localization of MSC (Figure 1), but they were also observed in the capillary network around the tubules. Additionally, a significant percentage of localised MSC was observed in the glomeruli in the 10 and 50 million MSC groups compared to 2 million MSC (p=0.002 and p 0.05). There is a significant increase in secreted inflammatory mediator PGE2 with time in all groups (P<0.05). DiscussionAdministration of different doses of MSC to the donor kidneys during NMP is safe and feasible. MSC successfully homed in the glomeruli. This model provides us with the opportunity of getting a better insight in the interaction between MSC and injured donor kidney: how do MSC or their released secretome affect tissue integrity and renal function.