LAUSR

Complement activation is a key mechanism of Ischaemia reperfusion injury, with the alternative pathway driving damage in particular. The main regulator of the alternative pathway is factor H. We hypothesised that homodimeric mini-factor H (HDM-FH; PMID:29588430) may protect transplanted kidneys from complement mediated damage when administered during normothermic perfusion machine perfusion. Kidneys were retrieved from female white landrace pigs following an optimised protocol. One kidney from each pair was randomised to receive 5mg of HDM-FH (∼8μg/mL). Kidneys were perfused at 37°C with autologous blood for 6 hours. HDM-FH binding was measured using ELISA and immunofluorescence. Complement activation was measured by quantifying Bb deposition in tissue. The ability of HDM-FH to inhibit complement in serum was measured using haemolytic assays. 4mgs of HDM-FH bound from perfusate during perfusion, with <10% lost in urine suggesting saturation was achieved. HDM-FH binding within the kidneys was confirmed using immunofluorescence. HDM-FH localised to glomeruli with deposition increasing over the time of the perfusion. Alternative pathway activation was reduced in kidneys receiving HDM-FH as demonstrated by reduced Bb deposition. Fibrinogen deposition was also reduced and found to colocalise with C3 in glomeruli. HDM-FH inhibits complement activity in serum in a dose-dependent manor. Infusion with HDM-FH prior to simulated kidney transplant conditions reduced complement activation and other secondary negative outcomes to the organ. Therefore, organ perfusion with HDM-FH is highly likely to help prolong graft survival after transplant and this will be assessed in future studies.