Evaluation of minimal Factor H therapy administered to kidneys during ex vivo normothermic perfusion as a treatment to reduce ischaemia reperfusion injury

Abstract

Introduction: Kidney availability for transplantation is limited, necessitating the use of marginal organs which are more susceptible to ischaemia reperfusion injury (IRI). A key driver of IRI is the complement system, particularly the alternative pathway (AP), of which a key regulator is factor H (FH). Homodimeric mini-factor H (HDM-FH) is an FH based construct with improved AP regulation compared to full length FH. Ex vivo normothermic perfusion (EVNP) can be used to administer therapeutics directly to organs to assess their efficacy. Methods: HDM-FH was produced in transfected mammalian cells and validated in vitro. Kidneys were retrieved from 6-week-old, 60 kg white landrace pigs. Initially, stepwise changes were made to an established EVNP model, N=1, then initial warm ischaemic times (WIT) and static cold ischaemic times (CIT) were standardised and extended, N=3. Following this, 5 mg HDM-FH was administered to one kidney of a pair via an EVNP circuit, N=8. Kidneys were perfused for 6 hours with whole autologous blood. Kidney function, complement activation and downstream ischaemic injury were measured to assess the efficacy of HDM-FH. Results: 25 minutes initial WIT and 16 hours CIT significantly increased C3 deposition (p=0.0104). HDM-FH bound within glomeruli of kidneys, particularly on the endothelium and basement membrane, and correlated with C3 deposition prior to perfusion (p=0.0482). HDMFH administration led to reduced deposition of Bb (p=0.0096) and C1q (p=0.0051), reduced urinary C5a (p=0.0022) reduced tissue apoptosis (p=0.0011) and reduced infiltration of neutrophils (p=0.0146) macrophages (p=0.0209) and T-cells (p=0.0404) at the end of perfusion, although it did not affect kidney function. Conclusions: Extended WIT and CIT of porcine kidneys can induce complement activation and ischaemic injury, which HDM-FH can reduce when administered during EVNP. HDM-FH has the potential therefore to improve graft survival in transplanted kidneys, particularly in kidneys from marginal donors.