SP22
ORGAN CROSS-TALK AFTER ACUTE KIDNEY INJURY IN A PORCINE MODEL
David S. Gardner PhD., Louise J. Dunford PhD., Simon J.M. Welham PhD., Rebecca
Fallman BSc., Saoirse O’Sullivan PhD and Mark Devonald PhD FRCPE.
University of Nottingham, Renal and Transplant Unit, NUH NHS Trust, City Hospital,
Nottingham.
Introduction: In laboratory animal models, experimental induction of AKI has had remote effects in other organs, such as the liver or lung. The mechanism for such organ cross-talk is thought to be mediated by inflammatory signals. Using a porcine model of AKI we have investigated any potential distant organ effects in the liver, lung and hippocampus by histology, tissue biochemistry and immunohistochemistry.
Methods: Thirty female pigs (50-60 kg) were anaesthetised (isoflurane in oxygen) for insertion of a jugular catheter and bilateral renal artery cross-clamping (IR, 40 mins or
Control, sham operated) via an abdominal incision. After 40 min, clamps were removed, pigs were recovered to a pen and reperfusion followed for 48h with blood being sampled at regular intervals. A further cohort of control and IR pigs (n=3/group) were followed to 5 weeks of age. At 48h and at 5 weeks, pigs were euthanised and samples of kidney, liver, lung, and brain (hippocampus) were frozen in liquid nitrogen or optimal cutting compound and stored at -80°C, or fixed in 4% paraformaldehyde. Paraffin embedded tissues were assessed for histopathologic indices of damage. Water retention was assessed in freeze dried tissue.
Apoptotic cells were determined using a fluorescent in situ TUNEL assay. Blood samples were assayed for liver transferase enzyme activity using an auto-analyser and organ tissues were digested for determination of total electrolyte and trace element composition (by ICP-
MS). A porcine multiplex cytokine array (Luminex) was used to assess levels of inflammatory infiltrate in tissue lysates, together with qPCR of select inflammatory cytokines.
Results: Our model of AKI in the pig induces significant histopathological injury in the kidneys at 48h that largely resolves by 2 weeks post-surgery, as determined by renal biopsy.
Short-term renal, but not liver or lung, water retention was noted after AKI, likely mediated by retention of cations (Na
+
, K
+
, Ca
++
, Mg
++
; P<.001 vs. control). Greater retention of liver and lung Ca ++ was also a notable response to AKI. Plasma concentrations of AST, ALT, ALP were significantly increased above sham-controls after AKI, indicative of hepatic injury, but had returned to baseline by 48h. There was no evidence of increased apoptosis or greater infiltration of inflammatory cytokines in liver or lung tissue after AKI and qPCR of selected inflammatory cytokines reiterated the array data.
Conclusions: For the first time using a large animal model of AKI we report some limited distant organ effects of acute kidney injury in the short-term, which resolved soon after. It is evident that the remote effects of AKI may be diluted somewhat in larger animals with greater metabolic reserve capacity.