P71
FUNCTIONAL OBSERVATIONS ON THE DARK AGOUTI TO WISTAR FURTH RAT
MODEL OF CHRONIC RENAL ALLOGRAFT INJURY
Butt, I, Shrestha, B, Haylor, J
Academic Nephrology Unit, Medical School, Sheffield University, Sheffield
INTRODUCTION: The Dark Agouti-to-Wistar Furth DA-WF model of chronic renal allograft
injury, unlike the Fisher-to-Lewis model, is fully mismatched at MHC loci and, as in clincial
renal transplantation, grafted kidneys are lost to acute rejection if immunosuppression is
withheld. In the original description of the DA-WF model, allografts were treated for episodes
of acute rejection as and when required, confirmed by biopsy. If the DA-WF allograft is to be
used for interventional studies, consistent immunosuppression is essential. A sub-therapeutic
dose of ciclosporin 1.5mg/kg has previously been used to accelerate the development of chronic
injury however, progressive functional changes for the DA-WF allograft, characteristic of
chronic renal allograft injury, have not been reported.
METHODS: Fully MHC mismatched inbred male DA rats (RT1av1) and WF rats (RT1u)
weighing 200-250 g were used. Kidney transplantation was performed under isoflurane
anaesthesia using end-to-side anastomosis of aortic and vena caval conduits to recipient aorta
and inferior vena cava. The systemic blood pressure of donor and recipient was maintained
during surgery by intravenous fluid administration. Recipient native right kidney was removed 2
to 3 weeks post-transplant. Recipient rats were followed for upto 12 weeks, receiving daily
ciclosporin 1.5 mg/kg subcutaneously, starting on the day of transplantation. Two isografts and
3 allografts were lost due to the development of hydronephrosis.
RESULTS: DA-DA isografts, receiving ciclosporin 1.5mg/kg, survived for 12 weeks post
transplant with normal tissue histology at termination. DA-DA isografts were normotensive for
both systolic blood pressure (135±5 v 135±2 mmHg) and diastolic blood pressure (82±8 v 89±2
mmHg). Serum creatinine remained unchanged (47±2 v 54±3 µmol/L) and values for protein
excretion at termination were within the normal range (46±3 mg/24h). In marked contrast, 9
DA-WF allografts receiving ciclosporin 1.5mg/kg, were lost to acute rejection following
removal of the right native kidney. The DA-WF allografts which survived to 12 weeks
developed inflammatory cell infiltration and tubulointerstitial fibrosis. Functional measurements
showed the DA-WF allografts to develop hypertension for both systolic (122±3 v 148±8 mmHg,
p<0.01) and diastolic (78±2 v 104±6 mmHg, p<0.01) blood pressure. Serum creatinine was
elevated at an early stage and the increase sustained (184±48 v 160±46 µmol/L) together with
an increase in urinary protein excretion at termination (77±10 mg/24h, p<0.05).
CONCLUSION: The DA-WF allografts which survived to 12 weeks had an elevated serum
creatinine developing hypertension and proteinuria associated with inflammatory cell
infiltration and tubulointerstitial fibrosis. The renal function of DA-DA isografts was stable over
a period of 12 weeks with no change in kidney histology. However, the recommended daily
dose of ciclosporin 1.5mg/kg, did not prevent acute rejection in 80% of the DA-WF allografts
studied. Titration studies are currently in progress to establish a protocol of immunosuppression
suitable for use in interventional studies, that obviates excess mortality from acute rejection and
allows the progressive changes in renal function to be detected in the DA-WF allograft