The effect of rapamycin after cyclosporin dose reduction on chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is the commonest cause of late decline in renal allograft function and subsequent failure. Histopathologically it is underpinned by the accumulation of extracellular matrix. The first chapter provides a thorough review of the current opinions regarding the aetiology, pathophysiology and management of this complex condition. Overexposure to Cyclosporin is a major risk factor for chronic allograft nephropathy and thus Cyclosporin dose reduction has been advocated in some reports. Rapamycin is a relatively new immunosuppressant, recently introduced in renal transplantation. The second chapter reviews this new agent and discusses experimental evidence supporting its use in patients with chronic allograft nephropathy. The aim of this work was to determine the impact of the addition of Rapamycin after Cyclosporin dose reduction in renal allograft recipients with chronic allograft nephropathy and thus to ascertain whether such a regimen was beneficial. In order to achieve this 31 renal transplant recipients with biopsy confirmed CAN were prospectively randomised to receive either a 40% dose reduction in Cyclosporin (control), or a 40% dose reduction in Cyclosporin with the addition of Rapamycin 2mg/day (Rapa). Renal function and side effect parameters were assessed at 1,2,4,6,8 weeks, 3 and 6 months. The third chapter presents the clinical results. Proteinuria, serum creatinine and calculated GFR were similar in both groups. However the rate of decline of the calculated GFR was reduced over the study in control but not Rapa patients. Furthermore radio-isotope GFR fell in those in the Rapa group but not controls. The use of Rapamycin was safe with only relatively minor side effects and some temporary haematological and hyperlipidaemic changes. The patients above had a renal allograft biopsy on recruitment and again at 6 months. Glomeruli were plucked from the surface of each biopsy core and these as well as a small sample of interstitium underwent total mRNA extraction. Complementary DNA was synthesized by reverse transcription and polymerase chain reactions used to amplify specific genes involved in the turnover of extracellular matrix in CAN. These were quantified using an ELISA technique. The fourth chapter details the changes in expression of some of these genes in. In glomeruli, TGF|3-1 remained constant in Rapa patients but fell in controls. Collagen III and TIMP-2 increased in those taking Rapamycin but not in controls. TIMP-1 and MMP-2 expression increased in a similar fashion in both groups. Glomerular TGFp-1, TIMP-1 and -2 expression appeared to be related to calculated GFR. There were fewer molecular changes within the interstitium but collagen III expression increased in Rapa patients. The fifth chapter discusses the use of Sirius red staining and computerised histomorphometry in order to obtain an accurate assessment of the impact of this regimen on the amount of collagen present in the biopsies taken above. The interstitial volume fraction of biopsy cores stained with Sirius Red fell over the study in controls but a similar effect did not occur in Rapa patients. The final chapter concludes that the addition of Rapamycin (2 mg/day) after Cyclosporin dose reduction in patients with CAN did not improve functional outcome or molecular and histological markers of CAN. Possible explanations are discussed and the need for a larger multicentre trial emphasised in order to substantiate these findings. Studies utilising complete Cyclosporin elimination with the addition of Rapamycin may have better prospects for the future.