Background: Extensive renal ablation is associated with progressive sclerosis of the remnant kidney. Because lymphocytes and monocytes accumulate in the remnant kidney, it is likely that they play a role in the renal scarring. Therefore, we treated rats with 5/6 nephrectomy (5/6Nx) with mycophenolate mofetil (MMF), a drug that has an antiproliferative effect and that suppresses the expression of intercellular adhesion molecules.
Methods: Sprague-Dawley rats with 5/6Nx received MMF (30 mg. kg-1. day-1 by daily gastric gavage, N = 15) or vehicle (N = 16). Ten additional rats were sham operated. All rats were fed a 30% protein diet. Body weight, serum creatinine, and urinary protein excretion were determined weekly. Lipid peroxidation, as a measure of oxidative stress observed by urinary malondialdehyde determinations, was performed every two weeks. Histologic studies were done in the remnant kidney four weeks (9 rats from the vehicle-treated group, 7 rats from the MMF group, and 5 sham-operated rats) and eight weeks after surgery (the remaining rats). Glomerular volume, sclerosis in glomeruli (segmental and global) and interstitium (semiquantitative scale), infiltrating lymphocytes and macrophages (CD43- and ED1-positive cells), and expression of adhesion molecules (CD54, CD18, and CD11b) were analyzed.
Results: MMF treatment prevented the progressive increment in serum creatinine and the proteinuria observed in the 5/6 nephrectomized rats during the eight weeks of observation (P < 0.01). Weight gain was comparable in the MMF-treated and sham-operated rats, whereas weight gain was decreased in untreated 5/6 nephrectomized rats. Excretion of malondialdehyde increased after surgery but returned sooner to control levels in the MMF-treated rats. Increments in glomerular size and mean arterial blood pressure induced by renal ablation were not modified by MMF treatment. Eight weeks after surgery, segmental sclerosis was present in 48.4 +/- 8.35% (+/- sd) glomeruli in the vehicle-treated group versus 25 +/- 10.5% in the MMF-treated group (P < 0.001). Interstitial fibrosis was reduced significantly with MMF treatment (P < 0.001). Infiltration with CD43- and ED1-positive cells in glomeruli and interstitium was two to five times lower in MMF-treated rats (P < 0.01). Expression of adhesion molecules CD18 and CD11b was similarly reduced.
Conclusion: MMF ameliorates the progressive renal damage in the remnant kidney after 5/6Nx. This effect is associated with a reduction in the infiltration of lymphocytes and monocytes, whereas glomerular hypertrophy and systemic hypertension are unchanged.