Renal Allograft Function and Histology Following Switching From A Tacrolimus to Sirolimus (SRL)-Based Immunosuppression-

The investigators hypothesize that Tacrolimus (Tac) withdrawal from a Tac, MMF and steroid based triple therapy regimen leads to long term improved/stabilized graft function (glomerular filtration rate, GFR) primarily as a consequence of halting CNI-induced fibrogenetic processes that mediate loss of functioning renal tissue. The investigators further hypothesize that the underlying fibrotic mechanism is mediated by pathophysiologic processes that promote epithelial to mesenchymal transition (EMT) (mediated by TGF- ƒÒ) and that early therapeutic intervention may reverse this process (mediated by BMP-7)4. To address these hypotheses the investigators propose the following clinical and mechanistic aims: The investigators will test the hypothesis that switching from Tac to SRL in a Tac based triple therapy regimen with MMF and steroids in living and or deceased donor renal transplant recipients leads to improvement in allograft structure and function at 2 years post-transplantation. The investigators will test this hypothesis in an open label controlled trial where stable renal allograft recipients on Tac, MMF, prednisone maintenance immunosuppression will undergo renal biopsy at 3-4 months post-transplantation and will be randomized to either a) Remain on Tac, MMF and prednisone (CNI-maintenance) or b) switch the Tac to SRL and continue MMF and prednisone. The investigators will then compare biopsy derived measures of allograft fibrosis (CADI, Sirius Red, Banff Chronicity Index) and GFR in the two groups