Histopathologic impacts of everolimus introduction on kidney transplant recipients

Introduction of everolimus (RAD) has been established as a new immunosuppressive medication for kidney transplant (KT) recipients. Administration of RAD is capable of reducing the dosage of coadministrated calcineurin inhibitors (CNI). However, histological investigations have rarely been performed.

To clarify histopathologic effects of RAD, a total of 9 adult KT recipients were enrolled (RAD group, n = 5; Mycophenolate mofetil (MMF) group, n = 4). Renal graft biopsies had been performed at 3 weeks and 1 year following KT.

There were no differences in 1-, 3-, and 5-year graft survival rates (RAD group: 100%, 100%, and 80%, respectively; MMF group: 100%, 100%, and 75%, respectively), and patient survival between the 2 groups (no deaths during the 5 years post-transplantation). Interestingly, although 2 patients in the RAD group had developed CNI nephrotoxicity clinically, renal biopsies had proven no CNI-related lesions 1 year later, which might be due to the reduction in CNI. On the other hand, 1 patient, in the MMF group, had been diagnosed histologically with new-onset CNI nephrotoxicity 1 year following KT. Importantly, the frequency and mean arteriolar hyalinosis (ah) scores, which reflect CNI nephrotoxicity, were significantly higher in the MMF group at 1-year biopsy (P < .05, P < .0001). Two patients in the RAD group improved their ah scores between 3 weeks and 1 year.

Pathological findings revealed that reversible CNI nephrotoxicity can be improved by RAD with reduced CNI maintenance therapy. It is reasonable to believe, therefore, that introduction of RAD is useful for patients who have been diagnosed with CNI nephrotoxicity.