Renal Allograft Fibrosis Study

Plain-language summary

Despite the reduction in acute rejection episodes in renal transplant patients due to modern immunosuppression, proportionate improvements in long-term allograft survival have not been achieved. Virtually any disease or injury affecting renal allografts can culminate in irreversible injury of tubular epithelial cells and the development of interstitial fibrosis and tubular atrophy (IFTA). Renal allograft fibrosis drives chronic kidney disease (CKD) progression, predicts allograft failure and is associated with increased patient mortality. Other prognostic and/or actionable diagnoses described by the pathologic Banff scheme, such as inflammation, often co-exist and contribute to IFTA. Immune cell infiltration within allografts and within areas of IFTA (i-IFTA) can drive progressive kidney injury, fibrosis and worsened outcome. Pathology is the reference standard for IFTA; however, allograft biopsy has many well-known limitations and is not an ideal method for monitoring patients during trials of new therapies aimed at improving allograft survival. There is an urgent and unmet need for non-invasive assessment of renal allograft IFTA. Multiparametric MRI (mpMRI), including relaxometry \[the spin-lock relaxation time T1ρ, a marker of interaction of water with macromolecules in tissues; the spin-lattice relaxation time T1, a marker of interstitial edema and collagen volume fraction)\] and advanced diffusion \[intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI), a marker of diffusion and perfusion\] provides insight into renal structure and function. Validation of advanced MRI methods as markers of renal allograft IFTA would be of major clinical significance to enable early detection, assess the efficacy of novel anti-fibrotic agents, and provide longitudinal disease monitoring. The study team has established proof-of-concept in renal allografts with stable function and IFTA without confounding rejection or infection that mpMRI techniques are feasible for measuring fibrosis, especially using the combination of T1 and DWI. The study has established that urinary biomarkers for renal allograft fibrosis are also promising and have been validated against pathology in initial studies. In this proposal, the researchers will develop a short, non-contrast multiparametric MRI (mpMRI) protocol, consisting of advanced relaxometry (T1 mapping and T1ρ) and advanced diffusion weighted imaging (IVIM-DWI) to accurately detect and stage allograft fibrosis, taking into account confounding Banff variables of inflammation and tested against biopsy. The researchers will also assess the added value of urinary biomarkers of IFTA and if successful, this study will benefit a large population of patients with renal allograft fibrosis in the United States, enabling early diagnosis, optimized treatment planning, prognostication and longitudinal disease monitoring.

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