Biomarkers of donor kidney quality as predictors of transplantation outcomes

Kidney transplantation is a lifesaving treatment for end stage kidney disease that offers considerable benefits to recipients in terms of survival and quality of life. The growing demand for transplants to treat conditions stemming from a rising prevalence of end stage renal disease, diabetes and cardiovascular diseases has to be met increasingly with donors who are older with a high incidence of comorbid conditions. Organs obtained from these higher risk donors are more likely to have either suboptimal short and long-term transplant outcomes or even fail to function altogether. Transplant clinicians, who have to balance the risk of patients dying while waiting for a transplant against the uncertainty of outcomes, often decline organs as transplants. These clinical challenges entail difficult decisions, and more refined tools to assess and quantify the risks of marginal donor organs are lacking. Diagnostic markers of donor kidney quality that can predict transplantation outcomes are highly desirable in order to discriminate the suboptimal from those allografts that will recover and have good long-term function. My doctoral research using donor samples collected within the Quality of Organ Donation (QUOD) programme has shown for first time that it is possible, on the basis of a tissue proteomic profile, to discriminate donor kidneys at the time of retrieval that will have suboptimal allograft function from those kidneys that could recover and have good function at three and 12 months post transplantation. Despite AKIN classification and Remuzzi scoring showing no evidence of acute kidney injury or chronic kidney disease in the analysed biopsies, quantitative mass spectrometry and degredomics experiments with a subsequent validation analysis on an independent cohort of biopsy samples confirmed the increased levels of inflammation and pro-fibrotic proteins in the allografts with suboptimal function, while increased levels of cytoprotective proteins were detected in the kidneys that recovered with a good function one year after transplantation. Furthermore, the kidneys with suboptimal function demonstrated enhanced degradation of cytoskeletal proteins that are vital in sustaining the glomerular basement membrane cytoskeleton. In addition, I conducted a pilot study using proteomic analysis of serum and urine of donors whose kidneys either developed delayed graft function or functioned immediately. This study confirmed that is feasible to identify alterations in the blood and urine proteome that are biologically meaningful. In preparation of the discovery and development of diagnostic biomarkers of long-term outcome after kidney transplantation using QUOD plasma samples, I assessed the pre-analytical variability associated with the processing of whole blood during QUOD sample collection in order to identify a baseline proteomic and peptidomic profile against which candidate protein markers relevant for clinical correlates can be selected. Based on the findings reported in this thesis, future work should aim to identify and develop better diagnostic tools that can more reliably predict donor organ quality. In addition, novel intervention strategies can be explored that either attenuate pro-fibrotic and proteolytic activities or enhance antioxidant and cytoprotective mechanisms in deceased donor kidneys prior to transplantation.