DCD and AKI Allografts Offer a Valuable Platform to Study Molecular Pathways Underlying Successful Adaptive Repair of the Kidney after Damage

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IntroductionAlthough the increased incidence of DGF in AKI/DCD recipients, DCD/AKI grafts typically recover and resume an excellent kidney function within one month from the surgery. Therefore, we hypothesize that comparative analysis of peripheral blood and renal allograft tissue throughout the initial 30 days of follow up after a kidney transplant will result in the identification and characterization of ongoing mechanisms of regeneration and repair (RR).MethodsPeripheral blood was collected from kidney transplant (KT) patients immediately prior to transplant, immediately after transplant (for up to 5 consecutive days), twice weekly for the next 3 weeks, and at post-transplant day 30 following transplantation of living donor (LD, control group), DCD or AKI donor grafts. Total RNA was isolated from each patient sample and assayed on whole genome microarrays. Longitudinal gene expression was evaluated to identify molecular pathways and processes involved in the recovery phase following KT.ResultsRemarkably, comparative analysis of longitudinal peripheral blood gene expression between recipients of AKI/DCD vs. LD grafts revealed two significant gene clusters, representing a total of 141 genes that show a different expression profile between AKI/DCD and LD samples. The 77 transcripts that comprise cluster 1 show a significant over-representation of genes in several key biological pathways including mTOR signaling, Granzyme B Signaling, and Th1 and Th2 Activation and wnt Pathway. Immunological Disease is the top diseases and disorders category over-represented in this cluster. The second cluster of differentially-expressed genes (N=64) in the comparison between AKI/DCD and LD are significantly over-represented in Toll-like Receptor Signaling, Adrenergic signaling, and fMLP Signaling in neutrophils pathways. The most significant diseases and disorders category over-represented in the set of transcripts is Inflammatory Response. The 141 transcripts that are differentially expressed in the longitudinal comparison between LD and AKI/DCD include genes found to be different in LD vs AKI only (N=65), LD vs DCD only (N=63) and LD vs AKI + DCD. The 13 transcripts found to differentially-expressed in both DCD and AKI samples compared to LD may represent the most biologically relevant gene targets differentiating the two groups and warrant further investigation.ConclusionsThe pattern of gene expression in the peripheral blood of KT patients is significantly different, depending upon the source of donor graft. These markedly different expression patterns, particularly the coordinate elevation hundreds of expressed genes seen in DCD and AKI recipients beyond post-transplant day 1, provide further insight into mechanisms (and timing) of kidney RR that occurs following kidney transplantation.

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