The pathological diagnosis of borderline rejection (BL‐R) denotes possible T cell–mediated rejection (TCMR), but its clinical significance is uncertain. This single‐center, cross‐sectional cohort study compared the functional and histological outcomes of consecutive BL‐R diagnoses (n = 146) against normal controls (n = 826) and acute TCMR (n = 55) from 551 renal transplant recipients. BL‐R was associated with the following: contemporaneous renal dysfunction, acute tubular necrosis, and chronic tubular atrophy (P < .001); progressive tubular injury with fibrosis by longitudinal sequential histology (45.3% at 1 year); increased subsequent acute rejection (39.4%), allograft failure (P < .001), and patient mortality (P = .007). BL‐R detected by biopsy indicated for impaired function was followed by suboptimal functional recovery (46.3%), persistent inflammation (27.2%), and acute rejection episodes (50.0%) despite antirejection treatment in 83.3%. By 1 year after BL‐R, the incidence of new‐onset microvascular inflammation (9.3%), C4d staining (22.3%), transplant glomerulopathy (13.3%), and de novo donor‐specific antibodies (31.5%) exceeded normal controls (P < .05‐.001). BL‐R inflammation in protocol biopsy persisted in 28.0% and progressed to acute rejection in 32.6%; however, it resolved in 61.6% of the untreated cases. In summary, BL‐R is a heterogeneous diagnostic grouping, ranging from mild inconsequential inflammation to clinically significant TCMR, which is capable of immune‐mediated tubular injury resulting in inferior functional, immunological, and histological consequences.

Tubulitis without interstitial inflammation (Banff i0), termed "isolated tubulitis" (ISO-T), has been controversially included within the Banff "borderline" category of acute T cell mediated rejection (TCMR). This single-center, retrospective, observational study of 2055 consecutive biopsies from 775 recipients, determined the clinical significance of ISO-T. ISO-T prevalence was 19.1%, comprising mild tubulitis (i0t1) in 97.2%. Independent clinical predictors of tubulitis were HLA mismatch, prior TCMR and antibody-mediated rejection, pulse corticosteroids, and BKVAN (P = .006 to P < .001 by multivariable analysis). Histological associations of tubulitis included interstitial inflammation, peritubular capillaritis, tubular atrophy, and SV40T (P = .005 to <.001). The dominant pathological diagnoses in ISO-T (n = 393) were interstitial fibrosis/tubular atrophy (IF/TA, 44.5%) or normal/minimal (31.8%). Subanalysis of ISO-T from indication biopsies (n = 107) found acute tubular injury (37.4%), IF/TA (28.0%), normal/minimal (12.1%), acute rejection (9.3%, vascular or antibody), chronic-active TCMR (2.8%), and BKVAN (5.6%). Allograft function of ISO-T frequently improved, affected by early biopsy timing and underlying disease diagnosis. Subsequent histology of 1197 ISO-T biopsy-pairs was generally benign. The 1- and 5-year death-censored graft survivals of ISO-T were 98.8% and 92.7%. In summary, tubulitis without inflammation does not represent borderline TCMR. We suggest its removal from the borderline category, and reinstatement of i1 as the diagnostic threshold.

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Transforming growth factor β (TGF-β) is the key cytokine involved in causing fibrosis through cross-talk with major profibrotic pathways. However, inhibition of TGF-β to prevent fibrosis would also abrogate its anti-inflammatory and wound-healing effects. β-catenin is a common co-factor in most TGF-β signaling pathways. β-catenin binds to T-cell factor (TCF) to activate profibrotic genes and binds to Forkhead box O (Foxo) to promote cell survival under oxidative stress. Using a proximity ligation assay in human kidney biopsies, we found that β-catenin/Foxo interactions were higher in kidney with little fibrosis, whereas β-catenin/TCF interactions were upregulated in the kidney of patients with fibrosis. We hypothesised that β-catenin/Foxo is protective against kidney fibrosis. We found that Foxo1 protected against rhTGF-β1induced profibrotic protein expression using a CRISPR/cas9 knockout of Foxo1 or TCF1 in murine kidney tubular epithelial C1.1 cells. Co-administration of TGF-β with a small molecule inhibitor of β-catenin/TCF (ICG-001), protected against kidney fibrosis in unilateral ureteral obstruction. Collectively, our human, animal and in vitro findings suggest β-catenin/ Foxo as a therapeutic target in kidney fibrosis.

(NMP) is especially promising, and is now the subject of a multi-center randomized control trial (RCT) comparing it to CS alone in DCD kidneys 10-13. Most pharmacotherapeutics shown to ameliorate renal IRI have been unable to bridge the 'valley of death' (translational gap) to the clinic. This is at least partly attributable to the inherent difficulties and ethical considerations associated with the systemic use of such therapies in donors or recipients 14,15. NMP can serve as a bridge across this valley by providing a platform for direct, non-systemic drug treatment of the kidney whilst it is undergoing normal metabolic processes 15,16. Amongst the multiple anti-IRI agents tested in pre-clinical models, CD47-blocking antibody (αCD47Ab), recombinant thrombomodulin (rTM), and soluble complement receptor 1 (sCR1) are especially translatable as they have been safely employed for other clinical applications 17-25. However, the comparative efficacy of these agents has not been established. αCD47Ab ameliorates thrombospondin (TSP)-1 mediated IRI signaling, including inhibition of nitric oxide and promotion of oxidative stress 21. sCR1 is an inhibitor of the classical and alternative complement pathways, activation of which is important in IRI 26. rTM is an anti-coagulant molecule involved in the generation of activated protein C, although its efficacy in IRI may be more attributable to anti-inflammatory effects 17,27. Because IRI is characterized by the activation of multiple intersecting pathways 28,29 , it is also plausible that synergistic anti-IRI effects may be derived by delivering two or more of these agents together. The aims of this study were to directly compare the acute effects of αCD47Ab, sCR1, and rTM in a murine model of renal IRI and to establish the combined efficacy of two of the best agents. We then show that the chosen drug could be directly delivered to porcine DCD kidneys using NMP to enhance renal perfusion parameters and ameliorate IRI. The primary focus of this study is the immediate phase of IRI, which correlates to the immediate post-transplant setting and the risk of delayed graft function in higher risk renal allografts. Methods Animal work-ethics. All protocols were approved by the Western Sydney Local Health District Animal Ethics Committee, in accordance with the Australian code for the care and use of animals for scientific purposes (8 th Ed., 2013), developed by the National Health and Medical Research Council. Animal experiments adhere to the ARRIVE guidelines.