P-NGAL Day 1 predicts early but not one year graft function following deceased donor kidney transplantation - The CONTEXT study

Correction: P-NGAL Day 1 predicts early but not one year graft function following deceased donor kidney transplantation-The CONTEXT study

[This corrects the article DOI: 10.1371/journal.pone.0212676.].

End-ischemic hypothermic oxygenated machine perfusion does not improve renal outcome following liver transplantation from aged donors: A single-center retrospective report

BACKGROUND

Organ transplantation using grafts from elderly donors entails a higher risk for severe ischemia-reperfusion injury (IRI). Advanced IRI after liver transplantation (LT) seems to be associated with the development of acute kidney injury (AKI). We studied if end-ischemic hypothermic oxygenated machine perfusion (HOPE) of liver grafts, aimed at mitigating liver IRI, impacts on the frequency and severity of AKI after LT.

METHODS

LTs performed at our center between January 2017 and December 2022 using organs from deceased brain-dead donors aged 70 or older were reviewed. From November 2020 on, HOPE was performed routinely in this donor category. The frequency and severity of AKI (KDIGO criteria) within 48 hours of graft reperfusion and the model of early allograft function (MEAF) were compared between HOPE-LTs (n = 30) and control LTs (n = 71).

RESULTS

AKI developed in 23/30 (77%) HOPE-LTs and in 40/71 (56%) control LTs (p = n.s.), with no difference in severity and timing between groups. Renal replacement therapy was required in 3/30 (10%) HOPE-LTs and 6/71 (8%) control LTs. In addition, transaminase leak during the first week (marker of IRI) and MEAF were similar between groups. These findings persisted after propensity matching. Histology showed more hepatocyte vacuolization and higher Suzuki score in HOPE-LTs. Although this analysis could have been underpowered, no trends supporting the benefit of HOPE on liver and renal injury after LT were ever identified.

CONCLUSIONS

In conclusion, HOPE in this group of older donors does not seem to improve either graft IRI, or the incidence of early AKI after LT.

Development and nationwide validation of kidney graft injury markers using urinary exosomes and microvesicles (complete English translation of the Japanese version)

BACKGROUND

Non-invasive, prompt, and proper detection tools for kidney graft injuries (KGIs) are awaited to ensure graft longevity. We screened diagnostic biomarkers for KGIs following kidney transplantation using extracellular vesicles (EVs; exosomes and microvesicles) from the urine samples of patients.

METHODS

One hundred and twenty-seven kidney recipients at 11 Japanese institutions were enrolled in this study; urine samples were obtained prior to protocol/episode biopsies. EVs were isolated from urine samples, and EV RNA markers were assayed using quantitative reverse transcription polymerase chain reaction. Diagnostic performance of EV RNA markers and diagnostic formulas comprising these markers were evaluated by comparison with the corresponding pathological diagnoses.

RESULTS

EV CXCL9, CXCL10, and UMOD were elevated in T-cell-mediated rejection samples compared with other KGI samples, while SPNS2 was elevated in chronic antibody-mediated rejection (cABMR) samples. A diagnostic formula developed through Sparse Logistic Regression analysis using EV RNA markers allowed us to accurately (with an area under the receiver operator characteristic curve [AUC] of 0.875) distinguish cABMR from other KGI samples. EV B4GALT1 and SPNS2 were also elevated in cABMR, and a diagnostic formula using these markers was able to distinguish between cABMR and chronic calcineurin toxicity accurately (AUC 0.886). In interstitial fibrosis and tubular atrophy (IFTA) urine samples and those with high Banff chronicity score sums (BChS), POTEM levels may reflect disease severity, and diagnostic formulas using POTEM detected IFTA (AUC 0.830) and high BChS (AUC 0.850).

CONCLUSIONS

KGIs could be diagnosed with urinary EV mRNA analysis with relatively high accuracy.

Endotrophin Levels Are Associated with Allograft Outcomes in Kidney Transplant Recipients

Early prediction of kidney graft function may assist clinical management, and for this, reliable non-invasive biomarkers are needed. We evaluated endotrophin (ETP), a novel non-invasive biomarker of collagen type VI formation, as a prognostic marker in kidney transplant recipients. ETP levels were measured with the PRO-C6 ELISA in the plasma (P-ETP) of 218 and urine (U-ETP/Cr) of 172 kidney transplant recipients, one (D1) and five (D5) days, as well as three (M3) and twelve (M12) months, after transplantation. P-ETP and U-ETP/Cr at D1 (P-ETP AUC = 0.86, p < 0.0001; U-ETP/Cr AUC = 0.70, p = 0.0002) were independent markers of delayed graft function (DGF) and P-ETP at D1 had an odds ratio of 6.3 (p < 0.0001) for DGF when adjusted for plasma creatinine. The results for P-ETP at D1 were confirmed in a validation cohort of 146 transplant recipients (AUC = 0.92, p < 0.0001). U-ETP/Cr at M3 was negatively associated with kidney graft function at M12 (p = 0.007). This study suggests that ETP at D1 can identify patients at risk of delayed graft function and that U-ETP/Cr at M3 can predict the future status of the allograft. Thus, measuring collagen type VI formation could aid in predicting graft function in kidney transplant recipients.

Renal Normothermic Machine Perfusion: The Road Toward Clinical Implementation of a Promising Pretransplant Organ Assessment Tool

The increased utilization of high-risk renal grafts for transplantation requires optimization of pretransplant organ assessment strategies. Current decision-making methods to accept an organ for transplantation lack overall predictive power and always contain an element of subjectivity. Normothermic machine perfusion (NMP) creates near-physiological conditions, which might facilitate a more objective assessment of organ quality before transplantation. NMP is rapidly gaining popularity, with various transplant centers developing their own NMP protocols and renal viability criteria. However, to date, no validated sets of on-pump viability markers exist nor are there unified NMP protocols. This review provides a critical overview of the fundamentals of current renal NMP protocols and proposes a framework to approach further development of ex vivo organ evaluation. We also comment on the potential logistical implications of routine clinical use of NMP, which is a more complex procedure compared with static cold storage or even hypothermic machine perfusion.

Plasma neutrophil gelatinase-associated lipocalin and kidney graft outcome

BACKGROUND

Plasma neutrophil gelatinase-associated lipocalin (pNGAL) has been investigated extensively in acute kidney injury. This study investigated its pathophysiological significance and utility as marker for graft failure and mortality in stable kidney transplant recipients (KTR).

METHODS

Baseline pNGAL was measured in 698 KTR (58% male, age 53 ± 13 years, estimated glomerular filtration rate 52.4 ± 20.4 mL/min/1.73 m2) at median 5.4 (interquartile range 1.8-12.0) years after transplantation, enrolled in the prospective TransplantLines Food and Nutrition Biobank and Cohort Study.

RESULTS

pNGAL concentrations were higher in males, younger patients, patients with a deceased-donor kidney and higher serum creatinine. Independent of these, pNGAL was positively associated with urinary protein excretion, systemic inflammation parameters and calcineurin inhibitor use. During median follow-up of 5.3 (4.5-6.0) years, death-censored graft failure rates were 3.9%, 7.3% and 25.0% across increasing tertiles of pNGAL (Plog-rank < 0.001). Cox-regression analyses showed no independent associations of pNGAL with mortality, but strong associations with graft failure (hazard ratio, per doubling 4.16; 95% confidence interval 3.03-5.71; P < 0.001), which remained independent of adjustment for confounders. These associations were present only in patients with pre-existent proteinuria and poor kidney function.

CONCLUSIONS

pNGAL is associated with parameters of kidney graft damage and with graft failure. The latter association is particularly present in KTR with pre-existent poor kidney function and proteinuria. Trial Registration: ClinicalTrials.gov NCT02811835.

Association of Postoperative Urinary Output in the First 24 Hours with Delayed Graft Function After Living and Deceased Donor Kidney Transplant: A Systematic Review

Context: Delayed graft function (DGF) is an important clinical outcome following renal transplantation; therefore, it is important to be correctly diagnosed. The DGF is thought to correlate with the first 24-hour urine output (UOP1), and this clinical sign is expected to predict DGF. Objectives: This study aimed to discover whether the UOP1 correlates significantly to the DGF incidence and can be a DGF predicting factor. Data Sources: This study compared the incidence of DGF with the UOP1 reported by studies obtained from the electronic databases, namely MEDLINE, Cochrane, and EBSCO. Studies that performed multivariate or bivariate analysis and/or reported sensitivity and specificity were included in this review. Results: A total of 1719 studies were obtained from the database search, and 2 studies were enrolled from other sources. Out of 1721 studies, 9 studies were recruited in this review, 5 of which reported sensitivity and specificity. Overall, nine of these studies had a low to moderate risk of bias. Almost all studies reported a significant relationship between the UOP1 and DGF. All studies agreed that the UOP1 is a sensitive predictive factor in predicting DGF. The specificity reported by the studies examined in this review varied greatly. The use of optimum cut-off in each study is considered to be the cause of this variability. Conclusions: The UOP1 is significantly related to the incidence of DGF and is a proper parameter for the prediction of DGF events.

Dynamics of circulating dendritic cells and cytokines after kidney transplantation-No effect of remote ischaemic conditioning

Inflammation resulting from ischaemia/reperfusion injury can cause kidney graft dysfunction, increase the risk of delayed graft function and possibly reduce long-term graft survival. Remote ischaemic conditioning may protect against ischaemia/reperfusion injury and mitigate the immunological response to the graft. We investigated the immunological effects of remote ischaemic conditioning on kidney transplantation from deceased donors in the randomized CONTEXT study. Three circulating dendritic cell (DC) subtypes identified in peripheral blood from kidney transplant recipients [myeloid DCs, plasmacytoid DCs and immunoglobulin-like transcript (ILT)3⁺ DCs] were measured at baseline, days 1, 3 and 5 and 1 and 3 months after transplantation. We also quantified 21 cytokines at baseline, days 1 and 5 and 3 months after transplantation. Neither DC counts nor cytokine levels differed between patients receiving remote ischaemic conditioning and controls; however, several parameters exhibited dynamic and parallel alterations in the two groups over time, reflecting the immunological response to the kidney transplantation and immunosuppression.

Elevated plasma free thiols are associated with early and one-year graft function in renal transplant recipients

Background

Reduced free thiols in plasma are indicative of oxidative stress, which is an important contributor to ischaemia-reperfusion injury (IRI) in kidney transplantation leading to kidney damage and possibly delayed graft function (DGF). In a post-hoc, exploratory analysis of the randomised controlled CONTEXT trial, we investigated whether higher (i.e. less oxidised) plasma levels of free thiols as a biomarker of reduced oxidative stress are associated with a better initial graft function or a higher GFR.

Methods

Free thiol levels were measured in plasma at baseline, 30 and 90 minutes after reperfusion of the kidney as well as at Day 1, Day 5 and twelve months after kidney transplantation in 217 patients from the CONTEXT study. Free thiol levels were compared to the kidney graft function measured as the estimated time to a 50% reduction in plasma creatinine (tCr50), the risk of DGF and measured GFR (mGFR) at Day 5 and twelve months after transplantation.

Results

Higher levels of free thiols at Day 1 and Day 5 are associated with higher mGFR at Day 5 (p<0.001, r²_adj. = 0.16; p<0.001, r²_adj. = 0.25), as well as with mGFR at twelve months (p<0.001, r²_adj. = 0.20; p<0.001, r²_adj. = 0.16). However, plasma levels of free thiols at 30 minutes and 90 minutes, but not Day 1, were significantly higher among patients experiencing DGF.

Conclusion

Higher levels of plasma free thiols at Day 1 and Day 5, which are reflective of lower levels of oxidative stress, are associated with better early and late graft function in recipients of a kidney graft from deceased donors.

Trial registration

ClinicalTrials.gov Identifier:NCT01395719.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

Role of novel biomarkers in kidney transplantation

Clinical application of biomarkers is an integral component of transplant care. Clinicians and scientists alike are in search of better biomarkers than the current serologic (serum creatinine, donor-specific antibodies), urine-derived (urinalysis, urine protein), and histologic ones we now use. The science behind recent biomarker discovery spans across multiple molecular biologic disciplines, including transcriptomics, proteomics, and metabolomics. Innovative methodology and integration of basic and clinical approaches have allowed researchers to unearth molecular phenomena preceding clinical disease. Biomarkers can be classified in several ways. In this review, we have classified them via their origin and outcome: Primarily immunologic, i.e., representative of immune regulation and dysfunction and non-immunologic, pertaining to delayed graft function, cardiovascular events/mortality, infection, malignancy, post-transplant diabetes, graft, and patient survival. Novel biomarker uses to guide the diagnosis and management of transplant-related outcomes is a promising area of research. However, the use of biomarkers to predict outcomes after kidney transplantation is not well studied. In this review, we summarize the recent studies illustrating biomarker use and transplant outcomes.

Noninvasive biomarkers in monitoring kidney allograft health

PURPOSE OF REVIEW

A key aspect of posttransplant management is to identify and treat graft injury before it becomes irreversible. The gold-standard for detection is histology, but biopsy is uncomfortable for the patient and carries a risk of complications. Detection of changes at a molecular level may preempt histological injury, and thereby identify injury earlier.

RECENT FINDINGS

Indicators of immune system activation, such as candidate chemokines CXCL9 and CXCL10, and by-products of neutrophil activity, have been related to acute rejection and early allograft function. Transcriptomic studies of multiple-gene panels have identified candidate combinations that have proven very promising in risk-stratification and prediction of acute rejection, as well as diagnosis of both T-cell-mediated and antibody-mediated rejection. Serum and urine cell-free DNA is also a promising area of investigation, particularly in antibody-mediated rejection.

SUMMARY

Noninvasive, rapid, and accurate tests for risk-prediction and diagnosis in renal transplant allografts are urgently required. The ideal candidate is one that can be measured in either urine or blood, is cheap, and is both sensitive and specific for the condition of interest. Numerous strategies have been proposed, with varying degrees of clinical and preclinical success. A few that meet the essential criteria have been evaluated; a few have made it as far as clinical testing.

Remote ischaemic conditioning and early changes in plasma creatinine as markers of one year kidney graft function-A follow-up of the CONTEXT study

BACKGROUND

Ischaemia-reperfusion injury in kidney transplantation leads to delayed graft function (DGF), which is associated with reduced long term graft function. Remote ischaemic conditioning (RIC) improved early kidney graft function in a porcine model of donation after brain death and was associated with improved long-term cardiac outcome after myocardial ischaemia. This randomised, double-blinded trial evaluated the effect of RIC on kidney graft outcome in the first year, and examined the predictive value of a new measure of initial kidney graft function, i.e. the estimated time to a 50% reduction in plasma creatinine post-transplantation (tCr50).

METHODS

A total of 225 patients undergoing deceased donor kidney transplantation were randomised to RIC or a sham procedure performed prior to kidney reperfusion. Up to four repetitive cycles of five minutes of leg ischaemia and five minutes of reperfusion were given. GFR, plasma creatinine, cystatin C and neutrophil gelatinase associated lipocalin (NGAL) were measured at three and twelve months and estimated GFR was calculated using four different equations. Other secondary outcomes were identified from patient files.

RESULTS

RIC did not affect GFR or other outcomes when compared to the sham procedure at three or twelve months. tCr50 correlated with one year graft function (p<0.0001 for both mGFR and eGFR estimates). In contrast, DGF i.e. "need of dialysis the first week" did not correlate significantly with one year GFR.

CONCLUSION

RIC during deceased donor kidney transplantation did not improve one year outcome. However, tCr50 may be a relevant marker for studies aiming to improve graft onset.

TRIAL REGISTRATION

www.ClinicalTrials.gov Identifier: NCT01395719.