Tacrolimus exposure and evolution of renal allograft histology in the first year after transplantation

The Influence of Tacrolimus Exposure and Metabolism on the Outcomes of Kidney Transplants

Tacrolimus (TAC) has a narrow therapeutic window and patient-specific pharmacokinetic variability. In our study, we analyzed the association between TAC exposure, metabolism, and kidney graft outcomes (function, rejection, and histological lesions). TAC trough (C0), coefficient of variation (TAC CV), concentration/dose ratio (C/D), and biomarkers related to kidney injury molecule-1 (KIM-1) and neutrophil gelatinase lipocalin (NGAL) were analyzed. We examined 174 patients who were subjected to a triple immunosuppressive regimen and underwent kidney transplantation between 2017 and 2022. Surveillance biopsies were performed at the time of kidney implantation and at three and twelve months after transplantation. We classified patients based on their Tac C/D ratios, classifying them as fast (C/D ratio < 1.05 ng/mL × 1/mg) or slow (C/D ratio ≥ 1.05 ng/mL × 1/mg) metabolizers. TAC exposure/metabolism did not significantly correlate with interstitial fibrosis/tubular atrophy (IF/TA) progression during the first year after kidney transplantation. TAC CV third tertile was associated with a higher chronicity score at one-year biopsy. TAC C/D ratio at three months and Tac C0 at six months were associated with rejection during the first year after transplantation. A fast TAC metabolism at six months was associated with reduced kidney graft function one year (OR: 2.141, 95% CI: 1.044-4.389, p = 0.038) and two years after transplantation (OR: 4.654, 95% CI: 1.197-18.097, p = 0.026), and TAC CV was associated with reduced eGFR at three years. uNGAL correlated with IF/TA and chronicity scores at three months and negatively correlated with TAC C0 and C/D at three months and one year. Conclusion: Calculating the C/D ratio at three and six months after transplantation may help to identify patients at risk of suffering acute rejection and deterioration of graft function.

Long-Term Outcomes after Conversion to a Belatacept-Based Immunosuppression in Kidney Transplant Recipients

BACKGROUND

Conversion to a belatacept-based immunosuppression is currently used as a calcineurin inhibitor (CNI) avoidance strategy when the CNI-based standard-of-care immunosuppression is not tolerated after kidney transplantation. However, there is a lack of evidence on the long-term benefit and safety after conversion to belatacept.

METHODS

We prospectively enrolled 311 kidney transplant recipients from 2007 to 2020 from two referral centers, converted from CNI to belatacept after transplant according to a prespecified protocol. Patients were matched at the time of conversion to patients maintained with CNIs, using optimal matching. The primary end point was death-censored allograft survival at 7 years. The secondary end points were patient survival, eGFR, and safety outcomes, including serious viral infections, immune-related complications, antibody-mediated rejection, T-cell-mediated rejection, de novo anti-HLA donor-specific antibody, de novo diabetes, cardiovascular events, and oncologic complications.

RESULTS

A total of 243 patients converted to belatacept (belatacept group) were matched to 243 patients maintained on CNIs (CNI control group). All recipient, transplant, functional, histologic, and immunologic parameters were well balanced between the two groups with a standardized mean difference below 0.05. At 7 years post-conversion to belatacept, allograft survival was 78% compared with 63% in the CNI control group ( P < 0.001 for log-rank test). The safety outcomes showed a similar rate of patient death (28% in the belatacept group versus 36% in the CNI control group), active antibody-mediated rejection (6% versus 7%), T-cell-mediated rejection (4% versus 4%), major adverse cardiovascular events, and cancer occurrence (9% versus 11%). A significantly higher rate of de novo proteinuria was observed in the belatacept group as compared with the CNI control group (37% versus 21%, P < 0.001).

CONCLUSIONS

This real-world evidence study shows that conversion to belatacept post-transplant was associated with lower risk of graft failure and acceptable safety outcomes compared with patients maintained on CNIs.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Long-term Outcomes after Conversion to Belatacept, NCT04733131 .

A Randomized Controlled Trial of Envarsus Versus Immediate Release Tacrolimus in Kidney Transplant Recipients With Delayed Graft Function

BACKGROUND

The incidence of delayed graft function (DGF) among kidney transplant recipients (KTRs) in the United States continues to increase. The effect of immediate-release tacrolimus (tacrolimus) compared with extended-release tacrolimus (Envarsus) among recipients with DGF is unknown.

METHODS

This was a single-center open-label randomized control trial among KTRs with DGF (ClinicalTrials. gov, NCT03864926). KTRs were randomized either to continue on tacrolimus or switch to Envarsus at a 1:1 ratio. Duration of DGF (study period), number of dialysis treatments, and need for adjustment of calcineurin inhibitor (CNI) doses during the study period were outcomes of interest.

RESULTS

A total of 100 KTRs were enrolled, 50 in the Envarsus arm and 50 in the tacrolimus arm; of those, 49 in the Envarsus arm and 48 in the tacrolimus arm were included for analysis. There were no differences in the baseline characteristics, all P > .5, except donors in the Envarsus arm had higher body mass index (mean body mass index 32.9 ± 11.3 vs 29.4 ± 7.6 kg/m2 [P = .007]) compared with the tacrolimus arm. The median duration of DGF (5 days vs 4 days, P = .71) and the number of dialysis treatments (2 vs 2, P = .83) were similar between the groups. However, the median number of CNI dose adjustments during the study period in the Envarsus group was significantly lower (3 vs 4, P = .002).

CONCLUSIONS

Envarsus patients had less fluctuation in the CNI level, requiring fewer CNI dose adjustments. However, there were no differences in the DGF recovery duration or number of dialysis treatments.

Controlled Donation After Circulatory Death Using Normothermic Regional Perfusion Does Not Increase Graft Fibrosis in the First Year Posttransplant Surveillance Biopsy

OBJECTIVES

The number of kidney transplants obtained from controlled donations after circulatory death is increasing, with long-term outcomes similar to those obtained with donations after brain death. Extraction using normothermic regional perfusion can improve results with controlled donors after circulatory death; however, information on the histological impact and extraction procedure is scarce.

MATERIALS AND METHODS

We retrospectively investigated all kidney transplants performed from October 2014 to December 2019, in which a follow-up kidney biopsy had been performed at 1-year follow-up, comparing controlled procedures with donors after circulatory death and normothermic regional perfusion versus donors after brain death. Interstitial fibrosis/tubular atrophy was assessed by adding the values of interstitial fibrosis and tubular atrophy, according to the Banff classification of renal allograft pathology.

RESULTS

When we compared histological data from 66 transplants with donations after brain death versus 24 transplants with donations after circulatory death and normothermic regional perfusion, no differences were found in the degree of fibrosis in the 1-year follow-up biopsy (1.7 ± 1.3 vs 1.7 ± 1.1; P = .971) or in the ratio of patients with increased fibrosis calculated as interstitial fibrosis/tubular atrophy >2 (18% vs 13%; P = .522). In our multivariate analysis, which included acute rejection, expanded criteria donation, and the type of donation, no variable was independently related to an increased risk of interstitial fibrosis/tubular atrophy >2.

CONCLUSIONS

The outcomes of kidney grafts procured in our center using controlled procedures with donors after circulatory death and normothermic regional perfusion were indistinguishable from those obtained from donors after brain death, showing the same degree of fibrosis in the 1-year posttransplant surveillance biopsy. Our data support the conclusion that normothermic regional perfusion should be the method of choice for extraction in donors after circulatory death.

An integrated device for fast and sensitive immunosuppressant detection

The present paper describes a compact point of care (POC) optical device for therapeutic drug monitoring (TDM). The core of the device is a disposable plastic chip where an immunoassay for the determination of immunosuppressants takes place. The chip is designed in order to have ten parallel microchannels allowing the simultaneous detection of more than one analyte with replicate measurements. The device is equipped with a microfluidic system, which provides sample mixing with the necessary chemicals and pumping samples, reagents and buffers into the measurement chip, and with integrated thin film amorphous silicon photodiodes for the fluorescence detection. Submicrometric fluorescent magnetic particles are used as support in the immunoassay in order to improve the efficiency of the assay. In particular, the magnetic feature is used to concentrate the antibody onto the sensing layer leading to a much faster implementation of the assay, while the fluorescent feature is used to increase the optical signal leading to a larger optical dynamic change and consequently a better sensitivity and a lower limit of detection. The design and development of the whole integrated optical device are here illustrated. In addition, detection of mycophenolic acid and cyclosporine A in spiked solutions and in microdialysate samples from patient blood with the implemented device are reported.

Clinical Relevance of Corticosteroid Withdrawal on Graft Histological Lesions in Low-Immunological-Risk Kidney Transplant Patients

The impact of corticosteroid withdrawal on medium-term graft histological changes in kidney transplant (KT) recipients under standard immunosuppression is uncertain. As part of an open-label, multicenter, prospective, phase IV, 24-month clinical trial (ClinicalTrials.gov, NCT02284464) in low-immunological-risk KT recipients, 105 patients were randomized, after a protocol-biopsy at 3 months, to corticosteroid continuation (CSC, n = 52) or corticosteroid withdrawal (CSW, n = 53). Both groups received tacrolimus and MMF and had another protocol-biopsy at 24 months. The acute rejection rate, including subclinical inflammation (SCI), was comparable between groups (21.2 vs. 24.5%). No patients developed dnDSA. Inflammatory and chronicity scores increased from 3 to 24 months in patients with, at baseline, no inflammation (NI) or SCI, regardless of treatment. CSW patients with SCI at 3 months had a significantly increased chronicity score at 24 months. HbA1c levels were lower in CSW patients (6.4 ± 1.2 vs. 5.7 ± 0.6%; p = 0.013) at 24 months, as was systolic blood pressure (134.2 ± 14.9 vs. 125.7 ± 15.3 mmHg; p = 0.016). Allograft function was comparable between groups and no patients died or lost their graft. An increase in chronicity scores at 2-years post-transplantation was observed in low-immunological-risk KT recipients with initial NI or SCI, but CSW may accelerate chronicity changes, especially in patients with early SCI. This strategy did, however, improve the cardiovascular profiles of patients.

Progression of Interstitial Fibrosis and Tubular Atrophy in Low Immunological Risk Renal Transplants Monitored by Sequential Surveillance Biopsies: The Influence of TAC Exposure and Metabolism

The combination of tacrolimus (TAC) and mycophenolate is the most widely employed maintenance immunosuppression in renal transplants. Different surrogates of tacrolimus exposure or metabolism such as tacrolimus trough levels (TAC-C₀), coefficient of variation of tacrolimus (CV-TAC-C₀), time in therapeutic range (TTR), and tacrolimus concentration dose ratio (C/D) have been associated with graft outcomes. We explore in a cohort of low immunological risk renal transplants (n = 85) treated with TAC, mycophenolate mofetil (MMF), and steroids and then monitored by paired surveillance biopsies the association between histological lesions and TAC-C₀ at the time of biopsy as well as CV-TAC-C₀, TTR, and C/D during follow up. Interstitial inflammation (i-Banff score ≥ 1) in the first surveillance biopsy was associated with TAC-C₀ (odds ratio (OR): 0.69, 95% confidence interval (CI): 0.50–0.96; p = 0.027). In the second surveillance biopsy, inflammation was associated with time below the therapeutic range (OR: 1.05 and 95% CI: 1.01–1.10; p = 0.023). Interstitial inflammation in scarred areas (i-IFTA score ≥ 1) was not associated with surrogates of TAC exposure/metabolism. Progression of interstitial fibrosis/tubular atrophy (IF/TA) was observed in 35 cases (41.2%). Multivariate regression logistic analysis showed that mean C/D (OR: 0.48; 95% CI: 0.25–0.92; p = 0.026) and IF/TA in the first biopsy (OR: 0.43, 95% CI: 0.24–0.77, p = 0.005) were associated with IF/TA progression between biopsies. A low C/D ratio is associated with IF/TA progression, suggesting that TAC nephrotoxicity may contribute to fibrosis progression in well immunosuppressed patients. Our data support that TAC exposure is associated with inflammation in healthy kidney areas but not in scarred tissue.

Proteomic Characterization of Urinary Extracellular Vesicles from Kidney-Transplanted Patients Treated with Calcineurin Inhibitors

Use of immunosuppressive drugs is still unavoidable in kidney-transplanted patients. Since their discovery, calcineurin inhibitors (CNI) have been considered the first-line immunosuppressive agents, in spite of their known nephrotoxicity. Chronic CNI toxicity (CNIT) may lead to kidney fibrosis, a threatening scenario for graft survival. However, there is still controversy regarding CNIT diagnosis, monitoring and therapeutic management, and their specific effects at the molecular level are not fully known. Aiming to better characterize CNIT patients, in the present study, we collected urine from kidney-transplanted patients treated with CNI who (i) had a normal kidney function, (ii) suffered CNIT, or (iii) presented interstitial fibrosis and tubular atrophy (IFTA). Urinary extracellular vesicles (uEV) were enriched and the proteome was analyzed to get insight into changes happening during CNI. Members of the uroplakin and plakin families were significantly upregulated in the CNIT group, suggesting an important role in CNIT processes. Although biomarkers cannot be asserted from this single pilot study, our results evidence the potential of uEV as a source of non-invasive protein biomarkers for a better detection and monitoring of this renal alteration in kidney-transplanted patients.

Impact of Induction Immunosuppression Strategies in Simultaneous Liver/Kidney Transplantation

BACKGROUND

There is scant data on the use of induction immunosuppression for simultaneous liver/kidney transplantation (SLKT).

METHODS

We analyzed the Organ Procurement and Transplant Network registry from 1996 to 2016 to compare outcomes of SLKT, based on induction immunosuppression.

RESULTS

Of 5172 patients, 941 (18%) received T-cell depletion induction, 1635 (32%) received interleukin 2 receptor antagonist (IL2-RA), and 2596 (50%) received no induction (NI). At 5 years, patient survivals were 68% in the T-cell group, 74% in the IL2-RA group, and 71% in the NI group (P = 0.0006). Five-year liver and kidney allograft survivals were 67% and 64% in the T-cell group, 73% and 70% in the IL2-RA group, and 70% and 68% in the NI group (P = 0.001 and 0.003), respectively. On multivariate analysis, the type of induction had no impact on patient or allograft survival. Maintenance steroids and calcineurin inhibitors (CNIs) at discharge were associated with improved patient and graft survival (steroids: patient survival hazard ratio [HR] 0.37 [0.27-0.52], liver survival HR 0.43 [0.31-0.59], kidney survival HR 0.46 [0.34-0.63]; P < 0.0001, CNI: patient survival HR 0.3 [0.21-0.43], liver survival HR 0.3 [0.2-0.44], kidney survival HR 0.4 [0.26-0.59]; P < 0.0001). CNI maintenance in patients who received T-cell induction was associated with decreased patient, liver, and kidney allograft survivals (respective HR: 1.4 [1.1, 1.8]; 1.5 [1.1, 1.9]; 1.3 [1.08, 1.7]; P < 0.05) CONCLUSION.: Induction immunosuppression had no impact on patient and allograft survival in SLKT, while maintenance steroids and CNI were associated with improved patient and graft survivals. Given the inherent limitations of a registry analysis, these findings should be interpreted with caution.

Impact of belatacept conversion on kidney transplant function, histology, and gene expression - a single-center study

Prior studies on belatacept conversion from calcineurin inhibitor (CNI) have been limited by an absence of postconversion surveillance biopsies that could underestimate subclinical rejection, or a case-controlled design. A total of 53 adult patients with allograft dysfunction underwent belatacept conversion (median: 6 months) post-transplant. At a median follow-up = 2.5 years, patient survival was 94% with a death-censored graft survival of 85%. Seven (13%) patients had acute rejection (including 3 subclinical) at median 6 months postconversion. Overall, eGFR improved (P = <0.001) from baseline = 31±15 to 40.2 ± 17.6 ml/min/1.73m² by 6 months postconversion, but then stayed stable. This improvement was also observed (P < 0.001) in comparison with a propensity matched control cohort on CNI, where eGFR stayed stable (mean ~ 32ml/min/1.72m² ) over 2-year follow-up. Patients converted < 6 months post-transplant were more likely to have a long-term improvement in kidney function. Paired gene expression analysis of 30 (of 53) consecutive pre- and postconversion surveillance biopsies did not reveal changes in inflammation/acute injury; although atrophy-fibrosis score worsened (mean = 0.28 to 0.44; P = 0.005). Thus, improvement in renal function with belatacept conversion occurred early and then sustained in comparison with controls where renal function remained unchanged overtime. We were unable to show molecular signals that could be related to CNI administration and regressed after withdrawal.

Time-Varying Covariates and Risk Factors for Graft Loss in Kidney Transplantation

OBJECTIVES

The present study was designed to evaluate the factors involved in long-term graft survival in recipients of kidney transplantation.

MATERIALS AND METHODS

We reviewed 755 Iranian adult recipients who underwent kidney transplantation at Shahid Labbafinejad Medical Center in Tehran, Iran. Patients were followed for 5 years after transplantation. The primary outcome was the time between transplantation and graft loss. Using Cox regression, we studied the effect of time-independent variables (recipients' age and sex, donors' age, and type of donor), time-dependent covariates (body mass index [BMI], systolic blood pressure, diastolic blood pressure, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol levels, proteinuria and serum creatinine level), and immunosuppressive drugs on graft loss 60 months after transplantation. The results are presented as the hazard ratio (HR) with 95% confidence intervals.

RESULTS

Result from Cox proportional hazards model showed that the HR of graft loss was 1.62 (95% CI: 1.03-2.54) in cadaveric donor compared with living donor kidney recipients. The HR of graft loss for recipient age was 1.02 (95% CI: 1.002-1.030). Moreover, according to obtained results, the risk of losing functional transplant increased for each mg/dL rise in serum creatinine at least 9% and at most 40%. Our results also showed that 1 unit increase of BMI has at least a 2% and at most a 15% decremented effect on the hazard ratio of graft loss.

CONCLUSIONS

Having lower levels of creatinine and receiving a kidney from a younger living donor were associated with a decreased risk of graft loss. Graft loss is more likely to occur in patients with lower BMI.

One-year Outcome of Everolimus With Standard-dose Tacrolimus Immunosuppression in De Novo ABO-incompatible Living Donor Kidney Transplantation: A Retrospective, Single-center, Propensity Score Matching Comparison With Mycophenolate in 42 Transplants

Background.

Despite improvement in immunosuppressive therapy, long-term kidney allograft survival remains a major challenge. The outcomes of therapy with everolimus (EVR) and standard-dose tacrolimus (Tac) have not been compared with those of mycophenolate mofetil (MMF) and standard-dose Tac in recipients of de novo ABO-incompatible (ABOi) living donor kidney transplantation (LDKT).

Methods.

This retrospective, observational, single-center, propensity score matching (PSM) study compared the outcomes of EVR and standard-dose Tac with those of MMF and standard-dose Tac following de novo ABOi LDKT. In total, 153 recipients of ABOi LDKT between January 2008 and March 2018 were screened for inclusion in the study. The variables considered for PSM were: recipient age/sex, duration of dialysis, cytomegalovirus mismatch (seronegative recipient and seropositive donor), cause of kidney disease, donor age/sex, and numbers of mismatches (HLA-A, HLA-B, and HLA-DR). After PSM, there were 21 patients in each group (n = 42 overall).

Results.

Four patients in the EVR group and 1 patient in the MMF group were withdrawn because of adverse effects. There were no significant differences between the 2 groups in 1-year outcomes regarding patient death, graft loss, delayed graft function, biopsy-proven acute rejection, infection requiring hospital admission, or estimated glomerular filtration rate. The 1-year protocol biopsy showed that the severity of interstitial fibrosis/tubular atrophy was significantly milder in the EVR group than in the MMF group.

Conclusions.

The findings suggest that the renal efficacy and safety of EVR and standard-dose Tac in recipients of de novo ABOi LDKT are comparable with those of MMF and standard-dose Tac.

Long-Term Kidney Transplant Outcomes: Role of Prolonged-Release Tacrolimus

Tacrolimus has significantly improved outcomes for kidney transplant patients and remains the cornerstone of immunosuppressive therapy. While improvements in short-term outcomes in transplantation have been achieved in recent years, maintaining long-term graft survival remains a challenge in kidney transplantation. Minimizing risk factors for poor long-term kidney graft function and survival, and modifying tacrolimus regimens in the early and maintenance phases post-transplantation are essential to maintain long-term kidney transplant outcomes. Tacrolimus has a narrow therapeutic window, resulting in a tightly defined range of optimal drug exposure. Underimmunosuppression is associated with long-term risks, such as the development of donor-specific antibodies and antibody-mediated rejection, with a high possibility of a decline in kidney function and progression to graft failure. Conversely, prolonged overimmunosuppression carries a risk of drug-related adverse events. This review provides an overview of the differences in the formulation, delivery, and pharmacokinetic profiles between immediate- and prolonged-release tacrolimus and evaluates the effect of prolonged-release tacrolimus on the risk factors for poor outcomes in kidney transplantation. Recent evidence is used to provide guidance on target tacrolimus trough levels in the early and maintenance phases post-transplantation, with a view to improving long-term kidney graft function.

High tacrolimus clearance - a risk factor for development of interstitial fibrosis and tubular atrophy in the transplanted kidney: a retrospective single-center cohort study

Patients with high tacrolimus clearance are more likely to experience transient under-immunosuppression in case of a missed or delayed dose. We wanted to investigate the association between estimated tacrolimus clearance and development of graft interstitial fibrosis and tubular atrophy (IFTA) in kidney transplant recipients. Associations between estimated tacrolimus clearance [daily tacrolimus dose (mg)/trough concentration (μg/l)] and changes in IFTA biopsy scores from week 7 to 1-year post-transplantation were investigated. Data from 504 patients transplanted between 2009 and 2013 with paired protocol biopsies (7 weeks + 1-year post-transplant) were included. There were no differences in baseline biopsy scores (7 weeks) in patients with different estimated tacrolimus clearance. Increasing tacrolimus clearance was significantly associated with increased ci + ct score of ≥2 at 1 year, odds ratio of 1.67 (95% CI; 1.11-2.51). In patients without fibrosis (ci + ct ≤ 1) at 7 weeks (n = 233), increasing tacrolimus clearance was associated with development of de novo IFTA (i + t ≤ 1 and ci + ct ≥ 2) at 1 year, odds ratio of 2.01 (95% CI; 1.18-3.50) after adjusting for confounders. High tacrolimus clearance was significantly associated with development of IFTA the first year following renal transplantation.

Late graft failure after kidney transplantation as the consequence of late versus early events

Beyond the first posttransplant year, 3% of kidney transplants fail annually. In a prospective, multicenter cohort study, we tested the relative impact of early versus late events on risk of long-term death-censored graft failure (DCGF). In grafts surviving at least 90 days, early events (acute rejection [AR] and delayed graft function [DGF] before day 90) were recorded; serum creatinine (Cr) at day 90 was defined as baseline. Thereafter, a 25% rise in serum Cr or new-onset proteinuria triggered graft biopsy (index biopsy, IBx), allowing comparison of risk of DCGF associated with early events (AR, DGF, baseline serum Cr >2.0 mg/dL) to that associated with later events (IBx). Among 3678 patients followed for 4.7 ± 1.9 years, 753 (20%) had IBx at a median of 15.3 months posttransplant. Early AR (HR = 1.77, P < .001) and elevated Cr at Day 90 (HR = 2.56, P < .0001) were associated with increased risk of DCGF; however, later-onset dysfunction requiring IBx had far greater impact (HR = 13.8, P < .0001). At 90 days, neither clinical characteristics nor early events distinguished those who subsequently did or did not undergo IBx or suffer DCGF. To improve long-term kidney allograft survival, management paradigms should promote prompt diagnosis and treatment of both early and later events.

Risk factors for calcineurin inhibitor nephrotoxicity after renal transplantation: a systematic review and meta-analysis

Background

Nephrotoxicity of calcineurin inhibitors (CNIs) is the major concern for long-term allograft survival despite its predominant role in current immunosuppressive regime after renal transplantation. CNI nephrotoxicity is multifactorial with demographic, environmental, and pharmacogenetic flexibility, whereas studies indicating risk factors for CNI nephrotoxicity obtained incomplete or conflicting results.

Methods

A systematic review and meta-analysis of risk factors for CNI nephrotoxicity was performed on all retrieved studies through a comprehensive research of network database. Data were analyzed by Review Manager 5.2 with heterogeneity assessed using the Cochrane Q and I² tests. CNI nephrotoxicity was primarily indicated with protocol biopsy or index-based clinical diagnosis, and the secondary outcome was defined as delayed graft function.

Results

Twelve observational studies containing a total of 2,849 cases were identified. Donor age (odds ratio [OR], 1.01; 95% CI, 1.01-1.03; p=0.02), recipient zero-time arteriosclerosis (OR, 1.44; 95% CI, 1.04-1.99; p=0.03), and CYP3A5*3/*3 genotype (OR, 2.80; 95% CI, 2.63-2.98; p=0.00) were confirmed as risk factors for CNI nephrotoxicity. Subgroup and sensitivity analysis claimed donor age as a significant contributor in Asian and Caucasian areas.

Conclusion

Older donor age, recipient zero-time arteriosclerosis, and CYP3A5*3/*3 genotype might add up the risk for CNI nephrotoxicity, which could be interpreted into a robust biomarker system.

Tacrolimus and mycophenolate regimen and subclinical tubulo-interstitial inflammation in low immunological risk renal transplants

The aim was to evaluate the relationship between maintenance immunosuppression, subclinical tubulo-interstitial inflammation and interstitial fibrosis/tubular atrophy (IF/TA) in surveillance biopsies performed in low immunological risk renal transplants at two transplant centers. The Barcelona cohort consisted of 109 early and 66 late biopsies in patients receiving high tacrolimus (TAC-C₀ target at 1-year 6-10 ng/ml) and reduced MMF dose (500 mg bid at 1-year). The Oslo cohort consisted of 262 early and 237 late biopsies performed in patients treated with low TAC-C₀ (target 3-7 ng/ml) and standard MMF dose (750 mg bid). Subclinical inflammation, adjusted for confounders, was associated with low TAC-C₀ in the early (OR: 0.75, 95% CI: 0.61-0.92; P = 0.006) and late biopsies (OR: 0.69, 95% CI: 0.50-0.95; P = 0.023) from Barcelona. In the Oslo cohort, it was associated with low MMF in early biopsies (OR: 0.90, 95% CI: 0.83-0.98; P = 0.0101) and with low TAC-C₀ in late biopsies (OR: 0.77, 95% CI: 0.61-0.97; P = 0.0286). MMF dose was significantly reduced in Oslo between early and late biopsies. IF/TA was not associated with TAC-C₀ or MMF dose in the multivariate analysis. Our data suggest that in TAC- and MMF-based regimens, TAC-C₀ levels are associated with subclinical inflammation in patients receiving reduced MMF dose.

Zero-Time Renal Transplant Biopsies: A Comprehensive Review

Zero-time kidney biopsies, obtained at time of transplantation, are performed in many transplant centers worldwide. Decisions on kidney discard, kidney allocation, and choice of peritransplant and posttransplant treatment are sometimes based on the histological information obtained from these biopsies. This comprehensive review evaluates the practical considerations of performing zero-time biopsies, the predictive performance of zero-time histology and composite histological scores, and the clinical utility of these biopsies. The predictive performance of individual histological lesions and of composite scores for posttransplant outcome is at best moderate. No single histological lesion or composite score is sufficiently robust to be included in algorithms for kidney discard. Dual kidney transplantation has been based on histological assessment of zero-time biopsies and improves outcome in individual patients, but the waitlist effects of this strategy remain obscure. Zero-time biopsies are valuable for clinical and translational research purposes, providing insight in risk factors for posttransplant events, and as baseline for comparison with posttransplant histology. The molecular phenotype of zero-time biopsies yields novel therapeutic targets for improvement of donor selection, peritransplant management and kidney preservation. It remains however highly unclear whether the molecular expression variation in zero-time biopsies could become a better predictor for posttransplant outcome than donor/recipient baseline demographic factors.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Early Conversion to Prednisolone/Everolimus as an Alternative Weaning Regimen Associates With Beneficial Renal Transplant Histology and Function: The Randomized-Controlled MECANO Trial

In renal transplantation, use of calcineurin inhibitors (CNIs) is associated with nephrotoxicity and immunosuppression with malignancies and infections. This trial aimed to minimize CNI exposure and total immunosuppression while maintaining efficacy. We performed a randomized controlled, open-label multicenter trial with early cyclosporine A (CsA) elimination. Patients started with basiliximab, prednisolone (P), mycophenolate sodium (MPS), and CsA. At 6 months, immunosuppression was tapered to P/CsA, P/MPS, or P/everolimus (EVL). Primary outcomes were renal fibrosis and inflammation. Secondary outcomes were estimated glomerular filtration rate (eGFR) and incidence of rejection at 24 months. The P/MPS arm was prematurely halted. The trial continued with P/CsA (N = 89) and P/EVL (N = 96). Interstitial fibrosis and inflammation were significantly decreased and the eGFR was significantly higher in the P/EVL arm. Cumulative rejection rates were 13% (P/EVL) and 19% (P/CsA), (p = 0.08). A post hoc analysis of HLA and donor-specific antibodies at 1 year after transplantation revealed no differences. An individualized immunosuppressive strategy of early CNI elimination to dual therapy with everolimus was associated with decreased allograft fibrosis, preserved allograft function, and good efficacy, but also with more serious adverse events and discontinuation. This can be a valuable alternative regimen in patients suffering from CNI toxicity.

Early Kidney Allograft Dysfunction (Threatened Allograft): Comparative Effectiveness of Continuing Versus Discontinuation of Tacrolimus and Use of Sirolimus to Prevent Graft Failure: A Retrospective Patient-Centered Outcome Study

Supplemental digital content is available in the text.

Background

Due to lack of treatment options for early acute allograft dysfunction in the presence of tubular-interstitial injury without histological features of rejection, kidney transplant recipients are often treated with sirolimus-based therapy to prevent cumulative calcineurin inhibitor exposure and to prevent premature graft failure.

Methods

We analyzed transplant recipients treated with sirolimus-based (n = 220) compared with continued tacrolimus-based (n = 276) immunosuppression in recipients of early-onset graft dysfunction (threatened allograft) with the use of propensity score-based inverse probability treatment weighted models to balance for potential confounding by indication between 2 nonrandomized groups.

Results

Weighted odds for death-censored graft failure (odds ratio [OR], 1.20; 95% confidence interval [95% CI], 0.66-2.19, P = 0.555) was similar in the 2 groups, but a trend for increased risk of greater than 50% loss in estimated glomerular filtration rate from baseline in sirolimus group (OR, 1.90; 95% CI, 0.96-3.76; P = 0.067) compared with tacrolimus group. Sirloimus group compared with tacrolimus group had increased risk for death with functioning graft (OR, 2.01; 95% CI, 1.29-3.14; P = 0.002) as well as increased risk of late death (death after graft failure while on dialysis) (OR, 2.39; 95% CI, 1.59-3.59; P < 0.001). Analysis of subgroups based on the absence or presence of T cell–mediated rejection or tubulointerstitial inflammation in the index biopsy, or the use of different types of induction agents, and all subgroups had increased risk of death with functioning graft and late death if exposed to sirolimus-based therapy.

Conclusions

Use of sirolimus compared with tacrolimus in recipients with early allograft dysfunction during the first year of transplant may not prevent worsening of allograft function and could potentially lead to poor survival along with increased risk of late death.

Impact of Trough Levels of Tacrolimus on Kidney Function and Graft Survival in Short and Longer Periods After Renal Transplantation

BACKGROUND

Optimizing immunosuppressive treatment in the early posttransplant period is important for achieving long-term graft function and survival.

MATERIAL AND METHODS

There were 205 renal transplant recipients involved in this study. Patients were divided into groups according to the induction therapy (no induction vs basiliximab/daclizumab vs rabbit antithymocyte globulin), maintenance therapy at the time of transplantation (tacrolimus [TAC] vs cyclosporine), the average trough TAC levels in months 4 to 6 after TO and serum creatinine 5 years after renal transplantation.

RESULTS

The incidence of acute rejection was significantly higher in cyclosporine than in TAC group of patients (P = .0364). The average TAC levels on elapsed time after transplantation significantly decreased (P < .0001). Five years after renal transplantation, there were higher TAC levels (5.6 ± 0.7 ng/mL) in the group with "zero" low levels than in the group with "zero" high levels (4.6 ± 1.1 ng/mL), which was statistically significant (P < .0001). We did not find any difference in graft and patient survival in posttransplant years 2 to 5 according to TAC levels or the induction treatment.

CONCLUSIONS

In our study, we have confirmed that better graft function 5 years after transplantation was connected with higher trough tacrolimus levels on elapsed time after renal transplantation.

Experience with belatacept rescue therapy in kidney transplant recipients

In kidney transplant recipients with chronic graft dysfunction, long-term immunosuppression with calcineurin inhibitors (CNIs) or mTOR inhibitors (mTORi) can be challenging due to adverse effects, such as nephrotoxicity and proteinuria. Seventy-nine kidney transplant recipients treated with CNI-based or mTORi-based maintenance immunosuppression who had CNI-induced nephrotoxicity or severe adverse events were switched to belatacept. Mean time from transplantation to belatacept conversion was 69.0 months. Mean estimated glomerular filtration rate (eGFR) ± standard deviation at baseline was 26.1 ± 15.0 ml/min/1.73 m² , increasing to 34.0 ± 15.2 ml/min/1.73 m² at 12 months postconversion (P < 0.0005). Renal function improvements were also seen in patients with low eGFR (<25 ml/min/1.73 m² ) or high proteinuria (>500 mg/l) at conversion. The Kaplan-Meier estimates for patient and graft survival at 12 months were 95.0% and 85.6%, respectively. The discontinuation rate due to adverse events was 7.9%. One case of post-transplant lymphoproliferative disorder occurred at 17 months postconversion. For comparison, a historical control group of 41 patients converted to mTORi-based immunosuppression because of biopsy-confirmed CNI-induced toxicity was examined; eGFR increased from 27.6 ± 7.2 ml/min/1.73 m² at baseline to 31.1 ± 11.9 ml/min/1.73 m² at 12 months (P = 0.018). Belatacept-based immunosuppression may be an alternative regimen for kidney transplant recipients with CNI- or mTORi-induced toxicity.

Medical management of chronic kidney disease in the renal transplant recipient

PURPOSE OF REVIEW

An updated overview of the state-of-the-art approaches to the care of chronic kidney disease-related issues in renal transplant recipients.

RECENT FINDINGS

These include the impact of immunosuppression therapy on kidney function, the management of cardiovascular risk, metabolic bone disease, and hematologic complications, with a focus on the care of the patient with a failing allograft.

SUMMARY

A kidney transplant improves patient morbidity and mortality, but almost all transplant patients continue to have morbidity related to chronic kidney disease. It is increasingly clear that the provision of adequate immunosuppression is important to preserve allograft function. Recent studies have lent support to current guidelines for the management of cardiovascular risk factors in transplant patients. New data regarding the management of metabolic bone disease are sparse. Erythropoietin replacement may improve outcomes in transplant recipients, but the optimal target hemoglobin level is not known. Cessation of immunosuppression in the failed allograft carries the risk of rejection and allosensitization. New evidence suggests that nephrectomy may reduce mortality in patients with a failed allograft, but likely enhances sensitization in the patient awaiting retransplantation.

A high intrapatient variability in tacrolimus exposure is associated with poor long-term outcome of kidney transplantation

Tacrolimus is a critical dose drug with a considerable intrapatient variability (IPV) in its pharmacokinetics. We investigated whether a high IPV in tacrolimus exposure is associated with adverse long-term renal transplantation outcomes. Tacrolimus IPV was calculated from predose concentrations measured between 6 and 12 months post-transplantation of 808 renal transplant recipients (RTRs) transplanted between 2000 and 2010. One hundred and eighty-eight (23.3%) patients reached the composite end point consisting of graft loss, late biopsy-proven rejection, transplant glomerulopathy, or doubling of serum creatinine concentration between month 12 and the last follow-up. The cumulative incidence of the composite end point was significantly higher in patients with high IPV than in patients with low IPV (hazard ratio: 1.41, 95% CI: 1.06-1.89; P = 0.019). After the adjustment for several factors, the higher incidence of the composite end point for RTRs with a high IPV remained statistically significant (hazard ratio: 1.42, 95% CI: 1.06-1.90; P = 0.019). Younger recipient age at transplantation, previous transplantation, worse graft function (at month 6 post-transplantation), and low mean tacrolimus concentration at 1 year post-transplantation were additional predictors for worse long-term transplant outcome. A high tacrolimus IPV is an independent risk factor for adverse kidney transplant outcomes that can be used as an easy monitoring tool to help identify high-risk RTRs.

Exploring genetic and non-genetic risk factors for delayed graft function, acute and subclinical rejection in renal transplant recipients

AIMS

This study aimed at identifying pharmacological factors such as pharmacogenetics and drug exposure as new predictive biomarkers for delayed graft function (DGF), acute rejection (AR) and/or subclinical rejection (SCR).

METHODS

Adult renal transplant recipients (n = 361) on cyclosporine-based immunosuppression were followed for the first 6 months after transplantation. The incidence of DGF and AR were documented as well as the prevalence of SCR at 6 months in surveillance biopsies. Demographic, transplant-related factors, pharmacological and pharmacogenetic factors (ABCB1, CYP3A5, CYP3A4, CYP2C8, NR1I2, PPP3CA and PPP3CB) were analysed in a combined approach in relation to the occurrence of DGF, AR and prevalence of SCR at month 6 using a proportional odds model and time to event model.

RESULTS

Fourteen per cent of the patients experienced at least one clinical rejection episode and only DGF showed a significant effect on the time to AR. The incidence of DGF correlated with a deceased donor kidney transplant (27% vs. 0.6% of living donors). Pharmacogenetic factors were not associated with risk for DGF, AR or SCR. A deceased donor kidney and acute rejection history were the most important determinants for SCR, resulting in a 52% risk of SCR at 6 months (vs. 11% average). In a sub-analysis of the patients with AR, those treated with rejection treatment including ATG, significantly less frequent SCR was found in the 6-month biopsy (13% vs. 50%).

CONCLUSIONS

Transplant-related factors remain the most important determinants of DGF, AR and SCR. Furthermore, rejection treatment with depleting antibodies effectively prevented SCR in 6-month surveillance biopsies.

Long-term study of steroid avoidance in renal transplant patients: a single-center experience

OBJECTIVES

Steroids have played a major role in renal transplantation for more than 4 decades. However, chronic use of steroids is associated with many comorbidities. This study aimed to assess the costs and benefits of a steroid-free immunosuppression regimen in a prospective randomized controlled study of living-donor renal transplantation, which was lacking in the literature.

MATERIALS AND METHODS

In our study, 428 patients were enrolled to receive tacrolimus (Tac), mycophenolic acid (MPA), basiliximab (Simulect, Novartis, Basel, Switzerland) induction and steroids only for 3 days (214 patients, study group) and steroid maintenance (214 patients, control group). Median follow-up was 66 ± 41 months.

RESULTS

We found that both groups showed comparable graft and patient survival, rejection episodes, and graft function. Posttransplantation hypertension was detected in 40% of the steroid-free group and 80% of the steroid maintenance group (P = .05), whereas posttransplantation diabetes mellitus was detected in 5% and 15% of these 2 groups, respectively (P = .3).

CONCLUSIONS

Among low-immunological-risk recipients of living-donor renal transplants, steroid avoidance was feasible, safe, and had less morbidity outcome using Simulect induction, then Tac and MPA as maintenance immunosuppression. Steroid avoidance was associated with a lower total cost despite comparable immunosuppression cost, which was attributed to the lower cost of associated morbidities.

Clinical significance of donor-specific human leukocyte antigen antibodies in liver transplantation

Antibody-mediated rejection (AMR) caused by donor-specific anti-human leukocyte antigen antibodies (DSA) is widely accepted to be a risk factor for decreased graft survival after kidney transplantation. This entity also plays a pathogenic role in other solid organ transplants as it appears to be an increasingly common cause of heart graft dysfunction and an emerging issue in lung transplantation. In contrast, the liver appears relatively resistant to DSA-mediated injury. This “immune-tolerance” liver property has been sustained by a low rate of liver graft loss in patients with preformed DSA and by the intrinsic liver characteristics that favor the absorption and elimination of DSA; however, alloantibody-mediated adverse consequences are increasingly being recognized, and several cases of acute AMR after ABO-compatible liver transplant (LT) have been reported. Furthermore, the availability of new solid-phase assays, allowing the detection of low titers of DSA and the refinement of objective diagnostic criteria for AMR in solid organ transplants and particularly in LT, have improved the recognition and management of this entity. A cost-effective strategy of DSA monitoring, avoidance of class II human leukocyte antigen mismatching, judicious immunosuppression attached to a higher level of clinical suspicion of AMR, particularly in cases unresponsive to conventional anti-rejection therapy, can allow a rational approach to this threat.

Safe Conversion From Tacrolimus to Belatacept in High Immunologic Risk Kidney Transplant Recipients With Allograft Dysfunction

There is no literature on the use of belatacept for sensitized patients or regrafts in kidney transplantation. We present our initial experience in high immunologic risk kidney transplant recipients who were converted from tacrolimus to belatacept for presumed acute calcineurin inhibitor (CNI) toxicity and/or interstitial fibrosis/tubular atrophy. Six (mean age = 40 years) patients were switched from tacrolimus to belatacept at a median of 4 months posttransplant. Renal function improved significantly from a peak mean estimated glomerular filtration rate (eGFR) of 23.8 ± 12.9 mL/min/1.73 m(2) prior to the switch to an eGFR of 42 ± 12.5 mL/min/1.73 m(2) (p = 0.03) at a mean follow-up of 16.5 months postconversion. No new rejection episodes were diagnosed despite a prior history of rejection in 2/6 (33%) patients. Surveillance biopsies performed in 5/6 patients did not show subclinical rejection. No development of donor-specific antibodies (DSA) was noted. In this preliminary investigation, we report improved kidney function without a concurrent increase in risk of rejection and DSA in six sensitized patients converted from tacrolimus to belatacept. Improvement in renal function was noted even in patients with chronic allograft fibrosis without evidence of acute CNI toxicity. Further studies with protocol biopsies are needed to ensure safety and wider applicability of this approach.

How to handle missed or delayed doses of tacrolimus in renal transplant recipients? A pharmacokinetic investigation

Every transplant patient will, at least occasionally, miss immunosuppressive drug doses or take them outside the prescribed times. This study aims at quantifying the impact of poor execution on tacrolimus exposure in renal transplant patients. Validated pharmacokinetic tools applied in clinical setting were used to simulate the steady-state pharmacokinetic profiles of the drug when given as the immediate-release formulation to renal transplant patients, being CYP3A5 expressors or not, and who have reached either a standard or a minimized exposure. Situations of interruption due to a missed or delayed dose were simulated and the impact on drug exposure was explored. In case of a missed dose, it was observed that: (i) a single forgotten dose can greatly impact exposure: up to 49% decrease for tacrolimus trough concentration and 70% for AUC0-12 h in patients with the highest clearance values; (ii) patients with a minimized exposure are the most affected by a missed dose; and (iii) a dose of 1.5 times the usual dose may be recommended after a total dose oversight. Considering that intra-patient exposure variability is a predictive factor of poor graft outcome, these modeling results may serve as recommendations for patients, both preventively and in response to their questions.

The impact of early and late acute rejection on graft survival in renal transplantation

Background

Advances in immunosuppression after kidney transplantation have decreased the influence of early acute rejection (EAR) on graft survival. Several studies have suggested that late acute rejection (LAR) has a poorer effect on long-term graft survival than EAR. We investigated whether the timing of acute rejection (AR) influences graft survival, and analyzed the risk factors for EAR and LAR.

Methods

We performed a retrospective cohort study involving 709 patients who underwent kidney transplantation between 2000 and 2009 at the Samsung Medical Center, Seoul, Korea. Patients were divided into three groups: no AR, EAR, and LAR. EAR and LAR were defined as rejection before 1 year and after 1 year, respectively. Differences in graft survival between the three groups and risk factors of graft failure were analyzed.

Results

Of the 709 patients, 198 (30%) had biopsy-proven AR [EAR=152 patients (77%); LAR=46 patients (23%)]. A total of 65 transplants were lost. The 5-year graft survival rates were 97%, 89%, and 85% for patients with no AR, EAR, and LAR, respectively. These differences were significant (P<0.001 for both by log-rank test). In time-dependent Cox regression analysis, EAR (hazards ratio, 3.37; 95% confidence interval, 1.90–5.99) and LAR (hazards ratio, 5.32; 95% confidence interval, 2.65–10.69) were significantly related to graft failure. When we set LAR as standard and compared it with EAR, there was no statistical difference between EAR and LAR (P=0.21).

Conclusion

AR, regardless of its timing, significantly worsened graft survival. Treatments to reduce the incidence of AR and improve prognosis are needed.

African-American race modifies the influence of tacrolimus concentrations on acute rejection and toxicity in kidney transplant recipients

STUDY OBJECTIVE

To determine the effect of tacrolimus trough concentrations on clinical outcomes in kidney transplantation, while assessing if African-American (AA) race modifies these associations.

DESIGN

Retrospective longitudinal cohort study of solitary adult kidney transplants.

SETTING

Large tertiary care transplant center.

PATIENTS

Adult solitary kidney transplant recipients (n=1078) who were AA (n=567) or non-AA (n=511).

EXPOSURE

Mean and regressed slope of tacrolimus trough concentrations. Subtherapeutic concentrations were lower than 8 ng/ml.

MEASUREMENTS AND MAIN RESULTS

AA patients were 1.7 times less likely than non-AA patients to achieve therapeutic tacrolimus concentrations (8 ng/ml or higher) during the first year after kidney transplant (35% vs 21%, respectively, p<0.001). AAs not achieving therapeutic concentrations were 2.4 times more likely to have acute cellular rejection (ACR) as compared with AAs achieving therapeutic concentrations (20.8% vs 8.5%, respectively, p<0.01) and 2.5 times more likely to have antibody-mediated rejection (AMR; 8.9% vs 3.6%, respectively, p<0.01). Rates of ACR (8.3% vs 6.7%) and AMR (2.0% vs 0.9% p=0.131) were similar in non-AAs compared across tacrolimus concentration groups. Multivariate modeling confirmed these findings and demonstrated that AAs with low tacrolimus exposure experienced a mild protective effect for the development of interstitial fibrosis/tubular atrophy (IF/TA; hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.47-1.32) with the opposite demonstrated in non-AAs (HR 2.2, 95% CI 0.90-5.1).

CONCLUSION

In contradistinction to non-AAs, AAs who achieve therapeutic tacrolimus concentrations have substantially lower acute rejection rates but are at risk of developing IF/TA. These findings may reflect modifiable time-dependent racial differences in the concentration-effect relationship of tacrolimus. Achievement of therapeutic tacrolimus trough concentrations, potentially through genotyping and more aggressive dosing and monitoring, is essential to minimize the risk of acute rejection in AA kidney transplant recipients.

The value of long-term protocol biopsies after kidney transplantation

Protocol biopsies for the detection and treatment of subclinical rejection in the early period after kidney transplantation are useful for preventing allograft dysfunction. However, little has been reported on the relationship between subclinical rejection and long-term protocol biopsies. In this review, we examine the potential benefits associated with long-term allograft biopsies focusing on the issue of immunological and non-immunological factors. Early detection and treatment of subclinical rejection improves outcome. However, the benefit of long-term allograft biopsies is largely unproved, and the strategy is yet to be widely implemented. The procurement of long-term protocol biopsies for the sole purpose of detecting subclinical rejection may be unwarranted. On the other hand, the early detection of IgA nephropathy using long-term protocol biopsy may improve graft survival. In addition, assessment of long-term protocol biopsies is useful not only for detection of calcineurin inhibitor nephrotoxicity, but also for follow-up after withdrawal of calcineurin inhibitor regimens. Also, identifying normal histology on a protocol biopsy may inform us about the safety of reducing overall immunosuppression. Thus, the potential benefit of long-term protocol biopsy may be of clinical significance for the detection of graft dysfunction as a result of non-immune factors, such as recurrence of glomerulonephritis and calcineurin inhibitor nephrotoxicity, rather than subclinical rejection.

Donor ABCB1 genetic polymorphisms influence epithelial-to-mesenchyme transition in tacrolimus-treated kidney recipients

Aim: The contribution of epithelial–mesenchymal transition (EMT) has been suggested in renal transplant recipients receiving calcineurin inhibitors and developing nephrotoxicity. Materials & methods: We assessed whether interindividual variability in tacrolimus pharmacokinetics is associated with the occurrence in tubular cells of two EMT markers (vimentin, β-catenin) detected at 3‐month in 140 allograft biopsies. We investigated whether genetic polymorphisms affecting CYP3A5 and ABCB1 influence EMT and kidney fibrosis. Results: In univariate analysis, the donor CYP3A5*1 allele was significantly associated with a lower vimentin expression. In multivariate analysis, grafts carrying ABCB1 3435T allele(s) developed significantly less EMT and less interstitial fibrosis. Conclusion: Donor SNPs significantly influence the epithelial program in the context of kidney transplantation, and the epithelial metabolism of tacrolimus is one key to understand graft fibrogenesis.

Biomarkers of calcineurin inhibitor nephrotoxicity in transplantation

Over 35 years of use has demonstrated the revolutionary therapeutic benefits of calcineurin inhibitors (CNI) in not only preventing transplant rejection, but also the renal and nonrenal toxicity of CNI. Acute reversible and insidious irreversible forms of CNI nephrotoxicity have been identified, with ischemia from an imbalance between vasoconstrictors and vasodilators playing an important role. The ongoing search to define toxicity pathways has been enriched by ‘Omics’ studies. Changes in proteins including those involved in activation of pro-inflammatory responses, oxidative stress, ER stress and the unfolded protein response have been identified, and these may serve as biomarkers of toxicity. However, the current standard of CNI toxicity, histology, lacks specificity, which creates challenges for biomarker validation. This review focuses on progress in nephrotoxic pathway identification of CNI and biomarker validation.

The Interplay between inflammation and fibrosis in kidney transplantation

Serial surveillance renal allograft biopsies have shown that early subclinical inflammation constitutes a risk factor for the development of interstitial fibrosis. More recently, it has been observed that persistent inflammation is also associated with fibrosis progression and chronic humoral rejection, two histological conditions associated with poor allograft survival. Treatment of subclinical inflammation with steroid boluses prevents progression of fibrosis and preserves renal function in patients treated with a cyclosporine-based regimen. Subclinical inflammation has been reduced after the introduction of tacrolimus based regimens, and it has been shown that immunosuppressive schedules that are effective in preventing acute rejection and subclinical inflammation may prevent the progression of fibrosis and chronic humoral rejection. On the other hand, minimization protocols are associated with progression of fibrosis, and noncompliance with the immunosuppressive regime constitutes a major risk factor for chronic humoral rejection. Thus, adequate immunosuppressive treatment, avoiding minimization strategies and reinforcing educational actions to prevent noncompliance, is at present an effective approach to combat the progression of fibrosis.

Single pediatric kidney transplantation in adult recipients: comparable outcomes with standard-criteria deceased-donor kidney transplantation

BACKGROUND

Single pediatric kidney transplantation (SKT) in adult recipients has traditionally been considered a high risk because of concerns of technical complications leading to poor graft outcomes. The primary goal of this single-center, retrospective analysis was to compare outcomes after SKT to standard-criteria deceased-donor kidney transplantation (SCDKT).

METHODS

We compared outcomes in adult recipients after SKT (n=31; mean donor weight, 27 kg); SCDKT (n=283); pediatric en bloc (n=21), living-donor (n=275), and extended criteria-donor (n=100) kidney transplantations.

RESULTS

The death-censored 5-year graft survival after SKT was significantly superior to SCDKT (81.4% vs. 74.5%, P=0.02). The serum creatinine level at 5 years after transplantation was significantly lower in SKT compared with that in SCDKT (1.2 vs. 1.6 mg/dL, P<0.0001). There was a significantly higher incidence of arterial anastomotic stenosis (6.8% vs. 0.4%, P=0.02) and hydronephrosis (12.9% vs. 5.3%, P=0.02) in the SKT cohort compared with SCDKT. Subgroup analysis of the SKT cohort by donor age less than 5 years vs. 6 to 10 years (mean weight, 16.4 vs. 32.7 kg) revealed no differences in patient or graft survival.

CONCLUSIONS

Despite a higher incidence of posttransplantation vascular and urological complications, long-term graft survival after SKT (in weight-matched pediatric donors and selected adult recipients) was comparable with that after SCDKT. SKT from very small donors (age, ≤5 years) yielded excellent long-term patient and graft survivals. The use of pediatric donor kidneys should be encouraged to address the problem of organ shortage.

Tacrolimus trough levels after month 3 as a predictor of acute rejection following kidney transplantation: a lesson learned from DeKAF Genomics

Most calcineurin inhibitor (CNI)-based protocols reduce blood trough goals approximately 2-3 months post-transplant in clinically stable kidney transplant recipients. The CNI target trough level to prevent rejection, after reduction, is unknown. Using a multivariate Cox proportional hazards model, we determined the association of time-varying tacrolimus (TAC) trough levels with acute rejection (AR) occurring in the first 6 months post-transplant, but specifically we assessed this association after 3 months. A total of 1930 patients received TAC-based immunosuppression prior to AR in a prospective study. Of the 151 (7.8%) who developed AR, 47 developed AR after 3 months post-transplant. In an adjusted time-varying multivariate model, each 1 ng/ml decrease in TAC trough levels was associated with a 7.2% increased risk of AR [hazards ratio (HR) = 1.07, 95% confidence interval (CI) (1.01, 1.14) P = 0.03] in the first 6 months. There was an additional 23% increased risk of AR with each 1 ng/ml decrease in the TAC trough levels in months 3-6 [HR = 1.23, 95% CI (1.06, 1.43) P = 0.008]. In conclusion, lower TAC trough levels were significantly associated with increased risk of AR in the first 6 months post-transplant with additional risk of AR between months 3 and 6 post-transplant. The timing and practice of TAC dose reduction should be personalized based on the individual's risk factors.

Calcineurin inhibitor nephrotoxicity: a review and perspective of the evidence

BACKGROUND

There is no doubt that acute calcineurin inhibitor (CNI) nephrotoxicity exists; however, chronic CNI nephrotoxicity is questionable at best.

METHODS

We reviewed the literature to identify original articles related to the use of CNIs in renal and nonrenal solid organ transplantation in order to examine the available evidence about their chronic nephrotoxicity and contribution to graft failure.

RESULTS

Early clinical experience and animal studies support the evidence of CNI nephrotoxicity. These findings evolved into the dogma that CNI nephrotoxicity is the major cause of late renal allograft failure. However, in transplanted kidneys the specific role of chronic CNI nephrotoxicity has been questioned. The emerging literature clearly highlights the lack of solid evidence for the role of CNIs as the sole and major injurious agents that cause chronic renal dysfunction and subsequent graft failure. Most of the evidence available to date is against complete CNI avoidance, and minimization appears to be a more viable strategy. It is becoming increasingly clear that the typical pathological lesions linked to chronic CNI use are highly nonspecific, and most of the chronic changes that have been attributed to chronic CNI nephrotoxicity are the consequences of previously unrecognized immunologic injuries. One needs to keep in mind that the potential risk of side effects of CNI use should be balanced against the risk of rejection.

CONCLUSIONS

More research should focus on addressing the true causes of chronic graft dysfunction rather than focusing on the overexaggerated contribution of CNIs to late graft loss.

Do protocol transplant biopsies improve kidney transplant outcomes?

PURPOSE OF REVIEW

The research undertaken on 'protocol' renal transplant biopsies has provided a rich, if not the richest, approach to better understanding of the immune and nonimmune impacts upon the transplant. The purpose of this review is to detail how the direct benefit to the patient also lies in these renamed 'surveillance' biopsies.

RECENT FINDINGS

Undertaken at fixed time points after transplantation, biopsy provides individual diagnoses with which the clinician can vary immunosuppression both in intensity and in the type of agent used to modify pathological processes early in their course. Initial nonfunction from acute tubular necrosis, subclinical cellular and humoral rejection, calcineurin inhibitor nephrotoxicity, BK virus nephropathy and recurrent glomerulonephritis are all important diagnoses for which early intervention provides better therapeutic outcomes than delaying until they are clinically evident.

SUMMARY

This review provides the recent evidence that has convinced many transplant units to embark upon surveillance programmes for their patients in order to individualize their immunosuppression and thus gain better outcomes.