Recent developments in kidney transplantation--a critical assessment

Novel intervention based on an individualized bundle of care to decrease infection in kidney transplant recipients

BACKGROUND

Infection remains a relevant complication after kidney transplantation (KT). A well-established strategy in modern medicine is the application of bundles of evidence-based practice in clinical settings. The objective of this study is to explore the application of a personalized bundle of measures aimed to reduce the incidence of infection in the first 12 months after KT.

METHODS

A single-center prospective cohort of 148 patients undergoing KT between February 2018 and September 2019 that received an individualized infection prevention strategy was compared to a preintervention cohort (n = 159). The bundle comprised a review of the patient's immunization history, infection risk by country of origin, screening for latent tuberculosis infection (LTBI), antimicrobial prophylaxis, and immunological assessment. Individualized recommendations were accordingly provided at a scheduled visit at day +30 after transplantation.

RESULTS

The intervention cohort showed a higher compliance rate with the recommended vaccine schedule, screening for geographically restricted infections and LTBI, and intravenous immunoglobulin and vitamin D supplementation (p values <.001). The 1-year incidence rate of infection was lower in the intervention cohort (42.6% vs. 57.9%; p value = .037), as was the rate of infection-related hospitalization (17.6% vs. 32.1%; p value = .003) and the incidence of severe bacterial infection. There were no differences in graft rejection or mortality rates between groups.

CONCLUSIONS

A multifaceted intervention, including a bundle of evidence-based practices, enhanced compliance with recommended preventive measures and was correlated with a reduction in the 12-month incidence of infection after KT.

Exercise and Prediabetes After Renal Transplantation (EXPRED-I): A Prospective Study

BACKGROUND

Post-transplant diabetes mellitus (PTDM) beyond 12 months (late PTDM) is a severe complication after renal transplantation. Late PTDM develops mostly in subjects with prediabetes. Although exercise may have a potential role in preventing late PTDM, there are no previous data on the effect of exercise in patients with prediabetes.

MATERIAL AND METHODS

The design was a 12-month exploratory study to test the capacity of exercise in reverting prediabetes in order to prevent late-PTDM. The outcome was the reversibility of prediabetes, assessed every 3 months with oral glucose tolerance tests (OGTT). The protocol included an incremental plan of aerobic and/or strength training as well as an active plan for promoting adherence (telephone calls, digital technology, and visits). A priori, a sample size cannot be calculated which makes this an exploratory analysis. Based on previous studies, the spontaneous reversibility of prediabetes was 30% and the reversibility induced by exercise will account for another 30%, a total reversibility of 60% (p value < 0.05, assuming a potency of 85%). Ad interim analysis was performed during follow-up to test the certainty of this sample calculation. Patients beyond 12 months after renal transplantation with prediabetes were included.

RESULTS

The study was interrupted early due to efficacy after the evaluation of the follow-up of 27 patients. At the end of follow-up, 16 (60%) patients reverted to normal glucose levels at fasting (from 102.13 mg/dL ± 11 to 86.75 ± 6.9, p = 0.006) and at 120 min after the OGTTs (154.44 mg/dL ± 30 to 113.0 ± 13.1, p = 0.002) and 11 patients had persistent prediabetes (40%). Also, insulin sensitivity improved with the reversibility of prediabetes, compared to those with persistent prediabetes: 0.09 [0.08-0.11] versus 0.04 [0.01-0.07], p = 0.001 (Stumvoll index). Most needed at least one increment in the prescription of exercise and compliance. Finally, measures aimed at the improvement of compliance were successful in 22 (80%) patients.

CONCLUSION

Exercise training was effective to improve glucose metabolism in renal transplant patients with prediabetes. Exercise prescription must be conducted considering both the clinical characteristics of the patients and pre-defined strategy to promote adherence. The trial registration number of the study was NCT04489043.

TIPE2 knockout reduces myocardial cell damage by inhibiting IFN-γ-mediated ferroptosis

Acute rejection of the transplanted heart is mediated by oxidative programmed cell death through the synergistic effects of the innate and adaptive immune systems. However, the role of ferroptosis, a newly discovered form of oxidative cell death, has not been widely evaluated. Tumor necrosis factor-α-induced protein-8 like 2 (TNFAIP8L2), also known as TIPE2, is required for maintaining immune homeostasis. To characterize the role of TIPE2 in mediating heart allografts, BALB/c hearts were transplanted into C57BL/6 wild-type (WT) and TIPE2^-/- recipient mice. In TIPE2^-/- recipient mice, allograft injury in BALB/c allograft hearts was significantly reduced through the inhibition of allograft ferroptosis. On day 3 and day 6 post-transplantation, the numbers of CD3⁺, CD4⁺, and CD8⁺ cells among splenocytes and draining lymph node cells were significantly decreased, and the activation of CD4⁺ and CD8⁺ cells in grafts was decreased in TIPE2^-/- recipient mice compared with WT mice. Moreover, CD4⁺ and CD8⁺ T cells in TIPE2^-/- recipient mice were characterized by deficient capacities for interferon-γ (IFN-γ) production through the TBK1 signaling axis and increased glutathione peroxidase 4 (GPX4). In cell experiments, treatment with IFN-γ enhanced ferroptosis-specific lipid peroxidation in myocardial cells and correlated inversely with GPX4 expression. Mechanistically, IFN-γ administration decreased the expression of GPX4 by inhibiting MEK/ERK phosphorylation. In summary, our findings demonstrated that TIPE2 deficiency inhibits T-cell production of IFN-γ to reduce ferroptosis in allografts by restraining lipid peroxidation.

Impact of obesity in kidney transplantation: a prospective cohort study from French registries between 2008 and 2014

BACKGROUND

The access of obese patients to kidney transplantation is limited despite several studies showing that obese transplant recipients had a better survival rate than those undergoing dialysis. The aim of this study was to compare patient and graft survival rates and post-renal transplant complications in obese patients and non-obese patients and to assess the effect of pre-transplant weight loss in obese patients on transplant outcomes.

METHODS

We carried out a prospective cohort study using two French registries REIN and CRISTAL on 7 270 kidney transplant patients between 2008 and 2014 in France. We compared obese patients with non-obese patients and obese patients who lost more than 10% of weight before the transplant (Obese WL and Obese nWL).

RESULTS

The mean BMI in our obese patients was 32 kg/m2. Graft survival was lower in obese patients than in non-obese patients (HR = 1.40, IC 95% [1.09; 1.78], P = 0.007) whereas patient survival was similar (HR = 0.94, IC 95% [0.73; 1.23], P = 0.66). Graft survival was significantly lower in Obese WL than in Obese nWL (HR = 2.17, CI 95% [1.02; 4.63], P = 0.045) whereas patient survival was similar in the two groups (HR = 0.79, IC 95% [0.35; 1.77], P = 0.56).

CONCLUSION

Grade I obesity does not seem to be a risk factor for excess mortality after kidney transplantation and should not be an obstacle to having access to a graft. Weight loss before a kidney transplant in this patients should not be essential for registration on waiting list.

New horizons in drug discovery of lymphocyte-specific protein tyrosine kinase (Lck) inhibitors: a decade review (2011-2021) focussing on structure-activity relationship (SAR) and docking insights

Lymphocyte-specific protein tyrosine kinase (Lck), a non-receptor Src family kinase, has a vital role in various cellular processes such as cell cycle control, cell adhesion, motility, proliferation, and differentiation. Lck is reported as a key factor regulating the functions of T-cell including the initiation of TCR signalling, T-cell development, in addition to T-cell homeostasis. Alteration in expression and activity of Lck results in numerous disorders such as cancer, asthma, diabetes, rheumatoid arthritis, atherosclerosis, and neuronal diseases. Accordingly, Lck has emerged as a novel target against different diseases. Herein, we amass the research efforts in literature and pharmaceutical patents during the last decade to develop new Lck inhibitors. Additionally, structure-activity relationship studies (SAR) and docking models of these new inhibitors within the active site of Lck were demonstrated offering deep insights into their different binding modes in a step towards the identification of more potent, selective, and safe Lck inhibitors.

Exercise and Prediabetes after Renal Transplantation (EXPRED): Protocol Description

BACKGROUND

Post-transplant diabetes mellitus (PTDM) is a frequent and severe complication after renal transplantation. In fact, PTDM is a risk factor for both infection and cardiovascular diseases. The prevalence and incidence of PTDM have a bimodal evolution: early (up to 3 months) and late PTDM (beyond 12 months). The majority of late PTDM occurs in subjects with prediabetes after transplantation. So, treating patients with prediabetes, a potentially reversible condition, might help preventing PTDM. In the general population, exercise prevents the evolution from prediabetes to diabetes. However, in renal transplantation, not enough evidence is available in this field.

OBJECTIVES

We designed an exploratory analysis to evaluate the feasibility of exercise to reverse prediabetes as a first step in the design of a trial to prevent PTDM.

METHODS

Only patients with prediabetes beyond 12 months after transplantation with capacity to perform exercise will be included. Prediabetes will be diagnosed based on fasting glucose levels and oral glucose tolerance tests (OGTTs). Patients will be treated with a stepped training intervention, starting with aerobic exercise training (brisk walking, swimming, and cycling) 5 times per week and 30 min/day. Aerobic exercise training will be gradually increased to 60 min/day or eventually combined with anaerobic exercise training in case of persistent prediabetes. The reversibility/persistence of prediabetes will be measured with fasting glucose and OGTTs every 3 months. This study will last for 12 months.

Development and evaluation of a BK polyomavirus serotyping assay using Luminex technology

BACKGROUND

The BK polyomavirus (BKPyV) is subdivided into four genotypes. The consequences of each genotype and of donor-recipient genotype (mis)match for BKPyV-associated nephropathy (BKPyVAN) in kidney transplant recipients (KTRs) are unknown.

OBJECTIVES

To develop and evaluate a genotype-specific IgG antibody-based BKPyV serotyping assay, in order to classify kidney transplant donors and recipients accordingly.

STUDY DESIGN

VP1 antigens of six BKPyV variants (Ib1, Ib2, Ic, II, III and IV) were expressed as recombinant glutathione-s-transferase-fusion proteins and coupled to fluorescent Luminex beads. Sera from 87 healthy blood donors and 39 KTRs were used to analyze seroreactivity and serospecificity against the different BKPyV genotypes. Six sera with marked BKPyV serotype profiles were analyzed further for genotype-specific BKPyV pseudovirus neutralizing capacity.

RESULTS

Seroreactivity was observed against all genotypes, with seropositivity rates above 77% comparable for KTRs and blood donors. Strong cross-reactivity (r > 0.8) was observed among genotype I subtypes, and among genotypes II, III and IV. Seroresponses against genotypes I and IV seemed genuine, while those against II and III could be out(cross)competed. GMT (Luminex) and IC₅₀ (neutralization assay) values showed good agreement in determining the genotype with the strongest seroresponse within an individual.

CONCLUSIONS

Despite some degree of cross-reactivity, this serotyping assay seems a useful tool to identify the main infecting BKPyV genotype within a given individual. This information, which cannot be obtained otherwise from nonviremic/nonviruric individuals, could provide valuable information regarding the prevalent BKPyV genotype in kidney donors and recipients and warrants further study.

Exploration of the therapeutic aspects of Lck: A kinase target in inflammatory mediated pathological conditions

Lck, a non-receptor src family kinase, plays a vital role in various cellular processes such as cell cycle control, cell adhesion, motility, proliferation and differentiation. As a 56 KDa protein, Lck phosphorylates tyrosine residues of various proteins such as ZAP-70, ITK and protein kinase C. The structure of Lck is comprised of three domains, one SH3 in tandem with a SH2 domain at the amino terminal and the kinase domain at the carboxy terminal. Physiologically, Lck is involved in the development, function and differentiation of T-cells. Additionally, Lck regulates neurite outgrowth and maintains long-term synaptic plasticity in neurons. Given a major role of Lck in cytokine production and T cell signaling, alteration in expression and activity of Lck may result in various diseased conditions like cancer, asthma, diabetes, rheumatoid arthritis, psoriasis, inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, atherosclerosis etc. This article provides evidence and information establishing Lck as one of the therapeutic targets in various inflammation mediated pathophysiological conditions.

Cell Therapy as a Tool for Induction of Immunological Tolerance after Liver Transplantation

Transplantation of solid organs, including liver, induces a number of serious complications related to immune incompatibility and requiring long-term use of immunosuppressive drugs. Finding the ways to inducing recipient immunological tolerance to the grafts is a top priority in organ transplantation and immunology. Along with the search for immunosupressive therapy, the development of alternative approaches to induction of immunological tolerance based on cell technologies is now in progress. In this regard, studies of the so-called spontaneous operational tolerance observed in ~20% patients after orthotopic liver transplantation is a promising trend. Understanding of this phenomenon can shed light on the mechanisms of immunological tolerance to allografts and will help to identify specific tolerance biomarkers and cell types with the aptitude for the induction of tolerance to liver allografts.

Clinical Pharmacokinetic Monitoring of Leflunomide in Renal Transplant Recipients with BK Virus Reactivation: A Review of the Literature

Leflunomide is an immunosuppressive drug with in vitro and initial observational evidence of antiviral activity against BK virus (BKV), a pathogen that causes opportunistic infection upon reactivation in renal transplant recipients. Leflunomide is considered an ancillary option to immunosuppression reduction in the management of BKV reactivation. Plasma or blood concentrations of teriflunomide, the active metabolite of leflunomide, are commonly monitored because of high leflunomide doses being used, known inter-individual variability in pharmacokinetics, and hepatotoxicity risk. However, the utility of clinical pharmacokinetic monitoring for leflunomide is as yet unclear. A literature search of MEDLINE (1946-December 2016), EMBASE (1974-December 2016), the CENTRAL database, and Google Scholar was performed to identify relevant English-language articles. Further articles were identified from references in relevant literature. A previously published 9-step decision-making algorithm was used to assess the available literature and determine the utility of clinical pharmacokinetic monitoring for leflunomide. Teriflunomide is readily measurable in the plasma or blood, but a clear relationship between concentration and efficacy or toxicity is lacking, and its therapeutic range is not well-established. Efficacy and toxicity endpoints such as renal function and BKV clearance can be readily assessed without measuring teriflunomide concentrations. Pharmacokinetic parameters are affected by genetic polymorphisms in cytochrome P450 CYP2C19 and ABCG2 genes. Therefore, routine clinical pharmacokinetic monitoring of leflunomide cannot be recommended based on current available evidence. However, it may provide clinical benefit in difficult situations when patients demonstrate a lack of therapeutic response or exhibit signs of drug toxicity.

LCK as a Potential Therapeutic Target for Acute Rejection after Kidney Transplantation: A Bioinformatics Clue

Objectives

We aim to identify the key biomarker of acute rejection (AR) after kidney transplantation via bioinformatics methods.

Methods

The gene expression data GSE75693 of 30 samples with stable kidney transplantation recipients and 15 AR samples were downloaded and analyzed by the limma package to identify differentially expressed genes (DEGs). Then, Gene Ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were done to explore the biological functions and potential important pathways of DEGs. Finally, protein-protein interactions (PPIs) and literature mining were applied to construct the cocitation network and to select the hub protein.

Results

A total of 437 upregulated genes and 353 downregulated genes were selected according to P < 0.01 and |log₂(fold change)| > 1.0. DEGs of AR are mainly located on membranes and impact the activation of receptors in immune responses. In the PPI network, Src kinase, lymphocyte kinase (LCK), CD3G, B2M, interferon-γ, CD3D, tumor necrosis factor, VAV1, and CD3E in the T cell receptor signaling pathway were selected as important factors, and LCK was identified as the hub protein.

Conclusion

LCK, via acting on T-cell receptor, might be a potential therapeutic target for AR after kidney transplantation.

[Impact of obesity in kidney transplantation: Monocentric cohort study and review of the literature]

Post-kidney transplantation outcomes in obese patients remain uncertain. The aim of this study is to compare patient and graft survival and post-transplant complications in obese patients and non-obese patients. We performed a retrospective analysis of a sample of 245kidney transplantations performed between 2008 and 2014 in Clermont-Ferrand. Obese patients and non-obese patients have been compared. Then we compared obese patients who have lost at least 5% of their weight (OPP) with obese patients who did not lose weight (OPS), and non-obese patients who have lost at least 5% of their weight (NOPP) with non-obese patients who did not lose weight (NOPS). Patient survival at 5years is similar between obese and non obese (84.06% versus 90.96%; P=0.49), between OPP and OPS (88.89% versus 81.82%; P=0.34) and between NOPP and NOPS (89.19% versus 91.05%; P=0.73). At 5years, graft survival is also comparable between obese and non obese (88.82% versus 81.86%; P=0.58), between OPP and OPS (85.56% versus 91.06%; P=0.98) and between NOPP and NOPS (88% versus 80.12%; P=0.31). The length of hospitalization and the rate of complications seem similar between obese and non obese and between OPP and OPS. Post-transplantation outcomes are similar between obese and non-obese patients and a weight loss for obese patients does not seem to decrease the risk of post-transplant complication.

KIR and their HLA Class I ligands: Two more pieces towards completing the puzzle of chronic rejection and graft loss in kidney transplantation

BACKGROUND

Kidney transplantation is a life-saving treatment for patients with end-stage renal disease. However, despite progress in surgical techniques and patient management, immunological rejection continues to have a negative impact on graft function and overall survival. Incompatibility between donors and recipients for human leukocyte antigens (HLA) of the major histocompatibility complex (MHC) generates a series of complex cellular and humoral immune response mechanisms that are largely responsible for rejection and loss of graft function. Within this context, a growing amount of evidence shows that alloreactive natural killer (NK) cells play a critical role in the immune response mechanisms elicited by the allograft. Killer immunoglobulin-like receptors (KIRs) are prominent mediators of NK cell alloreactivity.

METHODS AND FINDINGS

A cohort of 174 first cadaveric kidney allograft recipients and their donors were selected from a total cohort of 657 transplanted patients for retrospective immunogenetic analyses. Patients with HLA Class II mismatches were excluded. HLA Class I allele frequencies were compared among patients with chronic rejection, patients with stable graft function and a group of 2388 healthy controls. Activating and inhibitory KIR gene frequencies, KIR haplotypes, KIR-HLA ligand matches/mismatches and combinations of recipient KIRs and donor HLA Class I ligands were compared among patients with and without chronic rejection and a group of 221 healthy controls. Patients transplanted from donors homozygous for HLA-C1 antigens had a significantly higher risk for chronic rejection than patients transplanted from donors homozygous or heterozygous for HLA-C2 antigens or with epitopes belonging to the HLA-Bw4 ligand group. The Kaplan-Meier curves obtained by dividing the patients into 3 groups according to the presence or absence of one or both of the combinations of recipient KIRs and donor HLA ligands (rKIR2DL1/dHLA-C2 and rKIR3DL1/dHLA-Bw4) showed a significantly higher cumulative incidence of chronic rejection in the group of patients completely lacking these functional units. These patients showed a progressively stronger decline in modification of diet in renal disease-estimated glomerular filtration rate.

CONCLUSIONS

KIR genotyping should be performed at the time of enrolment of patients on the waiting list for organ transplantation. In our study, a significantly higher risk of chronic rejection after kidney transplantation was observed when recipient (r) and donor (d) pairs completely lacked the two functional rKIR-dHLA ligand combinations rKIR2DL1/dHLA-C2 and rKIR3DL1/dHLA-Bw4. This immunogenetic profile corresponds to low levels of NK cell inhibition. Therefore, patients with this high risk profile could benefit from immunosuppressive therapy aimed at reducing NK-cell cytotoxicity.

Looking for the needle in the kidney transplantation haystack

The diagnosis of acute rejection still relies on renal allograft biopsy. In fact, histological features including C4d staining can be useful to differentiate cellular and antibody-mediated acute rejection. However, the pathogenic mechanism to define the type of rejection is usually assessed by anti-HLA donor specific antibodies (DSA) monitoring. Suspicion of acute rejection is usually based on renal function deterioration. This method has low sensitivity. Moreover, creatinine increase follows graft injury and therefore the diagnosis is performed when there is an ongoing acute rejection. One strategy to overcome the limitation of serum creatinine as predictor of acute rejection is to perform surveillance protocol biopsies. However, the low incidence of subclinical acute rejection among patients treated with tacrolimus-based immunosuppression makes this procedure questionable in terms of cost-effectiveness. In this scenario new biomarkers predicting acute rejection are urgently needed. Ideally, such biomarkers should anticipate acute rejection, thus allowing preventive actions such as maintenance immunosupression intensification and/or modification. Alternatively, these new biomarkers should at least improve the predictive value of serum creatinine monitoring. Although many of the new biomarkers are promising, none have been translated to the clinic to date because of a lack of validation studies and the existence of major methodological concerns.

Immune monitoring as prerequisite for transplantation tolerance trials

Ever since its first application in clinical medicine, scientists have been urged to induce tolerance towards foreign allogeneic transplants and thus avoid rejection by the recipient's immune system. This would circumvent chronic use of immunosuppressive drugs (IS) and thus avoid development of IS-induced side effects, which are contributing to the still unsatisfactory long-term graft and patient survival after solid organ transplantation. Although manifold strategies of tolerance induction have been described in preclinical models, only three therapeutic approaches have been utilized successfully in a still small number of patients. These approaches are based on (i) IS withdrawal in spontaneous operational tolerant (SOT) patients, (ii) induction of a mixed chimerism and (iii) adoptive transfer of regulatory cells. Results of clinical trials utilizing these approaches show that tolerance induction does not work in all patients. Thus, there is a need for reliable biomarkers, which can be used for patient selection and post-therapeutic immune monitoring of safety, success and failure. In this review, we summarize recent achievements in the identification and validation of such immunological assays and biomarkers, focusing mainly on kidney and liver transplantation. From the published findings so far, it has become clear that indicative biomarkers may vary between different therapeutic approaches applied and organs transplanted. Also, patient numbers studied so far are very small. This is the main reason why nearly all described parameters lack validation and reproducibility testing in large clinical trials, and are therefore not yet suitable for clinical practice.

MiR-142-5p and miR-486-5p as biomarkers for early detection of chronic antibody-mediated rejection in kidney transplantation

De novo donor-specific HLA antibody (DSA) would not necessarily contribute to chronic antibody-mediated rejection (CAMR) in kidney transplantation. Here, we investigated whether PBMC miRNAs could be predictable biomarkers for CAMR. Microarray profiling of 435 mature miRNAs in pooled samples was conducted. Individual analysis revealed that miR-142-5p was significantly (p < 0.01) underexpressed in patients with DSA. After DSA production, miR-486-5p and its target PTEN/foxO3 mRNA were significantly overexpressed (p < 0.01) and underexpressed (p < 0.01), respectively, in patients with biopsy-proven CAMR, compared with non-CAMR. Our studies suggest that miRNA expression patterns may serve as noninvasive diagnostic biomarkers to evaluate immune response and kidney allograft status.

Kidney transplantation, bioengineering and regeneration: an originally immunology-based discipline destined to transition towards ad hoc organ manufacturing and repair

Kidney transplantation (KT), as a modality of renal replacement therapy (RRT), has been shown to be both economically and functionally superior to dialysis for the treatment of end-stage renal disease (ESRD). Progress in KT is limited by two major barriers: a) a chronic and burgeoning shortage of transplantable organs and b) the need for chronic immunosuppression following transplantation. Although ground-breaking advances in transplant immunology have improved patient survival and graft durability, a new pathway of innovation is needed in order to overcome current obstacles. Regenerative medicine (RM) holds the potential to shift the paradigm in RRT, through organ bioengineering. Manufactured organs represent a potentially inexhaustible source of transplantable grafts that would bypass the need for immunosuppressive drugs by using autologous cells to repopulate extracellular matrix (ECM) scaffolds. This overview discusses the current status of renal transplantation while reviewing the most promising innovations in RM therapy as applied to RRT.

Oxidative stress is associated with weight gain in recipients at 12-months following kidney transplantation

OBJECTIVE

Weight gain after kidney transplantation (Tx) is considered a risk factor for poor outcomes. Increased oxidative stress is associated with not only chronic renal disease and Tx, but also obesity and cardiovascular disease. The aim of this pilot study was to test whether oxidative stress is related to weight gain at 12-months after kidney Tx and to obtain preliminary insight into potential mechanisms involved.

DESIGN & METHODS

Recipients (n=33) were classified into two groups; weight loss and weight gain, based on their weight changes at 12-months post-transplant. Total antioxidant capacity (TAOC) and lipid peroxidation (TBARS) were measured to evaluate oxidative stress from plasma at baseline and 12-months. A secondary data analysis was conducted to identify potential gene regulation.

RESULTS

Seventeen recipients lost (-6.63±5.52kg), and sixteen recipients gained weight (8.94±6.18kg). TAOC was significantly decreased at 12-months compared to baseline for the total group, however, there was no significant difference between groups at either time point. TBARS was higher in weight gain group, at both time points, and it was significantly higher at 12-months (p=0.012). Gene expression profiling analysis showed that 7 transcripts annotated to reactive oxygen species related genes in adipose tissue were expressed significantly lower in weight gain group at baseline, which might be a negative feedback mechanism to reduce oxidative stress.

CONCLUSION

These results may indicate that elevated oxidative stress (TBARS) is associated with weight gain after kidney Tx and that incorporating early clinical prevention strategies known to decrease oxidative stress could be recommended.

Hemostatic Parameters according to Renal Function and Time after Transplantation in Brazilian Renal Transplanted Patients

Kidney transplantation is the key for patients with end-stage renal disease, improving quality of life and longer survival. However, kidney transplant triggers an intense inflammatory response and alters the hemostatic system, but the pathophysiological mechanisms of these changes are not completely understood. The aim of this cross-sectional cohort study was to investigate hemostatic biomarkers in Brazilian renal transplanted patients according to renal function and time after transplantation. A total of 159 renal transplanted patients were enrolled and D-Dimer (D-Di), Thrombomodulin (TM), von Willebrand Factor (VWF), and ADAMTS13 plasma levels were assessed by ELISA. An increase of D-Di was observed in patients with higher levels of creatinine. ADAMTS13 levels were associated with creatinine plasma levels and D-Di levels with Glomerular Filtration Rate. These results suggested that D-Di and ADAMTS13 can be promising markers to estimate renal function. ADAMTS13 should be investigated throughout the posttransplant time to clarify the participation of this enzyme in glomerular filtration and acceptance or rejection of the graft in Brazilian transplanted patients.

Everolimus and sirolimus in transplantation-related but different

INTRODUCTION

The inhibitors of the mammalian target of rapamycin (mTOR) sirolimus and everolimus are used not only as immunosuppressants after organ transplantation in combination with calcineurin inhibitors (CNIs) but also as proliferation signal inhibitors coated on drug-eluting stents and in cancer therapy. Notwithstanding their related chemical structures, both have distinct pharmacokinetic, pharmacodynamic and toxicodynamic properties.

AREAS COVERED

The additional hydroxyethyl group at the C(40) of the everolimus molecule results in different tissue and subcellular distribution, different affinities to active drug transporters and drug-metabolizing enzymes as well as differences in drug-target protein interactions including a much higher potency in terms of interacting with the mTOR complex 2 than sirolimus. Said mechanistic differences as well as differences found in clinical trials in transplant patients are reviewed.

EXPERT OPINION

In comparison to sirolimus, everolimus has higher bioavailability, a shorter terminal half-life, different blood metabolite patterns, the potential to antagonize the negative effects of CNIs on neuronal and kidney cell metabolism (which sirolimus enhances), the ability to stimulate mitochondrial oxidation (which sirolimus inhibits) and to reduce vascular inflammation to a greater extent. A head-to-head, randomized trial comparing the safety and tolerability of these two mTOR inhibitors in solid organ transplant recipients is merited.

Dendritic Cells in Kidney Transplant Biopsy Samples Are Associated with T Cell Infiltration and Poor Allograft Survival

Progress in long-term renal allograft survival continues to lag behind the progress in short-term transplant outcomes. Dendritic cells are the most efficient antigen-presenting cells, but surprisingly little attention has been paid to their presence in transplanted kidneys. We used dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin as a marker of dendritic cells in 105 allograft biopsy samples from 105 kidney transplant recipients. High dendritic cell density was associated with poor allograft survival independent of clinical variables. Moreover, high dendritic cell density correlated with greater T cell proliferation and poor outcomes in patients with high total inflammation scores, including inflammation in areas of tubular atrophy. We then explored the association between dendritic cells and histologic variables associated with poor prognosis. Multivariate analysis revealed an independent association between the densities of dendritic cells and T cells. In biopsy samples with high dendritic cell density, electron microscopy showed direct physical contact between infiltrating lymphocytes and cells that have the ultrastructural morphologic characteristics of dendritic cells. The origin of graft dendritic cells was sought in nine sex-mismatched recipients using XY fluorescence in situ hybridization. Whereas donor dendritic cells predominated initially, the majority of dendritic cells in late allograft biopsy samples were of recipient origin. Our data highlight the prognostic value of dendritic cell density in allograft biopsy samples, suggest a new role for these cells in shaping graft inflammation, and provide a rationale for targeting dendritic cell recruitment to promote long-term allograft survival.

The use of novel diagnostics to individualize immunosuppression following transplantation

Despite major improvements in short-term survival of organ allografts, long-term graft survival has not changed significantly. It is also known that toxic side effects of current immunosuppressive drugs (IS) especially calcineurin inhibitors (CNI) contribute to the unsatisfactory graft and patient survival following transplantation. Thus, clinicians strive to reduce or wean IS in potentially eligible patients. Research in the last 10 years has focussed on identification of biomarkers suitable for patient stratification in minimization or weaning trials. Most of the described biomarkers have been run retrospectively on samples collected within single-centre trials. Thus, often their performance has not been validated in other potentially multicentre clinical trials. Ultimately, the utility of biomarkers to identify potential weaning candidates should be investigated in large randomized prospective trials. In particular, for testing in such trials, we need more information about the accuracy, reproducibility, stability and limitations of the described biomarkers. Also, data repositories summarizing crucial information on biomarker performance in age- and gender-matched healthy individuals of different ethnicity are missing. This together with improved bioinformatics tools might help in developing better scores for patient stratification. Here, we will summarize the current results, knowledge and limitations on biomarkers for drug minimization or weaning trials.

Activation of the peroxisome proliferator-activated receptor γ counteracts sepsis-induced T cell cytotoxicity toward alloantigenic target cells

Sepsis still emerges as a major cause of patient death in intensive care units. Therefore, new therapeutic approaches are mandatory. Because during sepsis progression cytotoxic T lymphocytes (CTLs) can be activated in an autoimmune fashion contributing to multiorgan damage, it remains unclear whether CTLs are activated toward alloantigenic cells. This is important for patients receiving an immunosuppressive therapy to permit organ transplantation and, thus, known to be at high risk for developing sepsis. Therefore, we analyzed whether sepsis activates CTL toward alloantigenic target cells and whether this can be inhibited by PPARγ activation, known to block T helper cell responses. To mimic septic conditions, CTLs were isolated from cecal ligation and puncture-operated mice. CTL cytotoxicity was analyzed following a direct alloantigenic activation regime or following classical ex vivo splenocyte-driven activation in a cytotoxicity assay. With this readout, we found that CTL derived from septic mice enhanced cytotoxicity toward alloantigenic target cells, which was lowered by in vivo and ex vivo PPARγ activation. With CTL derived from T cell-specific PPARγ knockout mice, PPARγ activation was ineffective, pointing to a PPARγ-dependent mechanism. In vivo and ex vivo PPARγ activation reduced Fas and granzyme B expression in activated CTL.

KEY MESSAGE

In the sepsis CLP mouse model, CTLs are activated toward alloantigenic target cells. Sepsis-mediated alloantigenic CTL activation is blocked in vivo by PPARγ activation. PPARγ deletion or antagonization restored rosiglitazone-dependent inhibition of CTL cytotoxicity. PPARγ inhibits the expression of Fas and granzyme B in CTLs.

Effects of obesity on kidney transplantation outcomes: a systematic review and meta-analysis

BACKGROUND

The effects of obesity on outcomes reported after kidney transplantation have been controversial. The purpose of this systematic review and meta-analysis was to elucidate this issue.

METHODS

MEDLINE, EMBASE, Cochrane Library, and gray literature were searched up to August 6, 2013. Studies that compared obese and nonobese patients who underwent kidney transplantation and evaluated one of these outcomes-delayed graft function (DGF), acute rejection, graft or patient survival at 1 or 5 years after transplantation, or death by cardiovascular disease (CVD)-were included. Two independent reviewers extracted the data and assessed the quality of the studies.

RESULTS

From 1,973 articles retrieved, 21 studies (9,296 patients) were included. Obesity was associated with DGF (relative risk, 1.41; 95% confidence interval, 1.26-1.57; I=8%; Pheterogeneity=0.36), but not with acute rejection. Graft loss and death were associated with obesity only in the analysis of studies that evaluated patients who received a kidney graft before year 2000. No association of obesity with graft loss and death was found in the analysis of studies that evaluated patients who received a kidney graft after year 2000. Death by CVD was associated with obesity (relative risk, 2.07; 95% confidence interval, 1.17-3.64; I=0%; Pheterogeneity=0.59); however, most studies included in this analysis evaluated patients who received a kidney graft after year 2000.

CONCLUSION

In conclusion, obese patients have increased risk for DGF. In the past years, obesity was a risk factor for graft loss, death by CVD, and all-cause mortality. However, for the obese transplanted patient today, the graft and patient survival is the same as that of the nonobese patient.

Identification of expanded-criteria donor kidney grafts at lower risk of delayed graft function

BACKGROUND

Organ shortage leads to the increased use of expanded-criteria donor (ECD) kidneys, which contribute to a higher risk of delayed graft function (DGF) after transplantation. The aim of this study was to determine factors that may better predict the risk of DGF.

METHODS

Histologic assessments of donor renal biopsy were used with other clinical variables to predict the risk of DGF after kidney transplantation. The total Banff score equaled the sum of interstitial fibrosis (CI), tubular atrophy, arteriolar hyaline thickening, fibrous intimal thickening (CV), and fraction of sclerotized glomeruli.

RESULTS

In total, 126 of 344 patients developed DGF after kidney transplantation. The histologic score for CI, tubular atrophy, and CV and the total Banff score were increased in patients with DGF. Only CI and CV were independent predictors of DGF (P<0.01). A CIV score (CI+CV; odds ratio, 2.68; 95% confidence interval, 1.55-4.66; P<0.001) was superior to the combination of the total Banff score (odds ratio, 1.48; 95% confidence interval, 0.85-2.55; P=NS). A CIV score≥1, donor age more than 51 years, and anoxia donor brain injury were associated with the highest risk of DGF. A CIV<1 identified a subgroup of ECDs at a lower risk of DGF comparable with standard-criteria donors (29.3% vs. 28.4%).

CONCLUSIONS

Composite CIV score better identifies ECD kidneys with a lower risk of developing DGF. Morphologic evaluation of ECD kidneys and donor characteristics may improve kidney allocation.

Are killer cell immunoglobulin-like receptor genes important for the prediction of kidney graft rejection?

Killer cell immunoglobulin-like receptors (KIRs) are expressed on natural killer cells and minor subpopulations of thymus-derived (T) lymphocytes. KIRs may have a long cytoplasmic tail and inhibit cell activation upon ligand (HLA class I) binding, or they may have a short cytoplasmic tail and activate a cell after ligand binding. They are encoded by up to 14 genes present in different individuals in different combinations, whence their associations with several human diseases. KIR involvement in the fate of kidney allograft has not been extensively studied; nevertheless some associations had already been noticed. Their results are not concordant: some authors found no effect of KIR genotype, whereas others detected protective effect of KIR2DL2/KIR2DS2 or KIR-KIR ligand mismatch. We found an association of KIR2DS4 gene with acute rejection and a protective effect of KIR2DS5 gene. Interestingly, in patients, whose end-stage renal disease was caused by glomerulonephritis, the effect of KIR2DS4 was stronger than HLA mismatch, whereas opposite was true for recipients with other causes of renal failure.

Everolimus and sirolimus in combination with cyclosporine have different effects on renal metabolism in the rat

Enhancement of calcineurin inhibitor nephrotoxicity by sirolimus (SRL) is limiting the clinical use of this drug combination. We compared the dose-dependent effects of the structurally related everolimus (EVL) and sirolimus (SRL) alone, and in combination with cyclosporine (CsA), on the rat kidney. Lewis rats were treated by oral gavage for 28 days using a checkerboard dosing format (0, 3.0, 6.0 and 10.0 CsA and 0, 0.5, 1.5 and 3.0 mg/kg/day SRL or EVL, n = 4/dose combination). After 28 days, oxidative stress, energy charge, kidney histologies, glomerular filtration rates, and concentrations of the immunosuppressants were measured along with ¹H-magnetic resonance spectroscopy (MRS) and gas chromatography- mass spectrometry profiles of cellular metabolites in urine. The combination of CsA with SRL led to higher urinary glucose concentrations and decreased levels of urinary Krebs cycle metabolites when compared to controls, suggesting that CsA+SRL negatively impacted proximal tubule metabolism. Unsupervised principal component analysis of MRS spectra distinguished unique urine metabolite patterns of rats treated with CsA+SRL from those treated with CsA+EVL and the controls. SRL, but not EVL blood concentrations were inversely correlated with urine Krebs cycle metabolite concentrations. Interestingly, the higher the EVL concentration, the closer urine metabolite patterns resembled those of controls, while in contrast, the combination of the highest doses of CsA+SRL showed the most significant differences in metabolite patterns. Surprisingly in this rat model, EVL and SRL in combination with CsA had different effects on kidney biochemistry, suggesting that further exploration of EVL in combination with low dose calcineurin inhibitors may be of potential benefit.

Low-salt diet and cyclosporine nephrotoxicity: changes in kidney cell metabolism

Cyclosporine (CsA) is a highly effective immunosuppressant used in patients after transplantation; however, its use is limited by nephrotoxicity. Salt depletion is known to enhance CsA-induced nephrotoxicity in the rat, but the underlying molecular mechanisms are not completely understood. The goal of our study was to identify the molecular effects of salt depletion alone and in combination with CsA on the kidney using a proteo-metabolomic strategy. Rats (n = 6) were assigned to four study groups: (1) normal controls, (2) low-salt fed controls, (3) 10 mg/kg/d CsA for 28 days on a normal diet, (4) 10 mg/kg/d CsA for 28 days on low-salt diet. Low-salt diet redirected kidney energy metabolism toward mitochondria as indicated by a higher energy charge than in normal-fed controls. Low-salt diet alone reduced phospho-AKT and phospho-STAT3 levels and changed the expression of ion transporters PDZK1 and CLIC1. CsA induced macro- and microvesicular tubular epithelial vacuolization and reduced energy charge, changes that were more significant in low-salt fed animals, probably because of their more pronounced dependence on mitochondria. Here, CsA increased phospho-JAK2 and phospho-STAT3 levels and reduced the phospho-IKKγ and p65 proteins, thus activating NF-κB signaling. Decreased expression of lactate transport regulator CD147 and phospho-AKT was also observed after CsA exposure in low-salt rats, indicating a decrease in glycolysis. In summary, our study suggests a key role for PDZK1, CD147, JAK/STAT, and AKT signaling in CsA-induced nephrotoxicity and proposes mechanistic explanations on why rats fed a low-salt diet have higher sensitivity to CsA.

Killer immunoglobulin-like receptor (KIR) and HLA genotypes affect the outcome of allogeneic kidney transplantation

Background

Recipient NK cells may detect the lack of recipient's (i.e., self) HLA antigens on donor renal tissue by means of their killer cell immunoglobulin-like receptors (KIRs). KIR genes are differently distributed in individuals, possibly contributing to differences in response to allogeneic graft.

Methodology/Principal Findings

We compared frequencies of 10 KIR genes by PCR-SSP in 93 kidney graft recipients rejecting allogeneic renal transplants with those in 190 recipients accepting grafts and 690 healthy control individuals. HLA matching results were drawn from medical records. We observed associations of both a full-length KIR2DS4 gene and its variant with 22-bp deletion with kidney graft rejection. This effect was modulated by the HLA-B,-DR matching, particularly in recipients who did not have glomerulonephritis but had both forms of KIR2DS4 gene. In contrast, in recipients with glomerulonephritis, HLA compatibility seemed to be much less important for graft rejection than the presence of KIR2DS4 gene. Simultaneous presence of both KIR2DS4 variants strongly increased the probability of rejection. Interestingly, KIR2DS5 seemed to protect the graft in the presence of KIR2DS4fl but in the absence of KIR2DS4del.

Conclusions/Significance

Our results suggest a protective role of KIR2DS5 in graft rejection and an association of KIR2DS4 with kidney rejection, particularly in recipients with glomerulonephritis.

Tolerogenic therapies in transplantation

Since the concept of immunologic tolerance was discovered in the 1940s, the pursuit of tolerance induction in human transplantation has led to a rapid development of pharmacologic and biologic agents. Short-term graft survival remains an all-time high, but successful withdrawal of immunosuppression to achieve operational tolerance rarely occurs outside of liver transplantation. Collaborative efforts through the NIH sponsored Immune Tolerance Network and the European Commission sponsored Reprogramming the Immune System for Establishment of Tolerance consortia have afforded researchers opportunity to evaluate the safety and efficacy of tolerogenic strategies, investigate mechanisms of tolerance, and identify molecular and genetic markers that distinguish the tolerance phenotype. In this article, we review traditional and novel approaches to inducing tolerance for organ transplantation, with an emphasis on their translation into clinical trials.

Comparison of the long-term outcomes of kidney transplantation: USA versus Spain

BACKGROUND

The long-term outcomes of kidney transplantation are suboptimal because many patients lose their allografts or experience premature death. Cross-country comparisons of long-term outcomes of kidney transplantation may provide insight into factors contributing to premature graft failure and death. We evaluated the rates of late graft failure and death among US and Spanish kidney recipients.

METHODS

This is a cohort study of US (n = 9609) and Spanish (n = 3808) patients who received a deceased donor kidney transplant in 1990, 1994, 1998 or 2002 and had a functioning allograft 1 year after transplantation with follow-up through September 2006. Ten-year overall and death-censored graft survival and 10-year overall recipient survival and death with graft function (DWGF) were estimated with multivariate Cox models.

RESULTS

Among recipients alive with graft function 1 year after transplant, the 10-year graft survival was 71.3% for Spanish and 53.4% for US recipients (P < 0.001). The 10-year, death-censored graft survival was 75.6 and 76.0% for Spanish and US recipients, respectively (P = 0.73). The 10-year recipient survival was 86.2% for Spanish and 67.4% for US recipients (P < 0.001). In recipients with diabetes as the cause of ESRD, the adjusted DWGF rates at 10 years were 23.9 and 53.8 per 1000 person-years for Spanish and US recipients, respectively (P < 0.001). Among recipients whose cause of ESRD was not diabetes mellitus, the adjusted 10-year DWGF rates were 11.0 and 25.4 per 1000 person-years for Spanish and US recipients, respectively.

CONCLUSIONS

US kidney transplant recipients had more than twice the long-term hazard of DWGF compared with Spanish kidney transplant recipients and similar levels of death-censored graft function. Pre-transplant medical care, comorbidities, such as cardiovascular disease, and their management in each country's health system are possible explanations for the differences between the two countries.

Ocular nocardiosis in a renal transplant patient: a warning of life-threatening underlying systemic disease

PURPOSE

To describe a case of an immunosuppressed patient with history of renal transplant that presented with sudden unilateral loss of vision.

METHODS

Case report. Review of medical records.

RESULTS

A 49-year-old man with history of renal transplantation presenting with visual symptoms without initial systemic manifestations. Because of the rarity of ocular involvement, the patient's diagnosis of Nocardia asteroides endophthalmitis was delayed culminating in systemic involvement and necessitating enucleation of the eye.

CONCLUSION

Nocardiosis is a serious life-threatening complication in immunosuppressed patients. Visual symptoms and endophthalmitis in this population should raise the suspicion of a possible serious systemic infection like nocardia.

Urinary chemokines and anti-inflammatory molecules in renal transplanted patients as potential biomarkers of graft function: a prospective study

PURPOSE

Clinical- and histopathology-based scores are the limited predictors of allograft outcome. Thus, predictors of allograft survival still remain a challenge. This study aimed to evaluate the urinary levels of chemokines and anti-inflammatory molecules at 30, 90, and 300 days after renal transplantation and to further correlate these measurements to graft function.

METHODS

Glomerular filtration rate (GFR) and urinary levels of MCP-1/CCL2, MIP-1α/CCL3, RANTES/CCL5, IL-8/CXCL8, IP-10/CXCL10, interleukin-1 receptor antagonist, soluble tumor necrosis factor receptor-1, and receptor-2 were determined at 30, 90, and 300 days after renal transplantation in 22 patients. Transplanted patients were also divided according to the type of donor (living donor, LD, n = 13 or deceased donor, DD, n = 9).

RESULTS

Urinary levels of all molecules, except MIP-1α/CCL3, remained unchanged at 30, 90, and 300 days after transplantation in our 22 patients. MIP-1α/CCL3 levels significantly reduced from 30 to 300 days and showed a negative correlation with GFR at 30 days. The comparison between LD and DD groups showed similar levels of all markers, except for MCP-1/CCL2, which presented higher values in LD than in DD at 30 days. sTNFR1 and MCP-1/CCL2 significantly reduced from 30 to 300 days in LD group, but only sTNFR2 concentrations at 30 days were negatively correlated with GFR at 300 days. On the other hand, in DD group, IL-1Ra concentrations at 30 and at 90 days were positively correlated with GFR at 300 days.

CONCLUSION

Urinary chemokine and anti-inflammatory molecules measurements may be a promising tool in the follow-up of renal transplanted patients.

Comparative study on signal transduction in endothelial cells after anti-a/b and human leukocyte antigen antibody reaction: implication of accommodation

BACKGROUND

Recent development of immunosuppressive therapy has provided a platform for clinical human leukocyte antigen (HLA)- and ABO-incompatible kidney transplantation. However, the prognosis seems to be different between the two. Accommodation, the condition of no injury even in the presence of antidonor antibody, is one of the key factors for successful transplantation with antidonor antibody. The purpose of this study was to compare signal transduction between anti-A/B and anti-HLA antibody reaction and to elucidate the mechanisms underlying accommodation.

METHODS

Blood type A- or B-transferase gene was transfected into human EA.hy926 endothelial cells. After cell sorting, A- or B-expressing cells at high levels were obtained. The effects of anti-HLA and anti-A/B antibody binding on complement-mediated cytotoxicity and signal transduction were examined.

RESULTS

Preincubation with anti-HLA antibodies only at low levels (<10% of saturation level) or anti-A/B antibodies at high levels (even at near saturation levels) for 24 hr resulted in resistance to complement-mediated cytotoxicity. Anti-A/B antibody ligation inactivated ERK1/2 pathway and increased complement regulatory proteins such as CD55 and CD59, whereas anti-HLA ligation activated PI3K/AKT pathway and increased cytoprotective genes such as hemeoxygenase-1 and ferritin H.

CONCLUSION

Complement inhibition by upregulation of CD55 and CD59 through ERK1/2 inactivation might play a substantial role in accommodation after ABO-incompatible transplantation, which could also explain the intriguing finding of C4d deposition in the graft without rejection.

KAP degradation by calpain is associated with CK2 phosphorylation and provides a novel mechanism for cyclosporine A-induced proximal tubule injury

The use of cyclosporine A (CsA) is limited by its severe nephrotoxicity that includes reversible vasoconstrictor effects and proximal tubule cell injury, the latter associated whith chronic kidney disease progression. The mechanisms of CsA-induced tubular injury, mainly on the S3 segment, have not been completely elucidated. Kidney androgen-regulated protein (KAP) is exclusively expressed in kidney proximal tubule cells, interacts with the CsA-binding protein cyclophilin B and its expression diminishes in kidneys of CsA-treated mice. Since we reported that KAP protects against CsA toxicity in cultured proximal tubule cells, we hypothesized that low KAP levels found in kidneys of CsA-treated mice might correlate with proximal tubule cell injury. To test this hypothesis, we used KAP Tg mice developed in our laboratory and showed that these mice are more resistant to CsA-induced tubular injury than control littermates. Furthermore, we found that calpain, which was activated by CsA in cell cultures and kidney, is involved in KAP degradation and observed that phosphorylation of serine and threonine residues found in KAP PEST sequences by protein kinase CK2 enhances KAP degradation by calpain. Moreover, we also observed that CK2 inhibition protected against CsA-induced cytotoxicity. These findings point to a novel mechanism for CsA-induced kidney toxicity that might be useful in developing therapeutic strategies aimed at preventing tubular cell damage while maintaining the immunosuppressive effects of CsA.

Biomarkers of immunosuppressant organ toxicity after transplantation: status, concepts and misconceptions

INTRODUCTION

A major challenge in transplantation is improving long-term organ transplant and patient survival. Immunosuppressants protect the transplant organ from alloimmune reactions, but sometimes also exhibit limiting side effects. The key to improving long-term outcome following transplantation is the selection of the correct immunosuppressive regimen for an individual patient for minimizing toxicity while maintaining immunosuppressive efficacy.

AREAS COVERED

Proteomics and metabolomics have the potential to develop sensitive and specific diagnostic tools for monitoring early changes in cell signal transduction, regulation and biochemical pathways. Here, we review the steps required for the development of molecular markers from discovery, mechanistic and clinical qualification to regulatory approval, and present a critical discussion of the current status of molecular marker development as relevant for the management and individualization of immunosuppressive drug regimens.

EXPERT OPINION

Although metabolomics and proteomics-based studies have yielded several candidate molecular markers, most published studies are poorly designed, statistically underpowered and/or often have not gone beyond the discovery stage. Most molecular marker candidates are still at an early stage. Due to the high complexity of and the resources required for diagnostic marker development, initiatives and consortia organized and supported by funding agencies and regulatory agencies will be critical.