What we CAN do about chronic allograft nephropathy: Role of immunosuppressive modulations

Operations Research to Solve Kidney Allocation Problems: A Systematic Review

BACKGROUND

Operations research techniques enable health care administrators to optimize resource allocation and to find solutions to staff and patient scheduling problems. We aimed to conduct the first systematic review of the international literature on the use of operations research for allocating deceased-donor kidneys.

METHODS

We searched the MEDLINE, EMBASE, and PubMed databases from inception to February 2023. Two reviewers independently screened the title/abstract and subsequently the full text of potentially eligible articles and abstracted the data. Quality assessment of the final set of studies was conducted using Subben's checklist.

RESULTS

Of the 302 citations identified, 5 studies were included. These studies covered three themes, including (1) provider-facing decision aids to determine the timing of transplant for single or multiple patients; (2) system-level planning on kidney allocation based on blood type matching rules; and (3) patient-facilitated wait times estimation using incomplete information. Markov models, sequential stochastic assignment models, and queuing models were amongst the most used techniques. Although we found all included studies to meet Subben's criteria, we believe the checklist in its current form lacks items to assess the validity of model inferences. As such, we ended this review with a set of practical recommendations.

CONCLUSIONS

Our review demonstrated the utility of operations research techniques in assisting the system, healthcare providers, and patients in the transplantation process. More research is needed to reach a consensus on a model that can be used to support the decision-making of different stakeholders for efficient kidney allocation, with the ultimate goal of reducing the gap between kidney supply and demand and enhancing the population's well-being.

Machine learning for predicting long-term kidney allograft survival: a scoping review

Supervised machine learning (ML) is a class of algorithms that "learn" from existing input-output pairs, which is gaining popularity in pattern recognition for classification and prediction problems. In this scoping review, we examined the use of supervised ML algorithms for the prediction of long-term allograft survival in kidney transplant recipients. Data sources included PubMed, the Cumulative Index to Nursing and Allied Health Literature, and the Institute for Electrical and Electronics Engineers (IEEE) Xplore libraries from inception to November 2019. We screened titles and abstracts and potentially eligible full-text reports to select studies and subsequently abstracted the data. Eleven studies were identified. Decision trees were the most commonly used method (n = 8), followed by artificial neural networks (ANN) (n = 4) and Bayesian belief networks (n = 2). The area under receiver operating curve (AUC) was the most common measure of discrimination (n = 7), followed by sensitivity (n = 5) and specificity (n = 4). Model calibration examining the reliability in risk prediction was performed using either the Pearson r or the Hosmer-Lemeshow test in four studies. One study showed that logistic regression had comparable performance to ANN, while another study demonstrated that ANN performed better in terms of sensitivity, specificity, and accuracy, as compared with a Cox proportional hazards model. We synthesized the evidence related to the comparison of ML techniques with traditional statistical approaches for prediction of long-term allograft survival in patients with a kidney transplant. The methodological and reporting quality of included studies was poor. Our study also demonstrated mixed results in terms of the predictive potential of the models.

Urinary biomarkers of chronic allograft nephropathy

PURPOSE

Chronic allograft nephropathy (CAN) is widely accepted as the leading cause of renal allograft loss after the first year post transplantation. This study aimed to identify urinary biomarkers that could predict CAN in transplant patients.

EXPERIMENTAL DESIGN

The study included 34 renal transplant patients with histologically proven CAN and 36 renal transplant patients with normal renal function. OrbiTrap MS was utilized to analysis a urinary fraction in order to identify other members of a previously identified biomarker tree . This novel biomarker pattern offers the potential to distinguish between transplant recipients with CAN and those with normal renal function.

RESULTS

The primary node of the biomarker pattern was reconfirmed as β2 microglobulin. Three other members of this biomarker pattern were identified: neutrophil gelatinase-associated lipocalin, clusterin, and kidney injury biomarker 1. Significantly higher urinary concentrations of these proteins were found in patients with CAN compared to those with normal kidney function.

CONCLUSIONS AND CLINICAL RELEVANCE

While further validation in a larger more-diverse patient population is required to determine if this biomarker pattern provides a potential means of diagnosing CAN by noninvasive methods in a clinical setting, this study clearly demonstrates the biomarkers' ability to stratify patients based on transplant function.

Functional and histological improvement after everolimus rescue of chronic allograft dysfunction in renal transplant recipients

Background

We tested the strategy of mTOR inhibitors with calcineurin inhibitor minimization in renal transplant recipients with known chronic allograft dysfunction.

Methods

In this open-label, single-arm study, renal transplant patients were recruited after biopsy-confirmed chronic allograft dysfunction in the absence of acute rejection episode within 2 months, with proteinuria <0.8 g/day, and serum creatinine <220 μmol/L or estimated glomerular filtration rate >40 mL/min/1.73 m². They were converted to everolimus (aiming for trough everolimus level 3–8 ng/mL) with cyclosporine minimization, to assess the effect on renal function, rate of glomerular filtration rate decline, and longitudinal transplant biopsy at 12 months.

Results

Seventeen Chinese patients (median transplant duration, 4.2 years) were recruited; no patients discontinued study medication. The mean slope of the glomerular filtration rate over time was −4.31±6.65 mL/min/1.73 m² per year in the year before everolimus, as compared with 1.29±5.84 mL/min/1.73 m² per year in the 12 months of everolimus therapy, a difference of 5.61 mL/min/1.73 m² per year (95% confidence interval [CI], 0.40–10.8) favoring everolimus therapy (P=0.036). Serial renal biopsy histology showed significant decrease of tubular atrophy (15.7%±11.3% versus 7.1%±7.3%, P=0.005) and interstitial fibrosis (14.8%±11.5% versus 7.2%±8.2%, P=0.013). Intrarenal expression of TGF-β1 mRNA showed a nonsignificant decrease after everolimus treatment.

Conclusion

In renal transplant recipients with biopsy-confirmed chronic allograft dysfunction, we found a significant beneficial effect of everolimus rescue therapy and calcineurin inhibitor minimization strategy on the improvement of glomerular filtration rate decline rate. In secondary analysis, everolimus was shown to slow down the disease progression by reducing the tubular atrophy and interstitial fibrosis scoring.

Identification of β2-microglobulin as a urinary biomarker for chronic allograft nephropathy using proteomic methods

PURPOSE

Chronic allograft nephropathy (CAN) remains the leading cause of renal graft loss after the first year following renal transplantation. This study aimed to identify novel urinary proteomic profiles, which could distinguish and predict CAN in susceptible individuals.

EXPERIMENTAL DESIGN

The study included 34 renal transplant patients with histologically proven CAN and 36 patients with normal renal transplant function. High-throughput proteomic profiles were generated from urine samples with three different ProteinChip arrays by surface-enhanced laser-desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Following SELDI, a biomarker pattern software analysis was performed which led to the identification of a novel biomarker pattern that could distinguish patients with CAN from those with normal renal function.

RESULTS

An 11.7 kDa protein identified as β2 microglobulin was the primary protein of this biomarker pattern, distinguishing CAN from control patients (receiver operator characteristic [ROC]=0.996). SELDI-TOF-MS comparison of purified β2 microglobulin protein and CAN urine demonstrated identical 11.7 kDa protein peaks. Significantly, higher concentrations of 2 microglobulin were found in the urine of patients with CAN compared with the urine of normal renal function transplant recipients (p<0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

Although further validation in a larger more diverse patient population is required to determine if this β2 microglobulin protein biomarker will provide a potential means of diagnosing CAN by noninvasive methods in a clinical setting, this study clearly shows a capability to stratify control and disease patients.

The prognostic value of frozen section preimplantation graft biopsy in the outcome of renal transplantation

INTRODUCTION

Preimplantation biopsy provides a window on the state of the renal allograft. In this study, the prognostic value of frozen section preimplantation graft biopsy was estimated and compared to regularly processed formalin-fixed biopsy.

MATERIALS AND METHODS

Seventy-four renal allograft recipients were studied. The degree of glomerulosclerosis, acute tubular necrosis, interstitial fibrosis, arteriosclerosis, and arteriolosclerosis was rapidly estimated in frozen sections and correlated to the renal function in the immediate posttransplantation period and 3 months thereafter. The histological changes were also examined in paraffin-embedded sections.

RESULTS

The histological changes observed in rapidly processed frozen sections were comparable to those observed on regularly processed sections and their differences did not reach statistical significance. Glomerulosclerosis and arteriolosclerosis were underestimated, whereas acute tubular necrosis and interstitial fibrosis were overestimated, in the frozen sections compared to permanent ones, but those differences were not statistically significant. Immediate graft function was observed in 45 patients (61%). Delayed graft function was more frequently observed among recipients with donor age above 60 years (57% vs. 32%). Serum creatinine 3 months after transplantation was above 2 mg/dL in 33 recipients (44.5%) and was positively correlated to the degree of tubular necrosis (p = 0.04) and donor age (p = 0.03). Donor age was correlated to the degree of arteriolosclerosis (p < 0.01).

CONCLUSIONS

Frozen section preimplantation biopsy gives reliable information for the situation of the graft that is related to the outcome of renal transplantation.

Pathogenesis of tubulointerstitial fibrosis in chronic allograft dysfunction

The term chronic allograft nephropathy (CAN) was originally coined in 1991 to replace chronic rejection which was used too generalized. However, the revised Banff classification, published in 2007, eliminated the term CAN again because it was felt that the term was used too broadly and prevented the search for the underlying cause. Interstitial fibrosis and tubular atrophy are integral parts of chronic allograft dysfunction and represent in the new classification a separate entity with or without the identification of a specific etiology. Myofibroblasts are the key, albeit not exclusive, effector cells in renal fibrogenesis resulting in upregulated extracellular matrix synthesis and eventually in interstitial fibrosis. These cells are formed mainly by stimulation of resident interstitial fibroblasts but also by differentiation processes of periadventitial cells, bone marrow derived cells and by a process entitled epithelial mesenchymal transition (EMT) of tubular epithelial cells. EMT has been described by many groups to be of high prevalence in renal allograft dysfunction contributing to matrix accumulation and renal function deterioration. This is of particular interest because immunosuppressive therapy has differential effects on EMT with calcineurin inhibitors in particular inducing the process. Moreover, specific therapies inhibiting EMT have been applied in experimental studies although the effects of their application in chronic allograft dysfunction remain to be studied. At the same time, immunosuppression may interfere with physiologic clearance of myofibroblasts by apoptosis, explaining in part the high prevalence of interstitial fibrosis in allograft biopsies. The Fas system has been identified to be mainly responsible for this physiologic apoptosis in non-renal scarring models; however, its relevance for renal fibrosis and particular fibrosis in renal allograft dysfunction remains to be determined. These findings point to a cautious and individualized use of immunosuppressive therapy in patients with allografts and particular those with chronic allograft dysfunction not because of rejection processes. Protocols using CNI-free immunosuppression are interesting options to prevent fibrosis in chronic allograft dysfunction.

High pretransplant serum levels of CXCL9 are associated with increased risk of acute rejection and graft failure in kidney graft recipients

Several clinical and experimental models have underlined the role of the CXCR3-binding chemokines in the immune-mediated kidney diseases. This study aimed to investigate the predictive value of measuring pretransplant CXCL9 levels for acute rejection (AR) onset and kidney transplantation outcome. Pretransplantation serum levels of CXCL9 were tested retrospectively in 252 kidney graft recipients, whose stratification in two groups according to CXCL9 levels (<272.1 pg/ml vs. >272.1 pg/ml) showed highly significant differences in 5-year survival rates (97.7% vs. 73.3%; P < 0.001). Multivariate analysis demonstrated that among the analysed variables, CXCL9 [relative risk (RR) 11.708] and AR (RR 3.604) had the highest predictive power of graft loss. Accordingly, patients with AR (254.4 + or - 22.1; P < 0.05) and, even more, those with anti-thymoglobulin (ATG)-treated AR also showed increased pretransplant serum CXCL9 levels (319.3 + or - 28.1, P < 0.001). Moreover, CXCL9 expression and distribution were investigated in tissue specimens obtained from 10 patients affected by AR, and wide CXCL9 expression was detected not only in infiltrating inflammatory cells but also in vascular and tubular structures. Measurement of pretransplant serum CXCL9 levels might represent the tracking of a clinically useful parameter to identify subjects at high risk of AR and graft failure. These findings might be used for the individualization of immunosuppressive therapies.

Hydrolysis of coagulation factors by circulating IgG is associated with a reduced risk for chronic allograft nephropathy in renal transplanted patients

Chronic allograft nephropathy (CAN), a major cause of late allograft failure, is characterized by a progressive decline in graft function correlated with tissue destruction. Uncontrolled activation of the coagulation cascade by the stressed endothelium of the graft is thought to play an important role in the pathophysiology of CAN. In this study, we demonstrate that circulating IgG from renal-transplanted patients are endowed with hydrolytic properties toward coagulation factors VIII and IX, but fail to hydrolyze factor VII and prothrombin. The hydrolytic activity of IgG was reliably quantified by the measure of the hydrolysis of a fluorescent synthetic substrate for serine proteases: proline-phenylalanine-arginine-methylcoumarinamide (PFR-MCA). A retrospective case-control study indicated that an elevated hydrolysis rate of PFR-MCA by circulating IgG correlated with the absence of CAN lesions on protocol graft biopsy performed 2 years posttransplantation. We propose that circulating hydrolytic IgG may counterbalance the procoagulation state conferred by the activated endothelium by disrupting the amplification loop of thrombin generation which is dependent on factors VIII and IX. Interestingly, low rates of PFR-MCA hydrolysis, measured 3 mo posttransplantation, were predictive of CAN at 2 years down the lane. These data suggest that PFR-MCA hydrolysis may be used as a prognosis marker for CAN in renal-transplanted patients.

Predictors of renal function improvement following tacrolimus conversion in cyclosporine-treated kidney transplant recipients

The objective of this study was to evaluate the relationship between variability of cyclosporine (CsA) absorption and tacrolimus (TAC) conversion seeking factors that predict improvement in allograft function after TAC conversion. We performed a retrospective study of 44 adult kidney transplant recipients undergoing conversion from CsA to TAC-based immunosuppression. Before TAC conversion, patients had complete, consecutive, 6 monthly C2 levels and a follow-up duration beyond 6 months after TAC conversion. The patients were divided into 2 groups: one (n=23) with low variability of CsA absorption and one (n=21) with high variability of CsA absorption. At TAC conversion, the estimated glomerular filtration rate (eGFR) was similar in both patient groups. Six months after TAC conversion, eGFR improved in both groups. Stepwise regression analysis revealed the DeltaSCr6 (change in serum creatinine level at 6 months) to be independently associated with the preconversion serum creatinine (SCr; P<.0001) and the percent coefficient of variation (%CV) of SCr (P=.0034). DeltaSCr6 was inversely associated with posttransplantation years (P=.0033), and 6-month TAC blood levels (P=.0053). The DeltaSCr6 was not associated with variability of oral CsA absorption. The cutoff value of baseline SCr at TAC conversion differentiated an increase in or reduction of SCr to be about 1.0 mg/dL. Our study of CsA-treated kidney transplant recipients who underwent TAC conversion showed that a preconversion SCr>1.0 mg/dL, a high variability of SCr, and early TAC conversion predicted greater short-term benefit on graft function.

To Biopsy or Not to Biopsy? Should We Screen the Histology of Stable Renal Grafts?

Chronic allograft dysfunction is currently the main cause of late allograft failure. Recent encouraging evidence suggests that it may be possible to delay the development of graft damages if adequate management is initiated early in the course of the disease. These observations have renewed interest in the performance of protocol biopsies as routine follow-up procedure for the screening of renal transplants. In the present review, we summarize the available data from the literature to determine the pros and cons of protocol renal allograft biopsies. On the basis of this evidence, we discuss the ethical concerns raised by this procedure.

Prospective randomized study of azathioprine vs cyclosporine based therapy in primary haplo-identical living-donor kidney transplantation: 20-year experience

BACKGROUND

The achievements in short-term graft survival since the introduction of cyclosporine (CsA) have not been matched by improvements in long-term graft function. Chronic allograft nephropathy (CAN) remains the second most common cause of graft attrition over time, after patient mortality. We aimed to evaluate the long-term results of azathioprine vs CsA in live-donor kidney transplantation in a prospective randomized study.

METHODS

We studied 475 renal transplant recipients who had had transplantations performed at the Urology and Nephrology Center, Mansoura University, before 1988 and who had received a primary immunosuppressive protocol consisting of either steroid and azathioprine (steroid/Aza; group 1, 300 patients) or steroid and CsA (steroid/CsA; group 2, 175 patients). Only adult primary renal transplant recipients aged between 18 and 60 years and with one haplotype HLA mismatch were included. All patients received kidneys from living-related donors, with previous donor nonspecific blood transfusions. The study was based on the long-term follow-up data of these renal transplant recipients. Comparative analyses included patient and graft survival rates, condition at last follow up, rejection (acute and chronic), and graft function (serum creatinine and creatinine clearance).

RESULTS

The overall frequency of acute rejection episodes was not significantly different between the two groups. Graft survival rates were: group 1 vs group 2, 69% vs 58% at 5 years, and 52% vs 36% at 10 years, but at 20 years, graft survival rates had declined to 26% and 24%. No significant differences were encountered between the two groups regarding post-transplant malignancies, diabetes mellitus, hepatic impairment, or serious bacterial infections.

CONCLUSIONS

From this study we can conclude that the long-term result of historical conventional therapy (steroid/Aza) without induction therapy is effective for living-donor kidney transplants. In spite of the comparable graft function for the two groups, the steroid/CsA group experienced more hypertension, as well as many adverse reactions to CsA. Nowadays, since the introduction of induction therapy and the utilization of newer maintenance immunosuppressive agents - such as mycophenolate mofetil (MMF) and rapamycin - it is possible to achieve an excellent calcineurin inhibitors (CNI)-free regimen.

Anemia After Renal Transplantation

Anemia in the setting of chronic kidney disease is a well-recognized phenomenon that is associated with decreasing renal function and deficiency of or resistance to erythropoietin. However, anemia in the post-renal transplantation setting has received comparatively less attention in the literature. In this review, we aim critically to appraise the available literature regarding posttransplantation anemia, concentrating in particular on the prevalence of posttransplantation anemia, its etiopathogenesis, potential effects on morbidity and mortality, and the rationale for intervention and treatment. Despite deficiencies in the literature, we conclude that posttransplantation anemia is a common phenomenon that can occur either early or late posttransplantation, and its causation is usually multifactorial and includes contributions notably from poor or decreasing renal function, immunosuppression, and iron deficiency. Conversely, there is a shortage of well-conducted prospective studies looking at the morbidity attributable to posttransplantation anemia and a lack of trial evidence to determine whether intervention improves patient morbidity and outcome.