Proteomic analysis of urinary extracellular vesicles of kidney transplant recipients with BKV viruria and viremia: A pilot study

Future of non-invasive graft evaluation: A systematic review of proteomics in kidney transplantation

BACKGROUND

Despite the developments in the field of kidney transplantation, the already existing diagnostic techniques for patient monitoring are considered insufficient. Protein biomarkers that can be derived from modern approaches of proteomic analysis of liquid biopsies (serum, urine) represent a promising innovation in the monitoring of kidney transplant recipients.

AIM

To investigate the diagnostic utility of protein biomarkers derived from proteomics approaches in renal allograft assessment.

METHODS

A systematic review was conducted in accordance with PRISMA guidelines, based on research results from the PubMed and Scopus databases. The primary focus was on evaluating the role of biomarkers in the non-invasive diagnosis of transplant-related complications. Eligibility criteria included protein biomarkers and urine and blood samples, while exclusion criteria were language other than English and the use of low resolution and sensitivity methods. The selected research articles, were categorized based on the biological sample, condition and methodology and the significantly and reproducibly differentiated proteins were manually selected and extracted. Functional and network analysis of the selected proteins was performed.

RESULTS

In 17 included studies, 58 proteins were studied, with the cytokine CXCL10 being the most investigated. Biological pathways related to immune response and fibrosis have shown to be enriched. Applications of biomarkers for the assessment of renal damage as well as the prediction of short-term and long-term function of the graft were reported. Overall, all studies have shown satisfactory diagnostic accuracy of proteins alone or in combination with conventional methods, as far as renal graft assessment is concerned.

CONCLUSION

Our review suggests that protein biomarkers, evaluated in specific biological fluids, can make a significant contribution to the timely, valid and non-invasive assessment of kidney graft.

Exploring urinary extracellular vesicles for organ transplant monitoring: A comprehensive study for detection of allograft dysfunction using immune-specific markers

BACKGROUND

Allograft dysfunction (AGD) is a common complication following solid organ transplantation (SOT). This study leverages the potential of urinary extracellular vesicles (UEVs) for the non-invasive detection of AGD.

AIM

We aimed to assess the diagnostic value of T-cell and B-cell markers characteristic of T-cell-mediated and antibody-mediated rejection in UEV-mRNA using renal transplantation as a model.

MATERIALS AND METHODS

UEVs were isolated from 123 participants, spanning healthy controls, functional transplant recipients, and biopsy-proven AGD patients. T-cell and B-cell marker mRNA expressions were evaluated using RT-qPCR.

RESULTS

We observed significant differences in marker expression between healthy controls and AGD patients. ROC analysis revealed an AUC of 0.80 for T-cell markers, 0.98 for B-cell markers, and 0.94 for combined markers. T-cell markers achieved 81.3 % sensitivity, 80 % specificity, and 80.4 % efficiency. A triad of T-cell markers (PRF1, OX40, and CD3e) increased sensitivity to 87.5 % and efficiency to 82.1 %. B-cell markers (CD20, CXCL3, CD46, and CF3) delivered 100 % sensitivity and 97.5 % specificity. The combined gene signature of T-cell and B-cell markers offered 93.8 % sensitivity and 95 % specificity.

CONCLUSION

Our findings underscore the diagnostic potential of UEV-derived mRNA markers for T-cells and B-cells in AGD, suggesting a promising non-invasive strategy for monitoring graft health.

Risk factors for BK virus infection in DCD donor kidney transplant recipients

Background

BK virus infection after kidney transplantation can negatively impact the prognosis of patients. However, current risk factor analyses primarily focus on BK virus nephropathy, while BK viruria and BK viruria progressing to BK viremia receive less attention. This study aims to analyze the risk factors associated with BK viruria and BK viruria progressing to BK viremia in recipients of donation after cardiac death (DCD), with the goal of facilitating early intervention.

Methods

Donor characteristics and clinical data of recipients before and after transplantation were evaluated, and logistic univariate and multivariate analyses were performed to determine the risk factors associated with BK viruria and the progression of BK viruria to BK viremia. Additionally, machine learning techniques were employed to identify the top five features associated with BK viruria evolving into BK viremia.

Results

During a median follow-up time of 1,072 days (range 739-1,418), 69 transplant recipients (15.6% incidence rate) developed BK viruria after transplantation, with 49.3% of cases occurring within 6 months post-transplantation. Moreover, 19 patients progressed to BK viremia. Donor age [OR: 1.022 (1.000, 1.045), p = 0.047] and donor procalcitonin (PCT) levels [0.5-10 ng/ml; OR: 0.482 (0.280, 0.828), p = 0.008] were identified as independent risk factors for BK viruria. High BK viruria [OR: 11.641 (1.745, 77.678), p = 0.011], recipient age [OR: 1.106 (1.017, 1.202), p = 0.018], and immunoinduction regimen [ATG; OR: 0.063 (0.006, 0.683), p = 0.023] were independent risk factors for BK viruria progressing to BK viremia. Machine learning analysis confirmed the importance of high BK viruria, recipient age, and immunoinduction regimen (ATG) in predicting the progression of BK viruria to BK viremia.

Conclusion

The development and progression of BK virus in DCD kidney transplant recipients is influenced by multiple factors. Early intervention and treatment could potentially extend the lifespan of the transplanted organ.

Biomarker-Development Proteomics in Kidney Transplantation: An Updated Review

Kidney transplantation (KT) is the optimal therapeutic strategy for patients with end-stage renal disease. The key to post-transplantation management is careful surveillance of allograft function. Kidney injury may occur from several different causes that require different patient management approaches. However, routine clinical monitoring has several limitations and detects alterations only at a later stage of graft damage. Accurate new noninvasive biomarker molecules are clearly needed for continuous monitoring after KT in the hope that early diagnosis of allograft dysfunction will lead to an improvement in the clinical outcome. The advent of “omics sciences”, and in particular of proteomic technologies, has revolutionized medical research. Proteomic technologies allow us to achieve the identification, quantification, and functional characterization of proteins/peptides in biological samples such as urine or blood through supervised or targeted analysis. Many studies have investigated proteomic techniques as potential molecular markers discriminating among or predicting allograft outcomes. Proteomic studies in KT have explored the whole transplant process: donor, organ procurement, preservation, and posttransplant surgery. The current article reviews the most recent findings on proteomic studies in the setting of renal transplantation in order to better understand the effective potential of this new diagnostic approach.

Urinary Extracellular Vesicles in Chronic Kidney Disease: From Bench to Bedside?

Extracellular vesicles are a diverse group of particles that include exosomes, microvesicles, and apoptotic bodies and are defined by size, composition, site of origin, and density. They incorporate various bioactive molecules from their cell of origin during formation, such as soluble proteins, membrane receptors, nucleic acids (mRNAs and miRNAs), and lipids, which can then be transferred to target cells. Extracellular vesicles/exosomes have been extensively studied as a critical factor in pathophysiological processes of human diseases. Urinary extracellular vesicles could be a promising liquid biopsy for determining the pattern and/or severity of kidney histologic injury. The signature of urinary extracellular vesicles may pave the way for noninvasive methods to supplement existing testing methods for diagnosing kidney diseases. We discuss the potential role of urinary extracellular vesicles in various chronic kidney diseases in this review, highlighting open questions and discussing the potential for future research.