Assessment of chronic allograft injury in renal transplantation using diffusional kurtosis imaging.

BACKGROUND: Chronic allograft injury (CAI) is a significant reason for which many grafts were lost. The study was conducted to assess the usefulness of diffusional kurtosis imaging (DKI) technology in the non-invasive assessment of CAI. METHODS: Between February 2019 and October 2019, 110 renal allograft recipients were included to analyze relevant DKI parameters. According to estimated glomerular filtration rate (eGFR) (mL/min/ 1.73 m2) level, they were divided to 3 groups: group 1, eGFR ≥ 60 (n = 10); group 2, eGFR 30-60 (n = 69); group 3, eGFR < 30 (n = 31). We performed DKI on a clinical 3T magnetic resonance imaging system. We measured the area of interest to determine the mean kurtosis (MK), mean diffusivity (MD), and apparent diffusion coefficient (ADC) of the renal cortex and medulla. We performed a Pearson correlation analysis to determine the relationship between eGFR and the DKI parameters. We used the receiver operating characteristic curve to estimate the predicted values of DKI parameters in the CAI evaluation. We randomly selected five patients from group 2 for biopsy to confirm CAI. RESULTS: With the increase of creatinine, ADC, and MD of the cortex and medulla decrease, MK of the cortex and medulla gradually increase. Among the three different eGFR groups, significant differences were found in cortical and medullary MK (P = 0.039, P < 0.001, P < 0.001, respectively). Cortical and medullary ADC and MD are negatively correlated with eGFR (r = - 0.49, - 0.44, - 0.57, - 0.57, respectively; P < 0.001), while cortical and medullary MK are positively correlated with eGFR (r = 0.42, 0.38; P < 0.001). When 0.491 was set as the cutoff value, MK's CAI assessment showed 87% sensitivity and 100% specificity. All five patients randomly selected for biopsy from the second group confirmed glomerulosclerosis and tubular atrophy/interstitial fibrosis. CONCLUSION: The DKI technique is related to eGFR as allograft injury progresses and is expected to become a potential non-invasive method for evaluating CAI.

The role of toll-like receptors in multifactorial mechanisms of early and late renal allotransplant injury, with a focus on the TLR4 receptor and mononuclear cells.

The innate immune system is activated before an adaptive immune response. An expression of a particular toll-like receptor (TLR) in a transplanted kidney depends on the localization of specific cells (e.g., endothelium, elements of the nephron structure), recent pathology and the time passed since transplantation. The TLR4 receptor is expressed on renal tubular epithelial (RTE) and endothelial cells, podocytes, blood and interstitial monocytes/macrophages, and dendritic cells. While circulating in blood, some monocytes are attracted and penetrate the transplanted organ, where they supplement the donor's resident macrophages. The intensity of migration depends on the local activation of inflammation in the graft and on the expression of specific receptors on kidney endothelial cells and monocytes/macrophages. The percentage of cells with shifted TLR4 expression usually increases in circulating monocytes. The TLR4 and the biochemical stimulation cascade derived from it in any type of cell, including monocytes, undergo multi-level regulation with feedback loops with other components of the primary system, and are also dependent on the action of immunosuppression. Toll-like receptor 4 senses stimuli that make monocytes contribute differently both to acute/chronic kidney injuries and to the development of tolerance. After kidney transplantation, TLR4 expression and related cytokine production capacity may vary depending on past diseases and oncoming problems. Since conventional immunosuppression does not prevent chronic allograft injury (CAI), peripheral blood monocytes and TLR4 constitute candidates for diagnostic and therapeutic targets. Considering the mutual communication among various elements of the primary immune system, future therapeutic intervention should be directed toward factors directly or indirectly regulating the expression or post-receptor signaling of the TLR4 receptor.

Evidence of Chronic Allograft Injury in Liver Biopsies From Long-term Pediatric Recipients of Liver Transplants.

BACKGROUND & AIMS: A substantial proportion of pediatric liver transplant recipients develop subclinical chronic allograft injury. We studied whether there are distinct patterns of injury based on histopathologic features and identified associated immunologic profiles. METHODS: We conducted a cross-sectional study of 157 stable, long-term pediatric recipients of transplanted livers (70 boys; > 6 years old at time of transplantation; mean, 8.9 ± 3.46 years after liver transplantation) who underwent liver biopsy analysis from August 13, 2012, through May 1, 2014. Participants had received livers from a living or deceased donor and had consistently normal results from liver tests. Liver biopsy specimens were scored by a central pathologist; an unsupervised hierarchical cluster analysis of histologic features was used to sort biopsy samples into 3 clusters. We conducted transcriptional and cytometric analyses of liver tissue samples and performed a systems biology analysis that incorporated clinical, serologic, histologic, and transcriptional data. RESULTS: The mean level of alanine aminotransferase in participants was 27.6 ± 14.57 U/L, and the mean level of γ-glutamyl transferase was 17.4 ± 7.93 U/L. Cluster 1 was characterized by interface activity (n = 34), cluster 2 was characterized by periportal or perivenular fibrosis without interface activity (n = 45), and cluster 3 had neither feature (n = 78). We identified a module of genes whose expression correlated with levels of alanine aminotransferase, class II donor-specific antibody, portal inflammation, interface activity, perivenular inflammation, portal and perivenular fibrosis, and cluster assignment. The module was enriched in genes that regulate T-cell-mediated rejection (TCMR) of liver and other transplanted organs. Functional pathway analysis showed overrepresentation of TCMR gene sets for cluster 1 but not clusters 2 or 3. CONCLUSION: In an analysis of biopsies from an apparently homogeneous group of stable, long-term pediatric liver transplant recipients with consistently normal liver test results, we found evidence of chronic graft injury (inflammation and/or fibrosis). Biopsy samples with interface activity had a gene expression pattern associated with TCMR.

Long-term Graft Survival After Kidney Allograft Torsion: Rapid Diagnosis and Surgical Management Key to Reversibility of Injury.

INTRODUCTION: Kidney allograft torsion (KAT) is a rare complication of kidney transplantation (KT) that occurs when the transplanted kidney rotates around its vascular pedicle, which may result in a catastrophic compromise of the graft's blood supply, deterioration of kidney function, and eventually premature graft death. CASE REPORT: We report the case of a patient who had an acute kidney injury (AKI) episode from KAT. Her diagnosis was ascertained expeditiously and she had prompt surgical management. Five years after the KAT event, her baseline creatinine (Cr) stabilized around 1.6 mg/dL and she has achieved >8-year graft survival. DISCUSSION: This case illustrates the reversibility of injury that can occur after a KAT event with a commensurate return to baseline kidney function when KAT is promptly diagnosed and treated. A high index of suspicion of this uncommon but catastrophic complication of KT must be maintained to achieve desirable long-term outcomes. A diagnosis of KAT must be considered when routine etiologies of an acute deterioration of kidney allograft function have been excluded. Finally, prophylactic nephropexy must be strongly considered with intraperitoneal placement of a kidney allograft to avoid KAT.

Chronic Allograft Injury: An Overview of Pathogenesis and Treatment Strategies.

Chronic allograft injury (CAI) remains one of the biggest challenges in transplantation as it directly affects the long-term allograft survival, an area in which the scientific and transplantation communities have struggled to improve outcomes. Therefore, understanding the mechanisms of CAI is paramount to implement preventive measures and novel therapeutic options. In this review, we will address the latest evidence on CAI, potential etiologies and risk factors including non-adherence, antibody-mediated rejection, recurrence of glomerular disease, BK nephropathy, and calcineurin nephrotoxicity.

Evolution of the Concept and Pathogenesis of Chronic Renal Allograft Injury: An Updated Review.

The advantages conferred by renal transplant, such as the improved quality of life and survival, are compromised by the reduced half-life of the transplanted kidney to a decade because of chronic allograft injury, which is the leading cause of transplant loss. There has been a significant evolution in the concept of the nomenclature, grading of histologic changes, diagnostic markers, and the theories of the pathogenesis of chronic allograft injury in the past decade. This review sought to consolidate the published literature that contributes toward understanding the changing concepts and pathogenesis of the chronic allograft injury, which has implications to managing and preventing chronic allograft injury in experimental and clinical settings.

Donor-specific antibodies in allograft recipients: etiology, impact and therapeutic approaches.

PURPOSE OF REVIEW: Kidney transplantation remains the treatment of choice for patients with end-stage renal failure. However, despite significant advancements in detection of donor-specific human leukocyte antigen antibodies, improved immunosuppression and patient management, the durability of this life-saving therapy has not improved. This results in increased morbidity and mortality as well as increased cost to the healthcare system. RECENT FINDINGS: The identification of immune-pathogenic pathways responsible for allograft failure coupled with targeted interventions will represent one of the most important future objectives of transplant immunologist and physicians. The development of sensitive donor-specific antibody (DSA) detection techniques and advancements in renal allograft pathology assessments have revealed the importance of humoral immunity in mediating allograft failure. This is especially true for complement activating DSAs (C1q+). SUMMARY: Our current understanding suggests that reduction of immunosuppressive medications or medication nonadherence is now the major causes of DSA development and attendant pathology. Other important factors in initiation of de-novo DSA production include viral infections, human leukocyte antigen-DR/DQ mismatches and autoimmune diseases. Therapies aimed at antibody reduction, B-cell depletion and modification of the complement system will likely usher in new therapeutic approaches for prevention and treatment of DSA-mediated allograft dysfunction.

Histopathology and biomarkers in prediction of renal function in children after kidney transplantation.

BACKGROUND: Early detection of chronic allograft injury is a major challenge after kidney transplantation (RTx) in adults and children. We correlated the expression of four immunohistochemical biomarkers, P-selectin glycoprotein ligand-1 (PSGL-1), vimentin, α-smooth muscle actin (α-SMA) and collagen IV, to the kidney graft histology and function in pediatric RTx patients. METHODS: We analyzed the histopathology and immunohistochemical stainings of 165 biopsies from 56 patients. Histopathology was scored according to Banff '05 classification and biomarker expression semiquantitatively. Glomerular filtration rate (GFR) was measured annually by (51)Cr-EDTA clearance. RESULTS: In protocol biopsies, the expression of all four biomarkers correlated with the interstitial fibrosis and tubular atrophy (IF/TA) changes, which increased during the first 36months after RTx. At the time of 18month biopsy, we observed the deterioration of GFR in patients with high (≥2) IF/TA score (50 vs. 68ml/min/1.73m(2), p=0.004) or collagen IV expression (45 vs. 65ml/min/1.73m(2), p=0.016). Intense stainings of IF/TA, collagen IV and vimentin are also associated with poor GFR at 36 and 48months, however, the biomarker scores revealed no additional predictive value for concomitant or late GFR compared to IF/TA score. Patients with high and low biomarker expressions showed no significant differences in annual deterioration of GFR, which declined on average 2.2ml/min/1.73m(2)/year over the 7years follow-up. CONCLUSIONS: Overall, the results suggest that traditional histopathology is a sufficient predictor for graft function, and the routine use of these histochemical markers as surrogates for graft function deterioration is questioned.

Active haemorrhage of a renal allograft detected on portable ultrasound.

Function of a renal allograft relies on the integrity of its vascular anatomy. Renal biochemistry, ultrasound and percutaneous biopsy are used in combination to determine allograft function. Biopsy is not without risk, and in this case study we demonstrate a rare but a potentially life-threatening complication of renal allograft biopsy.