Characteristic immune, apoptosis and inflammatory gene profiles associated with intestinal acute cellular rejection in formalin-fixed paraffin-embedded mucosal biopsies

Immune cell profiling in intestinal transplantation

Since the first published case study of human intestinal transplantation in 1967, there have been significant studies of intestinal transplant immunology in both animal models and humans. An improved understanding of the profiles of different immune cell subsets is critical for understanding their contributions to graft outcomes. While different studies have focused on the contribution of one or a few subsets to intestinal transplant, no study has integrated these data for a comprehensive overview of immune dynamics after intestinal transplant. Here, we provide a systematic review of the literature on different immune subsets and discuss their roles in intestinal transplant outcomes on multiple levels, focusing on chimerism and graft immune reconstitution, clonal alloreactivity, and cell phenotype. In Sections 1, 2 and 3, we lay out a shared framework for understanding intestinal transplant, focusing on the mechanisms of rejection or tolerance in the context of mucosal immunology and illustrate the unique role of the bidirectional graft-versus-host (GvH) and host-versus-graft (HvG) alloresponse. In Sections 4, 5 and 6, we further expand upon these concepts as we discuss the contribution of different cell subsets to intestinal transplant. An improved understanding of intestinal transplantation immunology will bring us closer to maximizing the potential of this important treatment.

Role of Interleukin 1 Receptor 2 in Kidney Disease

The interleukin 1 (IL-1) family plays a significant role in the innate immune response. IL-1 receptor 2 (IL-1R2) is the decoy receptor of IL-1. It is a negative regulator that can be subdivided into membrane-bound and soluble types. IL-1R2 plays a role in the IL-1 family mainly through the following mechanisms: formation of inactive signaling complexes upon binding to the receptor auxiliary protein and inhibition of ligand IL-1 maturation. This review covers the roles of IL-1R2 in kidney disorders. Chronic kidney disease, acute kidney injury, lupus nephritis, IgA nephropathy, renal clear cell carcinoma, rhabdoid tumor of kidney, kidney transplantation, and kidney infection were all shown to have abnormal IL-1R2 expression. IL-1R2 may be a potential marker and a promising therapeutic target for kidney disease.

Intestinal Transplant Immunology and Intestinal Graft Rejection: From Basic Mechanisms to Potential Biomarkers

Intestinal transplantation (ITx) remains a lifesaving option for patients suffering from irreversible intestinal failure and complications from total parenteral nutrition. Since its inception, it became obvious that intestinal grafts are highly immunogenic, due to their high lymphoid load, the abundance in epithelial cells and constant exposure to external antigens and microbiota. This combination of factors and several redundant effector pathways makes ITx immunobiology unique. To this complex immunologic situation, which leads to the highest rate of rejection among solid organs (>40%), there is added the lack of reliable non-invasive biomarkers, which would allow for frequent, convenient and reliable rejection surveillance. Numerous assays, of which several were previously used in inflammatory bowel disease, have been tested after ITx, but none have shown sufficient sensibility and/or specificity to be used alone for diagnosing acute rejection. Herein, we review and integrate the mechanistic aspects of graft rejection with the current knowledge of ITx immunobiology and summarize the quest for a noninvasive biomarker of rejection.

The Proteomic Signature of Intestinal Acute Rejection in the Mouse

Intestinal acute rejection (AR) lacks a reliable non-invasive biomarker and AR surveillance is conducted through frequent endoscopic biopsies. Although citrulline and calprotectin have been suggested as AR biomarkers, these have limited clinical value. Using a mouse model of intestinal transplantation (ITx), we performed a proteome-wide analysis and investigated rejection-related proteome changes that may eventually be used as biomarkers. ITx was performed in allogenic (Balb/C to C57Bl) and syngeneic (C57Bl) combinations. Graft samples were obtained three and six days after transplantation (n = 4/time point) and quantitative proteomic analysis with iTRAQ-labeling and mass spectrometry of whole tissue homogenates was performed. Histology showed moderate AR in all allografts post-transplantation at day six. Nine hundred and thirty-eight proteins with at least three unique peptides were identified in the intestinal grafts. Eighty-six proteins varying by >20% between time points and/or groups had an alteration pattern unique to the rejecting allografts: thirty-seven proteins and enzymes (including S100-A8 and IDO-1) were significantly upregulated whereas forty-nine (among other chromogranin, ornithine aminotransferase, and arginase) were downregulated. Numerous proteins showed altered expression during intestinal AR, several of which were previously identified to be involved in acute rejection, although our results also identified previously unreported proteome changes. The metabolites and downstream metabolic pathways of some of these proteins and enzymes may become potential biomarkers for intestinal AR.

Optical coherence tomography of small intestine allograft biopsies using a handheld surgical probe

SIGNIFICANCE

The current gold standard for monitoring small intestinal transplant (IT) rejection is endoscopic visual assessment and biopsy of suspicious lesions; however, these lesions are only superficially visualized by endoscopy. Invasive biopsies provide a coarse sampling of tissue health without depicting the true presence and extent of any pathology. Optical coherence tomography (OCT) presents a potential alternative approach with significant advantages over traditional white-light endoscopy.

AIM

The aim of our investigation was to evaluate OCT performance in distinguishing clinically relevant morphological features associated with IT graft failure.

APPROACH

OCT was applied to evaluate the small bowel tissues of two rhesus macaques that had undergone IT of the ileum. The traditional assessment from routine histological observation was compared with OCT captured using a handheld surgical probe during the days post-transplant and subsequently was compared with histophaology.

RESULTS

The reported OCT system was capable of identifying major biological landmarks in healthy intestinal tissue. Following IT, one nonhuman primate (NHP) model suffered a severe graft ischemia, and the second NHP graft failed due to acute cellular rejection. OCT images show visual evidence of correspondence with histological signs of IT rejection.

CONCLUSIONS

Results suggest that OCT imaging has significant potential to reveal morphological changes associated with IT rejection and to improve patient outcomes overall.

Identification of Candidate Biomarkers for Transplant Rejection from Transcriptome Data: A Systematic Review

BACKGROUND

Traditional methods for rejection control in transplanted patients are considered invasive, risky, and prone to sampling errors. Using molecular biomarkers as an alternative protocol to biopsies, for monitoring rejection may help to mitigate some of these problems, increasing the survival rates and well-being of patients. Recent advances in omics technologies provide an opportunity for screening new molecular biomarkers to identify those with clinical utility.

OBJECTIVE

This systematic literature review (SLR) aimed to summarize existing evidence derived from large-scale expression profiling regarding differentially expressed mRNA and miRNA in graft rejection, highlighting potential molecular biomarkers in transplantation.

METHODS

The study was conducted following PRISMA methodology and the BiSLR guide for performing SLR in bioinformatics. PubMed, ScienceDirect, and EMBASE were searched for publications from January 2001 to January 2018, and studies (i) aiming at the identification of transplant rejection biomarkers, (ii) including human subjects, and (iii) applying methodologies for differential expression analysis from large-scale expression profiling were considered eligible. Differential expression patterns reported for genes and miRNAs in rejection were summarized from both cross-organ and organ-specific perspectives, and pathways enrichment analysis was performed for candidate biomarkers to interrogate their functional role in transplant rejection.

RESULTS

A total of 821 references were collected, resulting in 604 studies after removal of duplicates. After application of inclusion and exclusion criteria, 33 studies were included in our analysis. Among the 1517 genes and 174 miRNAs identifed, CXCL9, CXCL10, STAT1, hsa-miR-142-3p, and hsa-miR-155 appeared to be particularly promising as biomarkers in transplantation, with an increased expression associated with transplant rejection in multiple organs. In addition, hsa-miR-28-5p was consistently decreased in samples taken from rejected organs.

CONCLUSION

Despite the need for further research to fill existing knowledge gaps, transcriptomic technologies have a relevant role in the discovery of accurate biomarkers for transplant rejection diagnostics. Studies have reported consistent evidence of differential expression associated with transplant rejection, although issues such as experimental heterogeneity hinder a more systematic characterization of observed molecular changes. Special attention has been giving to large-scale mRNA expression profiling in rejection, whereas there is still room for improvements in the characterization of miRnome in this condition.

PROSPERO REGISTRATION NUMBER

CRD42018083321.

Advances in small bowel transplantation

Small bowel transplantation is a life-saving surgery for patients with intestinal failure. The biggest problem in intestinal transplantation is graft rejection. Graft rejection is the main reason for morbidity and mortality. Rejection has a negative effect on the survival of the graft. While 50%-75% of small bowel transplantation patients experience acute rejection, chronic rejection occurs in approximately 15% of patients. Immune monitoring is crucial after small bowel transplantation. Unlike other types of transplantation, there are no non-invasive or reliable markers to predict rejection in small bowel transplantation. The diagnosis of AR is confirmed by clinical symptoms, endoscopic appearance, and pathological specimens taken by endoscopy. Thus, histopathological examinations obtained by protocol biopsies remain as the gold standard for intestinal graft monitoring; however, biopsies have some complications, especially in small grafts. In addition to the high complication rate, biopsies are non-diagnostic; thus, multiple biopsies should be performed to exclude rejection. Therefore, auxiliary assays, such as measurements of citrulline and calprotectin in the blood, cytofluorographic examination of peripheral blood immune cells, cytokine profiling, and distinct gene-set-change measurements, are increasingly being used in small bowel transplantation. Developments in the understanding of genes seem to be promising that limited gene sets, taken from blood or from intestinal biopsies, will enhance pathological diagnosis. Bone marrow mesenchymal stem cell transplantation with SBT and tissue engineering are also promising procedures.

A combined biomarker and clinical panel for chronic graft versus host disease diagnosis

Whilst many chronic graft versus host disease (cGVHD) biomarkers have been previously reported, few have been verified in an independent cGVHD cohort. We aimed to verify the diagnostic accuracy of previously reported markers of cGVHD in a multi-centre Chronic GVHD Consortium. A total of 42 RNA and 18 protein candidate biomarkers were assessed amongst 59 cGVHD cases and 33 matched non-GVHD controls. Total RNA was isolated from PBMC, and RNA markers were quantified using PCR. Serum protein markers were quantified using ELISA. A combined 3 RNA biomarker (IRS2, PLEKHF1 and IL1R2) and 2 clinical variables (recipient CMV serostatus and conditioning regimen intensity) panel accurately (AUC 0.81) segregated cGVHD cases from controls. Other studied RNA and protein markers were not confirmed as accurate cGVHD diagnostic biomarkers. The studied markers failed to segregate higher risk cGVHD (per overall NIH 0-3 score, and overlap versus classic cGVHD status). These data support the need for multiple independent verification studies for the ultimate clinical application of cGVHD diagnostic biomarkers.

Updates on acute and chronic rejection in small bowel and multivisceral allografts

PURPOSE OF REVIEW

The surgical management of short bowel syndrome now includes intestinal (ITx) and multivisceral transplantation (MVTx), which has advanced and is now a sustainable option for the treatment of intestinal failure. Improvements in immunosuppressive therapies, excellence in surgical and medical management and enhanced post-transplant monitoring have all contributed to optimizing this solid organ transplant as a means of supplanting the diseased native bowel and alimentary tract with a functional alternative.

RECENT FINDINGS

Post-transplant management is a critical and challenging phase of gastrointestinal transplantation, and the transplant pathologist is an essential member of the transplant team who identifies many of the early and late complications after ITx and MVTx. Among the most injurious and common complications of ITx and MVTx is acute rejection and, to a lesser degree, chronic rejection. Both of these broad categories of rejection are principally identified by histopathological changes in the allograft; however, biomarkers and other laboratory analytes are rapidly evolving into critical ancillary tools in identifying and further characterizing the rejection process. Thus, the transplant pathologist must also be able to utilize numerous other laboratory tests and panels of molecular biomarkers that provide supplementary information to accompany the biopsy interpretation and clinical suspicion of rejection.

SUMMARY

Using biopsies and an assortment of additional approaches, the transplant pathologist is now able to provide swift and detailed information regarding the rejection process in the gastrointestinal transplant. This enables the clinical team to properly and successfully intercede, contributing to enhanced patient and graft survival.

Plasma microRNA, a potential biomarker for acute rejection after liver transplantation

BACKGROUND

Acute rejection (AR) of an organ transplant is a life-threatening complication. Currently, there are few diagnostic biomarkers suitable for clinical application. We aim to determine the potential of plasma microRNAs as biomarkers for AR.

METHODS

Using rat orthotopic liver transplantation model and microarrays, we compared the difference in the spectrum and levels of microRNAs in both plasma and grafts between AR rats and control. AR-related plasma microRNAs were selected and validated using real-time quantification polymerase chain reaction. Plasma from AR rats with or without tacrolimus treatment was used for microRNA dynamic monitoring. To clarify the origin of AR-related plasma microRNAs, drug-induced liver damage rat model were performed and in situ hybridization was used to detect and localize the specific microRNA in allografts.

RESULTS

We found that plasma miR-122, miR-192, and miR-146a was significantly up-regulated when AR occur (fold change>2; P<0.05) and the elevation could be repressed by immunosuppression. In liver injury rat model, up-regulated plasma miR-122 (fold change=22.126; P=0.002) and miR-192 (fold change=8.833; P<0.001) rather than miR-146a (fold change=1.181; P=0.594) were observed. Further study demonstrated that miR-146a was up-regulated by sixfold in microvesicles isolated from AR plasma, whereas miR-122 and miR-192 showed no distinct change. In situ hybridization revealed that the portal areas of the AR graft were brimming with lymphocytes, which showed highly intense staining for miR-146a.

CONCLUSIONS

Our study provides the global fingerprint of plasma microRNAs in AR rats and suggests that plasma miR-122 and miR-192 reflect liver injury, whereas miR-146a may associate with cellular rejection.

Identification of gene microarray expression profiles in patients with chronic graft-versus-host disease following allogeneic hematopoietic cell transplantation

Chronic graft-versus-host disease (GVHD) results in significant morbidity and mortality, limiting the benefit of allogeneic hematopoietic cell transplantation (HCT). Peripheral blood gene expression profiling of the donor immune repertoire following HCT may provide associated genes and pathways thereby improving the pathophysiologic understanding of chronic GVHD. We profiled 70 patients and identified candidate genes that provided mechanistic insight in the biologic pathways that underlie chronic GVHD. Our data revealed that the dominant gene signature in patients with chronic GVHD represented compensatory responses that control inflammation and included the interleukin-1 decoy receptor, IL-1 receptor type II, and genes that were profibrotic and associated with the IL-4, IL-6 and IL-10 signaling pathways. In addition, we identified three genes that were important regulators of extracellular matrix. Validation of this discovery phase study will determine if the identified genes have diagnostic, prognostic or therapeutic implications.

Molecular transplantation pathology: the interface between molecules and histopathology

PURPOSE OF REVIEW

In the last decade, high-throughput molecular screening methods have revolutionized the transplantation research. This article reviews the new knowledge that has emerged from transplant patient sample-derived 'omics data by examining the interface between molecular signals and allograft pathology.

RECENT FINDINGS

State-of-the-art molecular studies have shed light on the biology of organ transplant diseases and provided several potential molecular tests with diagnostic, prognostic, and theranostic applications for the implementation of personalized medicine in transplantation. By comprehensive molecular profiling of patient samples, we have learned numerous new insights into the effector mechanisms and parenchymal response during allograft diseases. It has become evident that molecular profiles are coordinated and move in patterns similar to histopathology lesions, and therefore lack qualitative specificity. However, molecular tests can empower precision diagnosis and prognostication through their objective and quantitative manner when they are integrated in a holistic approach with histopathology and clinical factors of patients.

SUMMARY

Despite clever science and large amounts of public money invested in transplant 'omics studies, multiparametric molecular testing has not yet been translated to patient care. There are serious challenges in the implementation of transplant molecular diagnostics that have increased frustration in transplant community. We appeal for a full collaboration between pathologists and researchers to accelerate transition from research to clinical practice in transplantation.

Invariant natural killer T cells infiltrate intestinal allografts undergoing acute cellular rejection

Immunological responses in human intestinal allografts are poorly understood and accurate diagnosis of acute cellular rejection remains difficult. Here, human intestinal allografts were analyzed by multi-color quantitative fluorescent immunohistochemical morphometry in order to monitor the clinical course of rejection. Morphometry gave two-dimensional plots based on size and circularity, and identified phenotypes of individual cells infiltrating the allograft by fluorescent staining. Using this method, invariant TCRVα24(+) NKT (iNKT) cells were observed in the intestinal allograft during rejection. Because these were not identified in the normal donor intestine before surgery, this finding was considered to be a signature of acute cellular rejection of the intestinal allograft. Infiltrating iNKT cells released IL-4 and IL-5, Th2-related cytokines that antagonize the Th1 responses that induce acute cellular rejection. Histological observation suggested eosinophilic enteritis in the mucosa with elevation of IL-4 and IL-5. In conclusion, iNKT cells were recruited to the intestine; however, because higher levels of IL-4 and IL-5 may contribute to eosinophilic enteritis, timely steroid administration is recommended for allograft injury due to enteritis, as well as acute cellular rejection.

MicroRNA signature of intestinal acute cellular rejection in formalin-fixed paraffin-embedded mucosal biopsies

Despite continuous improvement of immunosuppression, small bowel transplantation (SBT) is plagued by a high incidence of acute cellular rejection (ACR) that is frequently intractable. Therefore, there is a need to uncover novel insights that will lead to strategies to achieve better control of ACR. We hypothesized that particular miRNAs provide critical regulation of the intragraft immune response. The aim of our study was to identify miRNAs involved in intestinal ACR. We examined 26 small intestinal mucosal biopsies (AR/NR group; 15/11) obtained from recipients after SBT or multivisceral transplantation. We investigated the expression of 384 mature human miRNAs and 280 mRNAs associated with immune, inflammation and apoptosis processes. We identified differentially expressed 28 miRNAs and 58 mRNAs that characterized intestinal ACR. We found a strong positive correlation between the intragraft expression levels of three miRNAs (miR-142-3p, miR-886-3p and miR-132) and 17 mRNAs including CTLA4 and GZMB. We visualized these miRNAs within cells expressing CD3 and CD14 proteins in explanted intestinal allografts with severe ACR. Our data suggested that miRNAs have a critical role in the activation of infiltrating cells during intestinal ACR. These differences in miRNA expression patterns can be used to identify novel biomarkers and therapeutic targets for immunosuppressive agents.