Analysis of intragraft MicroRNA expression in a mouse-to-rat cardiac xenotransplantation model

MicroRNAs as theranostic markers in cardiac allograft transplantation: from murine models to clinical practice

Congestive heart failure affects about 23 million people worldwide, and cardiac allograft transplantation remains one of the last options for patients with terminal refractory heart failure. Besides the infectious or oncological complications, the prognosis of patients after heart transplantation is affected by acute cellular or antibody-mediated rejection and allograft vasculopathy development. Current monitoring of both conditions requires the performance of invasive procedures (endomyocardial biopsy sampling and coronary angiography or optical coherence tomography, respectively) that are costly, time-demanding, and non-comfortable for the patient. Within this narrative review, we focus on the potential pathophysiological and clinical roles of microRNAs (miRNAs, miRs) in the field of cardiac allograft transplantation. Firstly, we provide a general introduction about the status of cardiac allograft function monitoring and the discovery of miRNAs as post-transcriptional regulators of gene expression and clinically relevant biomarkers found in the extracellular fluid. After this general introduction, information from animal and human studies are summarized to underline the importance of miRNAs both in the pathophysiology of the rejection process, the possibility of its modulation by altering miRNAs levels, and last but not least, about the use of miRNAs in the clinical practice to diagnose or predict the rejection occurrence.

MicroRNAs in solid organ and vascularized composite allotransplantation: Potential biomarkers for diagnosis and therapeutic use

Nowadays, solid organ transplantation (SOT) is an established treatment for patients with end-organ dysfunction, which dramatically improves the quality-of-life. Vascularized composite allotransplants (VCAs) including hand and face have been reported worldwide over the last 20 years. However, VCAs, differently to SOT, are life-enhancing instead of life-saving and are not routinely performed due to the risk of immune rejection and the adverse effects of immunosuppression. Over the past decade, although considerable improvements in short-term outcomes after allotransplantation have been registered, these results have not been translated into major progress in long-term allograft acceptance and patient survival. Recently active researches in the field of biomarker discovery have been conducted to develop individualized therapies for allograft recipients. MicroRNAs (miRNAs) are a small noncoding RNAs functioning as critical regulators of gene and protein expression by RNA interference. They have been connected in numerous biological processes and diseases. Due to their immunomodulatory functions, miRNAs have been amended as potential diagnostic and prognostic biomarker for the detection of rejection in allotransplantation. Due to their specific circulating expression profile, they could act as noninvasive predictive tools for rejection that may help clinicians in an early adjustment of the immunosuppression protocol during acute rejections episodes. Indeed, specific anti-sense oligonucleotides suppressing miRNAs expressed in rejection could reduce the rejection rate in allografts and decrease the use of immunosuppressants. We present a literature review of the immunomodulatory properties and characteristics of miRNAs. We will summarize the current knowledge on miRNAs as potential biomarkers for allograft rejection and possible application in allotransplantation monitoring. Finally, we will discuss the advances in preclinical miRNA-based therapies for immunosuppression.

Identification of a Diagnostic Set of Endomyocardial Biopsy microRNAs for Acute Cellular Rejection Diagnostics in Patients after Heart Transplantation Using Next-Generation Sequencing

Introduction: Acute cellular rejection (ACR) of heart allografts represents the most common reason for graft failure. Endomyocardial biopsies (EMB) are still subject to substantial interobserver variability. Novel biomarkers enabling precise ACR diagnostics may decrease interobserver variability. We aimed to identify a specific subset of microRNAs reflecting the presence of ACR. Patients and Methods: Monocentric retrospective study. A total of 38 patients with the anamnesis of ACR were identified and for each patient three consecutive samples of EMB (with, prior and after ACR) were collected. Sixteen trios were used for next-generation sequencing (exploratory cohort); the resting 22 trios were used for validation with qRT-PCR (validation cohort). Statistical analysis was performed using R software. Results: The analysis of the exploration cohort provided the total of 11 miRNAs that were altered during ACR, the three of which (miR-144, miR-589 and miR-182) were further validated in the validation cohort. Using the levels of all 11 miRNAs and principal component analysis, an ACR score was created with the specificity of 91% and sensitivity of 68% for detecting the presence of ACR in the EMB sample. Conclusion: We identified a set of microRNAs altered in endomyocardial biopsies during ACR and using their relative levels we created a diagnostic score that can be used for ACR diagnosis.

Circulating miRNA-150-5p is associated with immune-mediated early β-cell loss in a humanized mouse model

BACKGROUND

Aberrant microRNA (miRNA) expression levels are associated with various graft rejections. We used our humanized mouse model with transplanted human islets to identify miRNAs in islet grafts related to xenograft rejection and circulating miRNAs associated with xenograft rejection-mediated β-cell loss.

METHODS

Diabetic immunodeficient NOD.scid mice were transplanted with human islets and subsequently achieved stable normoglycemia. Lymphocytes from NOD mice were then adoptively transferred to the humanized mice to induce human β-cell destruction. Islet graft and plasma were collected immediately once blood glucose reached >200 mg/dL. miRNAs in the islet grafts and in the plasma with or without adoptive lymphocyte transfer (ALT) were measured using NanoString nCounter® miRNA Expression Assay and qPCR.

RESULTS

A set of immune-related miRNAs was significantly increased in human islet grafts of ALT-treated mice compared to control mice. Of these miRNAs, miR-150-5p was significantly increased in the circulation of ALT-treated mice at tissue collection and the increase was a result of immune activation rather than simply the presence of lymphocytes in circulation. Furthermore, miR-150-5p was significantly increased in human islet graft and circulation prior to the development of hyperglycemia in the ALT-treated mice.

CONCLUSIONS

Our data demonstrated that immune-related miRNAs are associated with human islet xenograft rejection in mice. miR-150-5p is increased in human islet graft and in the circulation during islet xenograft rejection and β-cell destruction prior to hyperglycemia and may be an early biomarker for islet xenograft rejection.

Plasma microRNAs Are Potential Biomarkers of Acute Rejection After Hindlimb Transplantation in Rats

BACKGROUND

The development of effective immunosuppressive regimens has resulted in many cases of successful hand transplantation. Visual skin inspection and histological evaluation are used to assess the rejection of hand transplants, but these methods are largely subjective. In this study, we aimed to determine the potential of microRNAs (miRNAs) as biomarkers for acute rejection in vascularized composite allotransplants.

METHODS

In allograft group, 7 male Brown-Norway rats (RT1n) were used as donors and 13 male Lewis rats (RT1l) were used as recipients. In control group, 8 Lewis rats were used as donors and recipients. The hindlimbs of donor rats were transplanted orthotopically to recipient rats. Skin changes were noted daily. Skin biopsies were obtained from 5 recipients and evaluated histologically. Plasma samples were obtained from the other 8 recipients before transplant and 7, 10, and 14 days posttransplant and used to measure miRNA expression.

RESULTS

Skin changes occurred at a mean of 11.0 days posttransplant. Rejection in most skin biopsies taken 7 and 10 days posttransplant was histologically classified as grade 0, whereas that in most biopsies taken 14 days posttransplant was classified as grade 3. We found that expression of miRNA-146a and miRNA-155 was significantly upregulated at 10 and 14 days posttransplant compared with that at 7 days posttransplant. In control group, there were no significant changes in plasma miRNAs expressions.

CONCLUSIONS

The upregulation of plasma miRNA-146a and miRNA-155 was detected before the histological evaluation methods could diagnose complete rejection in the rat hindlimb transplantation model. Plasma miRNA-146a and miRNA-155 may be potential biomarkers of acute rejection after vascularized composite allotransplantation.

MicroRNAs Involved in Acute Rejection and Tolerance in Murine Cardiac Allografts

OBJECTIVES

Induction of immunologic tolerance is the ultimate goal of organ transplant. To investigate the involvement of microRNA in tolerance induction after organ transplant, murine cardiac allografts were performed and the expression of microRNA in the grafts was analyzed.

MATERIALS AND METHODS

Cardiac allografts were performed using C57BL/10 (H2-Kb) to CBA/N (H2-Kk) fully mismatched combination with or without eicosapentaenoic acid for tolerance induction. Ten microRNA, mir-146a, 15b, 223, 23a, 27a, 34a, 451, 101a, 101b, 148a, discovered in hepatic grafts were examined by quantitative reverse transcription polymerase chain reaction using RNA from the cardiac allografts.

RESULTS

The administration of eicosapentaenoic acid markedly prolonged the cardiac allograft survival (median survival time > 100 days) and decreased the pathological score. Quantitative reverse transcription polymerase chain reaction revealed that mir-223 was up-regulated in accordance with pathological deterioration as compared with the expression observed in the syngeneic grafts. In contrast, the other microRNA was down-regulated. Pearson product moment correlation analysis demonstrated that the expression patterns of mir-223 and mir-146a had high or moderate positive associations between the cardiac and haptic allografts in mice.

CONCLUSIONS

The change in the microRNA expression in the allografts suggests that microRNA plays a role in the induction and/or maintenance of tolerance after allograft transplant. Our findings suggest that mir-223 may be associated with rejection while mir-146a, -15b, -23a, -27a, -34a, -451, -101a, -101b, -148a may be involved in tolerance. A superior grasp of the mechanism for rejection and tolerance observed in the murine heart allotransplant model may provide a better curative treatment strategy to mitigate allograft rejection.

Identification of microRNAs involved in acute rejection and spontaneous tolerance in murine hepatic allografts

Graft acceptance without the need for immunosuppressive drugs is the ultimate goal of transplantation therapy. In murine liver transplantation, allografts are accepted across major histocompatibility antigen complex barriers without the use of immunosuppressive drugs and constitute a suitable model for research on immunological rejection and tolerance. MicroRNA (miRNA) has been known to be involved in the immunological responses. In order to identify mRNAs in spontaneous liver allograft tolerance, miRNA expression in hepatic allografts was examined using this transplantation model. According to the graft pathological score and function, miR-146a, 15b, 223, 23a, 27a, 34a and 451 were upregulated compared with the expression observed in the syngeneic grafts. In contrast, miR-101a, 101b and 148a were downregulated. Our results demonstrated the alteration of miRNAs in the allografts and may indicate the role of miRNAs in the induction of tolerance after transplantation. Furthermore, our data suggest that monitoring the graft expression of novel miRNAs may allow clinicians to differentiate between rejection and tolerance. A better understanding of the tolerance inducing mechanism observed in murine hepatic allografts may provide a therapeutic strategy for attenuating allograft rejection.