microRNA in Transplantation: Small in Name Only

Gene Ex Vivo Transduction Effects on Flap Survival and MicroRNAs Expression Analysis in Rat Allotransplantation Model

BACKGROUND

The lack of noninvasive biomarkers for graft rejection remains a challenge for the accurate monitoring of vascularized composite allotransplants. Viral vector-mediated gene transfer is a promising method for preventing graft rejection. In this study, we aimed to establish the expression profile of microRNAs (miRNAs) in skin flap allotransplantation, with or without gene transfer, and determine the potential role of several miRNAs as biomarkers of acute rejection and immune tolerance.

METHODS

An abdominal epigastric flap was transplanted from SD (RT1a) to Wistar rats (RT1Au). The adenoviral interleukin 10 (vIL-10) gene was transferred to the experimental group via flap pedicle injection. Postoperatively, flap appearance, hematoxylin and eosin staining, immunohistochemical staining, and miRNA expression analyses were performed.

RESULTS

The viral IL-10 gene-treated group showed improved flap survival and reduced acute rejection response compared with the control group. On postoperative day 7, IL-10 expression in the flap was identified using immunohistochemistry and real-time polymerase chain reaction. The expression of miR-191a, miR-31a, miR-16, and miR-3473 was upregulated in the skin tissue, and that of miR-484, miR-132, miR-139, miR-150, and miR-6216 was upregulated in the serum.

CONCLUSION

AV IL-10 gene transfer could be an effective immunosuppressive strategy for the prevention of skin flap allograft rejection. Additionally, some miRNAs were upregulated in the experimental group, serving as potential biomarkers of immune tolerance.

Overexpression of miR-223 Promotes Tolerogenic Properties of Dendritic Cells Involved in Heart Transplantation Tolerance by Targeting Irak1

Dendritic cells (DCs) are key mediators of transplant rejection. Numerous factors have been identified that regulate transplant immunopathology by modulating the function of DCs. Among these, microRNAs (miRNAs), small non-coding RNA molecules, have received much attention. The miRNA miR-223 is very highly expressed and tightly regulated in hematopoietic cells. It plays an important role in modulating the immune response by regulating neutrophils and macrophages, and its dysregulation contributes to multiple types of immune diseases. However, the role of miR-223 in immune rejection is unclear. Here, we observed expression of miR-223 in patients and mice who had undergone heart transplantation and found that it increased in the serum of both, and also in DCs from the spleens of recipient mice, although it was unchanged in splenic T cells. We also found that miR-223 expression decreased in lipopolysaccharide-stimulated DCs. Increasing the level of miR-223 in DCs promoted polarization of DCs toward a tolerogenic phenotype, which indicates that miR-223 can attenuate activation and maturation of DCs. MiR-223 effectively induced regulatory T cells (Tregs) by inhibiting the function of antigen-presenting DCs. In addition, we identified Irak1 as a miR-223 target gene and an essential regulator of DC maturation. In mouse allogeneic heterotopic heart transplantation models, grafts survived longer and suffered less immune cell infiltration in mice with miR-223-overexpressing immature (im)DCs. In the miR-223-overexpressing imDC recipients, T cells from spleen differentiated into Tregs, and the level of IL-10 in heart grafts was markedly higher than that in the control group. In conclusion, miR-223 regulates the function of DCs via Irak1, differentiation of T cells into Tregs, and secretion of IL-10, thereby suppressing allogeneic heart graft rejection.

Upregulation of microRNA 142-3p in the peripheral blood and urinary cells of kidney transplant recipients with post-transplant graft dysfunction

We analyzed microRNA (miR)-142-3p expression in leucocytes of the peripheral blood and urinary sediment cell samples obtained from kidney transplant recipients who developed graft dysfunction. Forty-one kidney transplant recipients with kidney graft dysfunction and 8 stable patients were included in the study. The groups were divided according to histological analysis into acute rejection group (n=23), acute tubular necrosis group (n=18) and stable patients group used as a control for gene expression (n=8). Percutaneous biopsies were performed and peripheral blood samples and urine samples were obtained. miR-142-3p was analyzed by real-time polymerase chain reaction. The group of patients with acute tubular necrosis presented significantly higher expressions in peripheral blood (P<0.05) and urine (P<0.001) compared to the stable patients group. Also, in the peripheral blood, miR-142-3p expression was significantly higher in the acute tubular necrosis group compared to the acute rejection group (P<0.05). Urine samples of the acute rejection group presented higher expression compared to the stable patients group (P<0.001) but the difference between acute tubular necrosis and acute rejection groups was not significant in the urinary analyzes (P=0.079). miR-142-3p expression has a distinct pattern of expression in the setting of post-operative acute tubular necrosis after kidney transplantation and may potentially be used as a non-invasive biomarker for renal graft dysfunction.