Tissue-Specific Expression Patterns of MicroRNA during Acute Graft-versus-Host Disease in the Rat.

Dasaradha Jalapothu,Marit Inngjerdingen,Ralf Dressel,Anne M Dickinson,Pranali Shah,Rachel E Crossland,Margherita Boieri,Isha A Butt,Jean Norden

doi:10.3389/fimmu.2016.00361

Abstract

MicroRNAs (miRNA) have emerged as central regulators of diverse biological processes and contribute to driving pathology in several diseases. Acute graft-versus-host disease (aGvHD) represents a major complication after allogeneic hematopoietic stem cell transplantation, caused by alloreactive donor T cells attacking host tissues leading to inflammation and tissue destruction. Changes in miRNA expression patterns occur during aGvHD, and we hypothesized that we could identify miRNA signatures in target tissues of aGvHD that may potentially help understand the underlying molecular pathology of the disease. We utilized a rat model of aGvHD with transplantation of fully MHC-mismatched T cell depleted bone marrow, followed by infusion of donor T cells. The expression pattern of 423 rat miRNAs was investigated in skin, gut, and lung tissues and intestinal T cells with the NanoString hybridization platform, in combination with validation by quantitative PCR. MHC-matched transplanted rats were included as controls. In the skin, upregulation of miR-34b and downregulation of miR-326 was observed, while in the intestines, we detected downregulation of miR-743b and a trend toward downregulation of miR-345-5p. Thus, tissue-specific expression patterns of miRNAs were observed. Neither miR-326 nor miR-743b has previously been associated with aGvHD. Moreover, we identified upregulation of miR-146a and miR-155 in skin tissue of rats suffering from aGvHD. Analysis of intestinal T cells indicated 23 miRNAs differentially regulated between aGvHD and controls. Two of these miRNAs were differentially expressed either in skin (miR-326) or in intestinal (miR-345-5p) tissue. Comparison of intestinal and peripheral blood T cells indicated common dysregulated expression of miR-99a, miR-223, miR-326, and miR-345-5p. Analysis of predicted gene targets for these miRNAs indicated potential targeting of an inflammatory network both in skin and in the intestines that may further regulate inflammatory cytokine production. In conclusion, comprehensive miRNA profiling in rats suffering from aGvHD demonstrate tissue-specific differences in the expression patterns of miRNA that may not be detected by profiling of peripheral blood T cells alone. These tissue-specific miRNAs may contribute to distinct pathologic mechanisms and could represent potential targets for therapy.

Highlights

Allogeneic hematopoietic stem cell transplantation is a treatment option for hematological malignancies or autoimmune disorders
No symptoms of Acute graft-versus-host disease (aGvHD) developed in these animals, but using the same protocol ensured that differential expression of miRNAs would be due to aGvHD responses
MicroRNAs are considered central regulators of gene expression, and miRNA expression is tightly linked to different cellular responses and may be predictive of underlying molecular mechanisms in complex diseases such as aGvHD

Summary

Introduction

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a treatment option for hematological malignancies or autoimmune disorders. Donor T cells are activated by host APC in draining lymph nodes, enter the circulation, and extravasate into the gastrointestinal tract, skin, lung, and liver, representing major target tissues for aGvHD, where they mediate further increased inflammation and tissue damage [2]. MiRNAs only partially pair with their target mRNA, implying that a single miRNA can target several different mRNA molecules and a given mRNA can be targeted by several miRNAs [9]. This infers that miRNAs are part of a complex regulatory network, potentially involving several different miRNAs simultaneously. Particular miRNAs associated with aGvHD include miRNAs that enhance T-cell activation, such as miR-155 [4, 10], miR-142 [11], miR-29a, miR-29b, and the miR-17-92 cluster [12], and miRNAs that repress T-cell activation, such as mir-146a [13], which is upregulated in T regulatory cells (Tregs) [14]

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Conclusion