Background: MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate the posttranscriptional expression of target genes and are important regulators in immune responses. Previous studies demonstrated that the miRNA, miR-182 was significantly increased during allograft rejection. Further, the transcription factor Forkhead box (FOX) protein 1, (FOXO1) was shown to be a target of miR-182. The aim of this study is to further examine the role of miR-182 in alloimmune responses.
Methods: Transplantation of BALB/c cardiac allografts was performed in C57BL/6, miR-182−/−, B6.129S-H2dlAb1-Ea (MHC II− and CD4+ T cell-deficient) and B6.129S2-Tap1tm1Arp (MHC I− and CD8+ T cell-deficient) mice, with or without CTLA-4Ig administration. T cell phenotype, FOXO1 protein levels and graft infiltrating lymphocytes were determined in C57BL/6 or miR-182−/− mice by flow cytometric analysis, Western blot, and immunohistochemistry, respectively.
Results: We now show that T cells, mainly CD4+ are the main cellular source of miR-182 during allograft rejection. In the absence of miR-182, CTLA-4Ig treatment significantly increased allograft survival (31.5 days C57BL/6 vs 60 days miR-182−/−; P < 0.01). Further, CTLA4-Ig treatment inhibits miR-182 expression, increases FOXO1 levels, and reduces the percentage of CD4+CD44hi T cells after transplantation. Fewer T cells infiltrate the cardiac allografts, and memory T cells are significantly decreased in allograft recipients deficient in miR-182 with CTLA4-Ig treatment (P < 0.01).
Conclusions: Our findings suggest that miR-182 contributes to the T-cell responses to alloantigen especially under costimulation blockade. Therapeutics that target specific miRNAs may prove beneficial in transplantation.
miR-182 controls the transcription factor FOXO1. miR-182-deficient mice show reduced IFN-y production. CD4+ cells are the main source of miR-182 during allograft rejection. In the absence of miR-182, CTLA-4Ig treatment significantly increases allograft survival, inhibits miR-182 expression, increases FOXO1 levels and reduces T cells infiltrating the cardiac allografts.
1 Division of Abdominal Transplantation, Department of Surgery, Stanford University School of Medicine, Stanford, CA.
2 Department of Anesthesia, Stanford University School of Medicine, Stanford, CA.
3 Division of Pediatric Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA.
4 Department of Genomic Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan.
5 Program in Immunology, Stanford University School of Medicine, Stanford, CA.
Received 15 December 2015. Revision received 18 April 2016.
Accepted 4 May 2016.
Current address of L.W.: School of Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.
V.K. and L.W. were supported by fellowships from the Transplant and Tissue Engineering Center of Excellence at Lucile Packard Children’s Hospital. A.L. was supported by an American Heart Association Early Career Award and a Pilot Early Career Award from the Stanford Child Health Research Institute.
Funded by an American Heart Association Grant-in-Aid to S.K.
The authors declare no conflicts of interest.
L.W. and V.K. contributed equally to the study.
L.W. and S.K. are responsible for the initial research design. L.W. and V.K. performed experiments. X.Q. performed the transplants. X.X. performed immunohistochemistry, and provided some mice. A.L. assisted with Flow Cytometry. N.I. provided miR-182−/− mice. O.M.M. provided critical review of the experimental design and manuscript. L.W. S.K. and V.K. wrote the manuscript. All authors reviewed and approved the final manuscript.
Correspondence: Sheri M. Krams, PhD, 1201 Welch Rd, MSLS P313, Stanford, CA 94305-5492. (firstname.lastname@example.org).
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