Key Points
mirn23a miRNAs repress inflammatory signaling in myeloid progenitors.
mirn23a−/− macrophages have enhanced M2 polarization and decreased responses to LPS.
mirn23a−/− macrophages enhance the growth of syngeneic tumors in vivo.
Abstract
Macrophages are critical for regulating inflammatory responses. Environmental signals polarize macrophages to either a proinflammatory (M1) state or an anti-inflammatory (M2) state. We observed that the microRNA (miRNA) cluster mirn23a, coding for miRs-23a, -27a, and -24-2, regulates mouse macrophage polarization. Gene expression analysis of mirn23a-deficient myeloid progenitors revealed a decrease in TLR and IFN signaling. Mirn23a−/− bone marrow–derived macrophages (BMDMs) have an attenuated response to LPS, demonstrating an anti-inflammatory phenotype in mature cells. In vitro, mirn23a−/− BMDMs have decreased M1 responses and an enhanced M2 responses. Overexpression of mirn23a has the opposite effect, enhancing M1 and inhibiting M2 gene expression. Interestingly, expression of mirn23a miRNAs goes down with inflammatory stimulation and up with anti-inflammatory stimulation, suggesting that its regulation prevents locking macrophages into polarized states. M2 polarization of tumor-associated macrophages (TAMs) correlates with poor outcome for many tumors, so to determine if there was a functional consequence of mirn23a loss modulating immune cell polarization, we assayed syngeneic tumor growth in wild-type and mirn23a−/− mice. Consistent with the increased anti-inflammatory/immunosuppressive phenotype in vitro, mirn23a−/− mice inoculated with syngeneic tumor cells had worse outcomes compared with wild-type mice. Coinjecting tumor cells with mirn23a−/− BMDMs into wild-type mice phenocopied tumor growth in mirn23a−/− mice, supporting a critical role for mirn23a miRNAs in macrophage-mediated tumor immunity. Our data demonstrate that mirn23a regulates M1/M2 polarization and suggests that manipulation of mirn23a miRNA can be used to direct macrophage polarization to drive a desired immune response.
Footnotes
This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases DK109051 (to R.D.), the Ralph W. and Grace M. Showalter Research Trust Fund (to R.D.), the Indiana Clinical and Translational Sciences Institute (to R.D.), National Cancer Institute CA204231 (to S.R.), the Walther Cancer Foundation Interdisciplinary Interface Training Program (to A.B.), and the Research Like a Champion Program, University of Notre Dame (to A.B.). This work was also supported by the Indiana University School of Medicine South Bend Imaging and Flow Cytometry Core Facility.
The sequences presented in this article have been submitted to the National Center for Biotechnology Information Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo/) under accession numbers GSE160214 and GSE159762.
The online version of this article contains supplemental material.
Abbreviations used in this article:
- ACK
- ammonium–chloride–potassium
- BMDM
- bone marrow–derived macrophage
- GSEA
- Gene Set Enrichment Analysis
- HSPC
- hematopoietic stem and progenitor cell
- iNOS
- inducible NO synthase
- IPA
- Ingenuity Pathway Analysis
- LLC
- Lewis lung carcinoma
- miRNA
- microRNA
- MSCV
- murine stem cell virus
- qPCR
- quantitative PCR
- qRT-PCR
- quantitative RT-PCR
- RNA-seq
- RNA sequencing
- TAM
- tumor-associated macrophage.
- Received October 23, 2019.
- Accepted November 17, 2020.
- Copyright © 2021 by The American Association of Immunologists, Inc.
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