GSE158666
Differential expression of Triggering Receptor Expressed on Myeloid Cells (Trem)-2 in tissue eosinophils
No longer regarded as simply end-stage cytotoxic effectors, eosinophils are now recognized as complex cells with unique phenotypes that develop in response to the local microenvironment. In our previous study, we documented eosinophil infiltration in association with characteristic muscle damage in the dystrophin-deficient (mdx) mouse model of Duchenne muscular dystrophy. In this earlier study, we found that eosinophils did not promote formation of muscle lesions, as these persisted in eosinophil-deficient mdx.PHIL mice. To obtain additional insight into these findings, we performed RNA sequencing on eosinophils isolated from muscle tissue of mdx, IL5tg, and mdx.IL5tg mouse strains. We discovered profound up-regulation of classical eosinophil effector proteins (major basic protein-1, eosinophil peroxidase, and eosinophil-associated ribonucleases, or RNases) in eosinophils isolated from lesion-free muscle from IL5tg mice. By contrast, we observed significant upregulation of tissue remodeling genes, including proteases, extracellular matrix components, collagen, and skeletal muscle precursors, as well as the immunomodulatory receptor, TREM2, in eosinophils isolated from skeletal muscle tissue from the dystrophin-deficient mdx mouse strain. The anti-inflammatory properties of TREM2 have been described in the monocyte/macrophage lineage; however, there are no previous studies documenting TREM2 expression in eosinophils. Here we show that TREM2 is critical for full growth and differentiation of bone marrow-derived eosinophil cultures and for full expression of toll-like receptor 4. Immunoreactive TREM2 was also detected on human eosinophils at levels that correlated with donor body mass index. Taken together, our findings provide important insight into the immunomodulatory and remodeling capacity of mouse eosinophils and the flexibility of their gene expression profiles in vivo. Overall design: 3 conditions (mdx, mdx+IL5, IL5), 3 biological replicates per condition