Irisin directly stimulates osteoclastogenesis and bone resorption in vitro and in vivo: RNAseq dataset

Irisin, a skeletal-muscle secreted myokine, facilitates muscle-bone crosstalk and skeletal remodeling in part by its action on osteoblasts and osteocytes. In this study, we investigated whether irisin directly regulates osteoclasts. In vitro, irisin (2–10 ng/mL) increased osteoclast differentiation in C57BL/6J mouse bone marrow progenitors; however, this increase was blocked by a neutralizing antibody to integrin αVβ5. Irisin also increased bone resorption on several substrates in situ. RNAseq revealed differential gene expression induced by irisin including upregulation of markers for osteoclast differentiation and resorption, as well as osteoblast-stimulating ‘clastokines’. Forced expression of the irisin precursor Fndc5 in transgenic C57BL/6J mice resulted in lower bone mass at three ages and greater in vitro osteoclastogenesis from Fndc5-transgenic bone marrow progenitors. This study demonstrates that irisin acts directly on osteoclast progenitors to increase differentiation and promote bone resorption, supporting the tenet that irisin not only stimulates bone remodeling but may also be an important counter-regulatory hormone.
Methods
Total RNA was isolated with Trizol reagent and RNeasy mini kit from primary bone marrow progenitors induced to osteoclast differentiation with RANKL and MCSF, cultured with or without 10 ng/mL irisin for 7days. mRNA enrichment from 100 ng of total purified RNA and Illumina sequencing libraries preparation was performed using Kapa stranded mRNA Hyper Prep (Roche Sequencing Solutions, Pleasanton, CA, USA). Gene libraries were multiplexed in an equimolar pool and were sequenced on an Illumina NextSeq 500 with single-end 75 bp reads. Raw reads were aligned to the UCSC mm10 reference genome using a STAR aligner (version STAR_2.4.2a), and raw gene counts were quantified using the quantMode GeneCounts flag. Differential expression testing was performed using Limma and DESeq2. RNAseq analysis was performed using the VIPER snakemake pipeline. See linked manuscript for full details.