Equine serum miRNA in asthma

MiRNAs regulate the transcription and/or translations of genes and can be exported outside the cells. It has been suggested that miRNA may act in a hormone-like manner and therefore circulating miRNAs are promising candidates for many diseases. We aimed to identify significant differences in the expression of serum miRNA in equine model of asthma. Serum RNA derived from 35 control and 37 asthmatic horses was used for the next generation sequencing and further differential expression analysis. We then retrieved gene targets of the most significantly regulated miRNA and investigated their differential expression in peripheral blood mononuclear cells (PBMCs) derived from the same blood collection as the serum samples used. We identified significant differences in the expression of 13 miRNA, including newly identified miRNAs, in the serum of asthmatic horses. The most significant difference we noticed in the expression of miR-128 and 30 of its potential gene targets were previously reported to be differentially expressed (DEGs) in unstimulated or stimulated with antigens PBMCs. The three up-regulated DEGs in unstimulated cells (RAB20, BAZ2B, and HLX) were previously reported as associated with asthma-like conditions in humans. The miR-128 has pro-apoptotic properties and cell cycle disruptions were already reported in horse and human asthma. The upregulation of miR-128 in serum most likely does not originate from the PBMCs, but rather other tissue (e.g. lungs) or neutrophils that are elevated in horses suffering from asthma. We propose the miR-128 as a potential new biomarker for asthma in horses, however, its potential as biomarker for human asthma requires further investigation.