miRNome Characterization of Milk-Derived Extracellular Vesicles in Recombinant Somatotropin-Treated Dairy Cows

The recombinant bovine somatotropin (rbST) is a synthetic hormone developed to mimic the effects of the endogenous growth hormone, also known as bovine somatotropin (bST). Although rbST use in dairy cows is authorized in several countries, it is currently banned in Europe. Different methods for screening and confirmatory detection of rbST were developed, mainly based on LC-MS/MS and immune-enzymatic assays. However, some commercial forms of rbST have above the same amino acid sequence of bST, making it difficult to produce a reliable differentiation of recombinant from endogenous forms. Complementary strategies for indirect detection of rbST can therefore be considered as alternative biomarker-based tools. Untargeted transcriptomics was applied to characterize the microRNAs (miRNA) isolated from milk extracellular vesicles (EVs) in rbST-treated animals, aiming the identification of non-coding biomarkers related to its administration. Sequencing analysis of 63 archive samples collected during previous animal trial allowed for the identification of 35 differentially expressed (DE) miRNAs. A validation study performed by qPCR on a further 70 milk samples from a field survey confirmed the significant upregulation of bta-miR-10167-3p in milk EV from rbST-treated cows. The results obtained suggest the potential use of bta-miR-10167-3p as a non-invasive biomarker to be considered in novel screening strategies, needed to tackle rbST misuse in dairy cows.