MicroRNA expression profiles of bovine milk exosomes in response to Staphylococcus aureus infection

Abstract

BackgroundMilk exosomes are a rich source of microRNAs (miRNAs) that are protected from degradation. Ingestion of milk and subsequent absorption of miRNAs into recipient cells by endocytosis may play a role in the regulation of neonatal innate and adaptive immunity. In contrast, the miRNA content of milk exosomes may also be indicative of a lactating animal’s health; whereby, the presence or absence of specific miRNAs could serve as biomarkers for early detection of bacterial infection that can lead to mastitis. In the present study, we therefore analyzed and compared miRNA expression profiles of milk exosomes from four Holstein cows obtained during mid-lactation prior to and after infection (48 h) of the mammary gland with Staphylococcus aureus.MethodsMilk exosomes, purified from control and S. aureus infected cows, were extracted for RNA. Following preparation indexed libraries from both groups the samples were subjected to next generation sequencing.ResultsNext generation sequencing of eight, unpooled small RNA libraries derived from milk exosomes produced about 60.5 million high-quality, bovine-specific sequence reads for comparison of miRNA expression between treatments. Sequence identity analysis showed the miRNAs make up about 13 % of the average RNA content of these exosomes. Although 417 known bovine miRNAs were identified, miRNAs represented the least diverse class of RNA accounting for only 1 % of all unique sequences. The 20 most prevalent unique sequences within this class accounted for about 90 % of the total miRNA-associated reads across samples. Non-annotated, unique reads provided evidence for another 303 previously unknown bovine miRNAs. Expression analyses found 14 known bovine microRNAs significantly differed in frequency between exosomes from infected and control animals.ConclusionsOur survey of miRNA expression from uninfected milk exosomes and those produced in response to infection provides new and comprehensive information supporting a role for delivery into milk of specific miRNAs involved in immune response. In particular, bta-miR-142-5p, and −223 are potential biomarkers for early detection of bacterial infection of the mammary gland. Additionally, 22 mammary-expressed genes involved in regulation of host immune processes and response to inflammation were identified as potential binding targets of the differentially expressed miRNAs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2044-9) contains supplementary material, which is available to authorized users.

Milk MicroRNAs in Health and Disease

“…The first study focusing on milk microRNAs was only reported in 2010 (Hata et al., ; Kosaka et al., ) and opened a very new field of research focused on milk microRNAs. From then on, a number of studies have focused on investigating milk microRNAs profiles in various conditions including mammary gland infections (Sun et al., ), breast cancer (Do Canto et al., ; Gu et al., ; Pigati et al., ), lactation periods (Hou et al., ; Na et al., ; Xi et al., ), milk processing (Howard et al., ; Oh et al., ), and digestion (Benmoussa et al., ; Kahn et al., ; Liao, Du, Li, & Lonnerdal, ).…”

Sexual Dimorphism of miRNAs Secreted by Bovine In vitro-produced Embryos

“…miRNAs can be secreted out of a cell through extracellular vesicles, via apoptotic bodies, or by being bound to AGO proteins (Turchinovich et al, 2013). In cattle, the presence of circulating miRNAs has been reported in bodily fluids such as milk (Sun et al, 2015), blood, and follicular fluid (Noferesti et al, 2015) and in the in vitro culture media of blastocysts (Kropp et al, 2014; Kropp and Khatib, 2015). miRNAs have shown involvement in a variety of biological processes including organismal development, cell proliferation, cell death, hematopoiesis, and immunity (Wahid et al, 2010).…”

Upregulated effects of miR-7 in methicillin-resistant Staphylococcus aureus

“…Recent findings suggested that there were new miRNAs in gram-positive Staphylococcus aureus . Of these, partly located in pathogenicity islands of Staphylococcus aureus genome or only existing in pathogenicity bacteria, indicated that miRNAs probably participated in regulating the expression of pathogenic bacteria toxicity (12). RNAIII of Staphylococcus aureus (a type of miRNA) was verified as a toxicity-associated gene, participating the regulation of Staphylococcus aureus pathogenicity (13).…”