Abstract
Breast milk is the primary source of nutrition for newborns, and is rich in immunological components. MicroRNAs (miRNAs) are present in various body fluids and are selectively packaged inside the exosomes, a type of membrane vesicles, secreted by most cell types. These exosomal miRNAs could be actively delivered into recipient cells, and could regulate target gene expression and recipient cell function. Here, we analyzed the lactation-related miRNA expression profiles in porcine milk exosomes across the entire lactation period (newborn to 28 days after birth) by a deep sequencing. We found that immune-related miRNAs are present and enriched in breast milk exosomes (p<10−16, χ 2 test) and are generally resistant to relatively harsh conditions. Notably, these exosomal miRNAs are present in higher numbers in the colostrums than in mature milk. It was higher in the serum of colostrum-only fed piglets compared with the mature milk-only fed piglets. These immune-related miRNA-loaded exosomes in breast milk may be transferred into the infant body via the digestive tract. These observations are a prelude to in-depth investigations of the essential roles of breast milk in the development of the infant’s immune system.
Highlights
Breast milk is the milk produced by the mammary glands of a female mammal for the infant offspring, and contains a balance of nutrients that closely matches infant requirements for brain development, growth, and a healthy immune system, which provides a distinct advantage over formula [1,2]
Results miRNAs-loaded Exosomes are Present in Breast Milk Exosomes were isolated from porcine breast milk by ultracentrifugation and were investigated using atomic force microscope (AFM) at the nanometer-scale
This study reports the comprehensive lactation-related miRNA expression profiles of porcine breast milk exosomes, generated using a deep sequencing approach
Summary
Breast milk is the milk produced by the mammary glands of a female mammal for the infant offspring, and contains a balance of nutrients that closely matches infant requirements for brain development, growth, and a healthy immune system, which provides a distinct advantage over formula [1,2]. The initial milk (usually 0 to 3 days after birth) is often referred to as colostrum, and is higher in immunological agents and other compounds that act against viruses, bacteria, and parasites [3] This helps to protect the newborn until its own immune system can function properly [4]. Extracellular miRNAs in various body fluids (such as amniotic fluid, breast milk, blood, bronchial lavage, malignant ascites fluid, tears, saliva, and urine) have recently been shown to be associated with various pathological conditions [8] These circulating miRNAs are mainly delivered by exosomes, which are membranous vesicles (30–100 nm in diameter) of endocytic origin that are released by a variety of cell types into the extracellular space [9]. Exosomes are present in human breast milk and are packaged with abundant immune-related proteins (such as MHC class II, CD86, and the tetraspanin proteins, CD63 and CD81) [13], as well as miRNAs, have the potential to influence the immune system of the infant [10,11]
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