Human Breast Milk microRNAs, Potential Players in the Regulation of Nervous System

Abstract

Human milk is the biological fluid with the highest exosome amount and is rich in microRNAs (miRNAs). These are key regulators of gene expression networks in both normal physiologic and disease contexts, miRNAs can influence many biological processes and have also shown promise as biomarkers for disease. One of the key aspects in the regeneration of the nervous system is that there are practically no molecules that can be used as potential drugs. In the first weeks of lactation, we know that human breast milk must contain the mechanisms to transmit molecular and biological information for brain development. For this reason, our objective is to identify new modulators of the nervous system that can be used to investigate neurodevelopmental functions based on miRNAs. To do this, we collected human breast milk samples according to the time of delivery and milk states: mature milk and colostrum at term; moderate and very preterm mature milk and colostrum; and late preterm mature milk. We extracted exosomes and miRNAs and realized the miRNA functional assays and target prediction. Our results demonstrate that miRNAs are abundant in human milk and likely play significant roles in neurodevelopment and normal function. We found 132 different miRNAs were identified across all samples. Sixty-nine miRNAs had significant differential expression after paired group comparison. These miRNAs are implicated in gene regulation of dopaminergic/glutamatergic synapses and neurotransmitter secretion and are related to the biological process that regulates neuron projection morphogenesis and synaptic vesicle transport. We observed differences according to the delivery time and with less clarity according to the milk type. Our data demonstrate that miRNAs are abundant in human milk and likely play significant roles in neurodevelopment and normal function.

Proteomic analysis of exosomes derived from human mature milk and colostrum of mothers with term, late preterm, or very preterm delivery

“…A recent study by our group in similar samples has identified 132 different miRNAs involved in the genetic regulation of dopaminergic/glutamatergic synapses and neurotransmitter secretion and related to the biological process that regulates neuronal projection morphogenesis and synaptic vesicle transport. 35 In this study, we analysed the proteins from exosomes obtained from different groups of breast milks.…”

“…Exosome extraction was done using an EX04 Exo-spinTM midi column (Cell Guidance Systems LTD, UK), optimized by our laboratory for human BM. 35 First, 1 mL of each milk sample was centrifuged at 16 000 × g for 30 min at 4 °C in order to remove cells and cellular debris. The entire supernatant including the layer of milk fat was transferred to a new 2 mL centrifuge and Exo-spinTM Buffer was added in a 1/1 ratio.…”

Recent insights into breast milk microRNA: their role as functional regulators

“…Bioinformatics analysis also offered indirect support for the functional hypothesis. For example, upregulated miRNAs in moderate/very preterm compared to term mature milk tended to be enriched in the neuro-related GO pathways ( 53 ). This result may indicate that BM miRNAs play a crucial role in infants' neurodevelopment ( 54 ).…”

Potential Epigenetic Effects of Human Milk on Infants’ Neurodevelopment

“…The neuroprotective effects of these miRNAs are exerted by promoting neurogenesis, neurite remodeling and survival, and neuroplasticity [ 59 ]. Especially regarding neuroplasticity, many miRNAs are involved in synaptic plasticity [ 60 ], whereas several human milk exosomal miRNAs are implicated in the gene regulation of brain synapses and in synaptic vesicle trafficking [ 61 ]. It is worth mentioning that almost half of miRNAs with possible effects on synaptic development in mammals were found to be present in the top 288 miRNAs identified in human milk exosomes [ 62 ].…”

“…Studies in animals also provided evidence that the exosomal content of human preterm breast milk has the potential to enable tissue healing in preterms with intestinal inflammation and protect against necrotizing enterocolitis [ 66 ]. Recent evidence has also shown significant differences between preterm and term human breast milk exosomes in several miRNAs associated with brain development and neurodevelopment including miR-3196, miR-1249-3p, miR-7847-3p, miR-1908-3p and miR-23b-3p, among others [ 61 ]. Further research in this area is needed.…”