Breast milk miRNAs and their potential role in the development of atopy in infants

Human breast milk is a dynamic biological fluid enriched with bioactive components, including extracellular vesicle-derived microRNAs (miRNAs), which have emerged as potential mediators of early immune programming. Growing evidence suggests that maternal atopic status can alter the breast milk miRNA profile, potentially shaping the infant's susceptibility to atopic disorders, such as atopic dermatitis, asthma, and food allergy. This review presents current research examining the link between breast milk miRNA composition and the development of atopy in infants, with a particular focus on maternal atopic status. Four studies met eligibility criteria and collectively demonstrate that maternal conditions such as asthma or atopic dermatitis are associated with distinct breast milk miRNA signatures. Certain miRNAs, e.g., miR-375-3p and miR-1290, show altered expression in the milk of atopic mothers. Elevated levels of miR-375-3p are associated with a reduced risk of infant atopic manifestations during the first year of life, including atopic dermatitis, food allergy, and wheezing. Conversely, miR-1290 is significantly upregulated in the milk of mothers with asthma and atopy during pregnancy, even after adjusting for confounders, highlighting its potential role as a biomarker of maternal allergic status. However, current findings rely primarily on statistical associations; no human study has yet demonstrated direct transfer or functional activity of milk-derived miRNAs in infants. Overall, while breast milk miRNAs represent a promising link between maternal health and infant atopy risk, conclusive evidence is lacking. Future large-scale, standardized, longitudinal studies integrating functional validation are needed to clarify mechanistic pathways and evaluate the potential of milk miRNAs as biomarkers or targets for early atopy prevention. Understanding the functional impact of breast milk miRNAs could facilitate the development of non-invasive biomarkers for predicting atopy risk, as well as early-life preventive strategies.