Protective Effects of Human Milk-Derived Exosomes on Intestinal Stem Cells Damaged by Oxidative Stress

Breastfeeding has been shown to have a protective effect on the occurrence of necrotizing enterocolitis (NEC), but the mechanism remains unclear. In the context of NEC pathogenesis, many of the protective properties of exosomes on the intestinal epithelial compartment make it an ideal therapeutic target. In the present study, our hypothesis was that intestinal stem cells (ISCs) would be protected from injury by human milk-derived exosomes (HMDEs). Human breast milk was collected, and exosomes were isolated using ExoQuick reagent. Magnetic-activated cell sorting isolation of prominin-1⁺ ISCs was performed from small intestines of neonatal rat. ISCs were treated with or without H₂O₂, and HMDEs, an equal volume of HMDE-free milk, or a control solution [phosphate-buffered solution (PBS)] was added, respectively. In the absence of HMDEs, exposure of ISCs to H₂O₂ led to decreased cell viability. However, addition of HMDEs to ISCs exposed to H₂O₂ led to significantly increased ISC viability. There was a significant upregulation of mRNA expression of Axin2, c-Myc, and Cyclin D1 genes of the Wnt/β-catenin axis in ISCs treated with HMDEs (6.99 ± 2.34, 4.21 ± 1.68, 6.17 ± 2.22, respectively, P < 0.05 for all), as compared to control. In the presence of carnosic acid (a specific Wnt/β-catenin signaling inhibitor), the cell viability was significantly decreased. Thus, HMDEs protect ISCs from oxidative stress injury in vitro, which were possibly mediated via the Wnt/β-catenin signaling pathway. Our findings indicate that oral administration of HMDEs might be a promising measure in treating NEC or in preventing the development of NEC in high-risk infants when breast milk is not available.