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Recovery of extracellular vesicles from human breast milk is influenced by sample collection and vesicle isolation procedures.

ABSTRACT: Extracellular vesicles (EV) in breast milk carry immune relevant proteins and could play an important role in the instruction of the neonatal immune system. To further analyze these EV and to elucidate their function it is important that native populations of EV can be recovered from (stored) breast milk samples in a reproducible fashion. However, the impact of isolation and storage procedures on recovery of breast milk EV has remained underexposed. Here, we aimed to define parameters important for EV recovery from fresh and stored breast milk. To compare various protocols across different donors, breast milk was spiked with a well-defined murine EV population. We found that centrifugation of EV down into density gradients largely improved density-based separation and isolation of EV, compared to floatation up into gradients after high-force pelleting of EV. Using cryo-electron microscopy, we identified different subpopulations of human breast milk EV and a not previously described population of lipid tubules. Additionally, the impact of cold storage on breast milk EV was investigated. We determined that storing unprocessed breast milk at -80°C or 4°C caused death of cells present in breast milk, leading to contamination of the breast milk EV population with storage-induced EV. Here, an alternative method is proposed to store breast milk samples for EV analysis at later time points. The proposed adaptations to the breast milk storage and EV isolation procedures can be applied for EV-based biomarker profiling of breast milk and functional analysis of the role of breast milk EV in the development of the neonatal immune system.

SUBMITTER: Zonneveld MI

PROVIDER: S-EPMC4139932 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Recovery of extracellular vesicles from human breast milk is influenced by sample collection and vesicle isolation procedures.

Zonneveld Marijke I MI Brisson Alain R AR van Herwijnen Martijn J C MJ Tan Sisareuth S van de Lest Chris H A CH Redegeld Frank A FA Garssen Johan J Wauben Marca H M MH Nolte-'t Hoen Esther N M EN

Journal of extracellular vesicles 20140814

Extracellular vesicles (EV) in breast milk carry immune relevant proteins and could play an important role in the instruction of the neonatal immune system. To further analyze these EV and to elucidate their function it is important that native populations of EV can be recovered from (stored) breast milk samples in a reproducible fashion. However, the impact of isolation and storage procedures on recovery of breast milk EV has remained underexposed. Here, we aimed to define parameters important ...[more]

PMID: 25206958

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Project description:Background: Maternal pre-pregnancy BMI is a critical factor influencing the composition of breast milk. Breast milk has abundant extracellular vesicles (EVs) containing various biological molecules (cargo), including miRNAs. EVs are not degraded in the gastrointestinal system and circulation; thus, breast milk EVs (bEVs) interact with other organs in breastfed infants and modify the gene expression of recipient cells using miRNAs. In maternal obesity, miRNAs in bEVs are deregulated, which might be associated with adverse health outcomes in infants. In this study, we examined 798 miRNAs to determine which miRNAs are altered in the bEVs of obese mothers and their potential impact on breastfed infants. Methods: We recruited healthy nursing mothers who were either obese (BMI≥30) or lean (BMI<25) based on their pre-pregnancy BMI, and delivered a singleton baby in the prior six months. EVs were isolated from breast milk with ultracentrifugation. bEV characteristics were examined by flow cytometry and fluorescence imaging of EV markers. A total of 798 miRNAs were screened using a NanoString human miRNA panel to find deregulated miRNAs in bEVs of obese mothers compared to lean mothers. Results: We included 65 nursing mothers: 47 lean and 18 obese mothers based on pre-pregnancy BMI. After bEV isolation, we confirmed the expression of general EV markers. Out of 37 EV markers, CD326 was the most highly expressed marker in bEVs. From miRNA analysis using NanoString, we found that the most abundant miRNAs include miR-30b-5p, miR-494-3p, and let-7 families, and the list of top 10 miRNAs was not different between lean and obese mothers. Target genes of the top 10 miRNAs were associated with the EGFR, ErbB, and FoxO signaling pathway. Nineteen miRNAs were deregulated in bEVs of obese mothers (adjusted p < 0.05 cut-off), including miR-575, miR-548g-3p, miR-582-3p, and miR-652-5p. The target genes of these miRNAs are associated with lipid metabolism, inflammatory diseases, and nervous/cardiovascular system development. Conclusion: In this study, we demonstrated altered miRNAs in bEVs of obese mothers and identified the pathways of their potential target genes. Our findings will provide insight for future studies investigating the role of bEVs in breastfed infants.

Project description:While extracellular vesicles (EVs) continue to gain interest for therapeutic applications, their clinical translation is limited by a lack of optimal isolation methods. We sought to determine how universally applied isolation methods impact EV purity and yield. EVs were isolated by ultracentrifugation (UC), polyethylene glycol precipitation, Total Exosome Isolation Reagent, an aqueous two-phase system with and without repeat washes or size exclusion chromatography (SEC). EV-like particles could be detected for all isolation methods but varied in their purity and relative expression of surface markers (Alix, Annexin A2, CD9, CD63 and CD81). Assessments of sample purity were dependent on the specificity of characterisation method applied, with total particle counts and particle to protein (PtP) ratios often not aligning with quantitative measures of tetraspanin surface markers obtained using high-resolution nano-flow cytometry. While SEC resulted in the isolation of fewer particles with a relatively low PtP ratio (1.12 × 107 ± 1.43 × 106 vs highest recorded; ATPS/R 2.01 × 108 ± 1.15 × 109, p ⩽ 0.05), EVs isolated using this method displayed a comparatively high level of tetraspanin positivity (e.g. ExoELISA CD63⁺ particles; 1.36 × 1011 ± 1.18 × 1010 vs ATPS/R 2.58 × 1010 ± 1.92 × 109, p ⩽ 0.001). Results originating from an accompanying survey designed to evaluate pragmatic considerations surrounding method implementation (e.g. scalability and cost) identified that SEC and UC were favoured for overall efficiency. However, reservations were highlighted in the scalability of these methods, which could potentially hinder downstream therapeutic applications. In conclusion, variations in sample purity and yield were evident between isolation methods, while standard non-specific assessments of sample purity did not align with advanced quantitative high-resolution analysis of EV surface markers. Reproducible and specific assessments of EV purity will be critical for informing therapeutic studies.

Dataset Information

Recovery of extracellular vesicles from human breast milk is influenced by sample collection and vesicle isolation procedures.

Publications

Recovery of extracellular vesicles from human breast milk is influenced by sample collection and vesicle isolation procedures.

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