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Updated: May 27, 2026
Rapid Isolation of Human Breast Milk-Derived Extracellular Vesicles
Published on: November 14, 2025
Bovine milk exosome proteome
Timothy A Reinhardt1, John D Lippolis, Brian J Nonnecke
1Ruminant Diseases and Immunology Unit, National Animal Disease Center, USDA/ARS, Ames, IA 50010, USA. tim.reinhardt@ars.usda.gov
Insights
Bovine milk exosomes, tiny vesicles involved in cell communication, were analyzed. Their protein content differs significantly from milk fat globule membranes, offering new insights into mammary gland physiology.
Area of Science:
- Proteomics
- Cell Biology
- Biochemistry
Background:
- Exosomes are nanoscale vesicles involved in intercellular communication and immune function.
- Bovine milk contains exosomes, which are extracellular organelles secreted by cells.
- Understanding the proteome of milk exosomes can illuminate milk production processes.
Purpose of the Study:
- To characterize the proteome of exosomes isolated from bovine milk.
- To compare the protein composition of milk exosomes with milk fat globule membranes (MFGM).
- To investigate the physiological significance of milk exosomes in mammary physiology.
Main Methods:
- Exosomes were isolated from mid-lactation cow milk.
- Proteomic analysis involved trypsin digestion, offline high pH reverse-phase chromatography, and nanoLC-tandem mass spectrometry.
- Protein identification and quantification were performed using mass spectrometry.
Main Results:
- Identification of 2107 proteins in milk exosomes, including canonical exosome markers.
- Major milk fat globule membrane (MFGM) proteins were identified but were less abundant in exosomes compared to MFGM isolates.
- Milk exosome secretion pathway differs from MFGM, with reduced MFGM protein presence.
Conclusions:
- The proteome of bovine milk exosomes provides novel information on milk composition.
- The distinct protein profile suggests a different secretion pathway for exosomes compared to MFGM.
- Milk exosomes may play a significant role in mammary gland physiology.
Abstract:
Exosomes are 40-100 nm membrane vesicles of endocytic origin, secreted by cells and are found in biological fluids including milk. These exosomes are extracellular organelles important in intracellular communication, and immune function. Therefore, the proteome of bovine milk exosomes may provide insight into the complex processes of milk production. Exosomes were isolated from the milk of mid-lactation cows. Purified exosomes were trypsin digested, subjected offline high pH reverse phase chromatography and further fractionated on a nanoLC connected to tandem mass spectrometer. This resulted in identification of 2107 proteins that included all of the major exosome protein markers. The major milk fat globule membrane (MFGM) proteins (Butyrophilin, Xanthine oxidase, Adipophilin and Lactadherin) were the most abundant proteins found in milk exosomes. However, they represented only 0.4-1.2% of the total spectra collected from milk exosomes compared to 15-28% of the total spectra collected in the MFGM proteome. These data show that the milk exosome secretion pathway differs significantly from that of the MFGM in part due to the greatly reduced presence of MFGM proteins. The protein composition of milk exosomes provides new information on milk protein composition and the potential physiological significance of exosomes to mammary physiology.
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