**5. Conclusions**

*Extracellular Vesicles and Their Importance in Human Health*

exosomes isolated from other milk sources is very actual.

The first paper describing human milk exosomes was published in 2007 [6] and dedicated to the interaction of exosomes with blood cells in cell cultures. Preparations of human milk vesicles inhibited interleukin-2, γ-interferon, and tumor necrosis factor α production by peripheral blood mononuclear cells and

Exosomes are natural vesicles with very promising perspectives for drug therapeutic nucleic acid delivery into the cells. One of the unresolved problems so far is the development of universal sources for isolation of preparative amounts of exosomes. The use of milk allows researchers to obtain exosome preparation several liters of milk at once that makes milk a cheap and unique source of

Milk exosomes can be used for targeted drug delivery to cells. It is shown that exosomes of cow [83] and human [88] milk penetrate intestinal crypt-like cells. The possibility of milk exosomes to be used as agents for delivery of proteins, nucleic acids, and drugs makes the subject of its investigation extremely relevant. Since the components of cow milk can be used for therapy with significant limitations, since in this case the transmission of prion diseases cannot be excluded [90], analysis of

Encapsulation of curcumin in buffalo milk exosomes increased its stability in salivary, gastric, pancreatic secrets as well as in bile juice. Also, curcumin encapsulated in milk exosomes was successfully uptaken and trans-epithelial transported in Caco-2 cells [91]. Since curcumin is a hydrophobic and water-insoluble molecule, it binds to the exosomes and probably incorporates in exosomal membranes. Hydrophobic drug molecules (paclitaxel [92], doxorubicin [93], and others) can also be delivered via milk exosomes with the same mechanism. Similar results were obtained in the case of chemically synthesized siRNA [86]. Transfection of siRNA in cow milk exosomes protects it from the activity of digestive juices and increases delivery to Caco-2 cells compared to the control

According to several works, milk exosomes contain antibody molecules on the surface. Transport of IgG molecules in the intestine occurs as a result of binding to neonatal Fc receptor (FcRn). Cow milk-derived exosomes were successfully delivered to the mice liver, heart, spleen, lungs, and kidneys after the oral

Auspicious work shows the possibility of transfer of bovine leukemia virus proteins Env (gp51) and Gag (p24), but not viral DNA with milk exosomes obtained

Incubation of human milk exosomes, but not the blood plasma exosomes with monocyte-derived dendritic cells, results in DC-SIGN inhibition of HIV infection

These results may partially explain why some breastfeed infants do not get infected

Yak milk exosomes facilitate survival of intestine cells in hypoxic conditions in vitro and have significantly higher activity than cow milk exosomes. Yak milkderived exosomes also decrease the expression of p53, increase the expression of oxygen-sensitive prolyl hydroxylase, and decrease the expression of vascular endothelial growth factor via the hypoxia-inducible factor-α in cell cultures [97]. Human milk exosomes protect intestinal epithelium cells in vitro from oxidative

T lymphocytes [96].

from infected cattle [95]. This route of viral protein delivery doesn't require viral infection since that may have the potential of use for immunization and/or

of dendritic cells and protects from HIV transfer to CD4+

stress and probably defend newborns from enterocolitis [98].

cell proportion in vitro.

**4. Milk exosomes: perspectives of use**

stimulated the increase of Foxp3+

exosomes.

samples.

administration [94].

from HIV-infected mothers.

vaccination.

**28**

Milk is more than a source of nutrients and vitamins for newborn [99]; it contains different proteins and protein complexes [100] with very diverse functions. Milk is a biological liquid containing vesicles of different size and shapes. Exosomes are natural vesicles with a diameter of 40–100 nm and are found in milk obtained from human, cow, horse, camel, mice, rat, swine, and some other mammalian species. There is no doubt that milk obtained from any source contains such structures. Many biological effects are attributed to exosomes, and researchers are particularly interested in milk exosomes, since they can be used as carriers of drugs and therapeutic nucleic acids for delivery to cells. The physicochemical properties and biological functions of exosomes are primarily determined by their biochemical composition—the structure of lipids, proteins, and nucleic acids. The prospects for the further practical use of milk exosomes in medicine and biotechnology largely depend on investigations of the fine structure and biological functions of exosomes free of various contaminating impurities.

## **Acknowledgements**

This research was made possible by a grant of the Russian Scientific Foundation to Sergey Sedykh #18-74-10055 (isolation, biochemistry, morphology of milk exosomes) and by the Russian State funded budget project of ICBFM SB RAS to Georgy Nevinsky # AAAA-A17-117020210023-1 (perspectives of use).
