Canine colostrum exosomes: characterization, anti-oxidative capacity and influence on canine mesenchymal stem cell

Background: Colostrum is a specific secretion of the mammary gland fundamental for the survival of the puppy during the first weeks after birth. It contains important bioactive molecules involved in the passive immunity and the maturation of various organs, highlighting small vesicles named exosomes. Exosomes have not been described yet in canine colostrum milk, where its role is crucial in dam-newborn communication for the development of the neonate. Results: Exosomes were abundant in canine colostrum milk and appeared with a characteristic cup-shaped morphology and well-defined round vesicles. Their size distribution was between 37−140 nm and western blot analysis showed an expression of specific exosomal markers. Proteomic analysis revealed a total of 826 proteins in exosomes cargo. We also found that exosomes modified proliferation and secretory profile in canine mesenchymal stem cells derived from bone marrow and adipose tissue, differently according to their origin. Besides, the exosomes of canine colostrum demonstrated a potent antioxidant effect. Conclusions: We described for the first time the isolation and characterization of milk exosomes from canine colostrum. Our findings highlight the abundant presence of exosomes in the colostrum of the canine species and contribute to explain their important antioxidant capacity after parturition and their role in the modulation of cell development and tissue differentiation in the newborn, where mesenchymal stem cells seem to play a key role.