Dromedary milk exosomes as mammary transcriptome nano-vehicle: Their isolation, vesicular and phospholipidomic characterizations

Abstract

Exosomes are extracellular nanovesicles that play a role in cellular trafficking and communication. Camel milk exosomes might carry the potential of recovery of several illnesses that coins the dromedary milk. This study shows for the first time their isolation and fine characterization. The differential ultracentrifugation was used for their isolation. Their recovery from dromedary milk during different lactation periods was evaluated. The vesicular characterization and stability testing of the recovered exosome were examined by transmission electron microscopy (TEM). The proteome footprinting was resolved by gel electrophoresis prior to their specific protein biomarker analysis. The immunoblotting of their specific protein biomarker TSG101 unexpectedly revealed a truncated 35KDa protein specific for dromedary milk exosome rather than the previously reported 43KDa mammalian one. The reversed-phase HPLC screening of their phospholipid makeup was compared with that of cattle milk exosomes at different lactation periods. Since dromedary milk exosomes reflect their mammary transcriptome outcome, further assessment of their content of αs1casein, αs2casein β-casein κ-casein mRNAs parallel with a constitutive glyceraldehyde dehydrogenase (GAPD) gene was performed using real-time PCR. The TEM scanning indicated that dromedary milk exosomes are freeze-stress unstable homogeneous with average size of 30nm. There was no significant difference in expression level of different casein genes in mid lactation period in dromedary milk exosomes over late lactation period. The phospholipidomic survey proved that phosphatidylcholine is the major candidate of the examined phospholipids in dromedary milk exosomes. The obtained data give novel interpretation about the content of camel milk exosomes with possible insight for use as potentially-safe nano carrier.