ABSTRACT
OBJECTIVE: To show the possible occurrence of exosomal transport of neprilysin from masseter muscle to hippocampus via trigeminal nerve in the living mouse. DESIGN: Mouse C2C12 myotube-derived exosomes were labeled with near-infrared (NIR) dye and injected into the masseter muscle to track their fluorescence from masseter muscle to hippocampus via trigeminal nerve. A plasmid vector encoding green fluorescent protein (GFP)-tagged neprilysin (GFP-neprilysin) was transfected into masseter muscle of C57BL/6â¯J mice. Expression of mRNA and encoded protein of the transgene was identified in masseter muscle, trigeminal nerve and hippocampus by RT-PCR and Western blot, respectively. RESULTS: Peak of exosomal NIR in masseter muscle at time 0 rapidly reduced at 3â¯h and 6â¯h along with the subsequent increases in trigeminal nerve and hippocampus. Expression of GFP-neprilysin mRNA was detected in masseter muscle, but not trigeminal nerve and hippocampus. On the other hand, the corresponding protein of GFP-neprilysin was identified in the three tissues on day 3 after transfection into masseter muscle as a single band on Western blots with anti-GFP and anti-neprilysin antibodies. CONCLUSION: The appearance of GFP-neprilysin protein in trigeminal nerve and hippocampus without a corresponding mRNA expression indicated the protein's origin from the masseter muscle. Concomitant migration of NIR-exosomes from masseter muscle to hippocampus via trigeminal nerve suggested the possible occurrence of exosomal transport of neprilysin.
