The involvement of perivascular spaces or tissues in the facial intradermal brain-targeted delivery

Our previous work indicates the lymphatic network and perivascular spaces or tissues might be involved in the facial intradermal brain-targeted delivery of Evans blue (EB). In this article, we presented the detailed involvement of both, and the linkage between lymphatic network and perivascular spaces or tissues. The in-vivo imaging, the trigeminal transection and immunohistochemistry were used. In-vivo imaging indicated intradermal injection in the mystacial pad (i.d.) delivered EB into the brain at 2-, 6- and 24 h, while intranasal injection (i.n.) delivered EB into the rostral head and intravenous injection (i.v.) diffused EB weakly into the brain. Trigeminal perineurial and epineurial EB occurred along the perivascular spaces or tissues and along brain vessels. EB diffused into the lymphatic vessels and submandibular lymph nodes. Moreover, perineurial and epineurial EB co-located or overlaid with Lyve1 immuno-reactivity and VEGF antibody, and lymphatic network connected with perivascular spaces or tissues, suggesting lymphatic system-perivascular spaces might involve in the EB delivery with i.d. The trigeminal transection reduced the trigeminal epineurial and perineurial EB and brain EB along vessels. EB diffused in the fasciculus and the perineurium, blood and lymphatic vessels in the mystacial pad, mystacial EB overlaid VEGF or Lyve1 antibody. In summary, the dermal-trigeminal-brain perivascular spaces or tissues and the linkage to the lymphatic network mediated the intradermal brain-targeted delivery.