Murine model of minimally invasive nasal depot (MIND) technique for central nervous system delivery of blood–brain barrier-impermeant therapeutics

The blood–brain barrier (BBB) poses a substantial obstacle to the successful delivery of therapeutics to the central nervous system (CNS). The transnasal route has been extensively explored, but success rates have been modest due to challenges related to the precise anatomical placement of drugs, the small volumes that the olfactory cleft can accommodate and short drug residence times due to mucociliary clearance. Here, to address these issues, we have developed a surgical technique known as the minimally invasive nasal depot (MIND), which allows the accurate placement of depot drugs into the submucosal space of the olfactory epithelium of rats. This technique exploits the unique anatomy of the olfactory apparatus to enable transnasal delivery of drugs into the CNS, bypassing the BBB. In our rat model, a bony window is created in the animal snout to expose the submucosal space. Using the MIND technique, we have successfully delivered oligonucleotides to the CNS in Sprague-Dawley and Long-Evans rats, leading to an upregulation of brain-derived neurotrophic factor in the substantia nigra and hippocampus. In this Protocol, we describe the procedural steps for MIND. This procedure takes about 45 min and can be performed by researchers with basic surgical skills. We additionally describe modifications to perform MIND in mice, which are anatomically smaller. The MIND procedure represents a unique platform that can be used to overcome the limitations posed by the BBB. This technique can potentially expand the therapeutic toolkit in the treatment of neurological diseases.