Intranasal Administration of a Naked Plasmid Reached Brain Cells and Expressed Green Fluorescent Protein, a Candidate for Future Gene Therapy Studies.

BACKGROUND: Intranasal administration (Int adm) has been well-studied and offers the possibility to deliver larger molecular weight biologics, such as proteins, viral vectors, nanoparticles, and naked plasmids to the brain and treat a variety of diseases in the central nervous system. The predominant challenge in this field is finding efficient vectors that are capable of crossing the blood-brain barrier (BBB).

OBJECTIVES: Here, we investigated whether a naked plasmid (pIRES-hrGFP-1a), could cross the BBB, reach brain cells and express green fluorescent protein (GFP) after int-adm and propose it as candidate for future gene therapy studies.

MATERIAL AND METHODS: Thirty-six mice were divided into 2 groups. Eighteen animals were assigned to each cluster. Mice from experimental groups received 25 μg of pIRES-hrGFP-1a. The control groups received 25 μl of PBS. Plasmids were given intranasally by applying little drops in both nostrils. Twenty-four hours later, the mice were sacrificed, and their brains were removed. Later, PCR, RT-PCR, and immunohistochemical techniques were performed.

RESULTS: pIRES-hrGFP-1a crossed the BBB and was mainly detected in the olfactory nerves (20%) and hypothalamus (16%). In contrast, GFP/18S-expressing mRNAs were detected mostly in the olfactory bulbs (95%), frontal cortex (71%) and amygdala (60%). GFP was detected in the olfactory bulb, hippocampus, frontal cortex and brainstem at 24 h.

CONCLUSIONS: pIRES-hrGFP-1a could be considered a good candidate for gene therapy studies. In the future could be cloned some therapeutic genes in the pIRES-hrGFP-1a and could transcribe and translates deficient proteins that are required to restore a function.