Cellular distribution of phosphorothioate oligonucleotide following intravenous administration in mice

Oligonucleotides are promising therapeutic agents for the prevention or tre atment of a variety of diseases. The therapeutic potential of oligonucleoti de therapy depends greatly on the bioavailability of oligonucleotides to th eir target cells and organs. We previously reported the pharmacokinetics an d distribution of phosphorothioate oligonucleotide in mice using [S-35]-lab eled oligonucleotide ([S-35]-oligo). TO extend this study, we administered 30 mg/kg of fluorescent-labeled oligonucleotide (FITC-oligo) to mice and ex amined oligonucleotide distribution by measuring the fluorescence intensity in various cells and tissues using flow cytometry, Following FITC-oligo ad ministration, fluorescence was detected in all the tissues examined. In ter ms of the fluorescent intensity, accumulation was greatest in liver and kid ney, intermediate in spleen and bone marrow, and very low in peripheral blo od mononuclear cells (PBMC), At 4 hours after administration, the level of oligonucleotide uptake in PBMC, spleen lymphocytes, and bone marrow cells r evealed the following pattern: monocytes/macrophages > B cells > T cells. C onfocal microscopy detected intracellular fluorescence in PBMC prepared und er the same conditions as those for flow cytometry, These studies provide a rationale for designing cell targets for antisense therapeutics.