Abstract

Background and aims Tumour necrosis factor α (TNFα) is a focal point of the inflammatory cascade in Crohn's disease (CD). As an emerging approach to block cytokines, antisense oligonucleotide (ASO) has developed quickly, but is thwarted by a key obstacle—safe and effective delivery to specified cells. Here a novel nano-complex, based on galactosylated low molecular weight chitosan (gal-LMWC) and an ASO against TNFα, is presented which may be effective for CD treatment. The aim of this study was to investigate the targeting delivery ability of the gal-LMWC/ASO complex into activated macrophages and its potential therapeutic action in experimental colitis.

Methods Gal-LMWC was associated with ASO to form a stable nano-complex and the complex was injected into mice by intracolonic administration. Cellular localisation of the gal-LMWC/ASO complex in the colon was determined. The therapeutic effects were further studied in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis and CD4⁺CD45RB^hi T cell transfer colitis.

Results Intracolonic administration of the gal-LMWC/ASO complex resulted in the successful delivery of ASO into activated colonic macrophages and a significant reduction of colonic TNFα in mice with colitis. A single injection in TNBS colitis or repeated treatment in CD45RB^hi transfer colitis both significantly ameliorated the clinical and histopathological severity of the wasting disease, reduced tissue levels of inflammatory cytokines and abrogated body weight loss, diarrhoea and intestinal protein loss.

Conclusions It is the first time a non-viral gene vector has been combined with an ASO targeted to activated macrophages in the treatment of CD. The inhibition of TNFα by this strategy represents a promising therapeutic approach for the treatment of CD.