1. ¹Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Aarhus C, Denmark
2. ²Department of Molecular Biology, University of Aarhus, Aarhus C, Denmark
3. ³Department of Medical Microbiology and Immunology, University of Aarhus, Aarhus C, Denmark
4. ⁴Integrated DNA Technologies, Inc. Coralville, Iowa, USA

Correspondence: Kenneth A Howard, Interdisciplinary Nanoscience Center, Ny Munkegade, Building 521, University of Aarhus, DK-800 Aarhus C, Denmark. E-mail: kenh@inano.dk

Received 2 May 2008; Accepted 12 September 2008; Published online 30 September 2008.

Abstract

Secretion of tumor necrosis factor- (TNF-) by macrophages plays a predominant role in the development and progression of rheumatoid arthritis. We demonstrate that knockdown of TNF- expression in systemic macrophages by intraperitoneal (i.p.) administration of chitosan/small interfering RNA (siRNA) nanoparticles in mice downregulates systemic and local inflammation. Chitosan nanoparticles containing an unmodified anti-TNF- Dicer-substrate siRNA (DsiRNA) mediated TNF- knockdown (~66%) in primary peritoneal macrophages in vitro. The presence of Cy3-labeled nanoparticles within peritoneal macrophages and specific TNF- knockdown (~44%) with TNF- siRNA after i.p. injection supports our therapeutic approach. Downregulation of TNF--induced inflammatory responses arrested joint swelling in collagen-induced arthritic (CIA) mice dosed i.p. with anti-TNF- DsiRNA nanoparticles. The use of 2'-O-Me-modified DsiRNA resulted in the lowest arthritic scores and correlated with reduced type I interferon (IFN) activation in macrophages in vivo compared with unmodified DsiRNA. Histological analysis of joints revealed minimal cartilage destruction and inflammatory cell infiltration in anti-TNF--treated mice. The onset of arthritis could be delayed using a prophylactic dosing regime. This work demonstrates nanoparticle-mediated TNF- knockdown in peritoneal macrophages as a method to reduce both local and systemic inflammation, thereby presenting a novel strategy for arthritis treatment.