PLGA microspheres encapsulating siRNA anti-TNFalpha: efficient RNAi-mediated treatment of arthritic joints.

The aim of this study was to investigate potentialities of poly(dl-lactide-co-glycolide) (PLGA) microspheres for the delivery of small interfering RNAs (siRNAs) against tumor necrosis factor α (TNF-α) to achieve prolonged and efficient inhibition of TNF-α for the treatment of rheumatoid arthritis (RA). PLGA microspheres were prepared by a modified multiple emulsion-solvent evaporation method. The formulations were characterized in terms of morphology, mean diameter and siRNAs distribution, encapsulation efficiency, and in vitro release kinetics. The efficiency of this system was then evaluated both in vitro and in vivo using the murine monocytic cell line J774 and a pre-clinical model of RA, respectively. siRNA-encapsulating PLGA microspheres were characterized by a high encapsulation efficiency and a slow and prolonged anti-TNF-α siRNAs. Our results provide evidence that, upon intra-articular administration, PLGA microspheres slowly releasing siRNAs effectively inhibited the expression of TNF-α in arthritic joints. Our system might represent an alternative strategy for the design of novel anti-rheumatic therapies based on the use of RNA interference in RA.

Cytosolic phospholipase A2α gene silencing in the myeloid lineage alters development of Th1 responses and reduces disease severity in collagen-induced arthritis.

OBJECTIVE: Several lines of evidence implicate cytosolic phospholipase A(2)α (cPLA(2)α) as a critical enzyme in inflammatory disorders, including rheumatoid arthritis. Since cells from the myeloid compartment regulate local and systemic disease pathogenesis, the present study was undertaken to examine the effect of cPLA(2)α inhibition in experimental arthritis, using a delivery system tailored to target monocyte functions by RNA interference (RNAi). METHODS: Mice with collagen-induced arthritis (CIA) were injected intravenously with an anti-cPLA(2)α small interfering RNA (siRNA) sequence (siPLA2) formulated as lipoplexes with the RPR209120/DOPE cationic liposome and a carrier DNA. The clinical course of joint inflammation was assessed, and the immunologic balance was analyzed by measuring T helper cell frequencies and cytokine expression. Biodistribution studies of siRNA were also performed. RESULTS: Weekly systemic injection of siPLA2 lipoplexes significantly reduced the incidence and severity of CIA, in both preventive and curative settings, as compared with findings in control animals. Histologic scores for inflammation and cartilage damage were reduced. The clinical effect was associated with local inhibition of tumor necrosis factor α secretion and lower cPLA(2)α expression and activity. The siPLA2 lipoplexes enabled triggering of in vivo RNAi-mediated gene silencing of cPLA(2)α in CD11b+ cells recovered from the spleen. While the treatment had no effect on anti-type II collagen (anti-CII) antibodies, CII-specific T helper cells producing interferon-γ, but not interleukin-17, in draining lymph node cells were decreased. CONCLUSION: Our findings indicate that systemic RNAi-mediated cPLA(2)α gene silencing in CD11b+ cells is effective in the treatment of CIA, and Th1 suppression is one of the potential underlying mechanisms, whereas Th17 suppression is not.