Background and Objectives Local gene therapy for arthritis, with the use of disease-inducible promoters, represents a promising alternative for coping with side effects of the conventional treatments. These disease-inducible promoters react to transcription factors that are released during inflammation and therefore only produce a therapeutic protein when necessary. Interleukin-10 (IL-10) could play an important regulatory role in streptococcal cell wall arthritis (SCW), and therapeutic effects are present when IL-10 was injected systemically (Lubberts et al, 1998).
In this study IL-10 was used to investigate the potential of intra-articular gene therapy in an acute model of arthritis.
Materials and Methods C57Bl6/N mice were injected intra-articularly in the kneejoint with lentivirus, expressing the therapeutic protein IL-10 or the luciferase reporter. Inducible promoters S100a8, Cxcl1, MMP13, Saa3, IL-1b, and TNFaip6, which were selected from endogenous genes differentially regulated in the inflamed synovium of collagen-induced arthritis mice, were used to express luciferase. The constitutive PGK promoter was used to express IL-10. Arthritis was induced by injection of 25 µg SCW into the knee joint cavity 4 days later. At 1, 4, and 7 days after arthritis induction, mice treated with PGK-IL10 were sacrificed, and knee joints were dissected for either histological analysis, or RNA isolation for qPCR analysis. At the same timepoints, in-vivo bioluminescent imaging was performed in mice treated with the inducible promoter reporter, using the IVIS Lumina system.
Results PGK-IL10 significantly decreased proteoglycan (PG) depletion at day 4 and 7 after arthritis induction, probably by inhibiting MMPs and upregulating TIMPs. No effects on inflammation were seen histologically, but synovial IL-1, IL-6 and TNFa gene expressions were markedly decreased at day 1. The inducible promoters all showed a different activation profile during the course of inflammation, meaning they all react differently during the disease process. The Saa3 promoter showed the highest upregulation (120 fold) and was the only promoter which showed an early peak in activation at day 1 after arthritis induction, resembling neutrophil influx.
Conclusions Effects of IL-10 were seen on PG depletion and gene expressions, therefore IL-10 can be a feasible therapeutic protein to modulate SCW arthritis. On the other hand, the Saa3 promoter seems to be the best candidate for local intra-articular gene therapy with the use of disease-inducible promoters, because it showed a high and quick upregulation during disease activity. Hence, combining the Saa3 promoter with the therapeutic protein IL-10, can be a promising combination to modulate an acute model of arthritis using disease regulated gene therapy.