Presentation: Elucidation of Promoters for Disease-Regulated Gene and Cell-Based Therapy for Rheumatoid Arthritis (2007)

149 Elucidation of Promoters for Disease-Regulated Gene and Cell-Based Therapy for Rheumatoid Arthritis

The application of disease-regulated promoters in gene and cell-based therapy for rheumatoid arthritis (RA) allows fine-tuned supply of biologicals in an offer meets demand fashion. Furthermore, disease-regulated expression potentially minimizes harmful side effects as described for long-term bulk delivery of biologicals. In this study, we sought to elucidate candidate promoters from unique gene expression profiling data sets of two distinct models of experimental arthritis.
Gene expression profiling was performed on synovial tissue from a chronic collagen-induced arthritis and relapsing streptococcal cell wall arthritis. The former model was explored for genes that correlate to disease severity, the latter for genes whose expression paralleled the repetitive inflammatory flares. From these, we deduced serum amyloid A3 (SAA3) as a promising candidate that met the prerequisites of a disease-regulated promoter: low expression under naïve conditions, highly upregulated during inflammatory flares, and expression levels correlated strongly to arthritis severity.
Next, promoter strength and responsiveness to proinflammatory stimuli in vitro and experimental arthritis in vivo were examined. For this, we generated a lentiviral luciferase reporter containing a minimal murine SAA3 (-314/+50) promoter. We first validated the responsiveness in primary human RA synovial fibroblasts (RASF), which represent the intended target cells for gene therapy. The promoter showed low basal activity and a strong response to IL-1β, TNF-α and a TLR4 agonist. Interestingly, the cytokine-induced promoter activities in the RASF correlated with the annotated disease severity in patients from which these cells were isolated: promoter responses were the strongest in RASF from patients with active RA. Next, the applicability of the SAA3 promoter for achieving disease-regulated expression in experimental arthritis was investigated. Lentivirus was injected in knee joints of C57Bl/6 mice and subsequently luciferase activities under naïve and arthritic conditions were measured. During an acute joint inflammation, luciferase levels were more than eighty fold upregulated over levels under naïve conditions.
This study clearly demonstrates that gene expression profiling provides a useful tool for extracting disease-regulated promoters. Based on the evaluation of promoter activity in RASF and experimental arthritis, SAA3 is an attractive candidate for application in gene or cell-based therapies for RA that require restricted and fine-tuned expression of biologicals.

 J. Geurts, None; O.J. Arntz, None; A. van Raaij, None; M.B. Bennink, None; N. Takahashi, None; L.A. Joosten, None; W.B. van den Berg, None; F.A. van de Loo, VIDI grant from The Dutch Organization for Scientific Research (917.46.363), 2.