Concurrent gene therapy strategies effectively destroy synoviocytes of patients with rheumatoid arthritis

Objectives. Rheumatoid arthritis (RA) is characterized by the chronic inflammation of the synovial joints resulting from the hyperplasia of synovial cells and the infiltration of lymphocytes, macrophages and plasma cells. Currently, the aetiology of RA is not known, and new treatment modalities are needed to prevent the disease progression. Apoptosis induction of synovial cells through the use of death ligands has been explored as a treatment modality for RA. Thus, the primary objective of this study was the testing of the efficacy of adenovirus delivery of human TRAIL (Ad5hTRAIL) for the treatment of patients with RA. Methods. Primary synovial cell cultures were established from eight patients with RA. Adenovirus permissiveness of synovial cells was determined by the infection of synoviocytes with adenovirus vector encoding green fluorescent protein (AdEGFP). TRAIL sensitivity of synoviocytes was assessed through the infection with Ad5hTRAIL vector using Live/Death Cellular Viability/Toxicity kit from Molecular Probe. TRAIL receptor profiles of synoviocytes were revealed by real-time RT-PCR assays followed by flow cytometric analyses. Results. While the presence of TRAIL death receptors were necessary for the induction of cell death, high levels of TRAIL-R4 decoy receptor expression on surface were correlated with TRAIL resistance. A DcR2 siRNA approach in combination with Ad5hTRAIL infection eliminated apoptosis-resistant RA synovial fibroblasts. Conclusion. Because a DcR2 siRNA approach in combination with Ad5hTRAIL infection exterminated RA synoviocytes to a greater extent than Ad5hTRAIL alone, the modulation of TRAIL receptor expression might be a new gene therapy strategy to sensitize RA synoviocytes to TRAIL.