RETROVIRUS-MEDIATED IN-VIVO GENE-TRANSFER TO SYNOVIUM IN BACTERIAL-CELL WALL-INDUCED ARTHRITIS IN RATS

Gene therapy may provide an effective alternative to conventional appr oaches for treating rheumatoid arthritis. Direct in vivo gene delivery to synovium has a distinct advantage with respect. To clinical use. T o date, retroviral vectors are the best studied constructs for gene de livery, and almost all approved gene therapy trials in humans rely on retroviral vectors. However, the applicability of retoviral transducti on is limited by requirement for cell division and attempts to transdu ce normal synovium in situ using retroviral vectors are reported to fa il. The present study was undertaken in order to investigate susceptib ility of inflamed synovium to retroviral infection in vivo. Using an e xperimental model of bacterial cell wail (BCW)- induced arthritis in r ats, we attempted two approaches for delivery of retroviral vectors to synovium. In the first approach, recombinant retroviral vectors carry ing reporter genes lacZ and neo were directly injected into inflamed r at ankle joints. Alternatively, inflamed joints were inoculated with g amma-irradiated murine retroviral vector-producing packaging cells. We found that about 1% of cells in explants from joints inoculated with packaging cells were lacZ- neo- positive. The lacZ(+) neo(+) cells in joint explants proliferated in culture and were of rat origin as deter mined using species-specific polymerase chain reaction (PCR) analysis. There was no evidence of transduction in explants from joints directl y injected with retroviral vectors or from contralateral, control join ts. These findings show that arthritic joints have a population of cel ls susceptible to retroviral infection in situ and demonstrate the pos sibility of using retroviral Vectors for direct gene delivery to infla med synovium.