GENE-TRANSFER TO HUMAN RHEUMATOID SYNOVIAL TISSUE ENGRAFTED IN SCID MICE

Objective, To assess the feasibility of gene therapy in rheumatoid art hritis (RA) and determine the appropriate vector. Methods. Human rheum atoid synovial tissue from 6 patients with RA was transduced ex vivo w ith a recombinant retroviral vector (pMFG.nlsLacZ) containing the Esch erichia coil beta-galactosidase (beta-gal) gene in a coculture assay i n the presence of 20 ng/ml tumor necrosis factor alpha (TNF-alpha) for promoting cell division. We also conducted in vitro infection experim ents using an adenoviral vector (AdCMVSp1.LacZ) containing the beta-ga l gene. After gene transduction, the synovial tissue was engrafted sub cutaneously in 8-week-old severe combined immunodeficiency (SCID) CB17 mice. beta-gal expression was then monitored as a function of lime (u p to 21 days) and of virus dose [up to 50 colony forming units (cfu)/c ell]. The efficacy of direct in vivo gene transfer was also tested by injection of 10(6) cfu of pMFG.nlsLacZ into rheumatoid synovial tissue engrafted in SCID mice. Results, When recombinant retroviral vector w as used, 30 +/- 5% of ex vivo infected synovial cells were positive fo r staining. In synovial tissue implanted in SCID mice, beta-gal expres sion declined to 5% after one week, but persisted for at least 21 days . Direct injection of pMFG.nlsLacZ vector into the rheumatoid synovial tissue implanted in SCID mice allowed efficient and stable in vivo in fection of the synovial tissue. Ex vivo gene transfer with adenoviral vector resulted in a 98% infection rare of the synovial lining cells. However, beta-gal activity declined 7 days after subcutaneous implanta tion. Conclusion. Highly efficient gene transfer in rheumatoid synovia l tissue is achievable with both adenoviral and retroviral vectors, bu t the results were transient. Exogenous gene transfer through retrovir al vectors required stimulation with TNF-alpha for synovial cell divis ion and proviral integration. Direct in vivo gene transfer with recomb inant retrovirus was shown to be efficient. Transduction of human syno vial tissue engrafted in SCID mice is a potent tool for developing pre clinical models of gene therapy in RA.