DIRECT GENE DELIVERY TO SYNOVIUM - AN EVALUATION OF POTENTIAL VECTORSIN-VITRO AND IN-VIVO

Objective. To assess the abilities of various vectors to transfer gene s to the synovial lining of joints. Methods. Vectors derived from retr ovirus, adenovirus, and herpes simplex virus as well as cationic lipos omes and naked plasmid DNA were evaluated. Each construct contained th e lac Z marker gene; and one retroviral construct, and one plasmid als o contained a gene encoding human interleukin-1 receptor antagonist. G ene expression was under the control of the human cytomegalovirus prom oter in ail vectors except the retrovirus, where the endogenous 5' lon g terminal repeat was retained as the promoter. Cultures of rabbit syn ovial fibroblasts were exposed to these vectors and stained with X-gal to identify lac Z+ cells. Vectors were then injected directly into ra bbits' knee joints, and gene transfer and expression were assessed by X-gal staining and polymerase chain reaction (PCR). Results. Adenoviru s was a highly effective vector both in vitro and in vivo, with lac Z gene expression persisting for at least 28 days. However, an inflammat ory response was noted in vivo, Cells infected in vitro and in vivo wi th herpes simplex virus also expressed the lac Z gene at high levels, but expression was limited by cytotoxicity. Retroviruses, in contrast, were effective only under in vitro conditions, permitting cell divisi on. Liposomes gave variable in vitro results; when injected into joint s in vivo, gene expression was low and was detectable for only a few d ays, even though a PCR signal persisted for at least 28 days. Unexpect edly, plasmid DNA was captured by the synoviocytes and expressed trans iently following intraarticular injection. Conclusion. None of the vec tors was ideal for in vivo gene delivery to synovium, although adenovi rus was clearly the most effective of those tested. Retroviruses, alth ough poor vectors for in vivo gene delivery, are well suited for ex vi vo gene transfer to the synovial lining of joints.