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OBJECTIVE This study explored the therapeutic effect of interleukin-1 receptor antagonist (IL-1Ra), administered by gene transfer, on the progression of osteoarthritic (OA) lesions in an experimental dog model. METHODS Seventeen mature mongrel dogs were divided into 3 groups. Group 1 (n = 7) had an anterior cruciate ligament (ACL) section of the right knee through a stab wound incision. Groups 2 and 3 (n = 5 per group), had an ACL section of the right knee and partial synovectomy of the left knee. Each dog's synovium was subjected to enzymatic digestion, and the synovial fibroblasts were propagated in monolayer culture. Synovial cells from each dog were transduced in vitro using the retrovirus MFG with either the Escherichia coli beta-galactosidase (lac Z) gene (group 2) or the human IL-1Ra gene (group 3). Two days after surgery, the dogs received intraarticular injections as follows: group 1 phosphate buffered saline (PBS) (2 ml); group 2 autologous cells (60 x 10(6) cells/2 ml of PBS) transduced with the lac Z gene; group 3 autologous cells transduced with the IL-1Ra gene. Synovial fluid was aspirated at 2 weeks and 4 weeks. All dogs were euthanized at 4 weeks postsurgery. The right knees were dissected, and lesions were scored for macroscopic and microscopic changes. Synovial explants were dissected and representative specimens were used for histology or were cultured for 48 hours. The levels of IL-1Ra in synovial fluid and synovial explant conditioned medium were measured by specific enzyme-linked immunosorbent assay. RESULTS The level of IL-1Ra in synovial fluid of group 3 was 202.8 +/- 131.5 ng/ml (mean +/- SEM) at 2 weeks and 2.8 +/- 2.2 ng/ml at 4 weeks after surgery. Membrane explants isolated from dogs that received synovial cells transduced with the IL-1Ra gene (group 3) actively produced IL-1Ra (4.0 +/- 2.0 ng/gm of tissue wet weight). The severity of OA cartilage lesions was similar in groups 1 and 2. In contrast, group 3 dogs had a marked reduction in macroscopic lesion severity on the tibial plateaus (P < 0.01 for grade; P < 0.04 for size) and femoral condyles. Moreover, the histologic lesion severity was decreased on both plateaus (P < 0.06) and condyles. CONCLUSION This study showed that a local increase in IL-1Ra production in OA knee joints by intraarticular injection of transduced synovial cells can reduce the progression of experimentally induced lesions.

Objective. To assess the abilities of various vectors to transfer genes to the synovial lining of joints. Methods. Vectors derived from retrovirus, adenovirus, and herpes simplex virus as well as cationic liposomes and naked plasmid DNA were evaluated. Each construct contained the lac Z marker gene; and one retroviral construct, and one plasmid also contained a gene encoding human interleukin-1 receptor antagonist. Gene expression was under the control of the human cytomegalovirus promoter in all vectors except the retrovirus, where the endogenous 5′ long terminal repeat was retained as the promoter. Cultures of rabbit synovial fibroblasts were exposed to these vectors and stained with X-gal to identify lac Z+ cells. Vectors were then injected directly into rabbits' knee joints, and gene transfer and expression were assessed by X-gal staining and polymerase chain reaction (PCR). Results. Adenovirus was a highly effective vector both in vitro and in vivo, with lac Z gene expression persisting for at least 28 days. However, an inflammatory response was noted in vivo. Cells infected in vitro and in vivo with 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 division. Liposomes gave variable in vitro results; when injected into joints in vivo, gene expression was low and was detectable for only a few days, even though a PCR signal persisted for at least 28 days. Unexpectedly, plasmid DNA was captured by the synoviocytes and expressed transiently following intraarticular injection. Conclusion. None of the vectors was ideal for in vivo gene delivery to synovium, although adenovirus was clearly the most effective of those tested. Retroviruses, although poor vectors for in vivo gene delivery, are well suited for ex vivo gene transfer to the synovial lining of joints.