Methods
Synovial fibroblasts were harvested from 9 postmenopausal women with advanced RA who were scheduled for sialastic arthroplasty of metacarpal-phalangeal (MCP) joints 2-5. Harvested synovial fibroblasts were cultured and divided into two groups for each donor. Half of the cultured fibroblasts were transduced with a retrovirus engineered with a coding sequence for human IL-1 receptor antagonist (IL-1Ra), an anti-inflammatory cytokine and antagonist of the pro-inflammatory cytokine IL-1. The other half of the cultured fibroblasts were used as non-transduced controls. After ensuring that the transduced synovial fibroblasts were capable of secreting IL-1-Ra, the control and transduced cells were injected back into the MCP joints of the donor (2 joints each, performed in a double-blind fashion) 1 week prior to MCP arthroplasty. The 9 patients were evenly allocated to receive low, intermediate, or high doses of transduced cells (or non-transduced control). At arthroplasty, the synovial tissue was retrieved and expression of IL-1Ra was examined by qualitative and quantitative methods.
Results
The nine participants were all Caucasian women, 51 to 73 years of age, with longstanding destructive RA (10 to 26 years duration). 8 of the 9 were receiving DMARD therapy. 5 of the 9 were receiving corticosteroids.
Upon retrieval of synovium, all of the joints injected with transduced fibroblasts demonstrated expression of transgenic mRNA, while only one of the control joints demonstrated transgene expression (in a patient who had received high dose injection of transduced cells into 2 other MCP joints). IL-1Ra expression was dose dependent, with the 3 patients receiving the lowest dose of transduced cells demonstrating little IL-1Ra expression. In situ hybridization and immunohistochemistry revealed surface clusters of IL-1Ra expressing cells in the synovia of joints injected with transduced cells. These surface clusters were not seen in joints injected with non-transduced cells.
No immediate or long-term (greater than 5 years) safety issues were reported associated with the gene transfer experiment.
Conclusion
Intra-articular transfer of genes capable of expressing anti-inflammatory cytokine products is feasible and appears to be safe.
Editorial Comment
This work is a novel and extraordinary first step into an unexplored area of therapeutic potential in inflammatory arthritis. Owing to its novelty, the authors were appropriately cautious in the design of this study and utilized a clever set of methods in which the patients were exposed to their own transduced fibroblasts and only for a very short time period. Accordingly, as this is a phase 1 study, no conclusions can be drawn about the efficacy of the intervention.
Even so, a few concerns may already be raised from these results. Either by unintentional inoculation, measurement error, or by migration between joints, transgene expression was measured in a joint not thought to have been inoculated with transduced cells. This may represent the potential for genetic material introduced into a joint to exhibit effects in remote areas. This may be problematic when envisioning scenarios in which high concentrations of genetic material may be required (i.e. gene transfer to an inflamed knee). Additional study is required to examine the potential for transduced genetic material to migrate throughout the body.
Indeed, RA may not prove to be the ideal disorder for this type of intervention. The large number of joints involved, the small size of some of the joints involved and difficulty in reliably delivering agents into small joints may be impractical for RA patients and practitioners. However, inflammatory arthropathies with fewer numbers of joints involved (i.e. the seronegative spondyloarthropaties) may truly benefit from this type of intervention in the future.
