Amelioration of antigen-induced arthritis in rabbits by induction of apoptosis of inflammatory cells with local application of transdermal photodynamic therapy.

OBJECTIVE

To study the efficacy and mechanism of local transdermal photodynamic therapy (tPDT) in rabbits with antigen-induced arthritis (AIA).

METHODS

AIA in rabbits on day 14 postinduction was treated with an intravenous injection of benzoporphyrin-derivative monoacid ring A (BPD; Verteporfin) and subsequent transdermal exposure of the knee joint to light. BPD uptake and PDT-induced apoptosis of the synovium was studied applying fluorescence confocal microscopy and immunohistochemistry. The (histo)pathology of the joints was assessed at day 28.

RESULTS

Treatment with tPDT resulted in significant amelioration of synovial inflammation and an almost complete prevention of pannus formation and bone and cartilage destruction. BPD uptake was detectable in activated T cells and macrophages, and there was significant PDT-induced increase in the number of apoptotic cells in the synovium.

CONCLUSION

Because photodynamic therapy is both specific and noninvasive, our findings suggest that it could be used for treating arthritic joints in humans.