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 ph otodynamic therapy (tPDT) in rabbits with antigen-induced arthritis (A IA). 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 joi nt to light. BPD uptake and PDT-induced apoptosis of the synovium was studied applying fluorescence confocal microscopy and immunohistochemi stry. The (histo)pathology of the joints was assessed at day 28. Resul ts. Treatment with tPDT resulted in significant amelioration of synovi al inflammation and an almost complete prevention of pannus formation and bone and cartilage destruction. BPD uptake was detectable in activ ated T cells and macrophages, and there was significant PDT-induced in crease in the number of apoptotic cells in the synovium. Conclusion. B ecause photodynamic therapy is both specific and noninvasive, our find ings suggest that it could be used for treating arthritic joints in hu mans.