INFLUENCE OF LIGHT DELIVERY ON PHOTODYNAMIC SYNOVECTOMY IN AN ANTIGEN-INDUCED ARTHRITIS MODEL FOR RHEUMATOID-ARTHRITIS

Background and Objective: Minimally invasive synovectomy techniques ha ve been unsuccessful due to lack of selectivity. The purpose of this s tudy was to evaluate the potential of photodynamic therapy to destroy diseased synovium in an antigen-induced arthritis model. Study Design/ Materials and Methods: Three sets of experiments evaluated the biodist ribution and treatment effects of Photofrin (PF) in rabbits with bilat eral knee antigen-induced arthritis. The first set of experiments eval uated the biodistribution of PF in articular tissues of 30 rabbits fro m 6-72 hours after systemic injection of 2 mg/kg. In the second series of experiments, light was delivered to the knee joint via cleaved opt ical fibers, whereas for the third, light was delivered via a 600 mu m diffusion tip fiber. Tissues were harvested at 2 and 4 weeks posttrea tment. Results: The biodistribution experiments demonstrated maximal u ptake in inflamed synovium at 48 hours and a lack of uptake in normal tissues. With bare cleaved fibers, necrosis was observed in one specim en at 2 weeks and was absent in all specimens at 4 weeks. In the third experiment, synovial necrosis was observed in 3 of 7 specimens at 2 w eeks and 3 of 8 at 4 weeks. No damage to articular cartilage or periar ticular tissues was seen with either mode of light delivery. Conclusio n: These studies indicate that selective destruction of synovium can b e achieved with PF and suggest that optimization of light delivery tec hniques will play an important role in development of this new techniq ue. (C) 1998 Wiley-Liss, Inc.