Transdermal photodynamic therapy—a treatment option for rheumatic destruction of small joints?

Abstract

Synovectomy of small joints is a therapeutic approach in patients suffering from rheumatoid arthritis (RA). We examined the feasibility of transdermal photodynamic therapy (tPDT) in a fibroblast-induced model of joint destruction using the novel photosensitizer (PS) tetrahydroporphyrin-tetratosylat that shows strong absorption at the near infra-red spectral region. The functionality of the PDT system was assessed in vitro. Following arthritis induction and PS application, tPDT was applied in vivo. Therapy results were evaluated by measuring joint swelling, serum amyloid A (SAA) and histologically. We were able to present a fully functional PDT in vitro. The in vivo therapy modalities were well tolerated by mice. We could demonstrate photodynamic ablation of subcutaneously located tissue (skeletal muscle) without skin damage. This study provides the basis for transdermal accessibility of tissue through a photodynamic process which may serve as a minimally invasive synovectomy strategy.