Study on Photodynamic Therapy with 8-MOP for Oral Mucosal Disease

Abstract

Psoralen ultraviolet A (PUVA) therapy using the cytotoxicity of ultraviolet radiation combined with 8-methoxypsoralen (8-MOP) is performed in the field of dermatology. As there are many disorders common to the oral mucosa and skin, treatments for refractory disorders of the skim may also be applicable to oral mucosal disorders. We, therefore, performed phototoxicity tests using 8-MOP primarily on cultured cells from oral tissues.

The cell lines used were the mouse Balb/3T3, rat osteosarcoma UMR-106, rat squamous cell carcinoma SCC-158, human oral squamous cell carcinoma HSC-2, and human tongue squamous cell carcinoma HSC-3 and HSC-4. 8-MOP was added to the culture medium in 2-dimensional culture and 3-dimensional culture using porcine Type I collagen gel. The cells were irradiated with ultraviolet light at 375 nm using an LED irradiation system. The control group was not irradiated. After 24-hour static culture, the cell survival rate was determined by MTT assay.

In 2-dimensional culture, strong phototoxicity tended to be observed in cells derived from tumors. In 3-dimensional culture, phototoxicity varied in strength among cell types, and it was milder than in 2-dimensional culture, suggesting insufficient transmission of ultraviolet light to cells through the collagen gel. In cultured cells derived from tumors, the effects of photoirradiation varied among cell lines. As collagen may have inhibited transmission of ultraviolet light, a method to more efficiently deliver ultraviolet light to cells in deep areas of the body is needed.