Biological effects of a new ultraviolet A1 prototype based on light-emitting diodes on the treatment of localized scleroderma

Ultraviolet A₁ (UVA₁) phototherapy (spectral range 340-400 nm) is a well-established treatment option for various skin diseases such as localized scleroderma. Recent improvements of conventional UVA₁ light sources (metal-halide or fluorescent lamps) have brought attention to a new light-emitting diode (LED) technology with remarkable advantages in handling and clinical routine. This study provides a preclinical histological and molecular evaluation of an LED-based UVA₁ prototype with a narrower spectral range (360-400 nm) for treating localized scleroderma. Scleroderma mouse models and fibroblasts in vitro were exposed to LED-based UVA₁ phototherapy or to irradiation with a commercially available metal-halide lamp emitting low-dose (20, 40 J/cm²), medium-dose (60 J/cm²) and high-dose (80, 100 J/cm²) UVA₁ light. Both UVA₁ light sources affected inflammatory genes (IL-1α and IL-6) and growth factors (TGFß-1 and TGFß-2). Increased collagen type 1 was reduced after UVA₁ phototherapy. Matrix metalloproteinase-1 was more enhanced after a medium dose of LED-based UVA₁ phototherapy than after conventional treatment. In vivo, dermal thickness and the amount of collagen were reduced after both treatment methods. Remarkably, myofibroblasts were more effectively reduced by a medium dose of LED-based UVA₁ phototherapy. The study indicates that LED-based UVA₁ phototherapy yields similar or even better results than conventional treatment. In terms of biosafety and patient comfort, LED-based UVA₁ phototherapy offers clear advantages over conventional treatment because of the use of a narrower and less harmful UVA₁ spectrum, less heat generation and shorter treatment times at the same irradiation intensity. Clinical studies are required to confirm these results in patients with localized scleroderma.