Work

Development of a Near-Infrared Laser Device to Establish a Preliminary Grading Scale for Photothermal Skin Injury in Rodents

Year: 2026

Type: article

Abstract: Purpose: Studies using animal models of laser-induced photothermal skin injury often report nominal rather than delivered laser output and assess lesions primarily shortly after exposure. A grading system that relates visible lesions to tissue damage throughout repair is also lacking. This study established a model in three rodent species using a characterized 808-nm laser and developed a five-grade scale for longitudinal assessment. Patients and Methods: An in-house 808-nm continuous-wave diode laser was characterized by its emission spectrum, beam profile, power linearity across 2-10-W settings, and output stability over 180-s exposures. Female Hartley guinea pigs (n = 4), Sprague-Dawley rats (n = 4), and BALB/c mice (n = 20) were irradiated at a 7-W setting for 180s. Lesions were photographed from 1 h after irradiation to day 28, with histological assessment on days 2, 7, 14, and 28. Three observers independently graded 60 images per species. Results: = 0.9997). At the 7-W setting, delivered power was 4.63 W, with within-run instability below 0.4%. Gross injury peaked on days 1-2, 2-3, and 3-4 in guinea pigs, rats, and mice, respectively. Lesions in all three species had re-epithelialized by day 28. At 1 h, the proportions of sites with Grade 2 or 3 injury were 58.3%, 75.0%, and 85.0%, respectively. Higher grades corresponded to deeper histological injury. Kendall's W was 0.81-0.90 (all nominal P < 0.001), and mean weighted κ was 0.42-0.49. Conclusion: This study established a photothermal skin injury model in three rodent species using an 808-nm laser with measured, stable output. The preliminary five-grade scale relates gross appearance to histological injury depth and can support longitudinal assessment of injury and repair.

Source: Clinical Cosmetic and Investigational Dermatology

DOI: 10.2147/ccid.s646914