Cutaneous Injuries From an Nd:YAG Laser Directed-Energy Source Utilizing a Murine Model

Background: Directed-energy sources such as Q-switched Nd:YAG lasers are widely used in clinical, cosmetic, and military settings, yet no standardized animal model exists for cutaneous laser burn injury. This pilot study aims to establish a reproducible murine laser burn model and qualitatively characterize the progressive histologic severity in cutaneous injury associated with increasing laser exposure duration. Methods: Laser burns were created on the back skin of anesthetized mice using a Q-switched Nd:YAG laser at a fixed fluence (12 J/cm 2 ) and spot size (3 mm), with exposure times of 5, 10, 15, and 30 seconds (s). Skin specimens were harvested 72 hours after laser application and evaluated histologically for collagen integrity, epidermal architecture, vascular changes, inflammatory infiltration, and adnexal structure preservation. Results: Laser exposure induced a time-dependent continuum of injury. Early exposures (5 and 10 s) produced first-degree burn injury with some degree of epidermal disruption and intact dermal layer. In contrast, longer exposures (15 and 30 s) resulted in progressive collagen disorganization, epidermal detachment, adnexal and vascular injury, and eventual coagulative necrosis. Masson trichrome staining revealed increasing thermal stiffening and loss of collagen structure with longer laser application, highlighting progressive cutaneous injury. These findings were consistently reproduced in 2 mice. Conclusion: This pilot study qualitatively characterizes the histologic response of skin to Nd:YAG laser exposure and establishes a reproducible murine model for cutaneous directed-energy injury, providing a foundation for future quantitative and therapeutic studies.