Terminal Deoxynucleotidyl Transferase-Mediated Deoxyuridine Triphosphate Nick End Labeling (TUNEL) Assay to Characterize Histopathologic Changes Following Thermal Injury

Abstract

Background: Despite the wide application of lasers and radiofrequency (RF) surgery in dermatology, it is difficult to find studies showing the extent of damage dependent on cell death.

Objective: We evaluated histopathologic changes following in vivo thermal damage generated by CO₂ laser, 1,444 nm long-pulsed neodymium:yttrium-aluminum-garnet (LP Nd:YAG) laser and RF emitting electrosurgical unit.

Methods: Thermal damage was induced by the above instruments on ventral skin of rat. Specimens were stained with hematoxylin and eosin, along with a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay, to highlight the degree of irreversible cellular injury.

Results: The volume of vaporization was largest with the CO₂ laser. Area of cell death area identified by TUNEL assay, when arranged from widest to narrowest, was 1,444 nm LP Nd:YAG laser, CO₂ laser, and RF emitting electrosurgical unit.

Conclusion: This histopathologic evaluation of the acute characterization of injury across devices may be advantageous for attaining better treatment outcomes.

Keywords: Carbon dioxide lasers; In situ nick-end labeling; Neodymiumdoped yttrium aluminum garnet lasers; Radiofrequency; Thermal destruction.

Fig. 1. Corresponding hematoxylin and eosin (H&E; A, C, E, ×20) and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-stained (B, D, F, ×20) histological skin sections following treatment with the CO₂ laser (A, B), 1,444 nm long-pulsed neodymium:yttrium-aluminum-garnet (C, D), and radiofrequency emitting electrosurgical unit (E, F). Note the bright yellow/green cells in the TUNEL-stained sections highlighting the necrotic cells within the treated section.

Fig. 2. Thermal effects of ablative laser and radiofrequency irradiation. (A) CO₂ laser and radiofrequency emitting electrosurgical unit. (B) 1,444 nm long-pulsed neodymium:yttrium-aluminum-garnet (LP Nd:YAG). 1,444 nm LP Nd:YAG laser resulted in smaller vaporized tissue volume and more extensive necrosis and coagulation compared with CO₂ laser and radiofrequency device.