title: TUNEL assay for histopathologic evaluation of irreversible chromosomal damage following nonablative fractional photothermolysis.
abstract: BACKGROUND
  Fractional photothermolysis is extremely popular in skin rejuvenation and remodeling procedures. However, the extent of thermal cellular injury beyond the borders of the coagulated microcolumns produced with fractional phototherapy is undefined.
  
  
  METHODS
  Six abdominoplasty patients were pretreated with the Lux1540 Fractional Erbium device (Palomar, Inc., Burlington, Mass.) at various clinical laser settings. After tissue excision, the panni were immediately biopsied. Biopsy specimens were fixed in formalin, embedded in paraffin, sectioned, and evaluated with the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) procedure for cellular necrosis/apoptosis. Tissue was sectioned horizontally and longitudinally to help define the depth and distribution of the microcolumns of injury in a three-dimensional plane.
  
  
  RESULTS
  The extent of cellular necrosis/apoptosis at variable depths within the epidermis and dermis was demonstrated successfully with the TUNEL technique. After the Lux1540 treatment, TUNEL-positive nuclei were identified in a vertically oriented fashion that extended from the epidermis into the papillary and reticular dermis, highlighting the areas of injury. The TUNEL-positive nuclei defined lesions that were approximately 175 to 225 microm in diameter and penetrated to variable depths (200 to 900 microm), depending on the fluence used for treatment (18 to 100 mJ).
  
  
  CONCLUSIONS
  TUNEL immunofluorescent labeling provided an accurate assessment of cellular damage within and surrounding the microthermal zones of coagulated collagen with respect to column depth and width. Because of its specificity, the TUNEL assay can be a useful adjunct to other histologic stains used to characterize cellular damage and matrix denaturation in skin treated with any fractional ablative or nonablative laser device.
authors.affiliation: Dallas, Texas From the Department of Plastic Surgery, Clinical Center for Cosmetic Laser Treatment, and the Departments of Pathology and Environmental Health and Safety, University of Texas Southwestern Medical Center at Dallas.
authors.forename: Jordan P
authors.initials: JP
authors.lastname: Farkas
authors.forename: James A
authors.initials: JA
authors.lastname: Richardson
authors.forename: John E
authors.initials: JE
authors.lastname: Hoopman
authors.forename: Spencer A
authors.initials: SA
authors.lastname: Brown
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Kenkel
mesh_terms: D000005:Abdomen / Q000473:pathology / Q000601:surgery; D017209:Apoptosis / Q000528:radiation effects; D001706:Biopsy; D025063:Chromosome Disorders / Q000209:etiology* / Q000473:pathology*; D020405:Dermis / Q000293:injuries / Q000473:pathology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004817:Epidermis / Q000293:injuries / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D020287:In Situ Nick-End Labeling; D053685:Laser Therapy / Q000009:adverse effects*; D008856:Microscopy, Fluorescence; D009336:Necrosis