title: UV fluorescence excitation imaging of healing of wounds in skin: Evaluation of wound closure in organ culture model.
abstract: Molecules native to tissue that fluoresce upon light excitation can serve as reporters of cellular activity and protein structure. In skin, the fluorescence ascribed to tryptophan is a marker of cellular proliferation, whereas the fluorescence ascribed to cross-links of collagen is a structural marker. In this work, we introduce and demonstrate a simple but robust optical method to image the functional process of epithelialization and the exposed dermal collagen in wound healing of human skin in an organ culture model.
  
  
  
  Non-closing non-grafted, partial closing non-grafted, and grafted wounds were created in ex vivo human skin and kept in culture. A wide-field UV fluorescence excitation imaging system was used to visualize epithelialization of the exposed dermis and quantitate wound area, closure, and gap. Histology (H&E staining) was also used to evaluate epithelialization.
  
  
  
  The endogenous fluorescence excitation of cross-links of collagen at 335 nm clearly shows the dermis missing epithelium, while the endogenous fluorescence excitation of tryptophan at 295 nm shows keratinocytes in higher proliferating state. The size of the non-closing wound was 11.4 ± 1.8 mm and remained constant during the observation period, while the partial-close wound reached 65.5 ± 4.9% closure by day 16. Evaluations of wound gaps using fluorescence excitation images and histology images are in agreement.
  
  
  
  We have established a fluorescence imaging method for studying epithelialization processes, evaluating keratinocyte proliferation, and quantitating closure during wound healing of skin in an organ culture model: the dermal fluorescence of pepsin-digestible collagen cross-links can be used to quantitate wound size, closure extents, and gaps; and, the epidermal fluorescence ascribed to tryptophan can be used to monitor and quantitate functional states of epithelialization. UV fluorescence excitation imaging has the potential to become a valuable tool for research, diagnostic and educational purposes on evaluating the healing of wounds. Lasers Surg. Med. 48:678-685, 2016. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachussets.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Centro de Ciencias Aplicadasy Desarrollo Tecnológico, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico.
authors.forename: Enoch
authors.initials: E
authors.lastname: Gutierrez-Herrera
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachussets.
authors.forename: Antonio
authors.initials: A
authors.lastname: Ortega-Martinez
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachussets.
authors.forename: Richard Rox
authors.initials: RR
authors.lastname: Anderson
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachussets.
authors.forename: Walfre
authors.initials: W
authors.lastname: Franco
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D006801:Humans; D061848:Optical Imaging / Q000379:methods*; D009924:Organ Culture Techniques; D062326:Re-Epithelialization / Q000502:physiology*; D012867:Skin / Q000000981:diagnostic imaging* / Q000293:injuries / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D015415:Biomarkers; D003094:Collagen
keywords: UV; autofluorescence; collagen; epithelialization; imaging; skin; wound healing