Visualization of neo-epidermis formation and evaluation of wound closure using UV fluorescence excitation imaging at two wavelengths (Conference Presentation)

Abstract

UV Fluorescence Excitation Imaging (u-FEI) is able to visualize the re-epithelialization of skin wounds at 295 nm excitation wavelength. In this work, we investigated the feasibility of using u-FEI at 295 and 335 nm to visualize the formation of neo-epidermis and evaluate wound closure of partial and full-thickness skin wounds in an animal model. Partial and full-thickness skin wounds were created in the tail of rats. Wounds were imaged at different time points using u-FEI at 295/340 nm and 335/395 nm excitation/emission wavelengths, which correspond to the fluorescence ascribed to tryptophan moieties and pepsin-digestible collagen crosslinks. Because of their penetration depth, these wavelengths probe superficial and deeper fluorophores. Biopsies were collected at specific time points for histology and immunohistology analysis. Neo-epidermis had higher fluorescence intensity at 295 nm than normal skin and lasted one week in both partial and full-thickness skin wounds, then decreased to normal skin intensity values in partial-thickness wounds or decreased even further in full-thickness wounds. In contrast, the fluorescence from the 335 nm excitation band began to increase when the fluorescence at 295 nm was decreasing and show uniform fluorescence distribution when the wound was fully closed. H&E and immunohistology show that fluorescence intensity changes at 295 nm wavelength correlates with keratinocytes proliferation. The combined fluorescence at 295 and 335 nm excitation wavelengths may be useful in evaluating short and mid-term wound healing processes, in particular, formation of neo-epidermis and wound closure.