Vibrational microspectroscopic imaging of normal, wounded, and artificial skin. I.Wound characterization in skin punch biopsies and diabetic foot ulcers. II. Molecular organization of human skin equivalents
Creators: name: Yu, Guo
Publisher: name: No Publisher Supplied
Year: 2013

description: Vibrational microspectroscopy and imaging offer several advantages for dermatological research, including drug permeation, monitoring of metabolism in vivo, and characterization of skin components. Applications of this technology to the investigation of wound healing in an ex vivo skin punch biopsy and in diabetic foot ulcers are demonstrated in this thesis, along with a comparison of the skin barrier in native skin and in human skin equivalents.  Three projects are described herein. The first is the study of lipid conformation in the migrating epithelial tongue during wound healing. The spatial distribution of lipid structure in an ex vivo skin wound healing model was studied using infrared microscopic imaging. Infrared images of samples at different times post wounding (Day 0, 2, 4 and 6) were collected and analyzed. The presence of a lipid class with disordered chains within and in the vicinity of the migrating epithelial tongue (MET) was revealed by analyzing spectra and spectral images of skin samples. The symmetric and asymmetric CH2 stretching frequencies revealed the presence of disordered lipid phases while factor analysis of spectral regions of lipids and univariate analysis of spectral regions provide the information concerning the spacial distribution of the lipids. Gene array analysis also provides evidence for an increase of an unsaturated lipid population. It is hypothesized that this lipid population increase might involve the epidermal growth factor receptor (EGFR) and that this lipid may play a role in controlling the migration of the MET and restoration of barrier functions at the wound site.   The second application concerns wound healing in diabetic foot ulcer (DFU). Wound healing in this pathological state is hindered by factors such as glycation of proteins and delayed inflammatory response; these factors also alter the structure and function of the wounded tissue itself. Our study revealed spectral differences between the healing DFU and non-healing DFU samples which were traced to glycation probably of keratin. These results might provide a better understanding wound healing mechanisms in this pathological state.  In the third project, vibrational microspectroscopy was applied to compare barrier physical properties in native and artificial skin. Barrier properties of human skin, pigskin, and two human skin equivalents (HSE), “Epiderm”TM 200X with an enhanced barrier, and “Epiderm”TM 200 with a normal barrier were studied. IR spectra reveal that the human stratum corneum (SC) contains a large portion of orthorhombically packed lipid chains at physiological temperature. However, this lipid packing motif occurs to a much lower extent or is absent entirely in pig skin and HSE. Confocal Raman microscopy revealed increased levels of cholesterol-enriched pockets within the HSE samples compared with native tissue. Taken together, these findings provide a useful set of experiments for preliminary characterization of HSE structure.