title: The effect of endothelialization on the epidermal differentiation in human three-dimensional skin constructs - A morphological study.
abstract: BACKGROUND
  Inducing vascularization in three-dimensional skin constructs continues to be difficult. In this study, two variations of human full-thickness skin constructs were examined. Type KCFB consists of keratinocytes (epidermal equivalent) and fibroblasts that were embedded in a collagen matrix (dermal equivalent). Type KCFB-EC consists of keratinocytes as well as fibroblasts and vascular endothelial cells. The epidermal equivalent of KCFB-EC constructs underwent cellular alterations in their differentiation possibly induced by the presence of endothelial cells. The objective of the study was to assess the effect of endothelial cells, i.e., endothelialization of the dermal equivalent on the differentiation of keratinocytes by comparing the morphology and ultrastructure of the two types of skin constructs, as well as to excised normal human skin.
  
  
  OBJECTIVE
  The differentiation of keratinocytes is influenced by the presence of endothelial cells.
  KCFB constructs (keratinocytes, fibroblasts) and KCFB-EC skin constructs(kera-tinocytes, fibroblasts, endothelial cells) were prepared according to Küchler et al. [25]. After two weeks, the skin constructs were processed for analysis by light microscopy (LM) and electron microscopy (TEM), followed by quantitative, semi-quantitative as well as qualitative assessment. For comparison, analysis by LM and TEM of excised normal human skin was also performed.
  
  
  RESULTS
  Both KCFB and KCFB-EC skin constructs and the human skin had all strata of stratified soft-cornified epidermis present. The comparison of the respective layers of the skin constructs brought the following characteristics to light: The KCFB-EC constructs had significantly more mitotic cells in the stratum spinosum, more cell layers in the stratum granulosum and more keratohyalin granules compared to KCFB skin constructs. Additionally, the epidermal architecture was unorganized in the endothelialized constructs and features of excessive epidermal differentiation appeared in KCFB-EC skin constructs.
  
  
  CONCLUSIONS
  The endothelialization of the dermal equivalent caused changes in the differentiation of the epidermis of KCFB-EC skin constructs that may be interpreted as an unbalanced, i.e., uncontrolled or enhanced maturation process.
authors.affiliation: Department of Veterinary Medicine, Institute for Veterinary Anatomy, Freie Universität Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Khiao In
authors.affiliation: Institute for Pharmacy, Pharmacology & Toxicology, Freie Universität Berlin, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Wallmeyer
authors.affiliation: Institute for Pharmacy, Pharmacology & Toxicology, Freie Universität Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Hedtrich
authors.affiliation: College of Veterinary Medicine, Murdoch University, Murdoch, WA, Australia.
authors.forename: K C
authors.initials: KC
authors.lastname: Richardson
authors.affiliation: Department of Veterinary Medicine, Institute for Veterinary Anatomy, Freie Universität Berlin, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Plendl
authors.affiliation: Department of Veterinary Medicine, Institute for Veterinary Anatomy, Freie Universität Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Kaessmeyer
mesh_terms: D002454:Cell Differentiation; D003094:Collagen; D042783:Endothelial Cells / Q000502:physiology*; D004817:Epidermis / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology*; D006801:Humans; D015603:Keratinocytes / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000502:physiology; D012867:Skin / Q000098:blood supply*; D046509:Tissue Culture Techniques
chemical_list: D003094:Collagen
keywords: Full-thickness skin constructs; endothelial cell; epidermis; fibroblast; human skin; keratinocyte