title: Comparison of in vivo immune responses following transplantation of vascularized and non-vascularized human dermo-epidermal skin substitutes.
abstract: OBJECTIVE
  Autologous bio-engineered dermo-epidermal skin substitutes (DESS) represent an alternative therapeutic option for a definitive treatment of skin defects in human patients. Largely, the interaction of host immune cells with transplanted DESS is considered to be essential for the granulation tissue formation, graft take, and its functionality. The aim of this study was to compare the spatiotemporal distribution and density of host-derived monocytes/macrophages and granulocytes in vascularized (vascDESS) versus non-vascularized DESS (non-vascDESS) in a rat model.
  
  
  METHODS
  Keratinocytes and the stromal vascular fraction (SVF) were derived from human skin or human adipose tissue, respectively. Human SVF containing both endothelial and mesenchymal/stromal progenitors was used to develop a vascularized collagen type I-based dermal component in vitro. The donor-matched, monolayer-expanded adipose stromal cells lacking endothelial cells were used as a negative control. Subsequently, human keratinocytes were seeded on top of hydrogels to build dermo-epidermal skin grafts. After transplantation onto full-thickness skin wounds on the back of immuno-incompetent rats, grafts were excised and analyzed after 1 and 3 weeks. The expression of distinct inflammatory cell markers specific for host-derived monocytes/macrophages (CD11b, CD68) or granulocytes (HIS48) was analyzed by immunofluorescence microscopy.
  
  
  RESULTS
  All skin grafts were infiltrated by host-derived monocytes/macrophages (CD11b+, CD68+) and granulocytes (HIS48+) between 1-3 week post-transplantation. When compared to non-vascDESS, the vascDESS showed an increased granulocyte infiltration at all time points analyzed with the majority of cells scattered throughout the whole dermal part. Whereas a moderate number of rat monocytes/macrophages (CD11b+, CD68+) were found in vascDESS at 1 week, only a few cells were detected in non-vascDESS. We observed a time-dependent decrease of monocytes/macrophages in all transplants at 3 weeks.
  
  
  CONCLUSIONS
  These results demonstrate a distinct spatiotemporal distribution of monocytes/macrophages as well as granulocytes in our transplants that closely resemble the one observed during physiological wound healing. The differences identified between vascDESS and non-vascDESS may indicate that human endothelial cells lining blood capillaries of vascDESS accelerate infiltration of monocytes and leukocytes.
authors.affiliation: Tissue Biology Research Unit, University Children's Hospital Zurich, Zurich, Switzerland.|Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
authors.forename: Agnes S
authors.initials: AS
authors.lastname: Klar
authors.affiliation: Tissue Biology Research Unit, University Children's Hospital Zurich, Zurich, Switzerland.|Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Biedermann
authors.affiliation: Department of Plastic, Reconstructive, Aesthetical, and Hand Surgery, Kantonsspital Aarau, Aarau, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Simmen-Meuli
authors.affiliation: Tissue Biology Research Unit, University Children's Hospital Zurich, Zurich, Switzerland.|Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland.
authors.forename: Ernst
authors.initials: E
authors.lastname: Reichmann
authors.affiliation: Department of Surgery, University Children's Hospital Zurich, Steinwiesstrasse 75, 8032, Zurich, Switzerland. martin.meuli@kispi.uzh.ch.|Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland. martin.meuli@kispi.uzh.ch.
authors.forename: Martin
authors.initials: M
authors.lastname: Meuli
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D020100:Hydrogels; D007109:Immunity / Q000276:immunology; D007223:Infant; D008297:Male; D008875:Middle Aged; D023421:Models, Animal; D051381:Rats; D012867:Skin / Q000098:blood supply* / Q000276:immunology*; D016038:Skin Transplantation / Q000379:methods*; D017768:Skin, Artificial; D023822:Tissue Engineering / Q000379:methods*; D055815:Young Adult
chemical_list: D020100:Hydrogels
keywords: Bio-engineered human skin graft; Granulocyte infiltration; Inflammatory tissue response; Macrophage recruitment; Skin vascularization