title: Tissue engineering of endothelial cells and the immune response.
abstract: BACKGROUND
  While tissue engineering offers promise for organ and tissue transplantation, it can also be used to examine transplant and immune biology. Endothelial cells engrafted within 3-dimensional matrices create stable units that produce all of the factors of a functional quiescent endothelium. Perivascular implantation of tissue engineered endothelial cell constructs provides long-term control of vascular repair after injury. This control is established without restoration of the natural luminal:mural endothelium, and most intriguingly, without engendering host allo- and xenogeneic immune responses. We examined how endothelial immunogenicity is controlled by interaction with 3-dimensional matrices.
  
  
  METHODS
  Human aortic endothelial cells (HAE) were either grown to confluence on polystyrene tissue culture plates or within 3-dimensional collagen-based matrices. Major histocompatibility complex (MHC) class II, integrin, interferon (IFN)-gamma receptor expression, and signaling were analyzed via confocal microscopy, flow cytometry, reverse transcription polymerase chain reaction (RT-PCR), and microarray. Splenocyte proliferation was assayed by thymidine incorporation.
  
  
  RESULTS
  Despite similar expression levels of IFN-gamma receptors, matrix-embedded HAE elicited far less STAT-1 phosphorylation upon IFN-gamma stimulation, and expressed 2-fold less MHC II than HAE grown to confluence on culture plates (P < .001). This effect correlated with reduced expression of integrin alpha(v) and beta(3) (P < .002), and muted proliferation of porcine splenocytes (P < .001).
  
  
  CONCLUSIONS
  Matrix architecture is critical for modulation of endothelial immunogenicity. Embedding HAE within a physiologic 3-dimensional environment affects activity of intracellular signaling pathways, MHC II expression, and subsequent activation of immune cells. These findings might offer novel insights into our understanding of endothelial-mediated diseases and might enhance our ability to leverage the potential for cell-based therapies.
authors.affiliation: Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. hmethe@mit.edu
authors.forename: H
authors.initials: H
authors.lastname: Methe
authors.forename: E R
authors.initials: ER
authors.lastname: Edelman
mesh_terms: D000818:Animals; D001011:Aorta; D018929:Cell Culture Techniques; D004730:Endothelium, Vascular / Q000166:cytology* / Q000276:immunology / Q000502:physiology* / Q000637:transplantation; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D007109:Immunity; D018613:Microscopy, Confocal; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D023822:Tissue Engineering / Q000379:methods*; D014183:Transplantation, Heterologous; D014184:Transplantation, Homologous