title: A new organotypic model to study cell interactions in the intestinal mucosa.
abstract: BACKGROUND
  Recently, we demonstrated that freshly elutriated monocytes differentiate into macrophages with a phenotype similar to that of intestinal macrophages in a three-dimensional model of intestinal epithelial cells. Here we describe a more organotypic model to study cell interactions in the intestinal mucosa.
  
  
  METHODS
  Primary intestinal fibroblasts and freshly elutriated blood monocytes (ratio 1:1) were embedded in collagen type I gels and cultured for 5 days. At day 5, intestinal epithelial cells (HT-29) were seeded on top of the collagen gels. After another 7 days collagen gels were harvested and fixed for immunohistochemical analysis. Cryosections of the aggregates were prepared and staining for monocyte/macrophage markers and basement membrane compounds was performed. Cell interactions inside the aggregates were examined by electron microscopy.
  
  
  RESULTS
  Intestinal fibroblasts contracted the collagen gels which formed stable three-dimensional aggregates within the first 5 days of culture. Intestinal epithelial cells formed a monolayer on top of the gels about 3 days after seeding. Intestinal fibroblasts were distributed randomly over the aggregate. Monocytes inside aggregates were localized in the vicinity to epithelial cells by positive staining for CD68. Typical monocyte/macrophage specific markers such as CD14, CD16, CD11b, CD11c and the co-stimulatory molecules CD80 and CD86 were down-regulated or not detectable on these cells after co-culture in three-dimensional aggregates. Omission of epithelial cells from the model was followed by impaired differentiation of intestinal macrophages.
  
  
  CONCLUSIONS
  In the three-dimensional organotypic cell culture model monocytes differentiate into intestinal-like macrophages when co-cultured with control intestinal fibroblasts and intestinal epithelial cells. Intestinal epithelial cells may be necessary for differentiation of intestinal macrophages.
authors.affiliation: Department of Internal Medicine I, University of Regensburg, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Spottl
authors.forename: Martin
authors.initials: M
authors.lastname: Hausmann
authors.forename: Manuela
authors.initials: M
authors.lastname: Gunckel
authors.forename: Hans
authors.initials: H
authors.lastname: Herfarth
authors.forename: Meenhard
authors.initials: M
authors.lastname: Herlyn
authors.forename: Juergen
authors.initials: J
authors.lastname: Schoelmerich
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
mesh_terms: D002450:Cell Communication / Q000502:physiology*; D018929:Cell Culture Techniques; D024042:Collagen Type I; D004847:Epithelial Cells / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology*; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology*; D008954:Models, Biological; D009000:Monocytes / Q000502:physiology*
chemical_list: D024042:Collagen Type I