@article{KollmannBuerkertMeiretal.2023,
  author    = {Kollmann, Catherine and Buerkert, Hannah and Meir, Michael and Richter, Konstantin and Kretzschmar, Kai and Flemming, Sven and Kelm, Matthias and Germer, Christoph-Thomas and Otto, Christoph and Burkard, Natalie and Schlegel, Nicolas},
  title     = {Human organoids are superior to cell culture models for intestinal barrier research},
  series = {Frontiers in Cell and Developmental Biology},
  volume    = {11},
  journal   = {Frontiers in Cell and Developmental Biology},
  issn      = {2296-634X},
  doi       = {10.3389/fcell.2023.1223032},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-357317},
  year      = {2023},
  abstract  = {Loss of intestinal epithelial barrier function is a hallmark in digestive tract inflammation. The detailed mechanisms remain unclear due to the lack of suitable cell-based models in barrier research. Here we performed a detailed functional characterization of human intestinal organoid cultures under different conditions with the aim to suggest an optimized ex-vivo model to further analyse inflammation-induced intestinal epithelial barrier dysfunction. Differentiated Caco2 cells as a traditional model for intestinal epithelial barrier research displayed mature barrier functions which were reduced after challenge with cytomix (TNFα, IFN-γ, IL-1ß) to mimic inflammatory conditions. Human intestinal organoids grown in culture medium were highly proliferative, displayed high levels of LGR5 with overall low rates of intercellular adhesion and immature barrier function resembling conditions usually found in intestinal crypts. WNT-depletion resulted in the differentiation of intestinal organoids with reduced LGR5 levels and upregulation of markers representing the presence of all cell types present along the crypt-villus axis. This was paralleled by barrier maturation with junctional proteins regularly distributed at the cell borders. Application of cytomix in immature human intestinal organoid cultures resulted in reduced barrier function that was accompanied with cell fragmentation, cell death and overall loss of junctional proteins, demonstrating a high susceptibility of the organoid culture to inflammatory stimuli. In differentiated organoid cultures, cytomix induced a hierarchical sequence of changes beginning with loss of cell adhesion, redistribution of junctional proteins from the cell border, protein degradation which was accompanied by loss of epithelial barrier function. Cell viability was observed to decrease with time but was preserved when initial barrier changes were evident. In summary, differentiated intestinal organoid cultures represent an optimized human ex-vivo model which allows a comprehensive reflection to the situation observed in patients with intestinal inflammation. Our data suggest a hierarchical sequence of inflammation-induced intestinal barrier dysfunction starting with loss of intercellular adhesion, followed by redistribution and loss of junctional proteins resulting in reduced barrier function with consecutive epithelial death.},
  language  = {en}
}
@article{KannapinSchmitzHansmannetal.2021,
  author    = {Kannapin, Felix and Schmitz, Tobias and Hansmann, Jan and Schlegel, Nicolas and Meir, Michael},
  title     = {Measurements of transepithelial electrical resistance (TEER) are affected by junctional length in immature epithelial monolayers},
  series = {Histochemistry and Cell Biology},
  volume    = {156},
  journal   = {Histochemistry and Cell Biology},
  number    = {6},
  issn      = {1432-119X},
  doi       = {10.1007/s00418-021-02026-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-267465},
  pages     = {609-616},
  year      = {2021},
  abstract  = {The measurement of transepithelial electrical resistance (TEER) is a common technique to determine the barrier integrity of epithelial cell monolayers. However, it is remarkable that absolute TEER values of similar cell types cultured under comparable conditions show an immense heterogeneity. Based on previous observations, we hypothesized that the heterogeneity of absolute TEER measurements can not only be explained by maturation of junctional proteins but rather by dynamics in the absolute length of cell junctions within monolayers. Therefore, we analyzed TEER in epithelial cell monolayers of Caco2 cells during their differentiation, with special emphasis on both changes in the junctional complex and overall cell morphology within monolayers. We found that in epithelial Caco2 monolayers TEER increased until confluency, then decreased for some time, which was then followed by an additional increase during junctional differentiation. In contrast, permeability of macromolecules measured at different time points as 4 kDA fluorescein isothiocyanate (FITC)-dextran flux across monolayers steadily decreased during this time. Detailed analysis suggested that this observation could be explained by alterations of junctional length along the cell borders within monolayers during differentiation. In conclusion, these observations confirmed that changes in cell numbers and consecutive increase of junctional length have a critical impact on TEER values, especially at stages of early confluency when junctions are immature.},
  language  = {en}
}