Background/Aims: TFF3, a member of the TFF (trefoil factor family) peptides, and epidermal growth factor (EGF) actively support the repair of mucosal barriers, particularly during restitution. The aim of this study was to compare the motogenic effects of TFF3 and EGF. Methods: The influence of recombinant human TFF3 (dimeric form) and EGF on the migration of IEC-18 cells was characterized in an in vitro restitution model (scratch wound assay) with the help of time-lapse video microscopy, morphometry, and immunocytochemistry including confocal laser scanning microscopy. Results: TFF3- and EGF-treated cells re-populated the wounded area via different migration patterns; TFF3 treatment resulted in the formation of continuous sheets of migrating cells with only a few gaps. In contrast, EGF-treated cells formed a network of migrating cells (often with a fibroblast-like morphology) with numerous gaps and only punctual contacts. TFF3 and EGF treatment also changed the localization of E-cadherin indicating endocytotic recycling and/or degradation of E-cadherin. Conclusion: TFF3, in contrast to EGF, enhanced a collective cell migration ensuring a precise coverage of the re-populated area avoiding gaps.

Rapid repair by cell migration, a process called “restitution”, is essential for wound healing of mucous epithelia. Here, an established in vitro model for restitution, i.e., migration of the non-transformed intestinal epithelial cell line IEC-18 after scratch wounding, was investigated. This cell line is also known for its retained differentiation potential. The aim of this study was to test by expression profiling whether the differentiation state is altered during restitution in vitro. Using a sensitive RT-PCR method a systematic analysis of separated stationary and migratory cells was performed 48 h after in vitro wounding. Most characteristically, the differentiation state was changed in migratory cells when compared with stationary cells. For example, migratory cells lost markers of terminal differentiation and changed to a phenotype that assists the process of restitution by up-regulating the expression of genes such as plasminogen activator inhibitor-1, transforming growth factor α, heparin-binding EGF-like growth factor, α-smooth muscle actin, ornithine decarboxylase, and glyceraldehyde-3-phosphate dehydrogenase. However, there were no unequivocal signs of epithelial-mesenchymal transition (EMT) found in migratory cells.

To elucidate the participation of fetal rat liver cells in the receptor-mediated internalization of low-density lipoproteins (LDL), rat fetuses were injected with either LDL-gold or albumin-gold conjugates. The degree of binding and uptake of LDL-gold and albumin-gold by parenchymal and sinusoidal cells of the fetal rat liver differs markedly. Endothelial cells exhibit low LDL-gold uptake. In contrast, parenchymal cells internalize LDL-gold more actively (45 +/- 8 LDL conjugates/100 micrometers2 cytoplasm within 60 min). Kupffer cells exceed this value by a factor of 20. The uptake of albumin-gold by endothelial and Kupffer cells is high, whereas it is extremely low in parenchymal cells. Estradiol pretreatment causes a significant doubling (p less than 0.05) of the LDL-gold particle density/100 micrometers2 cytoplasm both in parenchymal and Kupffer cells, whereas estradiol has no effect on the albumin uptake. The results strongly indicate that LDL uptake by parenchymal and Kupffer cells in the fetal rat liver is mediated by estrogen-inducible receptors, which may correspond to B, E receptors in the adult liver.

The binding and uptake of gold-labeled homologous, apolipoprotein E-free low-density lipoproteins (LDL) by isolated fetal rat liver parenchymal cells in suspension were studied ultrastructurally and morphometrically. Binding experiments using 125I-labeled LDL were also performed. After a 2-h preincubation in a lipoprotein-free medium and a subsequent 1-h postincubation in the presence of LDL-gold, fetal liver parenchymal cells exhibit a binding of 248 +/- 17 gold conjugates/100 micron plasma membrane and an uptake of 235 +/- 17 gold conjugates/100 micron2 cytoplasm. Compared with values obtained from freshly isolated non-preincubated cells, these data correspond to a 15-fold and an 18-fold increase in total binding and uptake of LDL-gold, respectively. Competition experiments reveal that this increase is mainly a result of a 23-fold stimulation of specific binding and a 44-fold stimulation of receptor-mediated uptake of LDL-gold. The 125I-LDL binding experiments give a Kd value of 6.3 X 10(-8) M and a maximum binding capacity of 17.3 fmol LDL/10(6) cells. Our data provide evidence, further to our in vivo studies, that fetal rat liver parenchymal cells possess high-affinity binding sites for native homologous apolipoprotein E-free LDL. These sites may correspond to B, E receptors of adult rat liver parenchymal cells.

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