Objective: Mesenchymal-epithelial transition may have crucial role in mucosal regeneration, hence we assayed epithelial growth factor receptor (EGFR), insulin-like growth factor receptor-1 (IGF1R), hepatocyte-derived growth factor receptor (HGFR), CDX2 and cytokeratin (CK) expression in lymphoid aggregates (LA) of ulcerative colitis (UC).
Material and methods: Tissue microarrays (TMAs) made of biopsy samples from 20 mildly, 20 moderately and 20 severely active UC, 12 non-specific colitis (NSC) and 20 healthy colon were prepared, and immunolabelled with anti-EGFR, -IGF1R, -HGFR, -CDX2, -CK antibodies. After virtual microscopic evaluation, one-way ANOVA and correlation analysis were performed. For validation, TaqMan real-time RT-PCR was performed by using RNA from laser microdissected LA from 10 healthy colon and 10 endoscopically active UC biopsies.
Results: The number of LA was in tight positive correlation with the severity of inflammation (r=0.9). The number of EGFR/HGFR positive subepithelial cells was found to be significantly elevated in severe (21.6+/-2.1%/21.3+/-1.9%), moderate (14.3+/-1.7%/14.6+/-1.6%) and mild (7.2+/-1.6%/7.4+/-1.3%) inflammation compared to healthy colon mucosa (2.6+/-1.4%/2.4+/-1.03%) (p < 0.005). Some alterations were found between UC and NSC samples regarding EGFR and HGFR expression. IGF1R immunoreactive cells were only found in a trace number in all cases. Increasing trend of CDX2 and CK positive subepithelial cells was found in active UC, but it was not in significant correlation with the severity of inflammation.
Conclusion: EGFR and HGFR positive subepithelial cells in LA may be involved in the induction of the regenerative mucosal processes. The presence of CDX2/CK positive subepithelial cells suggests that mesenchymal-to-epithelial transition may be located to lymphoid aggregates.