Epithelial down‐regulation of the miR‐200 family in fibrostenosing Crohn's disease is associated with features of epithelial to mesenchymal transition

Abstract

Intestinal mesenchymal cells deposit extracellular matrix in fibrotic Crohn's disease (CD). The contribution of epithelial to mesenchymal transition (EMT) to the mesenchymal cell pool in CD fibrosis remains obscure. The miR‐200 family regulates fibrosis‐related EMT in organs other than the gut. E‐cadherin, cytokeratin‐18 and vimentin expression was assessed using immunohistochemistry on paired strictured (SCD) and non‐strictured (NSCD) ileal CD resections and correlated with fibrosis grade. MiR‐200 expression was measured in paired SCD and NSCD tissue compartments using laser capture microdissection and RT‐qPCR. Serum miR‐200 expression was also measured in healthy controls and CD patients with stricturing and non‐stricturing phenotypes. Extra‐epithelial cytokeratin‐18 staining and vimentin‐positive epithelial staining were significantly greater in SCD samples (P = 0.04 and P = 0.03, respectively). Cytokeratin‐18 staining correlated positively with subserosal fibrosis (P < 0.001). Four miR‐200 family members were down‐regulated in fresh SCD samples (miR‐141, P = 0.002; miR‐200a, P = 0.002; miR‐200c, P = 0.001; miR‐429; P = 0.004); miR‐200 down‐regulation in SCD tissue was localised to the epithelium (P = 0.001‐0.015). The miR‐200 target ZEB1 was up‐regulated in SCD samples (P = 0.035). No difference in serum expression between patient groups was observed. Together, these observations suggest the presence of EMT in CD strictures and implicate the miR‐200 family as regulators. Functional studies to prove this relationship are now warranted.

Mechanism of fibrosis and stricture formation in Crohn's disease

“…Although fibrosis in the mucosa is relatively scarce, strictured mucosa displays changes in the staining pattern of mesenchymal cells. There is increased vimentin staining, predominantly in the peri‐cryptal region, and lamina propria 25 . This occurs together with extra‐muscular staining of α‐SMA, 13 especially in the peri‐cryptal area 12,15 .…”

“…This is based on observations that strictures show alterations in EMT-associated markers. 21,25,40,64 For example, several papers describe lower expression of epithelial cell markers (and/or increased extra-epithelial staining of such a marker) in stricture mucosa concomitant with increases in markers for mesenchymal cells or EMT onset. However, the contribution of EMT to the population of myofibroblasts in other fibrotic diseases has been questioned.…”

“…miRs are non‐coding RNAs that exert post‐transcriptional silencing of gene expression, and if dysregulated, can potentially influence critical pathogenic pathways. In particular, strictures show downregulation of the miRNA‐200 family 25 (including miR‐141, miR‐200, and miR‐429), as well as the miRNA‐29 family 35 (Figure 4A and B). Downregulation of these gene silencers is interesting, especially as both miRNA families are suggested to interfere with TGF‐β1 signalling, which, as mentioned above, is an important pro‐fibrotic factor.…”

“…In addition to fibroblasts and pericytes, epithelial cells, through an epithelial‐to‐mesenchymal transition (EMT), have also been suggested to aid in the generation of myofibroblasts in strictures (Figure 3: ⑧, and Figure 5B: ③). This is based on observations that strictures show alterations in EMT‐associated markers 21,25,40,64 . For example, several papers describe lower expression of epithelial cell markers (and/or increased extra‐epithelial staining of such a marker) in stricture mucosa concomitant with increases in markers for mesenchymal cells or EMT onset.…”

MicroRNA gga-miR-200a-3p modulates immune response via MAPK signaling pathway in chicken afflicted with necrotic enteritis

“…It was also involved in protecting thymosin β-4 in cardiac microvascular endothelial cells following hypoxia/reoxygenation injury via the NRF2 antioxidant pathway [13]. Moreover, expression of miR-200a was downregulated in fibrostenosing Crohn's disease [14], HBV-induced hepatocellular carcinoma [15] and human glioma [16], thereby highlighting its function as a suppressor of many diseases. In chicken, gga-miR-200a regulated cell differentiation and proliferation of breast muscle by target 3′-UTR of GRB2 [17].…”