Molecular Signature of Persistent Histological Inflammation in Ulcerative Colitis with Mucosal Healing

Therapeutic targets in ulcerative colitis (UC) have evolved over time from clinical remission to biological and endoscopic remission. Histologic remission remains a debatable outcome due to lack of data regarding its impact on long-term evolution. The development of histologic activity scores has brought standardization. We aimed to identify mucosal markers differentiating histological inflammation from histological remission in UC patients.

The gene expression levels of 84 genes associated with inflammatory bowel diseases have been analyzed in 43 colonic mucosa samples from 30 patients with UC. The gene expression levels have been correlated with histological inflammation score of Geboes. Patients with endoscopic remission were divided by histological activity into two groups and molecular results were compared in order to identify differences in the mucosal gene expression.

We found a significant Pearson correlation (p<0.001 and r>0.5) between the Geboes score and the expression of 29 genes, whereas negative correlation (p<0.001 and r<-0.50) was observed with two genes in the entire UC cohort. In the subgroup of patients with endoscopic remission three transcripts: formyl-peptide receptor 1 (FPR1), matrix metalloproteinases 1 (MMP1) and mucine 1 (MUC1) were significantly up-regulated in patients with histological inflammation compared to patients with histologic remission.

Our study further emphasizes the importance of histological assessment when endoscopic mucosal healing is present, as FPR1, MMP-1 and MUC1 were all significantly upregulated in patients with histological alterations.