Isolated Fusobacteria Strains Induce Mucin Genes Dysregulation in Korean Inflammatory Bowel Disease Patients

Abstract

Background Fusobacteria has been suggested to play an important role in the colorectal cancer as well as inflammatory bowel disease (IBD). We tried to isolate Fusobacteria strains from the mucosal tissues of Korean IBD patients and to evaluate whether the isolated strains induce mucin and pro-inflammatory cytokine gene expression signatures in vitro assay.

Methods Colonic mucosal tissue samples were obtained from the active inflammation sites in 54 Korean IBD patients (29 CD and 24 ulcerative colitis [UC]). Tissue specimens were spread across the Fusobacteria-selective agar plates and incubated under anaerobic conditions. Isolates were identified on the basis of their growth on the selective medium and their identity was confirmed by use of 16S PCR and 16S rRNA sequencing analysis. Isolated bacterial strains were added to several colon cancer cell lines (HT-29, SW480, RKO, HCT116) with near confluence and incubated for 4 hours. RNA was prepared from monolayered cell lines and RT-PCR for pro-inflammatory cytokine and MUC2-6 genes were performed.

Results All of 262 isolates were identified by 16S rRNA gene sequencing. A total of 10 Fusobacterium spp. (7 F. mortiferum, 2 F. varium and 1 F. nucleatum) were isolated from active colonic mucosal tissues of 9 patients (16.7%) among 54 Korean IBD patients. Both F. mortiferum and F. varium strains increased MUC2, MUC5AC, and pro-inflammatory cytokine (IL-8) RNA expressions in colon cancer cell lines infected with these strains.

Conclusions Several Fusobacteria strains are isolated from the active colonic mucosal tissues of Korean IBD patients. Isolated Fusobacteria strains induce mucin and pro-inflammatory cytokine gene expression signatures in vitro assay, suggesting that Fusobacteria could alter innate host defenses through mucin and cytokine gene dysregulation in IBD.