Background and Aims Ulcerative colitis (UC) is a chronic inflammatory disease of the colon with an intractable course. Although the goal of UC therapy is to achieve mucosal healing, the pathogenesis of mucosal injury caused by chronic inflammation remains unknown. We therefore aim to elucidate molecular mechanisms of mucosal injury by establishing in vitro and in vivo humanized UC mimicking models. Methods An in vitro model using human colon organoids was established by 60 weeks of inflammatory stimulation. The key gene for mucosal injury caused by long-term inflammation was identified by microarray analysis. An in vivo model was established by xenotransplantation of organoids into mouse colonic mucosa. Results An in vitro model demonstrated that long-term inflammation induced irrecoverable changes in organoids: inflammatory response and apoptosis with oxidative stress and suppression of cell viability. This model also mimicked organoids derived from patients with UC at the gene expression and phenotype levels. Microarray analysis revealed Schlafen11 (SLFN11) was irreversibly induced by long-term inflammation. Consistently, SLFN11 was highly expressed in UC mucosa but absent in normal mucosa. The knockdown of SLFN11 (SLFN11-KD) suppressed apoptosis of IECs induced by inflammation. Moreover, SLFN11-KD improved the take rates of xenotransplantation and induced regenerative changes of crypts observed in patients with UC in remission. Conclusions In vitro and in vivo UC mimicking models were uniquely established using human colonic organoids. They revealed SLFN11 is significant for mucosal injury in UC, and its potential as a novel target for mucosal regeneration.

Tumor protein p53 (TP53) mutation is a well-known occurrence at the late phase of carcinogenesis during the adenoma-carcinoma sequence of a sporadic colon cancer. Although numerous reports about clinical information of the patients with colon cancer have suggested that TP53 mutation might be related to various types of malignant potential, the direct effects of this mutation on the malignant potential of colon cancer remain unknown. Notably, no previous report has described a relationship between TP53 mutation and cancer stemness. We therefore aimed to assess the function of a TP53 mutant induced by the CRISPR-Cas9 system in colon cancer cells. In this study, two TP53 mutations, corresponding to exon 3 (TP53E3) and 10 (TP53E10), were generated in LS174T cells derived from a wild-type TP53 human colon cancer via a lentiviral CRISPR-Cas9 system. The loss of function of TP53 resulting from both mutations manifested as resistance to Nutlin3a-induced apoptosis and the downregulation of target genes of TP53. TP53 mutants exhibited an enhanced malignant potential, characterized by accelerated cell growth, invasiveness, chemoresistance, and cancer stemness. Interestingly, TP53E10 but not TP53E3 cells exhibited aberrant transcriptional activity of regenerating family member 1-a (REG1A) and expression of REG1A, resulting in the acquisition of enhanced malignant potential. In conclusion, we demonstrated for the first time that TP53 genomic mutation into human colon cancer cells affects the malignant potential. Implications: These findings suggest that both a loss of function and an aberrant gain of function of TP53 might promote high malignant potentials at the late phase of carcinogenesis in colon cancer.

Background and Aims Ulcerative colitis (UC) is a chronic inflammatory disease of the colon with frequent relapses. Telomere shortening in intestinal epithelial cells has been reported in severe or longstanding cases. However, its influence on UC pathogenesis remains unelucidated. To this end, we evaluated telomere shortening using a long-term organoid inflammation model that we had originally established. Methods A UC model using human colon organoids was established to assess telomere changes chronologically. MST-312 was used for the telomerase inhibition assay. The potential of telomerase activators as a novel UC treatment was evaluated with an in vitro model, including microarray analysis, and histologic changes were assessed using xenotransplantation into mouse colonic mucosa. Results Our UC model reproduced telomere shortening in vitro, which was induced by the continuous suppression of telomerase activity via P53. MST-312-based analysis revealed that telomere shortening was involved in the pathogenesis of UC. Madecassoside (MD) improved the telomere length of the UC model and UC patient-derived organoids, which further promoted cell proliferation in vitro and improved the graft take-rate of xenotransplantation. Moreover, histologic analysis revealed that MD induced normal crypt structure with abundant goblet cells. Conclusions This study is the first to reveal the mechanism and importance of telomere shortening in the pathogenesis of UC. MD could be a novel candidate for UC treatment beyond endoscopic mucosal healing.

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