Introduction

Primary sclerosing cholangitis (PSC) is an inflammatory disorder of the bile ducts, in which Inflammatory bowel disease (IBD) concomitantly occurs (PSC-IBD). Substantial differences in clinical presentation are observed between PSC-IBD and ulcerative colitis (UC).

Aims & Methods

In this study we aim to find distinct pathomechanisms for PSC-IBD using single-cell RNA sequencing. Forty-seven colonic samples of PSC-IBD (n=24), UC (n=18) and non-IBD subjects (n=5) were collected. Whole biopsies were dissociated into single cells using one-step collagenase digestion. Library preparation was done with 10x Genomics and sequencing was performed on an MGI2000 sequencer. Then, differential abundance, differential expression, cell-cell interaction analyses, and heritability analyses were performed. Stainings for DUOX2 and HLA-DR were performed on paraffin embedded colon mucosal slides

Results

In total, 71,798 high quality cells identified 54 distinct cell types, including a new type of epithelial cells: DUOX2+ enterocytes. DUOX2+ enterocytes are almost exclusively present in inflamed colon and can act as antigen presenting cells through the expression of MHC2 on its surface. A general shift in cell type composition upon inflammation was observed, comparable between PSC and UC samples. However, an increased abundance was seen for stem cells in non-inflamed (NI) PSC, and not in UC-NI nor non-IBD controls. Additionally, we found distinct gene expression patterns between PSC and UC inflammation: while activation of inflammatory monocytes was observed in PSC inflammation, several types of fibroblasts were activated upon UC inflammation. Through heritability analysis, we also highlighted how mucosal follicular B and CD4+ activated Fos-Hi cells carry the heaviest burden of PSC risk genes.

Conclusion

We describe DUOX2+ enterocytes, which may play a role in both PSC and UC colitis inflammation through antigen presentation. Furthermore, we show that intestinal inflammation in PSC-IBD, as compared to UC, is characterized by distinct mucosal cell composition and cell-specific gene expression patterns. PSC colitis, and not UC, is driven by activation of inflammatory monocytes, with antigen presentation through HLA-DRB1, and activation of specific CD4+ T cell subsets. Additionally, an increased abundance of stem cells in PSC-NI could be related with the increased colorectal cancer risk in PSC-IBD.

Disclosure

S.S. received a grant from China, J.B. received a grant from Searave Foundation, R.K.W., E.A.M.F. and K.N.F. received unrestricted research grants from Takeda, R.K.W. received an unrestricted grant from Tramedico and Ferring and is supported by a Diagnostics Grant from the Dutch Digestive Foundation (D16-14). W.T.C.U.V. and E.A.M.F. received a Gastrostart Grant from the Dutch Society of Gastroenterology. E.A.M.F. received a personalized medicine grant form the University of Groningen a personalized grant a Clinical Fellowship from the ZonMw, and is supported by a MLDS Career Development grant (CDG 14-04).

A.B., P.P., S.d.J., E.B., G.M.P.J.V., F.G.M.K., G.K., M.A.H., A.V.V. and M.G.P.v.d.W. disclose no conflicts of interest.