K. E. Bauer-Rowe1, A. Kim1, M. Griffin1, N. Liang1, D. Foster1, J. Guo1, H. Talbot1, S. Mascharak1, J. Norton1, J. Hyun1, M. Longaker1 1Stanford University, Department Of Surgery, Palo Alto, CA, USA
Introduction: Crohn’s disease (CD) is a subtype of inflammatory bowel disease (IBD) characterized by transmural inflammation and creeping fat (CF) formation. Thirty percent of CD patients eventually develop strictures, eighty percent of which will require surgery, and recurrence rates are as high as seventy percent. CF forms adjacent to strictures, but whether it promotes stricture formation or is a passive bystander is unclear. Here, we provide evidence that CF-derived fibroblasts may promote fibrosis and stricture formation.
Methods: We generated a model of human strictures by creating an anti-mesenteric colotomy in the style of a Heineke-Mikulicz strictureplasty in mice and assessed fibrosis by Masson's trichrome on post-operative day (POD) 14. We lineage traced mature adipocytes by creating colotomies in Adipoq-Cre; mTmG mice and staining for adipocyte and fibroblast markers. We then selectively ablated CF adipocytes by administering diphtheria toxin to Adipoq-Cre; DTR mice prior to creating colotomies and assessed fibrosis by Masson's trichrome. Finally, we performed single-cell RNA-sequencing separately on bowel and mesentery from control and wounded colons to identify fibroblast and stromal progenitor subpopulations.
Results: Our surgical model phenocopies clinical features of human strictures, including creeping fat formation, increased bowel wall thickness, and fibrosis (Figure 1A-D). Lineage tracing of mature adipocytes in Adipoq-Cre; mTmG mice revealed adipocyte-derived cells that lose adipocyte markers and acquire fibroblast markers at the colotomy site (Figure 1E, F). Selective ablation of CF adipocytes rescued the stricture phenotype compared to unablated controls (Figure 1G, H). scRNAseq demonstrated the expansion of pro-fibrotic fibroblast and stromal progenitor subpopulations in wounded bowel and creeping fat compared to controls (Figure 1I).
Conclusion: Our surgical model in combination with lineage tracing demonstrates the presence of CF-derived fibroblasts that infiltrate the bowel wall and promote fibrosis and stricture formation. CF ablation prior to wounding is sufficient to attenuate stricture formation. Finally, both wounded bowel and CF contain pro-fibrotic fibroblast and stromal progenitor subpopulations. Taken together, these findings suggest that CF may drive intestinal fibrosis in part through CF-derived fibroblasts.
