Investigation of Creeping Fat-Associated Fibroblasts in Smooth Muscle Cell Hypertrophy in Crohn’s Disease Stricture Formation

Introduction: Intestinal strictures significantly cause morbidity in Crohn’s disease (CD) patients. While smooth muscle (SM) expansion is a major histological characteristic of strictures, its origins are poorly understood. To better understand this phenomenon, we characterized SM expansion using a novel surgical mouse model of CD and used spatial transcriptomics to analyze gene expression from human stricture samples.

Methods: We created anti-mesenteric colotomies in C57/B6 mice and closed the bowel transversely under mechanical tension to generate strictures with creeping fat (CF) and fibrosis. The stricture samples were quantified for SM expansion versus unwounded controls. We performed lineage-tracing using GFP expressing Myh11+ smooth muscle cells (SMCs) from Myh11-CreERT2; mTmG mice and ACTA2 (marker for SMCs and myofibroblasts). Concurrently, we performed spatial transcriptomics and CellChat on three human pediatric strictures to spatially quantify differentially expressed genes and communication patterns.

Results: In our model, we found significant increases in SM thickness (Figure 1A). Through lineage tracing, we observed that SMCs expanded into the colotomy site adjacent to the CF (Figure 1B). Our spatial transcriptomics data revealed that the interface between bowel and CF was enriched for SM and myofibroblast genes (Figure 1C-F). We identified that Notch signaling, a potent stimulator of SMC growth, is enriched in CF (Figure 1G).

Conclusion: These observations suggest our model can replicate the SM expansion in human CD strictures. Our gene expression and cell signaling data indicate that SM expansion is affected by the interface. We present that CF-derived myofibroblast may acquire SMC characteristics and expand the SM layer in CD strictures.