Mapping and tracing Grem1⁺ stromal cells in an Apc mouse utilizing cryopreserved intestinal sections prepared via...

Grem1⁺ cancer-associated fibroblasts (CAFs) are crucial in colorectal cancer (CRC) development, yet technical challenges have limited understanding of their origins, spatiotemporal distribution, and potential roles. Here, we devised a custom mold, optimizing the gut Swiss-roll technique to create a single cryopreserved slide for comprehensive staining. Our integrated approach uncovered a marked increase in Grem1⁺ CAFs within Apc mouse tumors at 12 weeks, compared to normal mucosa. Subsequent lineage tracing in Grem1-CreER ; R26-LSL-tdTomato; Apc mice revealed that most Grem1⁺ CAFs infiltrating the tumor core originated from Grem1⁺ intestinal reticular stem cells (iRSCs). A minor subset of Grem1⁺ CAFs, located in the submucosa, retained characteristics of Grem1⁺ intestinal sub-epithelial myofibroblasts (ISEMFs). Altogether, CAFs derived from Grem1⁺ iRSCs may serve as a principal stromal cell type driving early-stage CRC progression, while Grem1⁺ ISEMFs contribute less from a more distant location. Hence, targeting Grem1⁺ CAFs presents an early and promising therapeutic strategy in CRC.