Indeed, when we carried out flow cytometric analysis after removing stromal cells from the chips, we found that PDPN expression was significantly higher in IBD fibroblasts that expressed high OSMR levels (Extended Data Fig. 2A,B) and that fibroblasts in IBD Chips lined by cells from both Crohn’s and UC patients secreted more inflammatory cytokines (e.g, IL6, IL8, MCP-1) from the basal channel than those in Healthy Chips (Fig. 1G). Here, IL6 is linked to inflammatory bowel disease.