Periductal fibroblasts participate in liver homeostasis, fibrosis, and tumorigenesis

Hepatic fibroblasts comprise groups of stromal cells in the liver that are phenotypically distinct from hepatic stellate cells. However, their physiology is poorly understood. By single-cell RNA sequencing, we identified Cd34 and Dpt as hepatic fibroblast-specific genes. Cd34-CreER labeled periportal-venous and periductal fibroblasts, but few pericentral-venous fibroblasts. Cd34+ fibroblasts generated ∼25% of myofibroblasts in periportal fibrosis and ∼40% of cancer-associated fibroblasts (CAFs) in intrahepatic cholangiocarcinoma (ICC). Myofibroblast formation by Cd34+ fibroblasts required Tgfbr2. Depletion of Cd34+ fibroblasts increased the frequency of the ductal epithelial cells under homeostasis and accelerated the progression of ICC. Dpt-CreER labeled periportal- and pericentral-venous fibroblasts, but much less periductal fibroblasts. Dpt+ cells generated ∼15% of myofibroblasts in periportal fibrosis, but few myofibroblasts in pericentral fibrosis or CAFs in ICC. Thus, an orthogonal combination of Cd34-CreER and Dpt-CreER dissected the fates of periductal, periportal-venous, and pericentral-venous fibroblasts. Both periductal and periportal-venous fibroblasts contribute to liver fibrosis. Periductal fibroblasts also contribute to ductal homeostasis and ICC progression.