PI16 and Myocardial fibrosis: Similar to the human data, we also found that one subset of fibroblasts (Cluster 7) displayed heightened expression of several progenitor cell markers, such as Cd34, Ly6a, Pi16, and Thy118, in mice (Fig. 3d), suggesting that Cd34-high fibroblasts may have distinct functions in myocardial fibrosis.