HAS1 and idiopathic pulmonary fibrosis: Fibroblasts, characterized by expression of CD34, FBN1, FBLN2, VIT, and myofibroblasts consistently expressing MYLK, NEBL, MYO10, MYO1D, RYR2, and ITGA8. The IPF lung in addition contained a myofibroblast phenotype enriched with fibrillar collagens, and ACTA2 and a fibroblast phenotype that exhibited increased expression of HAS1, HAS2, FBN1, and CXCL14. The authors suggest that pathological, ACTA2-expressing IPF myofibroblasts are not a discrete cell type, but rather one extreme pole of a continuum connected to a quiescent ACTA2-negative stromal population represented in control lungs (13).