Role of lung pericytes and resident fibroblasts in the pathogenesis of pulmonary fibrosis.

TLDR: The lung contains an extensive population of Foxd1 progenitor-derived pericytes that are an important lung myofibroblast precursor population, and these studies suggest a distinct lineage of collagen-I(α)1-expressing resident fibroblasts that also expands after lung injury is a second major source of my ofibro Blasts.

Abstract: Rationale: The origin of cells that make pathologic fibrillar collagen matrix in lung disease has been controversial. Recent studies suggest mesenchymal cells may contribute directly to fibrosis.Objectives: To characterize discrete populations of mesenchymal cells in the normal mouse lung and to map their fate after bleomycin-induced lung injury.Methods: We mapped the fate of Foxd1-expressing embryonic progenitors and their progeny during lung development, adult homeostasis, and after fibrosing injury in Foxd1-Cre; Rs26-tdTomato-R mice. We studied collagen-I(α)1–producing cells in normal and diseased lungs using Coll-GFPTg mice.Measurements and Main Results: Foxd1-expressing embryonic progenitors enter lung buds before 13.5 days post-conception, expand, and form an extensive lineage of mesenchymal cells that have characteristics of pericytes. A collagen-I(α)1–expressing mesenchymal population of distinct lineage is also found in adult lung, with features of a resident fibroblast. In contrast to resident f...