Figure 1.

Platelet-derived growth factor receptor α–green fluorescent protein (PDGFRα⁺-GFP) mice reveal two distinct fibroblast phenotypes. (A) Single cells isolated from adult mouse lungs were sorted into Lin^⁻ (CD45^⁻, CD31^⁻, CD326^⁻) and PDGFRα⁺GFP^dim or GFP^bright cells. (B) RNA was subjected to microarray analysis, and PCA mapping identified a myo- and a matrix messenger RNA signature. Using all probe sets, the first three principal components cover 75% of all variations across samples and clearly separate the two subpopulations (red and blue). (C) Collagen and matrix-related expression differences between PDGFRα-GFP^bright and PDGFRα-GFP^dim fibroblasts. Two-dimensional hierarchical clustering of 29 genes associated with extracellular matrix synthesis and collagen expression is differentially expressed between bright (B) and dim (D) cells. Red blocks represent up-regulation, and blue blocks represent down-regulated expression. (D) Three-dimensional confocal reconstruction of adult mouse lung demonstrate that PDGFRα-GFP⁺ cells (green) are adjacent to alveolar type-2 cells (pro-SPC; white) and are distributed evenly throughout the alveolar compartment. α-SMA, α-smooth muscle actin; FSC, forward scatter; GFP, green fluorescent protein; Lin⁻, lineage negative; PC, principal component; PCA, principal component analysis; pro-SPC, proprotein for surfactant protein C.