Platelet‐Derived Growth Factor Receptor‐Alpha‐Expressing Cells Localize to the Alveolar Entry Ring and Have Characteristics of Myofibroblasts During Pulmonary Alveolar Septal Formation

Platelet‐derived growth factor‐A and its receptor, platelet‐derived growth factor receptor‐alpha (PDGF‐Rα), are required for formation of the secondary pulmonary alveolar septa in mice. However, it remains unclear how these molecules direct the secondary septation process. We have examined the abundance, location, and the accumulation of alpha‐smooth muscle actin (αSMA), neutral lipid droplets, and elastin in the proximity of PDGF‐Rα‐expressing alveolar cells during postnatal days 4 through 12 in the mouse. PDGF‐Rα‐expressing cells preferentially have characteristics of myofibroblasts and were more likely to contain αSMA than are alveolar cells that do not express PDGF‐Rα. PDGF‐Rα expressing cells were preferentially located in the alveolar entry ring (AER) where αSMA and elastic fibers accumulate. In contrast, PDGF‐Rα expression inversely correlated with neutral lipid accumulation, which was more prominent at the alveolar base, distant from the AER. PDGF‐Rα‐expressing alveolar cells accumulate in the AER where they may promote mechanical stability during respiration. In addition to defining how alveolar septa form, these findings may have implications for the treatment of diseases which involve alveolar effacement such as emphysema and pulmonary fibrosis. Anat Rec, 2008. © 2008 Wiley‐Liss, Inc.