PDGFRα and αSMA mark two distinct mesenchymal cell populations involved in parenchymal and vascular remodeling in pulmonary fibrosis

We utilized a fate-mapping approach to investigate alpha-smooth muscle actin (αSMA)+ and platelet derived growth factor-alpha (PDGFRα)+ cells in two lung fibrosis models, complemented by cell-type specific next-generation sequencing and investigations on human lungs. Our data revealed that αSMA+ and PDGFRα+ cells mark two distinct mesenchymal lineages with minimal transdifferention potential during lung fibrotic remodeling. Parenchymal and perivascular fibrotic regions were populated predominantly with PDGFRα+ cells expressing collagen, while αSMA+ cells in the parenchyma and vessel wall showed variable expression of collagen and the contractile protein desmin. The distinct gene expression profiles found in normal conditions was retained during pathologic remodeling. Cumulatively, our findings identify αSMA+ and PDGFRα+ cells as two separate lineages with distinct gene expression profile in adult lungs. Pdgfra- or Acta2-CreERT2; tdTomatoflox reporte mice were treated with saline or bleomycin (n=4/group). A single cell suspension was made from the lung and tdTomato-positive cells were sorted directly into RNA lysis buffer (Qiagen, Venlo, Netherlands) using a FACSAria II cell sorter (BD Biosciences, San Jose, CA, USA). RNA was isolated with the RNeasy micro kit (Qiagen). Library preparation using the SmartSeq2 protocol and sequencing on the Illumina HiSeq 3000 platform was done by the Biomedical Sequencing Facility, CeMM, Vienna. NGS reads were aligned with the TopHat2 (v2.1.1) (Kim et al., 2013) splice junction mapper using the Bowtie2 short read aligner (v2.2.9) (Langmead and Salzberg, 2012). Transcriptome assembly and differential expressing calling was performed with Cufflinks (v2.1.1) (Trapnell et al., 2013). cells fromt he lungs were enzymatically isolated.