Transcriptomic analysis of control lung alveolar type 2 cells and constitutively active-BMPR1a overexpressing alveolar type 2 cells

The Bone Morphogenetic Protein (BMP) signaling pathway functions in lung development and the regeneration of adult tracheal epithelium from basal stem cells. Here, we explore its role in the alveolar region, where Type 2 epithelial cells (AT2s) and Pdgfrα+ Type 2 - associated stromal cells (TASCs) are components of the stem cell niche. We utilize both organoid assays and in vivo alveolar regrowth after pneumonectomy (PNX) - a process requiring proliferation of AT2s and differentiation into Type 1 cells (AT1). BMP signaling is normally active in AT2s and TASCs, transiently declines post-PNX, and is restored during differentiation of AT2s to AT1s. In organoids, BMP4 inhibits AT2 proliferation, while antagonists promote AT2 self-renewal at the expense of differentiation. Gain and loss-of function genetic manipulation reveals that loss of BMP signaling in AT2s after PNX allows their self-renewal but significantly reduces differentiation into AT1s; conversely, increased BMP signaling promotes AT1 formation. The transcriptome analysis of control AT2s and AT2s overexpressing constitutively active-Bmpr1a reveals that 119 genes are upregulated more than two-fold following enhancing BMP signaling. Of these genes, 10 % are normally preferentially expressed in AT1 cells. Of the 25 genes downregulated more than two-fold, 28 % are preferentially expressed in AT2s. mRNA was isolated from FACS-sorted cells and sequenced using Illumina HiSeq X