Project description:Regenerating new alveolar epithelium is essential for recovery from many lung diseases. This multi-cellular regenerative process occurs when type II alveolar pneumocytes (AT2), with support from mesenchymal niche cells, proliferate to generate more AT2 cells and transdifferentiate in type I pneumocytes. To elucidate how coordinated events between AT2 cells and mesenchyme restore alveolar epithelium we used unbiased genome-wide analysis of chromatin accessibility and gene expression in both cell types following acute lung injury. We observed that chromatin acessability in AT2 cells changes signficantly following acute lung injury. Newly accessible chromatin reveals new STAT3 binding motifs adjacent to genes that regulate essential regenerative pathways in AT2 cells. Restoration of alveolar structures following both sterile and infectious lung injuries was inhibited when STAT3 signaling was lost in AT2 cells. Single-cell transcriptome analysis of regenerating AT2 cells identified brain neurotrophic factor (Bdnf) as the sole STAT3 target gene whose chromatin becomes newly accessible in a regenerating population of AT2 cells. BDNF increased alveolar organoid size and forming efficiency in murine and human models. The receptor for BDNF, TrkB, is uniquely? expressed on mesenchymal alveolar niche cells (MANC). Exposure of BDNF to TrkB increases expression of fibroblast growth factor 7 (Fgf7), an essential regenerative cytokine, in MANCs. Blocking Bdnf signaling with a TrkB receptor antagonist abrogated murine and human alveolar organoid formation. Finally, a small molecule TrkB agonist improved functional and histological outcomes in vivo following sterile and infectious lung injuries. Collectively, these data highlight the biological and therapeutic importance of the Stat3-Bdnf-TrkB axis in orchestrating alveolar epithelial regeneration
Project description:Regenerating new alveolar epithelium is essential for recovery from many lung diseases. This multi-cellular regenerative process occurs when type II alveolar pneumocytes (AT2), with support from mesenchymal niche cells, proliferate to generate more AT2 cells and transdifferentiate in type I pneumocytes. To elucidate how coordinated events between AT2 cells and mesenchyme restore alveolar epithelium we used unbiased genome-wide analysis of chromatin accessibility and gene expression in both cell types following acute lung injury. We observed that chromatin acessability in AT2 cells changes signficantly following acute lung injury. Newly accessible chromatin reveals new STAT3 binding motifs adjacent to genes that regulate essential regenerative pathways in AT2 cells. Restoration of alveolar structures following both sterile and infectious lung injuries was inhibited when STAT3 signaling was lost in AT2 cells. Single-cell transcriptome analysis of regenerating AT2 cells identified brain neurotrophic factor (Bdnf) as the sole STAT3 target gene whose chromatin becomes newly accessible in a regenerating population of AT2 cells. BDNF increased alveolar organoid size and forming efficiency in murine and human models. The receptor for BDNF, TrkB, is uniquely? expressed on mesenchymal alveolar niche cells (MANC). Exposure of BDNF to TrkB increases expression of fibroblast growth factor 7 (Fgf7), an essential regenerative cytokine, in MANCs. Blocking Bdnf signaling with a TrkB receptor antagonist abrogated murine and human alveolar organoid formation. Finally, a small molecule TrkB agonist improved functional and histological outcomes in vivo following sterile and infectious lung injuries. Collectively, these data highlight the biological and therapeutic importance of the Stat3-Bdnf-TrkB axis in orchestrating alveolar epithelial regeneration
Project description:Alveolar epithelial regeneration is essential for recovery from devastating lung diseases. This process occurs when type II alveolar pneumocytes (AT2 cells) proliferate and transdifferentiate into type I alveolar pneumocytes (AT1 cells). We used genome-wide analysis of chromatin accessibility and gene expression following acute lung injury to elucidate repair mechanisms. AT2 chromatin accessibility changed substantially following injury to reveal STAT3 binding motifs adjacent to genes that regulate essential regenerative pathways. Single-cell transcriptome analysis identified brain-derived neurotrophic factor (Bdnf) as a STAT3 target gene with newly accessible chromatin in a unique population of regenerating AT2 cells. Furthermore, the BDNF receptor tropomyosin receptor kinase B (TrkB) was enriched on mesenchymal alveolar niche cells (MANCs). Loss or blockade of AT2-specific Stat3, Bdnf or mesenchyme-specific TrkB compromised repair and reduced Fgf7 expression by niche cells. A TrkB agonist improved outcomes in vivo following lung injury. These data highlight the biological and therapeutic importance of the STAT3-BDNF-TrkB axis in orchestrating alveolar epithelial regeneration.
