Prostaglandin I2 Receptor Activation Promotes Alveolar Regeneration via the JUN/p53 Pathway [scRNA-seq]
Rationale: Transdifferentiation of alveolar type 2 (AT2) epithelial cells into type 1 (AT1) cells is essential for maintaining lung homeostasis and facilitating repair following injury. However, the molecular mechanisms governing AT2-to-AT1 transdifferentiation remain unclear. Objectives: To investigate the role of the prostaglandin I2 receptor (IP) in regulating AT2-to-AT1 transdifferentiation and elucidate the underlying mechanisms. Methods: Alveolar organoid cultures and bleomycin- or lipopolysaccharide (LPS)-induced murine lung injury models were used to assess the role of IP in AT2-to-AT1 transdifferentiation and lung repair. Single-cell RNA sequencing (scRNA-seq), ATAC-seq, and biochemical assays were performed to explore the regulatory signaling pathways downstream of IP in AT2 cells. Measurements and Main Results: Among all prostaglandin receptors, IP exhibited the strongest association with AT1 gene enrichment in transitional AT2 cells from patients with idiopathic pulmonary fibrosis (IPF). Pharmacological inhibition or genetic deletion of IP significantly impaired the AT2-to-AT1 transition in organoid cultures. Conditional knockout of IP in AT2 cells exacerbated bleomycin- and lipopolysaccharide-induced lung injury by reducing epithelial regeneration and increasing fibrosis. Mechanistically, IP deficiency led to aberrant JUN activation, which suppressed p53-dependent AT1 gene expression. IP activation promoted PKA-mediated inhibition of MAP3K5, thereby suppressing the JNK/JUN axis and enhancing p53-driven AT2-to-AT1 transdifferentiation. Pharmacological activation of IP with selexipag promoted alveolar epithelial regeneration and reduced lung fibrosis in mice. IP agonist also enhanced AT2-to-AT1 transdifferentiation in primary AT2 cells from patients with IPF. Conclusions: IP is a key regulator of alveolar epithelial regeneration. Therapeutic activation of IP may be a promising strategy for promoting lung repair. Overall design: scRNA-seq, EpCAM+CD31-CD34-CD45-CD24-Sca-1- cells were  sorted by flow cytometry from WT or IP-/-(IPKO) mice and analyzed using scRNA-seq.