Maladaptive functional changes in alveolar fibroblasts due to perinatal hyperoxia impair epithelial differentiation

Infants born prematurely worldwide have up to a 50% chance of developing bronchopulmonary dysplasia (BPD), a clinical morbidity characterized by dysregulated lung alveolarization and microvascular development. It is known that PDGFR alpha–positive (PDGFRA(+)) fibroblasts are critical for alveolarization and that PDGFRA(+) fibroblasts are reduced in BPD. A better understanding of fibroblast heterogeneity and functional activation status during pathogenesis is required to develop mesenchymal population–targeted therapies for BPD. In this study, we utilized a neonatal hyperoxia mouse model (90% O(2) postnatal days 0–7, PN0–PN7) and performed studies on sorted PDGFRA(+) cells during injury and room air recovery. After hyperoxia injury, PDGFRA(+) matrix and myofibroblasts decreased and PDGFRA(+) lipofibroblasts increased by transcriptional signature and population size. PDGFRA(+) matrix and myofibroblasts recovered during repair (PN10). After 7 days of in vivo hyperoxia, PDGFRA(+) sorted fibroblasts had reduced contractility in vitro, reflecting loss of myofibroblast commitment. Organoids made with PN7 PDGFRA(+) fibroblasts from hyperoxia in mice exhibited reduced alveolar type 1 cell differentiation, suggesting reduced alveolar niche-supporting PDGFRA(+) matrix fibroblast function. Pathway analysis predicted reduced WNT signaling in hyperoxia fibroblasts. In alveolar organoids from hyperoxia-exposed fibroblasts, WNT activation by CHIR increased the size and number of alveolar organoids and enhanced alveolar type 2 cell differentiation.