The impact of hyperoxia and antibiotics on lung mesenchymal cells in experimental bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common adverse outcome in preterm neonates and a high risk for early-onset emphysema and asthma. BPD is characterized by disrupted alveolar and microvascular development due to a variety of pathogenic factors, such as hyperoxia, inflammation, and dysbiosis. The resulting clinical manifestations are challenging, and current treatment options are limited. To improve therapeutic options, it is imperative to understand underlying causes. Resident lung mesenchymal stromal cells (L-MSCs) are important for alveolar microvascularization, repair, and regeneration. Here, we report the immediate effects of hyperoxia- and antibiotics-induced reduced bacterial load on L-MSCs and alveolar development using the hyperoxia-induced BPD mouse model. Newborn mice were exposed to hyperoxia from postnatal day 4 (P4) to P14, with room air recovery from P14 to P21. Dams received antibiotics-supplemented water (ampicillin, gentamycin, and vancomycin) from embryonic day 15 (E15) to P21. Hyperoxia significantly impaired alveolar development between P14 and P21, whereas both hyperoxia and antibiotic exposure impaired lung microvascular development. Moreover, hyperoxia reduced the number of pericytes, proliferative mesenchymal progenitors, <i>Col13a1</i>^POS matrix fibroblasts, and P2RY14^POS alveolar myofibroblasts. RNA sequencing (RNA-seq) of LY6A-sorted L-MSCs revealed differential expression of 103 genes in hyperoxia, 10 of which are related to mast cell biology. Antibiotic exposure also altered mesenchymal cell distribution, suggesting an additional impact on lung development. The transcriptomic landscape and distribution of important L-MSC subtypes and microvascular development are affected by hyperoxia and antibiotic exposure in a BPD mouse model. In conclusion, we show that hyperoxia- and antibiotics-induced reduced bacterial load affect the mesenchymal cell population, which may contribute to the development of BPD.<b>NEW & NOTEWORTHY</b> Bronchopulmonary dysplasia (BPD) is associated with preterm-born children, and antibiotic treatment increases the incidence. Lung repair is affected in BPD, and here we focused on the LY6A^POS lung mesenchymal cells (L-MSCs), which modulate repair. We show that hyperoxia, which induces BPD in rodents, and antibiotics affect the transcriptome of these cells, resulting in altered signaling to mast cells. Antibiotics also affected the hyperoxia-induced changes in the cellular composition of L-MSCs at early alveologenesis.