Identifying a paracrine fibroblast-derived factor that stimulates fetal alveolar cells, thus potentially enhancing perinatal lung transition.

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Preterm infants represent the largest paediatric patient group and thus a large societal challenge. Lung immaturity in these infants is frequently associated with respiratory distress leading to significant morbidity and mortality. Currently, the treatment of infants with pulmonary complications is mainly symptomatic and rather unspecific with salient unwanted side effects. This situation highlights the urgent need to develop new therapeutic approaches aiming at a stimulation of lung maturation. Lung mesenchymal-derived paracrine cell signals stimulate alveolar functions like surfactant synthesis, but the contributing factors are largely unknown. In our previous work we determined a novel function of lung fibroblast-derived conditioned medium (LF-CM), the stimulation of epithelial sodium transport and ENaC gene expression in fetal alveolar cells. Vectorial sodium transport, a major function of lung epithelial cells, enables lung fluid absorption at birth and thus perinatal lung transition, which is impaired in preterm infants and possibly alleviated by LF-CM. In the proposed project our aim therefore is to identify the factor(s) responsible for the stimulation of sodium transport. The experimental setup will start with factor binding and separation by HPLC using a 4-dimensional separation scheme, followed by mass spectrometric factor identification and confirmation with synthetic compounds. The response of ENaC mRNA expression is tested and confirmed with every obtained LF-CM fraction as biological readout. Furthermore, it is planned to establish a faster, more robust readout, e.g. the Corning Epic System, to confirm the biological activity. The second strategy involves RNA-Sequencing comparing responder and non-responder cells to identify differentially regulated pathways by LF-CM. With these strategies, we expect to identify novel endogenous mesenchymal-derived factors able to stimulate lung maturation, and/or expand the knowledge about already known factors by determining additional previously unknown effects on lung epithelia. Furthermore, we want to characterize the involved pathways to identify new strategies to improve perinatal lung transition in preterm infants. Identifying these stimulating mesenchymal-derived paracrine components will enable clinical scientists in our group and elsewhere to develop urgently needed novel therapies with optimized effects and reduced side effects, thus improving the long term health of premature infants. Furthermore, these results may also open new therapeutic approaches for adult lung failure, including COVID-19 pneumonia, which also shows extreme distubances of alveolar fluid clearance. The joint effort of the Neonatology research group and the Institute of Bioanalytical Chemistry in cooperation with the Institute of Molecular Biochemistry and the Max Planck Institute für Heart- and Lung Research in Bad Nauheim will ensure successful execution of the project within the proposed time frame.