Abstract: The development of the human respiratory tract begins at five post-conception weeks (pcw) and continues to form both distal and proximal airways. Previous studies on human foetal airways have revealed the dynamic changes in cell populations during airway development and identified mature myeloid cells and a group of their secreted pro-inflammatory cytokines. Although the roles of these cytokines in host defence systems have been well-documented, their functions in healthy foetal airway epithelium remain poorly understood. To have a better understanding of the interaction between pro-inflammatory cytokines and airway epithelial cells, we used mice as a model and performed single-cell RNA sequencing on prenatal and neonatal airways. Consistent with human single-cell transcriptomic studies, we confirmed that myeloid cells are the primary source of pro-inflammatory cytokines secretion. Our findings further suggest that basal and secretory cells are the major responders to these inflammatory signals in the murine upper airway. By incorporating cytokines into mouse tracheal epithelial cell (mTEC) cultures, we observed that niche inflammatory signals influence airway morphogenesis by regulating basal cell fate at different developmental stages. Additionally, we tested our hypothesis utilizing human tissue-derived organoids and observed consistent changes in phenotypes and epithelial cell type transitioning. In conclusion, our study highlights the pleiotropic roles of inflammatory cytokines in the regulation of healthy airway development.
