Does PDE4 inhibition improve alveolarisation in hyperoxia-exposed immature rodents?

A recent European Respiratory Journal article by WOYDA et al. [1] discussed the effect of a phosphodiesterase (PDE)4 inhibitor, cilomilast, on alveolarisation in mouse pups exposed to hyperoxia. WOYDA et al. [1] claimed in the title and concluded in the text that this treatment had the beneficial effect of preventing hyperoxia-induced impairment of alveolarisation, and proposed that PDE4 inhibition could represent a potential new therapy for bronchopulmonary dysplasia. We think that this conclusion overstated the study design and the obtained results. Although we used a different inhibitor (rolipram), our recently published study indicated that PDE4 inhibition did not enhance alveolarisation in rat pups exposed to hyperoxia, and may even directly affect alveolarisation in rat pups exposed to room air [2].