Alveolization: does “A” stand for appropriate morphometry?

To the Editor: In a recent issue of the European Respiratory Journal , Hind and Maden 1 reported a series of well-designed experiments conducted to further enlighten the role of retinoic acid in alveolar regeneration. The ability of retinoic acid to rescue emphysematous lungs, which was initially reported by Massaro and Massaro 2, has attracted great attention. However, the potential of retinoic acid is still controversially discussed 3. Unquestionably, the study of Hind and Maden 1 added important new data to our knowledge of the role of retinoic acid in alveolization, as was emphasised in an accompanying editorial 4. In their editorial, Torday and Rehan 4 ask “Does “A” stand for alveolization?”. Can this question be answered on the basis of the data presented? In the context of lung development, alveolization is recognised as the process of subdivision of lung saccules by outgrowing secondary septa, which results in an increased number of smaller …