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This Article Full Text Full Text (PDF) Supplemental Video All Versions of this Article: 294/2/L246    most recent 00296.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Schittny, J. C. Articles by Stampanoni, M. Search for Related Content PubMed PubMed Citation Articles by Schittny, J. C. Articles by Stampanoni, M.

Evidence and structural mechanism for late lung alveolarization

¹Institute of Anatomy, University of Bern, Bern, and ²Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland

Submitted 27 July 2007 ; accepted in final form 19 November 2007

According to the current view, the formation of new alveolar septa from preexisting ones ceases due to the reduction of a double- to a single-layered capillaries network inside the alveolar septa (microvasculature maturation postnatal days 14–21 in rats). We challenged this view by measuring stereologically the appearance of new alveolar septa and by studying the alveolar capillary network in three-dimensional (3-D) visualizations obtained by high-resolution synchrotron radiation X-ray tomographic microscopy. We observed that new septa are formed at least until young adulthood (rats, days 4–60) and that roughly half of the new septa are lifted off of mature septa containing single-layered capillary networks. At the basis of newly forming septa, we detected a local duplication of the capillary network. We conclude that new alveoli may be formed in principle at any time and at any location inside the lung parenchyma and that lung development continues into young adulthood. We define two phases during developmental alveolarization. Phase one (days 4–21), lifting off of new septa from immature preexisting septa, and phase two (day 14 through young adulthood), formation of septa from mature preexisting septa. Clinically, our results ask for precautions using drugs influencing structural lung development during both phases of alveolarization.

septation; capillary remodeling; lung development