Compensatory Lung Growth. Relationship to Postnatal Lung Growth and Adaptation in Destructive Lung Disease.

This chapter illustrates the guiding principles of growth regulation by comparing the response to a specific signal, namely mechanical lung strain, during normal and compensatory lung growth, and interprets the growth response in the context of structure-function relationships with respect to the whole organ. Recent evidence directly supports mechanical lung strain as the major signal underlying postnatal and post-pneumonectomy (PNX) lung growth, although non-mechanical signals also play a role in modulating the growth response. Reducing lung strain markedly impairs normal lung development as well as post-PNX growth and compensation, and compensatory lung growth is clearly not a recapitulation of normal developmental events. As the magnitude of post-PNX lung strain increases, a disparate pattern of adaptation between lung parenchyma and conducting structures emerges, reflecting differences in the plasticity of the respective components. The extent of disparity or 'mismatch' between the adaptive potential of these components effectively limits the functional compensation that can be derived from alveolar septal growth and regeneration.