The pneumonectomy model of compensatory lung growth: insights into lung regeneration

Pneumonectomy (PNX) in experimental animals leads to a species- and age-dependent compensatory growth of the remaining lung lobes. PNX mimics the loss of functional gas exchange units observed in a number of chronic destructive lung diseases. However, unlike in disease models, this tissue loss is well defined, reproducible and lacks accompanying inflammation. Furthermore, compensatory responses to the tissue loss can be easily quantified. This makes PNX a potentially useful model for the study of the cellular and molecular events which occur during realveolarisation. It may therefore help to get a better understanding of how to manipulate these pathways, in order to promote the generation of new alveolar tissue as therapies for destructive lung diseases. This review will explore the insights that experimental PNX has provided into the physiological factors which promote compensatory lung growth as well as the importance of age and species in the rate and extent of compensation. In addition, more recent studies which are beginning to uncover the key cellular and molecular pathways involved in realveolarisation will be discussed. The potential relevance of experimental pneumonectomy to novel therapeutic strategies which aim to promote lung regeneration will also be highlighted.