ABSTRACT
Emphysema, a leading cause of respiratory disability and mortality in humans, is characterized by destruction of alveolar walls and enlargement of airspaces. Animal studies are critical in understanding the pathogenesis of emphysema. However, current measurements of airspace enlargement and emphysema in small laboratory animals are labor intensive and may not be sensitive enough for measuring alterations in lung function and structure at the early stages of emphysema. In this study, we have investigated the excised lung gas volume (ELGV) measurement as a potential index for determining airspace enlargement in pallid mice with developing emphysema, in tight-skin mice with developed emphysema, or in Wistar rats with emphysema induced by an intratracheal instillation of pancreatic elastase. Our results showed that values of both ELGV per lung and per gram lung tissue were significantly increased in all three emphysema models, compared to control. The ELGV values were correlated well with morphometric evaluation of emphysema. Variations in transpulmonary pressures caused by different termination procedures were critical factors influencing the ELGV values. The present study demonstrates that ELGV measurement is a simple and sensitive method to monitor the development of emphysema.
Subject(s)
Lung Volume Measurements/methods , Pancreatic Elastase/metabolism , Pulmonary Emphysema/etiology , Pulmonary Emphysema/metabolism , alpha 1-Antitrypsin Deficiency/complications , Age Factors , Animals , Bronchoalveolar Lavage Fluid , Disease Models, Animal , Female , Lung/metabolism , Lung/pathology , Lung Compliance , Male , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Organ Size/genetics , Pulmonary Alveoli , Pulmonary Emphysema/genetics , Pulmonary Emphysema/pathology , Rats , Rats, Wistar , Time Factors , alpha 1-Antitrypsin Deficiency/geneticsABSTRACT
Isolated blood eosinophils are routinely used to study eosinophil activation mechanisms. However, as revealed by ultrastructural analysis, different isolation protocols may yield purified eosinophils with marked variability in granule electron density. In this study, using eosinophil peroxidase (EPO) histochemistry and transmission electron microscopy (TEM), we have compared the morphology of eosinophils in immediately fixed whole blood (to represent a morphological baseline) with isolated eosinophils purified by a number of protocols. Eosinophils in whole blood contained intact specific secondary granules of which a few exhibited marginal coarsening of matrix electron density (4% (95% CI: 2 to 7) altered granules per eosinophil). By contrast, eosinophils purified according to standard protocols, which included erythrocyte lysis with either ammonium chloride or distilled water, showed moderate to extensive loss in density of secondary granule core and/or matrix (NH4Cl: 62% (95% CI: 58 to 66); dH2O: 37% (95% CI: 30 to 44) altered granules). Stepwise analysis of eosinophils during the cell separation processes indicated that the granule abnormalities seen following erythrocyte lysis were further increased following immunomagnetic separation. However, when erythrocyte lysis was omitted, by use of a two-layered Percoll gradient (1.076 g/ml/1.088 g/ml) to which diluted whole blood was applied directly, eosinophils with minimal granule abnormalities (11% (95%CI: 9 to 13) altered granules) could be obtained after immunomagnetic separation. In conclusion, to obtain eosinophils with granule morphology more closely resembling the whole blood baseline phenotype, erythrocyte lysis should be avoided when separating eosinophils from human blood. Thus it will be possible to study in vitro the early transformation of resting eosinophils into the degranulating phenotype found in diseased tissues.
