Noninvasive detection of pulmonary tissue destruction in a mouse model of emphysema using hyperpolarized 129Xe MRS under spontaneous respiration.
In the present study, a chemical shift saturation recovery method in hyperpolarized (129)Xe MR spectroscopy measurements was applied to two groups of spontaneously breathing mice, an elastase-induced emphysema model and a control group. Parameters detected were those related to lung structures and functions, such as alveolar septal thickness, h, the ratio of the alveolar septal volume relative to gas space volume, V(s)/V(a), and the transit time of blood through the gas exchange region, τ. To investigate the potential of these parameters as biomarkers, an attempt was made to detect physiologic changes in the lungs of elastase-treated mice. Our results showed that V(s)/V(a) was significantly reduced in elastase-treated mice, reflecting emphysema-like destruction of the alveolar wall. Compared with histologic results, this degree of reduction was shown to reflect the severity of wall destruction. On the other hand, significant changes in other parameters, h and τ, were not shown. This study is the first application of hyperpolarized (129)Xe MR spectroscopy to a mouse model of emphysema and shows that the V(s)/V(a) volume ratio is an effective biomarker for emphysema that could become useful in drug research and development through noninvasive detection of pathologic changes in small rodents.