Three-dimensional observation of mouse tongue muscles using micro-computed tomography

The aim of this study is to obtain information about the mouse tongue muscle rendered using micro-computed tomography (mu CT) at low, middle, and high magnifications. Three-dimensional (3D) mu CT is used in various fields. Most mu CT observations are restricted to hard tissue in biomaterial samples. Recently, with the use of osmium tetroxide, mu CT has been effectively employed to observe soft tissue; it is now believed that mu CT observation of soft tissue is feasible. On the other hand, the structure of the tongue muscle has been well studied, but cross-sectional imaging enhanced by 3D rendering is lacking. We chose the mouse tongue as a soft tissue case study for mu CT and generated cross-sectional images of the tongue enhanced by 3-D image rendering with histological resolution. During this observation, we developed new methods of low-magnification observation to show the relation between the tongue muscles and surrounding tissues. We also applied high-resolution mu CT in high-magnification observation of muscle fiber fascicles. Our methodological techniques give the following results: (1) For low-magnification observation (field of view: 12,000 mu m), pretreatment with decalcification and freeze drying is suitable for observing the area between the muscle of the tongue and the bone around the tongue using mu CT. (2) For middle-magnification observation (Field of view: 3,500 mu m), the use of osmium tetroxide to observe the muscle arrangement of the tongue by mu CT is suitable. (3) For high-magnification observation (Field of view: 450 mu m), high-resolution mu CT is suitable for observation of the transversus muscle fiber fascicles.