Anatomy of the murine and human cochlea visualized at the cellular level by synchrotron-radiation-based microcomputed tomography

Diseases of the hearing organ and impairment affect a significant fraction of population. Therefore, the hearing organ embedded as a helical structure in the cochlea within the hardest human osseous structure inside the petrous bone is intensively investigated. Currently, studies of the cochlea with true micrometer resolution or better are destructive. Membranes and three-dimensional vessel structures of post-mortem explanted human cochlea were only visualized with limited spatial resolution or deformed anatomical features resulting from preparation artifacts. We have applied a preparation and staining protocol developed for electron microscopy, which allows the visualization and quantification of a great variety of soft-tissue structures including the Reissner ́s membrane, the tectorial membrane, basilar membrane, modiolus, lamina radialis, and Nuel ́s space by the use of synchrotron-radiation-based micro computed tomography at the beamline BW 2 (HASYLAB at DESY). The level of detail can be even improved by the application of sophisticated computer vision tools, which enables the extraction of the vascular tree down to the capillaries and of the course of nerve fibers as well as the topology of the osseous lamina radialis, which assembles the nerve fibers from the hair-cells to the ganglia in the center of the cochlea, the modiolus. These non-destructively obtained three-dimensional data are principal for the refined understanding of the hearing process by membranes morphologies and further anatomical features at the cellular level and for teaching purposes in medical curricula.