Organ of Corti of the fetal mouse in culture Free

The organ of Corti of the fetal mouse in culture provides a unique opportunity to study the development of the afferent innervation of the hair cells. Cultures were explanted between 13 to 18 days of gestation and maintained up to 14 days. The leading finding is that all the major fiber systems that are present in the intact animal develop also in culture. Formation of radial patterns in the spiral ganglion follows (1) the disappearance of the subepithelial plexus and a pronounced reduction in the total number of peripheral fibers, and (2) rearrangement of spiral ganglion cells into distinct groups that give rise to individual radial bundles. Development of the innervation of inner hair cells begins with an arrest of the growth of radial fibers around the inner hair cells, formation of neurofibrillar caps, and formation of the inner spiral plexus and bundle. Outer spiral fibers penetrate the outer hair cell region as the “deep radial fibers” of Tello. This is followed in succession by (a) a stationary period during which growth is suspended, (b) positioning of the growing tips toward the base, (c) a period of resumed growth in a spiral direction, and (d) rearrangement of fibers into three outer spiral bundles and formation of neurofibrillar caps upon the outer hair cells. Our findings show that orderly innervation patterns, indistinguishable from those observed in the intact animal, are produced in culture. Thus the development of innervation in the organ of Corti of the mouse appears to be determined by local factors. [Work supported by NSH grants NS15061, NS12732, and NS2P3‐03352.]