Whole organ culture in rotating bioreactor: the rat embryonic inner ear

In eutherian mammals, the organ responsible for the transduction of sound waves into nerve impulses is called the organ of Corti. This structure located within the cochlea, a portion of the inner ear, is composed by two types of cells: sensory hair cells and non-sensory supporting cells. All these cells are distributed according to a specific arrangement along the whole length of the cochlea. So far, the mammalian inner ear is very sensitive to damage, with no hair cell replacement or cell proliferation occurring in the cochlea. That is why understanding the mechanisms that regulate the mammalian cochlear development is important for pursuing strategies to induce sensory hair cells regeneration. Here, we present a technique of whole embryonic inner ear culture in rotating bioreactors. Besides, we compare two different culture media, DMEM and Neurobasal-A.
Rat inner ears are sampled at the 16th embryonic day (E16) and grown in rotating bioreactors during 48h or six days. After 48h, semithin sections realized in the growing cochlea show the development of the ventral epithelium and ultrathin sections confirm the differentiation of the sensory hair cells. Using immunochemistry techniques on our material after 48h or six days in vitro, we show that all the cells of the organ of Corti are differentiating, whichever the culture medium used.
Our preliminary results demonstrate that organ culture of the embryonic inner ear in rotating bioreactor is possible. Such a method provides an in vitro model for the investigation of developmental, regulatory, and differentiation processes that could be helpful in the understanding of the mechanisms underlying the development of the mammalian cochlea.