Morphological aspects of Kölliker’s organ in the developing Mammalian Cochlea: A review

Abstract The development of the mammalian auditory system is a complex process characterized by cellular differentiation and morphological changes. It begins during embryogenesis and continues postnatally. This study focuses on Kölliker’s organ (KO), a transient structure which is essential for cochlea maturation and auditory function. A comprehensive literature search on the morphological features of KO in mammals was conducted across different databases. Following strict inclusion criteria, nine studies were selected for review. In addition, a histological analysis on murine embryos across various postnatal stages (P0, P5, P10, P15, P20, and P22) was performed, using traditional histochemical techniques. Images were stored from the Bioacoustics Laboratory at the University of Padua. From our study, it emerged that KO originates from the ectoderm. KO is characterized by closely spaced columnar cells with specific morphological traits, including extensive intercellular gap junctions, composed of Connexins. Significant cellular transformations occur in KO as its cells transit from columnar to cuboidal forms, ultimately leading to their disappearance by P15. This morphological progression is critical for the Corti’s organ formation and for the maturation of the auditory pathway. KO is also important for structural support, ATP signaling, and synapse formation in the inner hair cells. Thus, KO plays a pivotal role in cochlear maturation, and it is potentially involved in auditory disorders.