In vitro study of morphological changes of the cultured otocyst isolated from the chick embryo / Estudio in vitro de los cambios morfológicos del otocisto cultivado aislado del embrión de pollo

The aim of this study was to observe morphological changes of the cultured otocysts isolated from various stages of the chick embryo. Isolated otocysts were dissected from embryonic day, E2.5-4.5 of incubation (HH stage 16-26) according to stages of developing inner ear. Morphology of the chick otocyst exhibited an ovoid shape. The width and height of the otocyst were 0.2 mm and 0.3 mm, respectively. Elongation of a tube-like structure, the endolymphatic duct, was found at the dorsal aspect of the otocyst. The cultured otocyst is lined by the otic epithelium and surrounding periotic mesenchymal cells started to migrate outwards the lateral aspect of such epithelium. Notably, the acoustic-vestibular ganglion (AVG) was observed at the ventrolateral aspect of the otocyst. Appearance of AVG in vitro can be applied for studying chemical-induced ototoxicity and sensorineural hearing loss. It was concluded that the organ-cultured otocyst of the chick embryo could be used as a model to study sensory organ development of avian inner ear.

El objetivo de este estudio fue observar los cambios morfológicos de otocistos cultivados aislados en las diversas etapas del desarrollo del embrión de pollo. Otocistos aislados fueron obtenidos de embriones día, E2.5-4.5 de incubación (HH etapa 16-26) de acuerdo a las etapas de desarrollo del oído interno. El otocisto de pollo presentó una morfología ovoide. El ancho y la altura del otocisto fue de 0,2 mm y 0,3 mm, respectivamente. En la cara dorsal del otocisto se visualizó el alargamiento de una estructura similar a un tubo, el conducto endolinfático. El otocisto cultivado está revestido por epitelio ótico y células mesenquimatosas perióticas que comienzan a migrar hacia el exterior de la cara lateral en búsqueda del epitelio. En particular, el ganglio acústico-vestibular (GAV) fue observado en la parte ventrolateral del otocisto. La aparición de GAV in vitro puede ser aplicado para el estudio de la ototoxicidad inducida por productos químicos y la pérdida de audición neurosensorial. Se concluyó que el otocisto cultivado de embrión de pollo podría ser utilizado como un modelo para estudiar el desarrollo de órganos sensoriales del oído interno aviar.

The development of the ear of rabbit embryo.

The ear consists of three parts which are different origin but function as one unit. The internal ear originates from the surface ectoderm covering the lateral sides of myelencephalon at the fourth week. This ectoderm thickens to from the otic placode and then invaginates to form the otocyst and splits from the surface ectoderm. The otocyst or otic vesicle divides into 2 parts, the ventral cochlear and the dorsal utricular portions. The cochlear gives rise to the saccule and the cochlear duct while the utricular portions gives rise to the uteicle, semicircular ducts and endolymphatic duct. These epithelial structures so formed are known as the membranous labyrinth. The bony labyrinth and the perilymphatic space originate from the mesenchy otic capsule. The middle ear, consisting of the tympanic cavity and the auditory tube, are lined with epithelium of the endodermal origin of the first pharyngeal pouch. The ear ossicles, the malleus and incus are derived from the first and the stapes from the second arch cartilages. The external auditory meatus develops from the first pharyngeal cleft, while the tympanic membrane originates from the mesenchyme between. In order to understand ear development, pig and chick embryos were used in the laboratory studies. Since the pig embryos are presently not available, this compared the ear development of the pig and rabbit embryos, which indicate that the ear of the pig and rabbit develob in the same manner and the rabbit embryos can be used in the future instead of pig embryos for studying ear development.