In vitro cultivation of the fetal guinea pig inner ear

Fetal guinea pig inner ears, gestational age from 21 to 54 days, were cultivated in vitro and then observed with light and electron microscopes. Early 21-day gestation otocysts developed cartilaginous capsules from differentiating mesenchyme and discrete neurosensory structures from endolabyrinthine epithelium. Coiling of the cochlea occurred. Older, differentiated inner ears showed progressive increase in size and development of the labyrinth. The 26-day gestation cochlea, maintained for 12 days in vitro, doubled in size with development comparable to the 37-day gestation in vivo control. The large size of the guinea pig inner ear resulted in varying degrees of necrosis. However, the well-defined growth and development of the guinea pig fetal inner ear in vitro indicates the efficacy of the technique and suggests that similar success would be forthcoming with other animals used in audiologic research, such as chinchilla and hamster.