Inductive tissue interactions during inner ear development.

Inductive tissue interactions were studied in the otocyst of the CBA/CBA mouse. Otocysts with surrounding mesenchyme explanted at the 12.5-13th gestational day and cultured in vitro for 4 days underwent morphogenesis with formation of semicircular canals, vestibular organs, and some cochlear coiling. Without their surrounding mesenchyme only little, if any, development was seen. However, otocysts without mesenchyme but grown in a medium precultured with mesenchyme did develop normally. A soluble and diffusible induction factor is apparently produced by mesenchyme and also by other fetal organs. Cell-cell contact may not be needed for induction.