Transforming growth factor beta: does it direct otic capsule formation?

Interactions between the epithelium of the otocyst and surrounding periotic mesenchyme direct the formation of the capsule of the mammalian inner ear. In the present study, we have characterized the temporal-spatial distribution of transforming growth factor beta 1 (TGF-beta 1) in the epithelial and mesenchymal tissues that compose the inner ear between 10 and 14 days of embryonic development. In addition, using high-density cultures of periotic mesenchyme to model otic capsule formation, we have demonstrated that exogenous TGF-beta 1 can modulate otic chondrogenesis by acting as either an enhancer or a suppressor of this process. Our immunohistochemical and in vitro results suggest a paracrine action for this growth factor in modulation of epithelial-mesenchymal tissue interactions and otic morphogenesis.