Lens fibre transdifferentiation in cultured larval Xenopus laevis outer cornea under the influence of neural retina-conditioned medium.

The outer cornea of larval Xenopus laevis can reprogram cell differentiation when cultured in medium conditioned by X. laevis neural retina (XRCM) or by Rana esculenta neural retina (RRCM). Under these experimental conditions corneal cells showed the same series of cytological changes of fibre cell differentiation observed during ontogenesis and in vivo lens regeneration: enlargement of nuclei and nucleoli, increase of ribosomal population (cytoplasm-basophilia), cell elongation gradual loss of basophilic properties and acquisition of acidophilic properties for crystallin synthesis and accumulation. These events were completely dependent on XRCM or RRCM, suggesting that the neural retina secretes a factor(s) which initiates and sustains lens fibre transdifferentiation of the corneal epithelial cells. This culture system appears to be a suitable one for investigating the control of lens fibre transdifferentiation in vitro.