PAX6 and hydrops fetalis: Collectively, these data indicate that the phenotype and differentiation of HF epithelial stem cells can be influenced by a specific microenvironment and that factors derived from limbal fibroblasts appear to induce expression of the corneal epithelial differentiation marker K12 together with its transcription factor Pax6, whereas factors derived from corneal fibroblasts rather promote expression of the epidermal differentiation marker K10.