Fig. 9. FGF10 protein induces up-regulation of activin ßB and Tgfa mRNAs and promotes eyelid closure in an explant culture. An FGF10- or PBS-soaked bead was implanted in the eyelid mesenchyme. The expression patterns of activin ßB, Tgfa and F-actin were examined 12 hours after the culture of E15 normal eyelid anlagen. (A-D) The expression domain of activin ßB (indicated by the dotted lines in A and B) was enlarged after FGF10 bead implantation (B). (C) Higher magnification of the area boxed in B. Activin ßB is expressed by subsets of cells in the thickened epidermis after FGF10 application. (D) Histology of a serial section of the explant shown in C and I. The epidermis (shown by the green line) in the vicinity of an FGF10 bead was thickened, as compared with that in F. (E) Activin ßB is not expressed in the normal epidermis abutting a PBS bead. (F) Histology of a serial section of the explant shown in E and J. Normal thickness of the epidermis is indicated by the green line. (G-J) The expression domain of Tgfa is enlarged after FGF10-bead implantation (H). The arrowhead in G and H indicates the leading edge of the eyelid. (I) Tgfa is distinctly expressed in the thickened epithelium abutting the FGF10-bead. (K,L) Phalloidin staining of the eyelid tips after FGF10-bead (K) or PBS-bead (L) implantation. The area showing accumulation of F-actin is enlarged after FGF10 application (arrowheads in K). The arrows in K and L indicate the epithelial leading edge. (M) Schematic representation of an explant culture of Fgf10-null eyelid anlagen and calculation of the percentage of eyelid closure after FGF10 application. The area of the eyelid opening was measured before and after the culture. Two beads were implanted in the eyelid mesenchyme. (N) FGF10 protein can promote eyelid closure in the Fgf10-null eyelid anlagen. ActB, activin ßB; bd, bead; co, cornea; lld, lower eyelid; uld, upper eyelid. Scale bars: 100 µm (A,B,G,H); 50 µm (C-F,I,J); 50 µm (K,L).