Immunohistochemical study of genesis of the mouse oral vestibule.

Immunohistochemical light microscopy by the enhanced polymer one-step staining (EPOS) method and immunohistochemical confocal laser scanning microscopy by the labelled streptavidin biotin (LsAB) method were performed on the developing vestibular lamina (VL) of fetal mice at stages from E11 to E14, and the immunohistochemical findings were compared with the findings in the developing dental lamina (DL) and tooth germ. pRb and PCNA were immunolocalized and found to be related to the temporal and spatial expression of cytokines and receptors in the primary epithelial band, VL, DL/enamel organ, and associated mesenchyme. The following results were obtained: 1) EGF, TGFalpha, EGFR, PCNA, FGF2, pRb, and FGFR1-4 were immunolocalized in the developing tissues. 2) Cytokine expression patterns indicated that the EGF family and FGF2 essentially induced VL generation and cell proliferation. 3) FGFR1 was diffusely localized in the primary epithelial band, but was strongly expressed in the E12-14 VL and DL/enamel organ. By contrast, EGFR internalization was observed in the differentiating E13 VL. 4) Expression of pRb was intensely localized in the stratum germinativum of the E13 VL and corresponded to CK-10 expression in the keratinizing VL. The results of this study suggest a mechanism in which FGFR1 regulates pRb to induce proliferation of cells in the VL and DL/enamel organ, and, in particular, to incite keratocyte differentiation and subsequent exfoliation of keratinizing VL cells.