Immunolocalization of fibroblast growth factor-2 (FGF-2) during embryonic development of the rat submandibular gland

Morphogenesis and cytodifferentiation of the salivary glands are dependent on epithelio-mesenchymal interactions, which are mediated either by direct intercellular contacts or by the expression of signaling molecules. One of these signaling molecules, fibroblast growth factor (FGF), is known to play a crucial role in embryonic cell proliferation, cell differentiation and cell migration. FGF-2 has been identified as a factor facilitating neoplastic progression in salivary glands in humans. The aim of this study was to elucidate the spatial and temporal expression of fibroblast growth factor-2 (FGF-2) in the developing rat submandibular gland. Submandibular glands were removed from foetal rats on days E14.5, 15.5, 16.5, 18.5 and 19.5. Immunolocalization utilizing an antibody to FGF-2 was performed on sections of the submandibular gland at all the derived stages. Diffuse and faint immunolocalization of FGF-2 was seen in the epithelium and mesenchyme of the submandibular gland on days E14.5, E15.5 and E16.5. Intense immunoreactivity for FGF-2 was observed in epithelial components of the gland i.e. in the differentiating acini and ducts, on day E18.5, while on day E19.5, the signal was again less intense. These observations suggest that FGF-2 may play a specific role in cytodifferentiation of the submandibular gland at a particular stage of development.