EGF-dependent lobule formation and FGF7-dependent stalk elongation in branching morphogenesis of mouse salivary epithelium in vitro.
When supplemented with appropriate growth factors, salivary gland epithelial explants isolated from mouse embryos undergo branching morphogenesis in vitro in the absence of mesenchyme. Epidermal growth factor (EGF) induces lobule formation, while fibroblast growth factor 7 (FGF7) promotes stalk elongation. A mixture of EGF and FGF7 produces an intermediate morphology, which resembles the branching pattern of salivary epithelium observed in vivo. To investigate how lobule formation and stalk elongation are related to the pattern of epithelial cell proliferation induced by EGF and FGF7, we performed a bromodeoxyuridine labeling study in whole-mount preparations. During the initial steps of lobule formation in EGF cultures, cleft and non-cleft regions had similar proliferative activity. However, once clefts had fully deepened, cells with low proliferative activity appeared at the bottom of the clefts. In contrast, during stalk elongation in FGF7 cultures, distal regions of the explants always showed higher proliferative activity than proximal regions. These results suggest that stalk elongation, but not cleft formation, may result from differential cell proliferation.
Morita
K
K
Department of Biology, Faculty of Science, Chiba University, Japan.
Nogawa
H
H
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000196:embryology; D051526:Fibroblast Growth Factor 10; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D006133:Growth Substances / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D051379:Mice; D008813:Mice, Inbred ICR; D009024:Morphogenesis; D013363:Submandibular Gland / Q000187:drug effects / Q000196:embryology*; D013997:Time Factors
C496454:Fgf7 protein, mouse; D051526:Fibroblast Growth Factor 10; D006133:Growth Substances; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D004247:DNA