The distribution of the 2 homodimer isoforms of platelet-derived growth factor (PDGF)-AA and -BB, and their receptors (PDGF alpha-receptor and PDGF beta-receptor) were mapped immunocytochemically during the development of the embryonic mouse secondary palate, from embryonic day (E) 12 to E15. The staining patterns of PDGF-AA/alpha-receptor and PDGF-BB/beta-receptor are different. Generally, the former is present and the latter is sparse/absent during the period of palate development. The localisations of PDGF-AA and alpha-receptor are more intensive in the epithelia than in the mesenchyme, and change temporally during palatal shelf elevation, midline epithelial seam formation and disruption. Before the palatal shelf has elevated (E13), PDGF alpha-receptor is present in the palatal mesenchyme, nasal and medial edge epithelia (MEE), whilst PDGF-AA stains lightly in the palatal epithelia. During palatal midline epithelial seam formation and following its degeneration throughout E14, PDGF-AA and PDGF alpha-receptor were intensively colocalised in the nasal and midline seam epithelia. These findings indicate that the interaction between PDGF-AA and its receptor may participate in palate development, particularly in regulating palatal midline epithelial seam formation and degeneration.
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