Method: Embryonic day eight (E8) chicken palatal shelves were cultured on nucleopore polycarbonate membranes in isolation from each other for 24, 48, or 72 h in 37oC with 5% CO2. Medium was replaced every 24 h with fresh TGFß3 (50 ng/ml), clustered EphB2/Fc (4 µg/ml), or control IgG Fc (also 4 µg/ml). TGFß3 or EphB2/Fc at these concentrations normally cause complete fusion within 72 h when shelves are in contact.
Result: We predicted that clustered (bioactive) Eph/B2/Fc would cause EMT and epithelial seem degradation even in the absence of shelf-to-shelf MEE contact. Instead, we observed an unusual hypertrophy of the epithelial layer. The cells in this layer lacked the polarity and organization of a normal epithelium, but neither did they display the fibroblastic morphology of the underlying mesenchyme.
Conclusion: Application of clustered, soluble EphB2/Fc is not sufficient to cause palatal EMT and epithelial layer degradation without shelf-shelf contact. Instead, ephrin signaling in the absence of the contact-mediated signal appears to initiate a growth/proliferation program in the epithelium. We are currently characterizing the consequences of this signaling and its underlying mechanism.
Supported by Baylor Oral Health Foundation
Keywords: Cleft lip-palate, Embryology, Ephrins, Growth & development and Tissue or organ culture
See more of: Craniofacial Biology