Biglycan and Decorin expressed in MEE cells during palatal fusion

Background: Palatal fusion requires medial edge epithelia (MEE) from adjacent palatal shelf adherence. Previous investigators have shown that chondroitin sulfate proteoglycans (CSPG) were secreted apically on the MEE prior to palatal fusion. The appearance of CSPG on the apical surface of MEE was mediated by TGFβ3; however, it was not clear which CSPG core protein was expressed to mediate palatal shelf adherence.

Objectives: To determine the core protein(s) associated with the CSPG expressed on the surface of the MEE.

Methods: Palatal shelves from E8 chicken embryos were cultured in serum-free media with or without TGFβ3 (10ng/ml) for 24, 48, or 72 hours. After culture, the MEE was separated from the underlying mesenchyme by using Dispase II (2.4U/ml). RNA was extracted from epithelium and mesenchyme separately and reverse transcribed into cDNA. mRNA expression levels of aggregan, decorin, and versican were analyzed using realtime PCR. Protein expression levels of these core proteins were examined on both chicken palate and the E13.5 mouse palate by immunofluorescent staining.

Results: Biglycan and decorin were expressed in the palatal shelf epithelium and mesenchyme during fusion in both mice and chickens. Before fusion, biglycan and decorin were expressed on the surface of the epithelium. Aggrecan and versican were not found on the surface of the palatal shelves during fusion. Neutralizing antibodies specific for TGFβ3 decreased the protein expression of the biglycan and decorin.

Conclusion:Biglycan and decorin are small leucine-rich repeat proteins in the extracellular matrix of connective tissues. Their expression on the surface of the palatal MEE during fusion suggests that they have a role in mediating the adherence of the palatal shelves. In addition, their expression was regulated by TGFβ3 signaling, suggesting they may be important in the morphological and cytoskeletal changes during EMT of the MEE cells.

Supported: Baylor Oral Health Foundation, March of Dimes