To explore the expression and roles of versican during the development of the embryonic tooth germ.
Methods:
The mandibular first molar tooth germs were obtained from E12, E13.5, E15, E16, E18.5 ICR mouse. The core protein of versican and its CS chains were detected by immunohistochemical method, its mRNA were investigated by in situ hybridization. To confirm versican mRNA signals were expressed in dental epithelium,Total RNA were extracted from enamel organ and dental mesenchyme of E16 tooth germ. semi-quantitative RT-PCR were performed.To further investigate the biosynthetic activity of versican, the separated enamel organ and dental mesenchyme from E16 were cultured, matablic labelled with 35S,and biochemical analysis were performed.
Result:
1. The expression of versican was stage-related. futhermore,it was unexpectedly expressed in dental epithelium as early as E12, and then detected in its underlying dental mesenchymal tissues at E13.5,this pattern maintained to E18.5. its mRNA signals were dissapeared from the differentiated cells such as stellate reticulum, ododntoblasts and ameloblasts, but its core protein can be detected in stellate reticulum. The immunohistochemical result of CS-GAGs indicated that the sulfate pattern of versican core protein in dental epithelia was C4S, while it was C6S and C4S in dental mesenchyme.
2. The semi-quantitative RT-PCR results confirmed that dental epithelium at E16 expressed versican mRNA at comparable level to that in dental mesenchyme.
3. The separated organ culture system combined with metablic labeling of 35S indicated that about 5/8 volume of 35S –labeled versican-like PG was synthesized by dental epithelium as compared to dental mesenchyme.
Conclusion:
The present study confirmed for the first time that dental epithelium can synthesize significant amount of versican. versican may act roles by modifying the ECM and cell-matrix interactions directly or indirectly during early embryonic tooth germ development through its core protein and its sulfated CS chains.