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Vertical development of the secondary palate in hamster embryos following exposure to 6-mercaptopurine
D N Burdett1, J D Waterfield, R M Shah
1Department of Oral Biology, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
Insights
6-mercaptopurine (6MP) treatment disrupts hamster secondary palate development by inhibiting mesenchymal cell DNA synthesis and causing cell damage. This leads to reduced cell numbers and retarded vertical shelf development.
Area of Science:
- Developmental biology
- Teratology
- Cell biology
Background:
- Secondary palate formation is crucial for oral function.
- Understanding cellular mechanisms driving palate development is essential.
- Disruptions during development can lead to congenital defects.
Purpose of the Study:
- To investigate the cellular basis of secondary palate vertical development in hamster embryos.
- To determine the effects of 6-mercaptopurine (6MP) on palatal shelf development.
- To elucidate the role of mesenchymal cell proliferation and integrity in palate formation.
Main Methods:
- Quantification of palatal shelf cross-sectional area and cell counts (epithelial and mesenchymal).
- Assessment of mesenchymal cell damage in 6MP-treated embryos.
- Measurement of DNA synthesis using 3H-thymidine incorporation in control and treated groups.
Main Results:
- Both control and 6MP-treated palates showed increases in shelf area and cell numbers with age.
- Mesenchymal cell density and DNA synthesis peaks observed in controls were absent in 6MP-treated embryos.
- 6MP treatment induced progressive mesenchymal cell damage, peaking mid-gestation, and reduced DNA synthesis.
Conclusions:
- Mesenchymal cell DNA synthesis and proliferation are critical for initial palatal shelf development.
- 6MP-induced depression of DNA synthesis, reduced cell numbers, and cell damage significantly retard vertical palate development.
- This study highlights the sensitivity of developing palates to antimetabolite exposure.
Abstract:
Cellular aspects of vertical development of the secondary palate were examined in control and 6-mercaptopurine (6MP)-treated hamster embryos. Cross-sectional area of the palatal shelf was measured and the numbers of both epithelial and mesenchymal cells counted. Also, in 6MP-treated palates the damaged mesenchymal cells, characterized by the presence of dense bodies, were counted. DNA synthesis in both control and treated fetuses was measured by 3H-thymidine incorporation. The results indicated that both the shelf area and cell numbers increased with age in control and 6MP-treated palates. However, in controls the mesenchymal cell density and DNA synthesis showed two peaks that were absent following 6MP treatment. Unlike controls, in treated embryos the damage to mesenchymal cells became increasingly pronounced between days 10:00 and 10:12 but subsided by day 11:00 of gestation. It is suggested that a major force in the development of the initial primordia and early vertical development of the palatal shelf may be provided by a spurt of DNA synthesis in the mesenchymal cells resulting in their increased number. After 6MP treatment, depression of DNA synthesis and consequent reduction in the mesenchymal cell number and density followed by cell damage lead to retardation in the vertical development of the palatal shelves.