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Histological study of cell death in digital malformations induced by 5-azacytidine: suppressive effect of caffeine
1Radiation Biology Center, Kyoto University, Japan.
Abstract:
The present study investigated microscopically the process of 5-azacytidine (5-AC)-induced digital teratogenesis and caffeine's suppressive effect on this process. Three distinct zones of programmed cell death were observed in control and caffeine-treated embryos 3 hours after 5-AC injection: the preaxial and postaxial ectodermal regions and the central part of the mesodermal regions. 5-AC temporarily suppressed programmed cell death in the ectoderm and mesoderm 3 hours after it was injected. However, caffeine promoted programmed cell death; normal programmed cell death was observed in the limb buds of embryos whose dams were treated with 5-AC and caffeine. The percentage of total cell death in hindlimb buds of embryos treated with 5-AC and caffeine was higher than that from embryos treated with 5-AC, whereas 5-AC-induced digital malformations were reduced by post-treatment with caffeine. Cell death reached a maximum 12 hours after the injection in limb buds from 5-AC and caffeine-treated embryos and at 24 hours in the 5-AC treated embryos. Furthermore, in the 5-AC and caffeine-treated embryos, the frequency of cell deaths at 12 hours increased almost linearly with the doses of caffeine in parallel with the reduction of 5-AC-induced malformation frequency by caffeine. These results suggest that although induced cell death may be one of the factors leading to digital malformations produced by 5-AC, it is not essential, and the existence of other factors affecting the pattern formation of the limb bud is proposed.
Insights
Caffeine counteracts 5-azacytidine (5-AC)-induced digital malformations by promoting programmed cell death. While 5-AC suppresses cell death, caffeine restores it, reducing birth defects.
Area of Science:
- Developmental Biology
- Teratology
- Pharmacology
Background:
- 5-azacytidine (5-AC) is a known teratogen that can induce digital malformations.
- Programmed cell death (apoptosis) plays a crucial role in limb development.
- Caffeine's effects on 5-AC-induced teratogenesis are not fully understood.
Purpose of the Study:
- To investigate the microscopic mechanisms of 5-azacytidine (5-AC)-induced digital teratogenesis.
- To evaluate the suppressive effect of caffeine on 5-AC-induced digital malformations.
- To elucidate the role of programmed cell death in this process.
Main Methods:
- Microscopic examination of programmed cell death zones in 5-AC and caffeine-treated embryos.
- Quantification of cell death percentages in hindlimb buds at different time points post-injection.
- Dose-dependent analysis of caffeine's effect on malformation frequency.
Main Results:
- 5-AC temporarily suppressed programmed cell death in limb bud ectoderm and mesoderm.
- Caffeine promoted programmed cell death, counteracting 5-AC's suppressive effect.
- Caffeine treatment reduced the incidence of 5-AC-induced digital malformations, with increased cell death correlating with reduced malformations.
Conclusions:
- Induced cell death is a significant factor, but not the sole cause, of 5-AC-induced digital malformations.
- Caffeine mitigates 5-AC teratogenicity by restoring programmed cell death.
- Other factors influencing limb bud pattern formation likely contribute to 5-AC-induced defects.