Effetti teratogeni del 4-metilzimosterone: studi prliminari

Hydroxysteroid (17-beta) dehydrogenase 7 (HSD17B7) is a short-chain dehydrogenase reductase involved in the post-squalene cholesterol biosynthesis and responsible of the conversion of zymosterone to zymosterol. Rudolph mouse, a model presenting a mutated allele of HSD17B7, showed pronounced defects in both central nervous system and skeletal development, together with a reduction of Sonic Hedgehog (SHH) signalling. Furthermore, consistent with a reduction of HSD17B7, an accumulation of 4-methylzymosterone and zymosterone was detected by chromatography-mass spectrophotometry in tissues as liver and brain in embryos. In this study, mice were treated with a mixture of 4-methylzymosterone and 4-methylfecosterone (termed ¿keto 1¿ fraction: 10 mg/kg) and embryos were collected at E 10.5, E 14.5 and E 16.5, in order to detect the possible teratogenic effects of 4methylzymosterone and compare the observed phenotypes with the Rudolph mouse. The hypothesis behind this study is that the accumulation of 4-methylzymosterone, because of the defects of HSD17B7, might downregulate the SHH signaling, which is crucial for the mouse development. Although embryos at E 10.5 treated with keto 1 did not showed holoprosencephaly (the brain morphology is comparable with the control group), a real time PCR showed that at E 10.5 the expression of SHH is dramatically decreased in treated group. Embryos at E14.5 treated with keto 1 showed important hemorrhages throughout the body, despite of the control group; moreover, E 14.5 embryos showed apoptosis in aortic trunk area by immunohistochemistry (IHC) with caspase 3 and TUNEL, and in the forming telencephalic vesicle by IHC with caspase 3. Finally, Alcian Blue staining for bones and cartilages performed on E 16.5 embryos showed some differences in the development of forelimbs of the treated group. Although these preliminary data produced some encouraging answers, further studies will be conducted, to produce statistically reliable data.