1693-P: Rapamycin Reduces Maternal Diabetes-Induced Neural Tube Defects by Suppressing Premature Senescence

Maternal diabetes significantly increases the risk of structural birth defects. Senescence occurs after neural tube closure. We aimed to determine whether maternal diabetes induces premature senescence in the developing neuroepithelium. Maternal diabetes induced robust senescence associated β-galactosidase (SAβG) activity in the apical side of the developing neuroepithelium at embryonic day 8.5 (E8.5). The major senescence mediator p21 was induced preceding the SAβG signal at the same region. p21 gene deleted embryos of diabetic dams had a significantly lower neural tube defects (NTDs) incidence (3.6%) compared to wild type litter mates (25.9%). The transcriptional factor Forkhead transcription factor 3a (FoxO3a) is activated in diabetic embryopathy, and Foxo3a knockout reduces maternal diabetes-induced NTDs. Our data showed Foxo3a deletion diminished the signals of SAβG, and abrogated diabetes-increased abundance of p21 and DNA damage response proteins. MicroRNAs have been identified as novel inducers of cellular senescence. Two FoxO3a binding sites were found in the promote region of miR-200c. In vitro study confirmed both FoxO3a and high glucose stimulated miR-200 promoter activity. miR-200c null embryos had a lower NTD rate (4.3%) compared with that of WT embryos (29.2%) from diabetic dams. miR-200c repressed the expression of ZEB1 and ZEB2, which are transcription repressors for p21. In addition to the revelation of the gene regulation pathway in maternal diabetes-induced premature senescence, we found intraperitoneal injection of the senescence inhibitor Rapamycin in diabetic dams during E5.5-E9.5 diminished SAβG signal, and reduced the NTD rate from 24.0% to 4.5%) in diabetic pregnancy. Thus, our study revealed a novel FoxO3a-miR-200c-p21-mediated premature senescence pathway, and provided the mechanistic basis for targeting premature senescence in preventing diabetes-induced NTDs.