Fetal hypoxia and hyperglycemia in the formation of phenytoin-induced cleft lip and maxillary hypoplasia

LncRNA HOTAIRM1 promotes dental follicle stem cell-mediated bone regeneration by regulating HIF-1α/KDM6/EZH2/H3K27me3 axis

Large bone defect reconstruction undergoes hypoxia and remains a major practical challenge. Bone tissue engineering with a more promising stem cell source facilitates the development of better therapeutic outcomes. Human dental follicle stem cells (hDFSCs) with superior multipotency, osteogenic capacity, and accessibility have been proven a promising cell source for bone regeneration. We previously identified a novel long noncoding RNA (lncRNA), HOTAIRM1, to be highly expressed in hDFSCs. Here we found that HOTAIRM1 overexpressed hDFSCs promoted bone regeneration in rat critical-size calvarial defect model. Mechanically, HOTAIRM1 was induced in hDFSCs under hypoxic conditions and activated HIF-1α. RNA-sequencing analysis indicated that HOTAIRM1 upregulated oxygen-sensing histone demethylases KDM6A/B and suppressed methyltransferase EZH2 via targeting HIF-1α. The osteogenic differentiation of hDFSCs was accompanied with demethylation of H3K27, and HOTAIRM1 overexpression decreased the distribution of H3K27me3 in osteogenic genes, including ALP, M-CSF, Wnt-3a, Wnt-5a, Wnt-7a, and β-catenin, thus promoted their transcription. Our study provided evidence that HOTAIRM1 upregulated KDM6A/B and inhibited EZH2 in a HIF-1α dependent manner to enhance the osteogenesis of hDFSCs. HOTAIRM1-mediated hDFSCs may serve as a promising therapeutic approach to promote bone regeneration in clinical practice.

Preventing Teratogenicity in Women with Epilepsy

Over the last 50 years there has been a significant increase in our understanding of the issues faced by women with epilepsy, in both planning and undertaking pregnancy. The risks of teratogenicity associated with antiseizure medications have emerged slowly. The major pregnancy registers have substantially contributed to our knowledge about teratogenic risk associated with the commonly used antiseizure medications. However, there are substantial gaps in our knowledge about the potential risks associated with many third-generation drugs. The remit of the pregnancy registers and the wider research focus has moved beyond anatomical major congenital malformations. Increasingly neurodevelopmental and behavioral abnormalities have been investigated after in utero exposure to antiseizure medications. Public health approaches can help reduce the risk of teratogenicity. However, neurologists still have a vital role in reducing the risk of teratogenicity at an individual level for women attending their clinic. They also have responsibility to ensure that women with epilepsy are aware of the rationale for the different available options.

The effect of phenytoin on embryonic heart rate in Vivo

Phenytoin is a known human teratogen with unknown etiology. Several mechanisms have been proposed including disturbances in folate metabolism, induction of embryonic hypoxia following phenytoin-induced bradycardia, free radical formation following re-oxygenation and phenytoin-induced maternal hyperglycemia. Using high frequency ultrasound, we demonstrated that phenytoin induced a dramatic decrease in the heart rate of embryos. This coincided with a moderate transient decrease in maternal heart rate and blood glucose levels. Embryonic heart rate had not fully recovered 24 h later in some embryos despite normal maternal physiological parameters. In a separate study, extent of hypoxia was measured using the marker pimonidazole. Phenytoin-exposed embryos did not demonstrate increased hypoxia compared to control embryos at 2, 4, 8 or 24 h dosing. Together our results show that phenytoin induces malformations as a result of a combination of insults: embryonic bradycardia, maternal bradycardia and maternal hyperglycemia. However, this does not appear to result in measurable embryonic hypoxia in our animal model.

Phenytoin Inhibits Cell Proliferation through microRNA-196a-5p in Mouse Lip Mesenchymal Cells

Cleft lip (CL) is one of the most common birth defects. It is caused by either genetic mutations or environmental factors. Recent studies suggest that environmental factors influence the expression of noncoding RNAs [e.g., microRNA (miRNA)], which can regulate the expression of genes crucial for cellular functions. In this study, we examined which miRNAs are associated with CL. Among 10 candidate miRNAs (miR-98-3p, miR-101a-3p, miR-101b-3p, miR-141-3p, miR-144-3p, miR-181a-5p, miR-196a-5p, miR-196b-5p, miR-200a-3p, and miR-710) identified through our bioinformatic analysis of CL-associated genes, overexpression of miR-181a-5p, miR-196a-5p, miR-196b-5p, and miR-710 inhibited cell proliferation through suppression of genes associated with CL in cultured mouse embryonic lip mesenchymal cells (MELM cells) and O9-1 cells, a mouse cranial neural crest cell line. In addition, we found that phenytoin, an inducer of CL, decreased cell proliferation through miR-196a-5p induction. Notably, treatment with a specific inhibitor for miR-196a-5p restored cell proliferation through normalization of expression of CL-associated genes in the cells treated with phenytoin. Taken together, our results suggest that phenytoin induces CL through miR-196a-5p induction, which suppresses the expression of CL-associated genes.