tretinoin and Teratogenesis

Appropriate levels of retinoic acid (RA) signaling are critical for normal heart development in vertebrates. A fascinating property of RA signaling is the thoroughness by which positive and negative feedback are employed to promote proper embryonic RA levels. In the present short review, we first cover the advancement of hypotheses regarding the impact of RA signaling on cardiac specification. We then discuss our current understanding of RA signaling feedback mechanisms and the implications of recent studies, which have indicated improperly maintained RA signaling feedback can be a contributing factor to developmental malformations.

Topics: Animals; Heart; Heart Defects, Congenital; Humans; Teratogenesis; Tretinoin

In vitro human induced pluripotent stem (iPS) cells testing (iPST) to assess developmental toxicity, e.g., the induction of malformation or dysfunction, was developed by modifying a mouse embryonic stem cell test (EST), a promising animal-free approach. The iPST evaluates the potential risks and types of drugs-induced developmental toxicity in humans by assessing three endpoints: the inhibitory effects of the drug on the cardiac differentiation of iPS cells and on the proliferation/survival of iPS cells and human fibroblasts. In the present study, the potential developmental toxicity of drugs was divided into three classes (1: non-developmentally toxic, 2: weakly developmentally toxic and 3: strongly developmentally toxic) according to the EST criteria. In addition, the type of developmental toxicity of drugs was grouped into three types (1: non-effective, 2: embryotoxic [inducing growth retardation/dysfunction]/deadly or 3: teratogenic [inducing malformation]/deadly) by comparing the three endpoints. The present study was intended to validate the clinical predictability of the iPST. The traditionally developmentally toxic drugs of aminopterin, methotrexate, all-trans-retinoic acid, thalidomide, tetracycline, lithium, phenytoin, 5-fluorouracil, warfarin and valproate were designated as class 2 or 3 according to the EST criteria, and their developmental toxicity was type 3. The non-developmentally toxic drugs of ascorbic acid, saccharin, isoniazid and penicillin G were designated as class 1, and ascorbic acid, saccharin and isoniazid were grouped as type 1 while penicillin G was type 2 but not teratogenic. These results suggest that the iPST is useful for predicting the human developmental toxicity of drug candidates in a preclinical setting.

Topics: Aminopterin; Animals; Ascorbic Acid; Cell Differentiation; Cell Proliferation; Cells, Cultured; Drug Evaluation, Preclinical; Fibroblasts; Humans; Isoniazid; Methotrexate; Mice; Pluripotent Stem Cells; Saccharin; Teratogenesis; Toxicity Tests; Tretinoin

The frog embryo teratogenesis assay-Xenopus (FETAX) is an established method to evaluate the developmental toxicity of chemicals. In FETAX, a 48 h continuous exposure is usually conducted when the X. tropicalis embryo is used as the test model. In the present study, we exposed X. tropicalis embryos to nine known teratogens for four separate 12-h periods. The embryos showed great variations in response to nine tested compounds during different exposure periods. Based on the value of the score of malformations, the most sensitive 12 h exposure periods of embryos were significantly distinguished for all the compounds with the exception of NiCl2 . The embryos were the most sensitive to retinols (e.g. all-trans-retinoic acid and 9-cis-retinoic acid) during 0-12 h and to metal compounds (e.g. triphenlytin and CdCl2) during a 24 to 36 h exposure period. In the further 3 h exposure experiment, the most sensitive period could only be determined for one of three tested compounds. Based on the present results, we proposed an assay to determine a 12 h sensitive window of embryos to chemical exposure using Xenopus tropicalis.

Topics: Alitretinoin; Animals; Cadmium Chloride; Embryo, Nonmammalian; Nickel; Teratogenesis; Teratogens; Time Factors; Toxicity Tests; Tretinoin; Xenopus

To investigate the protective effect of folinic acid on the hatching ability and developmental defects in a retinoic acid-induced teratogenic model of chick embryo.. The experimental study was conducted at the Department of Anatomy, Regional Centre of the College of Physicians and Surgeons Pakistan, Islamabad, from February 2009 to February 2010. Chicken eggs were divided into two experimental groups and a control group. The first experimental group was injected with retinoic acid to induce a defective model, while the second experimental group was concomitantly injected folinic acid to observe its protective effects on retinoic acid-induced defects in the development and hatching process. Both groups were compared with the age-matched control group.. A total of 90 fertilised eggs were divided into three groups. The experimental groups had significantly more delayed and assisted hatchings compared to the control group (p<0.05) but the difference between the experimental groups regarding the mode and day of hatching was insignificant (p>0.05).. Irrespective of the presence of folinic acid, prenatal retinoic acid exposure significantly altered the hatchability characteristics in the experimental groups compared to the control.

Topics: Abdominal Wall; Abnormalities, Drug-Induced; Animals; Chick Embryo; Leucovorin; Limb Deformities, Congenital; Teratogenesis; Teratogens; Tretinoin; Vitamin B Complex

Holoprosencephaly (HPE) is a developmental anomaly characterized by inadequate or absent midline division of the embryonic forebrain and midline facial defects. It is believed that interactions between genes and the environment play a role in the widely variable penetrance and expressivity of HPE, although direct investigation of such effects has been limited. The goal of this study was to examine whether mice carrying a mutation in a gene encoding the bone morphogenetic protein (BMP) antagonist twisted gastrulation (Twsg1), which is associated with a low penetrance of HPE, are sensitized to retinoic acid (RA) teratogenesis. Pregnant Twsg1(+/-) dams were treated by gavage with a low dose of all-trans RA (3.75 mg/kg of body weight). Embryos were analyzed between embryonic day (E)9.5 and E11.5 by microscopy and geometric morphometric analysis by micro-computed tomography. P19 embryonal carcinoma cells were used to examine potential mechanisms mediating the combined effects of increased BMP and retinoid signaling. Although only 7% of wild-type embryos exposed to RA showed overt HPE or neural tube defects (NTDs), 100% of Twsg1(-/-) mutants exposed to RA manifested severe HPE compared to 17% without RA. Remarkably, up to 30% of Twsg1(+/-) mutants also showed HPE (23%) or NTDs (7%). The majority of shape variation among Twsg1(+/-) mutants was associated with narrowing of the midface. In P19 cells, RA induced the expression of Bmp2, acted in concert with BMP2 to increase p53 expression, caspase activation and oxidative stress. This study provides direct evidence for modifying effects of the environment in a genetic mouse model carrying a predisposing mutation for HPE in the Twsg1 gene. Further study of the mechanisms underlying these gene-environment interactions in vivo will contribute to better understanding of the pathogenesis of birth defects and present an opportunity to explore potential preventive interventions.

Topics: Animals; Bone Morphogenetic Protein 2; Caspase 3; Caspase 7; Embryo, Mammalian; Enzyme Activation; Face; Female; Gene Expression Regulation, Developmental; Holoprosencephaly; Mice, Inbred C57BL; Mutation; Neural Tube Defects; Oxidative Stress; Pregnancy; Proteins; Signal Transduction; Teratogenesis; Tretinoin; Tumor Suppressor Protein p53; Up-Regulation

Mammalian fetal development is easily disrupted by exogenous agents, making it essential to test new drug candidates for embryotoxicity and teratogenicity. To standardize the testing of drugs that might be used to treat pregnant women, the U.S. Food and Drug Administration (FDA) formulated special grade categories, labeled A, B, C, D and X, that define the level of risk associated with the use of a specific drug during pregnancy. Drugs in categories (Cat.) D and X are those with embryotoxic and/or teratogenic effects on humans and animals. However, which stages of pregnancy are affected by these agents and their molecular mechanisms are unknown. We describe here an embryonic stem cell test (EST) that classifies FDA pregnancy Cat.D and Cat.X drugs into 4 classes based on their differing effects on primitive streak formation. We show that ~84% of Cat.D and Cat.X drugs target this period of embryogenesis. Our results demonstrate that our modified EST can identify how a drug affects early embryogenesis, when it acts, and its molecular mechanism. Our test may thus be a useful addition to the drug safety testing armamentarium.

Topics: Animals; Benzodiazepines; Biomarkers; Cell Differentiation; Embryoid Bodies; Embryonic Development; Gene Expression; Mice; Mouse Embryonic Stem Cells; Teratogenesis; Teratogens; Toxicity Tests; Tretinoin

Embryonic exposure to excess circulating fuels is proposed to underlie diabetic embryopathy. To isolate the effects of hyperglycemia from the many systemic anomalies of diabetes, we infused 4 mg/min glucose into the left uterine artery of non-diabetic pregnant rats on gestation days (GD) 7-9. Right-sided embryos and dams exhibited no glucose elevation. Embryos were assessed on GD13, comparing the left versus right uterine horns. Hyperglycemic exposure increased rates of embryopathy, resorptions, and worsened embryopathy severity. By contrast, saline infusion did not affect any of these parameters. To assess for possible embryopathy susceptibility bias between uterine horns, separate dams were given retinoic acid (25mg/kg, a mildly embryopathic dose) systemically on GD7.5. The resultant embryopathy rates were equivalent between uterine horns. We conclude that hyperglycemia, even in the absence of systemic maternal diabetes, is sufficient to produce in vivo embryopathy during organogenesis.

Topics: Animals; Diabetes Mellitus, Experimental; Female; Fetal Diseases; Glucose; Hyperglycemia; Organogenesis; Pregnancy; Pregnancy Outcome; Rats; Rats, Sprague-Dawley; Teratogenesis; Tretinoin

Xenopus tropicalis embryos were exposed for 48 hr to the mixtures of 5 μg Sn/L triphenyltin (TPT), which is a well-known endocrine disruptor, and 0.25-5 μg/L 9-cis retinoic acid (9c-RA), which is the natural ligand of retinoid X receptor. The phenotypes induced by combined exposure were more variable than those resulting from single exposure to either TPT or 9c-RA. The prominent phenotypes included underdeveloped head structures, abnormal eyes, narrow fins, enlarged proctodaeum, etc. Especially, combined exposure induced unexpected notochord malformations, which ranged from small swellings of the surface of the tails to the extension and extrusion of notochord out of the posterior tails. Compared with the 5 μg Sn/L TPT-treated group, the index of fin deficiency was not affected, and the index of axis deficiency was significantly increased with increasing RA concentrations in the mixtures. Our results suggest that combined exposure to TPT and 9c-RA induced not only more variable phenotypes of malformations than exposure to single compound but also some new and unexpected phenotypes.

Topics: Abnormalities, Drug-Induced; Alitretinoin; Animals; Drug Interactions; Embryo, Nonmammalian; Embryonic Development; Female; Male; Organotin Compounds; Phenotype; Retinoid X Receptors; Teratogenesis; Tretinoin; Xenopus

Normal embryonic development and tissue homeostasis require precise levels of retinoic acid (RA) signaling. Despite the importance of appropriate embryonic RA signaling levels, the mechanisms underlying congenital defects due to perturbations of RA signaling are not completely understood. Here, we report that zebrafish embryos deficient for RA receptor αb1 (RARαb1), a conserved RAR splice variant, have enlarged hearts with increased cardiomyocyte (CM) specification, which are surprisingly the consequence of increased RA signaling. Importantly, depletion of RARαb2 or concurrent depletion of RARαb1 and RARαb2 also results in increased RA signaling, suggesting this effect is a broader consequence of RAR depletion. Concurrent depletion of RARαb1 and Cyp26a1, an enzyme that facilitates degradation of RA, and employment of a novel transgenic RA sensor line support the hypothesis that the increases in RA signaling in RAR deficient embryos are the result of increased embryonic RA coupled with compensatory RAR expression. Our results support an intriguing novel mechanism by which depletion of RARs elicits a previously unrecognized positive feedback loop that can result in developmental defects due to teratogenic increases in embryonic RA.

Topics: Animals; Animals, Genetically Modified; Cytochrome P-450 Enzyme System; Embryo, Nonmammalian; Embryonic Development; Female; Gene Expression Regulation, Developmental; Receptors, Retinoic Acid; Retinoic Acid 4-Hydroxylase; Signal Transduction; Teratogenesis; Tretinoin; Zebrafish; Zebrafish Proteins