Valproic acid‐induced spina bifida: A mouse model

Abstract

Prenatal exposure to the antiepileptic drug valproic acid (VPA) has been associated with the formation of spina bifida aperta, meningocele, and meningomyelocele in the human. Until now, a direct relationship between VPA application and spina bifida has not been experimentally demonstrated. VPA was known only to induce exencephaly in mice, a defect of the anterior neural tube. Maximal sensitivity toward production of this defect was on day 8 of gestation (plug day = day 0). The closure of the posterior neuropore occurs later in the development of mice than the closure of the anterior neuropore. To investigate whether there is a direct relationship between VPA application during pregnancy and induction of spina bifida in mice, we administered various doses of the drug on day 9 of gestation, at three time intervals (at 0, 6, and 12 hr). This administration of VPA produced spina bifida aperta and spina bifida occulta in mice. High doses of VPA (3 x 450 and 3 x 500 mg/kg) induced a low rate of spina bifida aperta in the lumbosacral region. High incidences of spina bifida occulta, a less serious form of spina bifida, were induced with lower doses. This malformation was demonstrated in double-stained fetal skeletons by measurements of the distance between the cartilaginous ends of each vertebral arch. The occurrence of this defect and its localization was dose-dependent. The lumbar region was affected by all doses investigated (3 x 300, 3 x 350, 3 x 400, 3 x 450, and 3 x 500 mg/kg). The sacral/coccygeal region was affected additionally, but with higher doses (3 x 400, 3 x 450, and 3 x 500 mg/kg). A comparison of the results obtained with day 16 and 17 control fetuses showed that the pattern of gaps present in the lumbar and sacral region of the spinal cord in treated groups was drug-specific and not related to a developmental delay. Our results indicate that multiple administrations of VPA on day 9 of gestation in mice result in a low incidence of spina bifida aperta and a high incidence of spina bifida occulta, and provides a relevant model for the study of human spina bifida defects.

Modulation of Peroxisome Proliferator-Activated Receptor δ Activity Affects Neural Cell Adhesion Molecule and Polysialyltransferase ST8SiaIV Induction by Teratogenic Valproic Acid Analogs in F9 Cell Differentiation

“…The structural elements previously shown to be essential for teratogenicity have been confirmed by the results of the expression of NCAM and PST1: the molecule has to bear a carboxylic group, and the carbon atom adjacent to the carboxylic group has to have one hydrogen atom (Ehlers et al, 1992). In addition, the sp 3 configuration at carbon atom C-2 is essential, because analogs (E-2-en-VPA) in which carbon atom C-2 is sp 2 -hybridized were not active either in vitro or in vivo.…”

“…In the mouse, the predominant neural tube defect after single VPA injection on day 8 of gestation is exencephaly, an anterior neural tube defect. Repeated treatment on day 9 of gestation induces posterior neural tube defects (spina bifida aperta and occulta) (Ehlers et al, 1992). In the search for new drugs with selective anticonvulsant activities and less toxicity, numerous derivatives and various metabolites of VPA have been investigated and found to exert anticonvulsant activity in rodents (Nau et al, 1991;Ehlers et al, 1992).…”

“…Repeated treatment on day 9 of gestation induces posterior neural tube defects (spina bifida aperta and occulta) (Ehlers et al, 1992). In the search for new drugs with selective anticonvulsant activities and less toxicity, numerous derivatives and various metabolites of VPA have been investigated and found to exert anticonvulsant activity in rodents (Nau et al, 1991;Ehlers et al, 1992). It has been shown that the teratogenic effects are caused by VPA itself, not one of its metabolites (Ehlers et al, 1992).…”

“…In the search for new drugs with selective anticonvulsant activities and less toxicity, numerous derivatives and various metabolites of VPA have been investigated and found to exert anticonvulsant activity in rodents (Nau et al, 1991;Ehlers et al, 1992). It has been shown that the teratogenic effects are caused by VPA itself, not one of its metabolites (Ehlers et al, 1992). The teratogenic effects in vivo and in vitro depend on structural requirements (Nau et al, 1991;Bojic et al, 1996;Lampen et al, 1999).…”

Antiepileptic Drugs and Pregnancy Outcomes

“…VPA treatment during early neural tube formation (E8 in the mouse) results in exencephaly, which is the rodent equivalent of human anencephaly. Others reported that spina bifida can be induced in some mouse strains when injected three times at 6-h intervals on E9 [Ehlers et al, 1992;Emmanouil-Nikoloussi et al, 2004;Finnell et al, 1988;Menegola et al, 1996]. Pharmacokinetic study showed that VPA can induce neural tube defects in exposed mouse embryos when this drug reaches maternal plasma concentrations of 225 μg/ml, irrespectively of the route of administration [Nau, 1985].…”