Retinoic-acid-induced limb malformations resulting from apical ectodermal ridge cell death

Area of Science:

• Developmental biology
• Teratology
• Pharmacology

Background:

• 13-cis retinoic acid (isotretinoin, Accutane) is a known teratogen.
• Previous studies on retinoid-induced limb malformations focused on later exposure times.

Purpose of the Study:

• To investigate the effects of early embryonic exposure to 13-cis retinoic acid on limb development.
• To elucidate the mechanism of retinoid-induced limb malformations.

Main Methods:

• Pregnant C57Bl/6J mice were administered a single oral dose of 400 mg/kg 13-cis retinoic acid at 9 days, 12 hours postfertilization.
• Fetuses were examined at 16 days for malformations.
• Scanning electron microscopy and light microscopy were used to analyze developmental alterations.

Main Results:

• 46% of fetuses exposed to 13-cis retinoic acid exhibited limb malformations, including digit abnormalities and radial defects.
• Abnormalities in the apical ectodermal ridge (AER), characterized by excessive cell death, were observed in treated embryos.
• These AER abnormalities occurred 12 hours after treatment in 27-30 somite embryos.

Conclusions:

• Early embryonic exposure to 13-cis retinoic acid induces significant limb malformations in mice.
• Excessive programmed cell death in the AER is a key mechanism underlying these malformations.
• Findings suggest a critical window for retinoid teratogenicity impacting limb development via AER apoptosis.