Malformations of the maxillofacial region induced by retinoids in an experimental system.

Treatment of pregnant Sprague-Dawley rats with etretinate or retinoic acid on pregnancy Day 8.5-9.0 resulted in craniofacial malformations in 100% of the embryos. A morphological investigation of the maxillofacial malformations was undertaken. Retinoid-exposed embryos showed a reduced skull base, flattened and elongated occiput and micrognathia. The malar bones were reduced or missing. Meckel's cartilage was delayed in differentiation as was the mandibular bone. The fusion between different facial processes was disturbed which resulted in facial and palatal clefts. Disturbance of the development of the hypophysis was combined with persisting Rathke's pouch. Aplasia of incisor and molar tooth buds was seen as was aplasia of salivary gland ducts. The facial artery was hyperplastic.