Defects in embryonic hindbrain development and fetal resorption resulting from vitamin A deficiency in the rat are prevented by feeding pharmacological levels of all- trans- retinoic acid

Abstract

Vitamin A is required for reproduction and normal embryonic development. We have determined that all-trans-retinoic acid (atRA) can support development of the mammalian embryo to parturition in vitamin A-deficient (VAD) rats. At embryonic day (E) 0.5, VAD dams were fed purified diets containing either 12 g of atRA per g of diet (230 g per rat per day) or 250 g of atRA per g of diet (4.5 mg per rat per day) or were fed the purified diet supplemented with a source of retinol (100 units of retinyl palmitate per day). An additional group was fed both 250 g of atRA per g of diet in combination with retinyl palmitate. Embryonic survival to E12.5 was similar for all groups. However, embryonic development in the group fed 12 g of atRA per g of diet was grossly abnormal. The most notable defects were in the region of the hindbrain, which included a loss of posterior cranial nerves (IX, X, XI, and XII) and postotic pharyngeal arches as well as the presence of ectopic otic vesicles and a swollen anterior cardinal vein. All embryonic abnormalities at E12.5 were prevented by feeding pharmacological amounts of atRA (250 g͞g diet) or by supplementation with retinyl palmitate. Embryos from VAD dams receiving 12 g of atRA per g of diet were resorbed by E18.5, whereas those in the group fed 250 g of atRA per g of diet survived to parturition but died shortly thereafter. Equivalent results were obtained by using commercial grade atRA or atRA that had been purified to eliminate any potential contamination by neutral retinoids, such as retinol. Thus, 250 g of atRA per g of diet fed to VAD dams (Ϸ4.5 mg per rat per day) can prevent the death of embryos at midgestation and prevents the early embryonic abnormalities that arise when VAD dams are fed insufficient amounts of atRA.

The role of retinoic acid in embryonic and post-embryonic development

“…More recently, interest in this experimental paradigm has re-awakened, and a rat and mouse model (Morriss-Kay & Sokolova, 1996;Dickman et al 1997;Antipatis et al 1998;White et al 1998) as well as a chick and quail model (Thompson et al 1969;Heine et al 1985;Dersch & Zile, 1993) have been developed. In the former system embryos can be deprived at chosen stages of development to investigate the dependency of particular organ systems, and in the latter systems the embryos are deprived from the start of development.…”

“…Rat embryos which are deprived at later stages have an underdeveloped hindbrain, loss of posterior cranial nerves and posterior branchial arches, microphthalmia, narrow limb buds, neural crest cell death, failure or hypoplasia of lung development, failure of septation of the trachea and oesophagus, and lack of differentiation of neuronal populations in the brain (Dickman et al 1997;Antipatis et al 1998;White et al 1998). These studies have confirmed the role that RA plays in many systems of the embryo and at many times throughout development rather than at any one stage of development.…”

Crk‐associated substrate (Cas) family member, NEDD9, is regulated in human neuroblastoma cells and in the embryonic hindbrain by all‐trans retinoic acid

“…With excess atRA, the phenotype is stage-de-pendent, and either a loss and/or posteriorization of the anterior hindbrain results (Morriss-Kay et al, 1991;Conlon and Rossant, 1992;Marshall et al, 1992;Cunningham et al, 1994;Wood et al, 1994;Simeone et al, 1995). On the other hand, vitamin A-deficient (VAD) rat embryos exhibit a loss of posterior hindbrain segmentation, anteriorization of r5 through r7/8, with the accompanying loss of the associated postotic cranial nerves (White et al, 1998(White et al, , 2000. In both atRA deficiency and excess, changes in gene expression occurring within the presumptive rhombomeres are believed to play an important role in altering hindbrain morphology, including segment identity and their derivative structures (Clagett-Dame and Plum, 1997;Gavalas and Krumlauf, 2000;Begemann and Meyer, 2001;Gavalas, 2002).…”

Astrocytes as a regulated source of retinoic acid for the brain

“…Tissue for immunohistochemical studies was taken from perfusion-fixed animals. The vitamin A-deficient (VAD) rats (Sprague-Dawley) were depleted of vitamin A stores until physiological signs of vitamin A deficiency were evident ( 3 months) as described in White et al (1998) and then maintained for another 2 weeks deficient before sacrifice. The control diet was identical to the VAD diet; with the addition of vitamin A (retinyl palmitate) food intake did not differ between the control and VAD groups so that changes could be attributed to vitamin A and not other nutritional variables.…”