Acetylsalycilic acid protects rat embryos from teratogenic effects of 5-azacytidine

Background and purpose: 5-azacytidine (5azaC) is a demethylating agent and consequently a potential therapeutic for conditions where hypermethylation of genes is the cause of the disease. But prenatal exposure of rat and mice to a single dose of 5azaC resulted in fetal forelimb and hindlimb malformations as well as growth reduction. Pretreatment with acetylsalicylic acid (ASA) was able to diminish teratogenic effect of a single dose of 5azaC. In this work we tried to investigate ASA protective effect upon 5azaC teratogenicity if 5azaC was applied twice during pregnancy which caused more severe malformations in embryos. Material and Methods: 5azaC was dissolved in PBS and injected intraperitonealy at a concentration of 5 mg/kg body weight to pregnant rat females on 12th and again on 13th day of pregnancy. ASA was dissolved in PBS and administered every time 2 hr before 5azaC at a concentration of 75 mg/kg. Controls were treated with PBS on the same days of pregnancy. Animals were sacrificed in ether the day before birth. Fetuses and placentas were isolated from uteri, measured and weighted. For the differential staining of cartilage and bone fetuses were stained with alizarin red S and alcian blue. Results and Conclusions: All fetuses from 5azaC treated females showed both front and hind limb adactyly. If ASA was applied prior to 5azaC treatment, 46% of fetuses were normal with no malformations at all, while the rest showed only hind limb oligodactyly. In front limbs no malformations were discovered. Growth retardation caused by 5azaC was restored with ASA pretreatment in both embryos and placentas.