Developmental Exposures to Three Mammalian Teratogens Produce Dysmorphic Phenotypes in Adult Caenorhabditis elegans

Efficient new methods are needed to support initiatives to reduce, refine, and/or replace toxicity testing in vertebrates. 5-fluorouracil (5FU), hydroxyurea (HU), and ribavirin (RV) are mammalian teratogens. Skeletal, endocrine organ, and cardiac effects are often associated with teratogenesis, and a simple nematode like <i>C. elegans</i> lacks these systems. However, many genetic pathways required for mammalian morphogenesis have at least some conserved elements in this small, invertebrate model. The <i>C. elegans</i> lifecycle is 3 days. The effects of 5FU, HU, and RV on the <i>C. elegans</i> morphology were evaluated on day 4 post-initiation of the feeding after hatching for continuous and 24 h (early-only) developmental exposures. Continuous exposures to 5FU and HU induced increases in the incidences of abnormal gonadal structures that were significantly reduced in early-only exposure groups. The incidence of prolapse increased with continuous 5FU and HU exposures and was further increased in early-only exposure groups. Intestinal prolapse through the vulval muscle in <i>C. elegans</i> may be related to reported 5FU and HU effects on skeletal muscle and the gastrointestinal tract in mammals. Continuous RV exposures induced a phenotype lacking a uterus and gonad arms, as well as vulval anomalies that were largely, but not completely, reversed with early-only exposures, which is consistent with reported reversible reproductive tract anomalies after an RV exposure in mammals. These findings suggest that <i>C. elegans</i> can be used to detect the hazard risk from chemicals that adversely affect conserved pathways involved in organismal morphogenesis, but to determine the fit-for-purpose use of this model in chemical safety evaluations, further studies using larger and more diverse chemical test panels are needed.