Bovine Oocyte Maturation Assay

The bovine in vitro maturation test assesses oocyte maturation. The method is based on the use of immature oocytes from bovine animals.

The physiology of the bovine reproductive cycle is more similar to humans than conventional laboratory animals for a number of reproductive parameters including kinetics of oocyte growth, oocyte size, mechanisms of ovulation and maturation, timing of fertilisation and first cleavage, kinetics of pre- and post-implantation development, mechanisms of gastrulation, cell cycle and gestation length. Finally, at the genetic level, the homologies between human and cattle are higher than human and rodent,

The toxicological endpoint evaluated is the completion of meiosis up to the metaphase II stage, which is reached after 24h in in vitro culture. The analysis is based on microscopic inspection. Matured oocytes are characterised by the extrusion of the first polar body associated to the second metaphase stage.

The assay investigates the potential for interaction of a chemical substance with meiosis and as such investigates events within an adverse outcome pathway (AOP) associated with perturbation of fertilisation. Such assay could be used within an Integrated Testing Strategy (ITS) or Integrated Approaches to Testing and Assessment (IATA) for identification of reproductive toxicants.