In vitro maturation of porcine oocytes as a potential alternative testing model for reproductive toxicology studies

Numerous chemicals have been reported to be detrimental to human and animal health, particularly to the female reproductive system. Chemical exposure can lead to reproductive disorders by disrupting the hypothalamic-pituitary-gonadal axis and affecting the endocrine system, ovaries, follicular fluid, and germ cells. In addition, chemical exposure can impair female reproduction by directly affecting oocyte maturation, which is completed within the follicular fluid before ovulation. Therefore, evaluating the toxic effects of these chemicals on oocyte maturation has become increasingly important. In vitro maturation (IVM) of oocytes is an essential platform for elucidating the mechanisms underlying oocyte maturation. In particular, IVM of porcine oocytes may be a more suitable model for studying human oocyte maturation because pigs share greater physiological and genetic similarities with humans than other commonly used animal models do. Moreover, because porcine oocyte IVM uses immature oocytes obtained from ovaries collected as slaughterhouse by-products, this system avoids the use of experimental animals, offering both ethical and practical advantages. Despite the growing number of reproductive toxicology studies using porcine oocyte IVM, comprehensive summaries of the indicators used for porcine oocyte quality assessment remain limited. Therefore, this review aims to summarize the methods for assessing porcine oocyte quality, along with their underlying principles and applications, thereby providing an integrative overview to advance the use of porcine IVM as a model for reproductive toxicity evaluation.