Background and Aims: Disorders of human male reproductive health include cryptorchidism, hypospadias, infertility/subfertility, testicular germ cell cancer and primary hypogonadism. The ‘testis dysgenesis syndrome’ hypothesis proposes that ALL of these problems have a shared origin during fetal life: if testis development is perturbed during a critical window of time whilst in the womb, reproductive health and function is affected. These disorders are escalating at such high rates that it is presumed that environmental causes are to blame, and the key suspect is our increasing exposure to ‘endocrine disrupting chemicals’.
The balance of retinoic acid (RA) signalling is particularly crucial for correct fetal testis development: Normally, a P450 enzyme, CYP26B1, degrades RA during testis development, but if CYP26B1 does not function, ectopic RA leads to partial testicular feminisation and perturbation to secondary sexual structures.
Methods: By combining classic developmental biology and mouse transgenic expertise with reproductive toxicology, we have developed a novel ex-vivo testis culture system as a read-out for RA-Cyp26b1 signalling perturbation. Transgenic fetal testes at 12.5 dpc were cultured in hanging drops for 48 hours in the presence or absence of a panel of agricultural chemicals before harvesting for qRT-PCR analysis, histological examination, staining or imaging.
Results: We have used this transgenic system to evaluate the molecular effects of a common agricultural azole, Flusilazole, and related compounds. Flusilazole is a fungicide that works by inhibiting the fungal P450 enzyme CYP51, though it is likely that it can also inhibit mammalian CYP enzymes. We found that ectopic RA signalling could be detected in testes in response to azole exposure at a range of concentrations.
Conclusions and Significance/Impact: Our work indicates possible consequences for reproductive development and function following common azole exposure. Our ongoing work will have future translational importance, in particular, for the refinement of current chemical screening methodologies.