ESPE Abstracts

Background: Alterations in the timing or expression level of players involved in sex determination and differentiation can cause disorders of sex development, gonadal dysgenesis and germ cell neoplasms later in life. The mitosis–meiosis switch is one of the first manifestations of female sex differentiation and we hypothesise that a conflict between meiosis-inhibiting (male pathway) and meiosis-inducing signals (female pathway) is one of the possible mechanisms for disruption of gonocyte differentiation in dysgenetic fetal testes.

Objective and hypotheses: To establish an experimental model that allows studies of germ cell–somatic niche interactions in human fetal gonad cultures and determine effects of manipulating signaling pathways involved in meiosis regulation.

Method: Fetal gonadal tissue from first trimester induced abortions was isolated and set-up in ‘hanging drop’ cultures for 2 weeks with and without addition of 1 μM retinoic acid (RA). Samples were subsequently formalin-fixed and protein expression was investigated by immunohistochemistry.

Results: An ex vivo model for normal fetal testes and ovaries was successfully established, with continued cell proliferation and lack of apoptosis for 2 weeks of culture. This model enabled manipulation studies resulting in specific outcomes related to meiosis regulation. In cultured fetal ovaries treated with RA we found a higher number of oogonia positively stained with the meiosis marker γH2AX, thereby confirming that RA induces meiosis. In fetal testes treated with RA we found a decrease in the number of proliferating gonocytes, decreased expression of the immature Sertoli cell marker AMH and disrupted seminiferous cord formation.

Conclusion: Culture of human fetal gonads in ‘hanging drops’ maintains normal tissue morphology, proliferation of germ- and somatic-cells and preserves signaling activity within the niche. RA-induced stimulation of meiosis in fetal testes results in a phenotype that resembles gonadal dysgenesis. Further studies of effects on the expression of pluripotency factors are in progress.