Background: Phthalate exposure results in endocrine disruption by inhibiting steroidogenesis, inducing focal dysgenesis and disrupting germ cell development in the rat fetal testis. Whilst phthalate exposure does not reduce testosterone production by the human fetal testis, its effects on germ cells and induction of dysgenetic areas in the developing human testis are less well described.
Objective and Hypotheses: To determine the effects of phthalate exposure on human fetal germ cells and seminiferous cords using an established dynamic xenograft model. We hypothesized that the rat is an appropriate model for investigating such germ cell effects.
Method: Immunohistochemistry, immunofluorescence, and quantitative real-time PCR for Sertoli cell adhesion proteins (Espin, vimentin, and N-cadherin), germ cell markers (OCT4-undifferentiated; VASA differentiated) on DBP-exposed rat testis and human fetal testis xenografts and proliferation markers (Ki67).
Results: DBP-induced germ cell loss in human (and rat) fetal testes is confined to undifferentiated (OCT4+) germ cells (16 vs 12%: P=0.019) with no effect on germ cell proliferation (59 vs 61%, P>0.05). DBP also induces aggregation of differentiated germ cells, albeit sporadically in the human; however no focal dysgenetic areas were seen. The underlying mechanism for germ cell aggregation is loss of Sertoligerm cell membrane adhesion, probably due to microfilament redistribution within Sertoli cells.
Conclusion: Our findings demonstrate the endocrine disrupting effects of DBP in vivo on germ cell differentiation and aggregation in the human and rat. In the human, loss of undifferentiated germ cells is the main effect of DBP exposure, which may have potential health implications for the next generation. These results also demonstrate that the rat may represent a human-relevant model in which to explore the underlying mechanisms for the germ cell effects of DBP.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology