Xenopus embryonic epidermis as a mucociliary cellular ecosystem to assess the effect of sex hormones in a non-reproductive context.

BACKGROUND: How important are sexual hormones beyond their function in reproductive biology has yet to be understood. In this study, we analyzed the effects of sex steroids on the biology of the embryonic amphibian epidermis, which represents an easily amenable model of non-reproductive mucociliary epithelia (MCE). MCE are integrated systems formed by multiciliated (MC), mucus-secreting (MS) and mitochondrion-rich (MR) cell populations that are shaped by their microenvironment. Therefore, MCE could be considered as ecosystems at the cellular scale, found in a wide array of contexts from mussel gills to mammalian oviduct. RESULTS: We showed that the natural estrogen (estradiol, E2) and androgen (testosterone, T) as well as the synthetic estrogen (ethinyl-estradiol, EE2), all induced a significant enhancement of MC cell numbers. The effect of E2, T and EE2 extended to the MS and MR cell populations, to varying degrees. They also modified the expression profile of RNA MCE markers, and induced a range of "non-typical" cellular phenotypes, with mixed identities and aberrant morphologies, as revealed by imaging analysis through biomarker confocal detection and scanning electron microscopy. Finally, these hormones also affected tadpole pigmentation, revealing an effect on the entire cellular ecosystem of the Xenopus embryonic skin. CONCLUSIONS: This study reveals the impact in vivo, at the molecular, cellular, tissue and organism levels, of sex steroids on non-reproductive mucociliary epithelium biogenesis, and validates the use of Xenopus as a relevant model system in this field.