Feminization of the reproductive tract of teleost fish is an environmental problematic impacting population of fish living downstream sewage treatment plants (STP). Indeed, treated wastewaters contain a number of diverse man-made molecules which can mimic the effects of the endogenous estrogen, 17ß-estradiol. Deleterious effects provoked by exposure to “xenoestrogens” are diverse and can lead to a feminization of the male reproductive tract. This disturbance is commonly called “ovotestis” and is described as the presence of oocyte(s) within a functional testis. Within the framework of the present thesis, we engaged the understanding of ovotestis development through 2 approaches. The first was an environmental approach. Campaigns of fish sampling were led downstream STP of Walloon Region in order to estimate the impact of wastewater refusals on wild populations of gudgeon (Gobio gobio L.). In parallel, an assessment of the estrogenicity of effluents was evaluated through MCF-7 assay to determine the consistency between effects observed through the monitoring of common fish biomarkers of estrogenicity to the real estrogenicity released into water. Results of this environmental approach showed a moderate impact on gudgeon population caught in Walloon Region. In the second approach, we based our research on an original hypothesis to understand molecular and cellular mechanisms of oocyte development within the testis when teleost are subjected to xenoestrogens. This approach used an in vitro culture of testis pieces of gudgeon exposed to the most potent xenoestrogen found in the environment, the ethinylestradiol (EE2). The analyzed parameters were the apoptosis, cell proliferation, sex steroids, as well as 2 genes involved in the apoptosis pathway, Bcl-2 and Caspase 3. The analysis revealed that the spermatogenesis was disrupted when the gudgeon testis was exposed to EE2 (0,1 and 0,01 µg/L). Indeed, an inhibition of the apoptosis was observed for the benefit of a cell proliferation in an estrogenic environment detected by the increase production of 17 ß-estradiol in the tissue culture medium. Finally, we demonstrated an over-expression of Bcl-2 and Caspase 3 at concentration of 0,1µg/L in EE2. In conclusion, we can assert that xenoestrogens present at environmental concentrations is able to disrupt the reproductive tract of male gudgeon. Nevertheless, the provoked effects are, in Walloon Region, moderated. Furthermore, a hypothesis involving the balance between apoptosis and cell proliferation could be the basis of oocyte development within the testis subjected to EE2.
L’ovotestis chez le goujon (G. gobio): occurrence environnementale et approche in vitro des mécanismes cellulaires et moléculaires
Nadzialek, S. (Author). 29 Jan 2010
Student thesis: Doc types › Doctor of Sciences