Estrogen-induced inhibition of spermatogenesis in zebrafish is largely reversed by androgen

Abstract

The hormonal regulation of spermatogenesis involves both gonadotropins and steroid hormones. Long-term exposure of adult zebrafish to estrogen impaired spermatogenesis associated with an androgen insufficiency, possibly induced by inhibiting gonadotropin release. Using this experimental model, we investigated if androgen treatment could enhance spermatogenesis, while maintaining the inhibition of gonadotropin release through continued estrogen exposure. Moreover, we also exposed animals to androgen alone, in order to examine androgen effects in the absence of estrogen-induced gonadotropin inhibition. Estrogen exposure depleted type B spermatogonia, meiotic and postmeiotic germ cells from the adult testis, but promoted the proliferation of type A undifferentiated spermatogonia, which accumulated in the testis. This change in germ cell composition was accompanied by reduced mRNA levels of those growth factors (e.g. and ) expressed by testicular somatic cells and known to stimulate spermatogonial differentiation in zebrafish. Additional androgen (11-ketoandrostenedione, which is converted to 11-ketotestosterone) treatment reversed most of the effects of estrogen exposure on spermatogenesis while and transcript levels remained suppressed. When androgen treatment was given alone, it promoted the production of haploid cells at the expense of spermatogonia, and increased transcript levels of some growth factor and hormone receptor genes, but not those of or We conclude that estrogen exposure efficiently inhibits spermatogenesis because it induces androgen insufficiency and suppresses gonadotropin-regulated growth factors known to stimulate germ cell differentiation. Moreover, our results suggest that androgens and the growth factors Insl3 and Igf3 stimulate spermatogenesis via independent pathways.

Ovarian transcriptomic signatures of zebrafish females resistant to different environmental perturbations

“…The downregulation of T A B L E 1 Top 10 upregulated and downregulated genes in the Sets A and D of genes commonly expressed in ovaries of females exposed to elevated density or temperature | 61 cyp19a1a in ovaries was described in zebrafish exposed to elevated temperature (Ribas, Liew, et al, 2017) and to hypoxia conditions (Shang, Yu, & Wu, 2006), as well as in other fish species such as the olive flounder (Kitano, Takamune, Kobayashi, Nagahama, & Abe, 1999) and in the European sea bass (Díaz & Piferrer, 2015;Navarro-Martín et al, 2011) when subjected to HT. Thus, environmental stress reduced the expression of cyp19a1a in the gonads and this is in agreement with the observed masculinization since cyp19a1a is necessary for ovarian development, as demonstrated in the loss-offunction experiments (de Castro Assis, de Nóbrega, Gómez-González, Bogerd, & Schulz, 2018;Lau, Zhang, Qin, & Ge, 2016). In the testes, dmrt1, a transcription factor that plays a key role in male-sex determination in zebrafish (Webster et al, 2017), and amh, a gene involved in male sexual differentiation by suppressing the estrogen production (Rodríguez -Marí et al, 2005), did not show differences in gene expression due to HD confinement, suggesting no conspicuous effects of density at least in these two important genes for male sexual differentiation.…”

Retinoic acid and androgens interact to regulate spermatogenesis in a non-mammalian vertebrate lackingstra8

“…To further investigate retinoid effects on spermatogonial proliferation, we used an experimental model based on estrogen-inhibited Fsh and androgen levels causing an accumulation of type A spermatogonia (36, 59) (see Fig. 8 E ).…”

“…Depleted testis tissue was characterized by the transcriptional enrichment of the “Retinol metabolism” and of the “Steroid hormone biosynthesis” pathways, the latter being consistent with the enhanced androgen production found in busulfan-depleted testis tissue in our previous study (54). Increased androgen signaling may have supported the spermatogenic recovery, considering the stimulatory effect of androgens on zebrafish spermatogenesis (36, 45, 46) (Fig. 6).…”

“…Adult male fish were submitted to water containing 100 nM 11-ketoandrostenedione (OA) or control untreated conditions in vivo for 5 weeks with a daily change of water (as described in (36)). Stock solutions were prepared in deionized water by extensive stirring at 37°C, which were further diluted to the proper concentration in aquarium water.…”

“…In teleost fish, 11-ketotestosterone (11-KT) is considered to be the main androgen (32) and its stimulatory effect on spermatogenesis has been shown in various species such as Japanese eel ( Anguilla japonica ; (33)), Atlantic salmon ( Salmo salar ; (34)), African catfish ( Clarias gariepinus ; (35)) or zebrafish (36, 37). Androgens stimulate the onset of puberty in fish (38, 39) and modulate the testicular expression of genes potentially involved in spermatogenesis (40-42).…”