PGE2 inhibits spermatogonia differentiation in zebrafish: interaction with Fsh and an androgen

Abstract

Changes in zebrafish testicular gene expression induced by follicle-stimulating hormone (Fsh) or anti-Mullerian hormone (Amh) suggested that Amh inhibition and Fsh stimulation of spermatogenesis involved up and downregulation, respectively, of prostaglandin (PG) signaling. We found that Sertoli cells contacting type A undifferentiated (Aund) and differentiating (Adiff) spermatogonia expressed a key enzyme of PG production (Ptgs2); previous work showed that Sertoli cells contacting Adiff and B spermatogonia and spermatocytes showed ptges3b expression, an enzyme catalyzing PGE2 production. In primary testis tissue cultures, PGE2, but not PGD2 or PGF2α, reduced the mitotic activity of Adiff and their development into B spermatogonia. Vice versa, inhibiting PG production increased the mitotic activity of Adiff and B spermatogonia. Studies with pharmacological PG receptor antagonists suggest that an Ep4 receptor mediates the inhibitory effects on the development of spermatogonia, and cell-sorting experiments indicated this receptor is expressed mainly by testicular somatic cells. Combined inhibition of PG and steroid production moreover reduced the mitotic activity of Aund spermatogonia and led to their partial depletion, suggesting that androgens (and/or other testicular steroids), supported by PGE2, otherwise prevent depletion of Aund. Androgens also decreased testicular PGE2 production, increased the transcript levels of the enzyme-catabolizing PGs and decreased PGE2 receptor ptger4b transcript levels. Also Fsh potentially reduced, independent of androgens, PGE2 production by decreasing ptges3b transcript levels. Taken together, our results indicate that PGE2, via Ep4 receptors, favors self-renewal in conjunction with androgens and, independent of Fsh and androgens, inhibits differentiating divisions of spermatogonia.

Insulin-like 3 Affects Zebrafish Spermatogenic Cells Directly and via Sertoli Cells

“…However, Insl3 effects are not drastic, and testicular defects in insl3 mutants are not noticeable initially. Overall, previous and present results show that Fsh uses different, locally produced signaling molecules (growth factors, including Insl3, but also low molecular weight molecules like RA , sex steroids 32,33 and prostaglandins 52 ) to implement specific regulatory effects on spermatogenesis. Since several of these Fsh-regulated pathways operate in parallel in zebrafish, the impact of an individual pathway usually is not overwhelming, allowing follow-up research to examine compensatory mechanisms.…”

Strong regulatory effects of vgll3 genotype on reproductive axis gene expression in immature male Atlantic salmon

“…Another likely scenario for inhibition of spermatogonial differentiation in vgll3*LL individuals could be the increased expression of ptgs2a and ptger4b , which are known to be transcriptionally induced by amh in fish testis (Morais et al, 2017). ptgs2a encodes a key enzyme involved in production of a prostaglandin (PGE 2 ), which reduces the mitotic activity of differentiating spermatogonia, and thereby inhibits spermatogenesis (Crespo et al, 2020). The inhibition of PGE 2 on the development of spermatogonia seems to be mediated through a receptor encoded by ptger4b expressed mainly by testicular somatic cells (Crespo et al, 2020).…”

“…ptgs2a encodes a key enzyme involved in production of a prostaglandin (PGE 2 ), which reduces the mitotic activity of differentiating spermatogonia, and thereby inhibits spermatogenesis (Crespo et al, 2020). The inhibition of PGE 2 on the development of spermatogonia seems to be mediated through a receptor encoded by ptger4b expressed mainly by testicular somatic cells (Crespo et al, 2020). Taken together, these findings imply that in immature salmon with the late vgll3 allele, sexual maturation is delayed through an amh dependent mechanism and probably at the differentiation stage of spermatogonia (summarized in Figure 2A).…”

An ex vivo Approach to Study Hormonal Control of Spermatogenesis in the Teleost Oreochromis niloticus

“…The 10% proportion of FBS in the medium reduces the final concentration of testosterone to 0.035 ng/ml. Using a back calculation from zebrafish testis organ cultures (19,28,53), where a basal 11-KT concentration of around 1 ng per mg testis tissue was determined in the medium, then the media concentrations lays in a range of 1-2 ng 11-KT per ml. That means the FBS derived testosterone content of the medium used in our cultures was low but constituted round about 1/50 of average basal 11-KT level in zebrafish organ cultures, what seems to be sufficient for the observed preservation of SgA in the testis cultures.…”