Immunoexpression of aromatase and estrogen receptors β in stem spermatogonia of bullfrogs indicates a role of estrogen in the seasonal spermatogonial mitotic activity

Abstract

Bullfrog stem spermatogonia, also named primordial germ cells (PGCs), show strong testosterone immunolabeling in winter, but no or weak testosterone immunoexpression in summer. Thus, the role of testosterone in these cells needs to be clarified. In this study, we proposed to evaluate whether PGCs express aromatase and estrogen receptors, and verify a possible role of estrogen in PGCs seasonal proliferation. Testes of male adult bullfrogs, collected in winter (WG) and summer (SG), were fixed and embedded in historesin, for quantitative analysis, or paraffin for immunohistochemistry (IHC). The number of haematoxylin/eosin stained PGCs/lobular area was obtained. Proliferating cell nuclear antigen (PCNA), aromatase, estrogen receptor β (ERβ) and PCNA/ERβ double immunolabeling were detected by IHC. The number of PCNA-positive PGCs and the histological score (HSCORE) of aromatase and ERβ immunolabeled PGCs were obtained. Although the number of PGCs increased significantly in WG, a high number of PCNA-positive PGCs was observed in summer. Moreover, aromatase and ERβ HSCORE was higher in SG than WG. The results indicate that PGCs express a seasonal proliferative activity; the low mitotic activity in winter is related to the maximal limit of germ cells which can be supported in the large lobules. In SG, the increased ERβ and aromatase HSCORE suggests that testosterone is converted into estrogen from winter to summer. Moreover, the parallelism between the high PGCs mitotic activity and ERβ immunoexpression suggest a participation of estrogen in the control of the PGCs seasonal proliferative activity which guarantee the formation of new germ cysts from summer to next autumn.

Effect of estradiol on apoptosis, proliferation and steroidogenic enzymes in the testes of the toad Rhinella arenarum (Amphibia, Anura)

“…In Lithobates catesbeianus estrogens play an important role in the control of primordial germ cells during the seasonal spermatogenesis (Caneguim et al, 2013a(Caneguim et al, , 2013b. Moreover, in juveniles Xenopus laevis estradiol (E 2 ) induces an acceleration of spermatogenesis (Hu et al, 2008).…”

Differential expression of RNA exosome subunits in the amphibian Lithobates catesbeianus during reproductive and non-reproductive periods

“…To study the RNA exosome during spermatogenesis, we analyzed the subcellular localization of its subunits LcRRP40, LcRRP42, LcRRP6 and LcRRP44 in testes of L. catesbeianus during the reproductive and quiescent periods, focusing on PGCs and interstitial cells because of the morphological changes they undergo in these periods [10, 11]. The results show that the exosome subunits were present in the cytoplasm of both interstitial cells and PGCs, in both periods (Fig.…”

“…The historesin sections were stained by Gill’s hematoxylin and eosin—H.E. [13], and the paraffin sections were subjected to immunohistochemical reactions as described [11].…”

Effect of Wuzi Yanzong on Reproductive Hormones and TGF-β1/Smads Signal Pathway in Rats with Oligoasthenozoospermia

“…FSH enhances the effects of LH, and acts on the Sertoli cells to promote the development of secondary spermatocytes into spermatozoa, as well as the synthesis of androgen binding proteins which maintain high levels of testosterone in the spermatogenic microtubules. The latter is one of the key factors necessary for maintaining spermatogenesis, and testosterone deficiency affects spermatogenesis, and the vitality and fertilization ability of the spermatozoa [34–36]. Recent studies have shown that estrogen is almost involved in the whole process of spermatogenesis and is an essential hormone for spermatogenesis and maturation [37–40].…”