Endocrine and paracrine regulation of the spermatogonial niche in Astyanax altiparanae (Teleostei, Characidae): the role of AMH

Abstract

In fish, in addition to the classical regulation by the luteinizing hormone (LH), the follicle stimulating hormone (FSH) is also a potent steroidogenic hormone and plays a role in inducing androgens release. Among the growth factors regulated by FSH, the Anti-Müllerian hormone (AMH) is a glycoprotein belonging to the Transforming Growth Factor Beta family (TGF²) and it is present in the Sertoli cells performing an inhibitory function in the spermatogonial differentiation. Aiming the understanding of the role of AMH, the cloning and molecular characterization of the amh gene will be performed, followed by the investigation of its possible expression in different organs and its expression during the reproductive cycle of our model species, in captivity. To detect the expression sites, the in situ hybridization technique will be performed. Also, to evaluate the expression of amh in the testes under the influence of FSH and 17²-estradiol, the tissue culture with testis fragments will be standardized and established .Subsequently, the FSH and 17b-estradiol ability to modulate the spermatogonial proliferation will be assessed with the addition of 5-bromo-2'-deoxyuridine (BrdU). For a comprehensive understanding of the endocrine and paracrine regulation of the spermatogonial niche, Astyanax altiparanae (popularly known as lambari-do-rabo-amarelo) will be used as a model species in this present study. This species has been used by our research group that aims to characterize the cellular, molecular, and hormonal aspects of the hypothalamic-pituitary-gonadal axis of this characiform. The results obtained here will provide support for a better understanding of the reproductive biology of this species, as well as about the homeostasis of spermatogenesis. Moreover, the results about the spermatogonial niche regulation, especially by amh action, will give new insights on how these characteristics may influence the self-renewal and differentiation of undifferentiated spermatogonia, possible candidates for spermatogonia stem cells. (AU)