Analysis of activin/TGFB-signaling modulators within the normal and dysfunctional adult human testis reveals evidence of altered signaling capacity in a subset of seminomas

Abstract

Activin is a pleiotropic growth factor belonging to the transforming growth factor-b (TGFB) superfamily of signaling molecules. Regulated activin signaling is known to influence several steps in rodent male gamete differentiation. TGFB ligand isoforms, TGFB1-B3, also influence germ cell survival in the rodent testis at the onset of spermatogenesis and around the time of puberty. Given the importance of regulated activin and TGFB signaling in testis development and function, we sought to investigate the cellular production sites of activin/TGFB-signaling modulators in normal and dysfunctional adult human testes samples. Signaling transducers phosphorylated SMAD2/3, and signaling modulators SMAD6, MAN-1, inhibin a (INHA), and b-glycan were detected in Bouins fixed, paraffin-embedded adult human testis sections using immunohistochemistry. Additional samples examined were from testicular cancer patients and from normal men subjected to gonadotropin suppression with androgen-based contraceptives. Our findings identify distinct differences between normal and gonadotropin-deprived human testis in the expression and cellular localization of activin/TGFB-signaling modulators. The presence of a nuclear phosphorylated SMAD2/3 signal in all analyzed seminoma specimens indicated active activin/TGFB signaling. Moreover, a subset of seminoma specimens exhibited selective enhanced expression of b-glycan (4 out of 28 seminoma tumors), INHA (6 out of 28), and MAN-1 (6 out of 28), highlighting potential functional differences between individual tumors in their capacity to regulate activin/TGFB signaling. Within the heterogenous nonseminomas, expression of signaling modulators was variable and reflected the degree of somatic differentiation. Thus, synthesis of activin and TGFB-signaling modulators may be affected by spermatogenic disruption and altered hormone levels in the testis. Reproduction (2009) 138 801-811

A genome-wide association study of men with symptoms of testicular dysgenesis syndrome and its network biology interpretation

“…TGFBR3 and its co-receptors and ligands are expressed in most endocrine tissues, including the testis. TGFBR3 has been identified in human Sertoli cells and Leydig cells, both in the normal testis and in tubules with CIS 36. In this study, we found that TGFBR3 was expressed in both Leydig and peritubular cells in fetal as well as adult testis, but was absent from Sertoli cells.…”

Hanging drop cultures of human testis and testis cancer samples: a model used to investigate activin treatment effects in a preserved niche

“…Whether the outcome reported in this study reflects direct or indirect effects on the seminoma cells remains to be determined. The absence of an opposing response in the testis tissues following culture with follistatin suggests that these tumours already contain several mechanisms by which activin signalling is suppressed, as shown previously (Dias et al , 2009) and which can be overcome only by the presence of a highly potent exogenous signalling factor. The investigation of treatment effects in this culture system has clearly demonstrated a specific response, which indicates that the hanging drop culture approach is appropriate for delineation of the specific effects of growth factors, inhibitors and other experimental treatments which will be required to understand the basis of normal testis function and to devise new strategies to ameliorate the burden of testicular pathologies.…”

“…Our previous studies have linked activin bioactivity to changes in germ cell differentiation and KIT levels (Mithraprabhu et al , 2010), and we have identified activin receptor expression in human spermatogonia, CIS and seminoma cells (Dias et al , 2008, 2009; Young et al , 2011). We therefore explored the effects of 48 h treatment with activin A and its antagonist, follistatin, on seminoma samples in hanging drop cultures.…”

Activin A Balances Sertoli and Germ Cell Proliferation in the Fetal Mouse Testis

“…These data collectively suggest that Inhba dosage does not have a general effect on transcript levels of the main signaling components in the activin pathway, but instead causes transcriptional changes at specific developmental time points. Using this and other models to understand how the complex milieu of TGFB superfamily signaling components act in the fetal testis is an important challenge that is of relevance to understanding the etiology of testicular cancer in humans [46], where activin and TGFB superfamily receptor subunits, ligands, and inhibitors have been implicated [47,48].…”