Suppression of the high endogenous levels of plasma FSH in infertile men are associated with improved Sertoli cell function as reflected by elevated levels of plasma inhibin B

Human Reproduction Vol.19, No.6 pp. 1431±1437, 2004 Advance Access publication April 29, 2004 DOI: 10.1093/humrep/deh255 Suppression of the high endogenous levels of plasma FSH in infertile men are associated with improved Sertoli cell function as re¯ected by elevated levels of plasma inhibin B C.Foresta1,2, A.Bettella1, D.Spolaore1, M.Merico1, M.Rossato1 and A.Ferlin1 1 Centre for Male Gamete Cryopreservation, Department of Medical and Surgical Sciences, Via Ospedale 105, 35128 Padova, Italy 2 To whom correspondene should be addressed. E-mail Key words: desensitization/FSH treatment/inhibin B/male infertility/Sertoli cell function Introduction FSH plays a crucial role in the induction and maintenance of spermatogenesis in humans. This hormone acts by binding to speci®c receptors (FSH-Rs) con®ned to the gonads (Matsumoto, 1989; Sharpe, 1989), and Sertoli cells are the only cell type expressing the FSH-R (Kangasniemi et al., 1990; Heckert and Griswold, 1991; Kliesch et al., 1992; Bockers et al., 1994; Rannikki et al., 1995). Therefore, the action of FSH on germ cells has to be indirect and mediated by paracrine signals from Sertoli cells, and a close Sertoli±germ cell interaction is required to allow a normal spermatogenetic process. In man, the feedback control system regulating FSH secretion in a physiological setting appears to involve mainly inhibin B secreted by Sertoli cells (Anderson and Sharpe, 2000; Hayes et al., 2001; Ramaswamy and Plant, 2001). The contribution of testicular steroids to the regulation of FSH secretion is noticeably less important than that exerted by inhibin B signalling (Tilbrook and Clarke, 2001). The production of inhibin B by Sertoli cells is stimulated by FSH (Foresta et al., 1999b, 2000, 2002; Hayes et al., 2001), but it also re¯ects interactions between these and the neighbouring germ cells (Pineau et al., 1990; Allenby et al., 1991). In men affected by primary testicular disorders, inhibin B falls in parallel with an increase in FSH plasma levels (Anawalt et al., 1996; Foresta et al., 1999a; de Kretser et al., 2000). Therefore, the presence of high FSH concentrations in infertile patients is considered a marker of spermatogenic failure. The FSH-R is a seven transmembrane receptor belonging to the large family of GTP-binding protein (G-protein)-coupled receptors. The binding of FSH to its receptor results in a stimulation of the Gs protein, which in turn activates the membrane-associated adenylate cyclase causing an elevation of intracellular camp (Simoni et al., 1997). In addition, the signal transduction triggered by FSH may involve the entry of extracellular calcium through voltage-dependent and -independent calcium channels and through the PKG/PI signalling pathway (Simoni et al., 1997) Human Reproduction vol. 19 no. 6 ã European Society of Human Reproduction and Embryology 2004; all rights reserved 1431 Downloaded from http://humrep.oxfordjournals.org/ at MIT Libraries on January 22, 2017 BACKGROUND. In vitro continuous stimulation of Sertoli cells with FSH leads to a desensitization of these cells to FSH action. To evaluate the presence of a desensitization of FSH receptor on Sertoli cells in vivo, we performed a controlled clinical study in 97 men affected by severe oligozoospermia. METHODS. On the basis of FSH and inhibin B plasma concentrations, these subjects were divided into three groups: group A, 33 subjects with high FSH and low inhibin B plasma levels; group B, 32 subjects with high FSH plasma levels and inhibin B concentrations at the lower limit of the normal range; and group C, 32 subjects with normal FSH and inhibin B plasma levels. Patients with high FSH plasma levels (groups A and B) were prospectively randomized into two subgroups, called A1, A2, B1 and B2. Patients of groups A1 and B1 were treated with a GnRH agonist, leuprolide acetate, to induce a hypogonadotrophic state and then were treated with recombinant human FSH (r-hFSH; 100 IU/day) and hCG (2000 IU/ twice a week) for 2 months. Subjects of groups A2, B2 and C were treated only with r-hFSH for the same period. RESULTS. In patients of group A1, inhibin B remained unmodi®ed during the whole period of study, whereas in subjects of group B1, we observed a signi®cant reduction of this hormone during the hypogonadotrophic period and then an increase of inhibin B plasma levels that were higher that those observed before therapy. In patients of groups A2 and B2, FSH treatment did not induce a signi®cant increase in inhibin B concentrations. In patients of group C, FSH induced a signi®cant increase in inhibin B plasma levels. CONCLUSIONS. In infertile men, suppression of the high endogenous levels of plasma FSH associated with much lower exogenous FSH levels is able to evoke higher inhibin B production, which may indicate improved Sertoli cell function and the possibility that this could have a positive effect on spermatogenesis. C.Foresta et al. Materials and methods Subjects The local hospital ethical committee approved the study protocol, and written informed consent was obtained from each patient. Ninetyseven men affected by oligozoospermia, sperm count <10 3 106/ml, due to different causes and a history of infertility for at least 2 years were enrolled in the present study. The baseline characteristics and causes of testicular alteration in the different groups are reported in Table I. Each subject was evaluated with a clinical examination pointing to clinical andrological characteristics. All semen samples were obtained by masturbation after 3 days of sexual abstinence and were evaluated on at least three separate occasions, separated by a 3 week interval. After liquefaction at room temperature, semen volume, pH, sperm concentration, motility and morphology were determined following WHO guidelines for semen analysis (World Health Organization, 1999). The presence of antisperm antibodies was evaluated utilizing the immunobead and the Sperm-Mar test (Ortho Diagnostic System, Milan, Italy). To exclude infections, a microbiological culture was performed in each subject before starting the treatment. The spermatogenic activity was studied by means of bilateral testicular ®ne needle aspiration cytology (FNAC), performed as previously described (Foresta and Varotto, 1992; Foresta et al., 1992, 1995). This method allows the identi®cation of all germinal cells at their different stages of maturation as well as of Sertoli cells; furthermore, it permits the characterization of speci®c tubular damage. The Sertoli index (the ratio of Sertoli to spermatogenic cells) constitutes an attempt to simplify the understanding of cytological 1432 Table I. Baseline characteristics and causes of testicular alteration in oligozoospermic subjects Age (years) Body mass index (kg/m2) Causes of oligozoospermia Varicocele Cryptorchidism Post-mumps orchitis Testicular torsion Trauma Idiopathic Group A (n =33) Group B (n = 32) Group C (n = 32) 33.8 6 4.8 26.2 6 2.9 (...truncated)