Proliferation Of Spermatogonial Cells Research Articles

Activin stimulates Sertoli cell proliferation in a defined period of rat testis development

The action of activin-A on Sertoli and spermatogonial cell proliferation during early postnatal life was studied by using in vitro organ culture of testis fragments from 9-day-old rats. Activin significantly stimulated 3H-thymidine incorporation into testis fragments cultured for 3 days in the presence of FSH, whereas it had no effect in the absence of the hormone. This effect was dose dependent in the range 10-200 ng/ml and was specifically inhibited by the activin-binding protein, follistatin. The effect of activin upon proliferation of different testicular cells was studied in detail by 5-bromo-2'-deoxyuridine-labeling fragments at the end of in vitro culture and then determining percentages of different labeled cells on immunostained histological sections. Concomitant treatment with FSH and activin, but not with FSH or activin alone, significantly stimulated Sertoli cell proliferation but markedly depressed that of differentiating type A spermatogonia. In contrast, proliferative activity of undifferentiated type A spermatogonia was independent of activin, irrespective of the presence of FSH. The effect of donor animal age was then investigated by culturing fragments derived from 3- and 18-day-old rats for 3 days. An age-related response was evident. Sertoli cell proliferation was stimulated by FSH alone in fragments from 3-day-old rats, activin having no apparent effect at this age. In contrast, none of the hormones tested either alone or in combination was effective in 18-day-old animals. These results demonstrate that activin acts with FSH in maintaining mitotic potentiality of Sertoli cells in a defined phase of their maturation path, when their proliferative activity is approaching the final arrest. These findings suggest that activin may be an important local factor in regulating Sertoli cell number and that the mitosis of differentiating spermatogonia subsides during Sertoli cell proliferation.

Spermatogonial Cell Proliferation in Organ Culture of Immature Rat Testis1

Regulatory mechanisms of male germ cell proliferation in mammals were investigated by using in vitro organ culture of immature rat testis. Nutritional and hormonal requirements for maintenance and differentiation of germ cells in vitro were first characterized by testing different culture conditions. FSH was essential for the progression of type A spermatogonia up to the stage of pachytene spermatocytes after 3 wk of in vitro culture, while vitamins A, C, and E, LH, and testosterone were not effective. The proliferative activity of Sertoli cells markedly declined after 1 wk of in vitro culture, irrespectively of the presence of FSH in the medium. In addition, basal testosterone production by Leydig cells was maintained after 1 wk of culture, provided that FSH was present in the medium. The appearance of differentiating type I and type B spermatogonia and meiotic cells in the seminiferous cords throughout culture was accompanied by a significant reduction in the number of undifferentiated spermatogonia. Moreover, a similar labeling index of undifferentiated spermatogonia was observed in both unstimulated and FSH-stimulated testis fragments at all culture times considered. Therefore, FSH did not influence the mitotic activity of undifferentiated spermatogonia, suggesting a differential role of this gonadotropin during the mitotic phase of spermatogenesis. These results indicate that the organ culture system of immature rat testis represents a useful experimental model for studying regulatory mechanisms of spermatogonial cell proliferation.

Regulation of c‐fos Messenger Ribonucleic Acid by Fibroblast Growth Factor in Cultured Sertoli Cellsa

The data reported here demonstrate that basic FGF and Sertoli-cell-derived FGF have rapid stimulatory effects on c-fos mRNA levels. Basic FGF appears to utilize a signal transduction pathway that is distinct from that used by FSH and serum but similar in its potency and transiency. This is consistent with other reports in the literature on FGFs mechanism of action. For example, a monoclonal antibody to phosphatidyl 4,5-biphosphate will block the effects of PDGF on thymidine incorporation into NIH 3T3 cells but has no effect on basic FGF. Our data support the emerging possibility of a novel pathway mediating FGF actions. A similar precedent has been established for serotonin-induced DNA synthesis in smooth muscle cells. The rat Sertoli cell, with both FSH and FGF rapidly inducing c-fos, is an excellent model system for addressing the mechanism of action of basic FGF, the specificity of the c-fos response and the role of FGF in the reproductive system. Stimulation of c-fos mRNA by basic FGF in the cultured Sertoli cell presents questions regarding the role of FGF and c-fos in the male reproductive system. Basic FGF has been shown to stimulate cell division and plasminogen activator activity in cultured immature porcine Sertoli cells. Plasminogen activator may play a critical role in the tissue remodeling required for spermiogenesis. Interestingly, fos has been shown to be expressed preferentially in pachytene spermatocytes in the mouse. These observations taken together with the finding that basic FGF mRNA levels in Xenopus oocytes are markedly elevated, suggests that basic FGF may be important for Sertoli cell function, spermatogonial cell proliferation and subsequent meiotic and sperm maturational events.

Effect of gonadotropins in the induction of spermatogenesis in human prepubertal testis.

ABSTRACT The effects were studied of the separate and combined administration of hCG and hMG on the qualitative progression of spermatogenesis in normal human prepubertal testis. It was observed: 1) hCG alone induce enlargement of seminiferous tubules, maturation of Sertoli cells, proliferation of spermatogonial cells, development of primary spermatocytes not beyond the pachytene stage and differentiation of Leydig cells from precursors fibroblasts. 2) hMG with highly predominant FSH activity only increased the diameter of seminiferous tubules and the number of immature Sertoli cells. hMG with a ratio FSH LH equal to unit or slightly in favor of LH, provokes similar changes, but there is in addition, a proliferation of spermatogonial cells and a tendency to develop primary spermatocytes and Leydig cells. 3) Combined doses of hCG plus hMG with ratios FSH/LH largely favoring LH, provokes the maximal stimulation of the germinative epithelium reaching earlier spermatid stages and complete maturation of Sertol...

EFFECT OF HUMAN URINARY FSH AND LH ON THE RECOVERY OF SPERMATOGENESIS IN HYPOPHYSECTOMIZED PATIENTS

Centro de Investigaciones sobre Reproducción, Facultad de Medicina, Buenos Aires, Argentina, and Laboratorio de Ricercha, Istituto Serono, Roma, Italia

Effect of human urinary FSH and LH on the recovery of spermatogenesis in hypophysectomized patients.

ABSTRACT The effects were studied of the separate, successive, and simultaneous administration of purified preparations of human urinary FSH and LH on the qualitative progression of spermatogenesis in hypophysectomized patients. It was observed that: 1. Neither the separate nor the successive administration of FSH and LH or vice versa stimulates adequately the germinal epithelium. 2. FSH induces only morphologic repair of Sertoli cells. 3. LH has the same effect on Sertoli cells but provokes, in addition, proliferation of spermatogonial cells and development of primary spermatocytes up to pachytene stage. At the same time begins enlargement of the diameter of the tubules, reduction of hyalinosis, and differentiation of Leydig cells from precursor fibroblasts. 4. Both FSH and LH given simultaneously in a ratio equal to one induce the spermatogenic process up to spermatids, but differentiation of Leydig cells is poor. 5. Of the other FSH/LH ratios used, only that favoring LH results in full development of s...