Testicle

Abstract: I. Introduction The concept that proteins, in addition to steroid hormones, of gonadal origin could play a role in the inhibition of gonadatropin secretion from the anterior lobe of the pituitary was proposed more than 65 yr ago. Only recently, however, has the elucidation of the chemistry and physiology of these proposed gonadal hormones actually been achieved. Mottram and Cramer (1) reported pituitary hypertrophy as determined by the appearance of so-called castration cells in the anterior lobe of pituitary after treatment of the testes with radium. The removal of the testes leads to the development of highly vacuolated, signet-shaped basophil cells in the pituitary (2), termed castration cells, demonstrating a reciprocal relationship between the pituitary and the gonads and suggesting that a secretion of the testes has an inhibitory effect on the pituitary (3). The pituitary hypertrophy after castration or irradiation of the testes was postulated to be due to a lack of some substance from the seminal e...

Abstract: Reproducing the complex process of spermatogenesis in vitro might lead to the development of new diagnostic and therapeutic techniques for male infertility. Takehiko Ogawa and colleagues have now established in vitro organ culture conditions that can support the production of fertile sperm from spermatogonia of neonatal mice. Spermatids and sperm that were derived in vitro produced healthy and fertile mice. In addition, neonatal testis tissues that were cryopreserved for several months resumed complete spermatogenesis in vitro on thawing. The organ culture method is simple and, with further refinements, could be applicable to a variety of mammalian species. This work suggests that cryopreservation of the testis tissue of paediatric cancer patients could become a practical way of ensuring future fertility. Reproducing the complex process of spermatogenesis in vitro might lead to the development of new diagnostic and therapeutic techniques for male infertility. This study establishes in vitro organ culture conditions that can support complete spermatogenesis in mice. The in-vitro-derived spermatids and sperm produced healthy and fertile mice, and testis tissue fragments used as a starting material for in vitro spermatogenesis could be cryopreserved for months and then resumed full spermatogenesis in vitro. Spermatogenesis is one of the most complex and longest processes of sequential cell proliferation and differentiation in the body, taking more than a month from spermatogonial stem cells, through meiosis, to sperm formation1,2. The whole process, therefore, has never been reproduced in vitro in mammals3,4,5, nor in any other species with a very few exceptions in some particular types of fish6,7. Here we show that neonatal mouse testes which contain only gonocytes or primitive spermatogonia as germ cells can produce spermatids and sperm in vitro with serum-free culture media. Spermatogenesis was maintained over 2 months in tissue fragments positioned at the gas–liquid interphase. The obtained spermatids and sperm resulted in healthy and reproductively competent offspring through microinsemination. In addition, neonatal testis tissues were cryopreserved and, after thawing, showed complete spermatogenesis in vitro. Our organ culture method could be applicable through further refinements to a variety of mammalian species, which will serve as a platform for future clinical application as well as mechanistic understanding of spermatogenesis.

Abstract: Sex in mammals is determined in the fetal gonad by the presence or absence of the Y chromosome gene Sry, which controls whether bipotential precursor cells differentiate into testicular Sertoli cells or ovarian granulosa cells. This pivotal decision in a single gonadal cell type ultimately controls sexual differentiation throughout the body. Sex determination can be viewed as a battle for primacy in the fetal gonad between a male regulatory gene network in which Sry activates Sox9 and a female network involving WNT/β-catenin signalling. In females the primary sex-determining decision is not final: loss of the FOXL2 transcription factor in adult granulosa cells can reprogram granulosa cells into Sertoli cells. Here we show that sexual fate is also surprisingly labile in the testis: loss of the DMRT1 transcription factor in mouse Sertoli cells, even in adults, activates Foxl2 and reprograms Sertoli cells into granulosa cells. In this environment, theca cells form, oestrogen is produced and germ cells appear feminized. Thus Dmrt1 is essential to maintain mammalian testis determination, and competing regulatory networks maintain gonadal sex long after the fetal choice between male and female. Dmrt1 and Foxl2 are conserved throughout vertebrates and Dmrt1-related sexual regulators are conserved throughout metazoans. Antagonism between Dmrt1 and Foxl2 for control of gonadal sex may therefore extend beyond mammals. Reprogramming due to loss of Dmrt1 also may help explain the aetiology of human syndromes linked to DMRT1, including disorders of sexual differentiation and testicular cancer.

Abstract: Background The disorders comprising human 'testicular dysgenesis syndrome' (TDS) may be increasing in incidence. TDS originates in fetal life but the mechanisms are not known, and discerning them requires an animal model. Methods and results The study investigated whether male rats exposed in utero to dibutyl phthalate [DBP; 500 mg/kg on gestational days (GD) 13-21] would provide a suitable model for human TDS. DBP induced a high rate (>60%) of cryptorchidism (mainly unilateral), hypospadias, infertility and testis abnormalities, similar to those in human TDS. Cell-specific immunohistochemistry and confocal microscopy were used to track development of Sertoli [anti-Mullerian hormone (AMH), Wilm's tumour (WT-1) protein, p27(kip)], Leydig [3beta-hydroxysteroid dehydrogenase (3beta-HSD)], germ (DAZL protein) and peritubular myoid (smooth muscle actin) cells from fetal life to adulthood. In scrotal and cryptorchid testes of DBP-exposed males, areas of focal dysgenesis were found that contained Sertoli and Leydig cells, and gonocytes and partially formed testicular cords; these dysgenetic areas were associated with Leydig cell hyperplasia at all ages. Suppression ( approximately 90%) of testicular testosterone levels on GD 19 in DBP-exposed males, coincident with delayed peritubular myoid cell differentiation, may have contributed to the dysgenesis. Double immunohistochemistry using WT-1 (expressed in all Sertoli cells) and p27(kip) (expressed only in mature Sertoli cells) revealed immature Sertoli cells in dysgenetic areas. DBP-exposed animals also exhibited Sertoli cell-only (SCO) tubules, sporadically in scrotal and predominantly in cryptorchid, testes, or foci of SCO within normal tubules in scrotal testes. In all SCO areas the Sertoli cells were immature. Intratubular Leydig cells were evident in DBP-exposed animals and, where these occurred, Sertoli cells were immature and spermatogenesis was absent. Abnormal Sertoli cell-gonocyte interaction was evident at GD 19 in DBP-exposed rats coincident with appearance of multinucleated gonocytes, although these disappeared by postnatal day 10 during widespread loss of germ cells. Conclusions Abnormal development of Sertoli cells, leading to abnormalities in other cell types, is our hypothesized explanation for the abnormal changes in DBP-exposed animals. As the testicular and other changes in DBP-exposed rats have all been reported in human TDS, DBP exposure in utero may provide a useful model for defining the cellular pathways in TDS.