New horizons for in vitro spermatogenesis? An update on novel three-dimensional culture systems as tools for meiotic and post-meiotic differentiation of testicular germ cells.

Culture and differentiation of male germ cells has been performed for various purposes in the past. To date, none of the studies aimed at in vitro spermatogenesis has resulted in a sufficient number of mature gametes. Numerous studies have revealed worthy pieces of information, building up a body of information on conditions that are required to maintain and mature male germ cells in vitro. In this review, we report on previously published and unpublished experiments addressing murine germ cell differentiation in three-dimensional (3D) in vitro culture systems. In a systematic set of experiments, we examined the influence of two different matrices (soft agar and methylcellulose) as well as the need for gonadotrophin support. For the first time, we demonstrate that pre-meiotic male germ cells [revealed by the absence of meiotic marker expression (e.g. Boule)] obtained from immature mice pass through meiosis in vitro. After several weeks of culture, we obtained morphologically normal spermatozoa embedded in the matrix substance. Complete maturation relied on support from somatic testicular cells and the presence of gonadotrophins but appeared independent from the matrix in a 3D culture environment. Further research efforts are required to reveal the applicability of this culture technique for human germ cells and the functionality of the spermatozoa for generating offspring.

Changes in endocrine profile and reproductive organs during puberty in the male marmoset monkey (Callithrix jacchus).

Data on pubertal maturation in male marmoset, a model for human reproduction, are scant and conflicting. We collected data on novel parameters to characterize puberty. Twenty-five marmoset monkeys were assigned to five age groups by weeks (wk): 21 (pre-pubertal), 43 (onset of puberty), 52 (fully pubertal), 70 (mature), and 116 (fully adult). Serum and intratesticular testosterone and pituitary bioactive chorionic gonadotropin (bioCG) were measured. Testicular development was assessed by ultrasonography, histology, and flow cytometry. Three consecutive blood samples revealed extreme fluctuations in testosterone concentrations, suggesting an erratic secretion. Age-related changes in serum testosterone and pituitary bioCG concentrations were observed. Intratesticular androgens (ITAs) showed high fluctuations within groups at all ages and were high in some animals by 21 wk. Unexpectedly, no correlation between pituitary bioCG and serum testosterone or ITAs was found, but these parameters significantly correlated with testicular weight and volume. These observations were consistent a dependence on the testis growth on bioCG. Unfortunately, the low serum levels of bioCG were not measurable in this study. At 43 wk, the animals reached puberty. At 52 wk of age, animals attained maximum body and epididymal weights and qualitatively normal spermatogenesis, but testes continued growing, reaching a maximum of all parameters at 70 wk of age, without further major changes at the age of 116 wk. It is concluded that (1) gonadal activation is evident at wk 21, (2) the male marmoset reaches the pubertal threshold around 43 wk of age, attains qualitative parameters at 52 wk, matures further to sexual maturity at 70 wk, and (3) serum testosterone and ITAs are highly variable without any identifiable correlation with pituitary bioCG.

Elevated follicle-stimulating hormone levels and the chances for azoospermic men to become fathers after retrieval of elongated spermatids from cryopreserved testicular tissue.

OBJECTIVE: To assess individual chances for a live-born child in azoospermic men by performance of testicular sperm extraction (TESE) followed by intracytoplasmatic sperm injection (ICSI). DESIGN: A retrospective cohort study. SETTING: An academic fertility care center and research unit. PATIENT(S): Two hundred three couples who wished to have a child; all men had azoospermia. INTERVENTION(S): All men were operated for TESE; 112 men were found to have elongated spermatids (ES), and 209 ICSI cycles were performed in these men using cryopreserved tissue. MAIN OUTCOME MEASURE(S): Predictors for the chances to obtain live sperm and for probabilities of fertilization, clinical pregnancies, and live births. RESULT(S): Testicular volume, FSH, and inhibin B levels were predictors for the presence of ES. Intracytoplasmic sperm injection resulted in 23 pregnancies, leading to 20 live births. Despite the presence of ES and performance of ICSI in cases of FSH levels >or=20 IU/L, no pregnancy resulted in these men (n = 21). Receiver operating characteristics revealed FSH levels of >or=20 IU/L as cutoff for treatment success. The number of testicular tubuli containing ES served as a predictor for clinical pregnancy as well as for live birth. Cigarette smoking by the male partner exerted a significant negative influence on treatment success. CONCLUSION(S): The degree of completely maintained spermatogenesis within the biopsy appears to reflect intrinsic abilities of spermatozoa to induce normal embryo development. Charts based on regression models are presented for counseling patients before TESE; these explain chances of finding ES and probability of successful ICSI. Obtaining offspring is unlikely in cases of azoospermia and of FSH levels of >or=20 IU/L.

Clonal organization of proliferating spermatogonial stem cells in adult males of two species of non-human primates, Macaca mulatta and Callithrix jacchus.

The present study examines the existence of clonogenic patterns in the proliferation and differentiation of spermatogonial stem cells in two species of non-human primates, the marmoset and the rhesus monkey. We developed a novel approach to detect proliferating spermatogonial clones in whole mounts of seminiferous tubules. Dual fluorescence labeling of bromodeoxyuridine and acrosin in conjunction with confocal microscopy allows the description of the clonogenic and spatial arrangement of proliferating spermatogonia at specific stages of the seminiferous epithelial cycle. Cross-sections of paraffin-embedded tissue were labeled by the same approach. For both monkey species we demonstrate the presence of proliferating spermatogonial clones of variable size at specific stages of the cycle of the seminiferous epithelium. Detailed analysis of the rhesus monkey reveals proliferating Apale spermatogonia at stages VII and IX of the cycle of the seminiferous epithelium, and of proliferating B spermatogonia at stages II, IV, VI, and XII. Proliferating Apale spermatogonia at stages VII and IX of the cycle are organized in pairs or quadruplets. B1 spermatogonia appear as quadruplets or eight-cell clones, and B2 spermatogonia as 8- or 16-cell clones. We conclude that spermatogenesis in the rhesus monkey is initiated by two divisions of duplets or quadruplets of Apale spermatogonia: a first division at stage VII, after which the clones of Apale spermatogonia separate, and a second division at stage IX, which leads to clones of B1 spermatogonia as well as pairs and quadruplets of Apale spermatogonia replenishing the seminiferous epithelium to maintain the original size of the A spermatogonial population.