BACKGROUNDThe spermatogonial stem cell (SSC) pool in the testes of non-human primates is poorly defined.METHODSTo begin characterizing SSCs in rhesus macaque testes, we employed fluorescence-activated cell sorting (FACS), a xenotransplant bioassay and immunohistochemical methods and correlated our findings with classical descriptions of germ cell nuclear morphology (i.e. Adark and Apale spermatogonia).RESULTSFACS analysis identified a THY-1+ fraction of rhesus testis cells that was enriched for consensus SSC markers (i.e. PLZF, GFRα1) and exhibited enhanced colonizing activity upon transplantation to nude mouse testes. We observed a substantial conservation of spermatogonial markers from mice to monkeys [PLZF, GFRα1, Neurogenin 3 (NGN3), cKIT]. Assuming that molecular characteristics correlate with function, the pool of putative SSCs (THY-1+, PLZF+, GFRα1+, NGN3+/−, cKIT−) comprises most Adark and Apale and is considerably larger in primates than in rodents. It is noteworthy that the majority of Adark and Apale share a common molecular phenotype, considering their distinct functional classifications as reserve and renewing stem cells, respectively. NGN3 is absent from Adark, but is expressed by some Apale and may mark the transition from undifferentiated (cKIT−) to differentiating (cKIT+) spermatogonia. Finally, the pool of transit-amplifying progenitor spermatogonia (PLZF+, GFRα1+, NGN3+, cKIT+/−) is smaller in primates than in rodents.CONCLUSIONSThese results provide an in-depth analysis of molecular characteristics of primate spermatogonia, including SSCs, and lay a foundation for future studies investigating the kinetics of spermatogonial renewal, clonal expansion and differentiation during primate spermatogenesis.

The purpose of the present study was to determine whether dark and pale type A spermatogonia (Ad and Ap, respectively) are mitotically active during prepubertal development and whether proliferation of these germ cells during this protracted phase of primate development occurs predominantly during infancy before gonadotropin secretion is arrested. Four neonate (1-2 days of age), four infant (4-5 mo of age), and four juvenile (14-17 mo of age) rhesus monkeys (Macaca mulatta) were castrated 2 h after receiving an i.v. bolus of 5-bromo2'-deoxy-uridine (BrdU, 33 mg/kg body weight). Tissue was fixed in Bouin solution, and 5-microm paraffin sections were cut. Using periodic acid-Schiff reagent/Gill hematoxylin staining, the number per testis of Ad and Ap spermatogonia were determined. BrdU S-phase-labeled nuclei were identified using immunofluorescence. Conservative criteria were employed for classifying cell types, and this resulted in a fraction of A spermatogonia remaining unclassified. Ad, Ap, and the unclassified A spermatogonia each showed an approximately 4-fold increase over the 5-mo period from birth to infancy, and a similar increase was observed over the 10-mo period between infancy and the juvenile stage of development. Both Ad and Ap (and unclassified A spermatogonia) exhibited robust and similar S-phase labeling at the three stages of development. We conclude that the prepubertal expansion of Ad and Ap spermatogonia is achieved by mitotic proliferation that is relatively gonadotropin independent. This conclusion raises the question of the nature of the signal that arrests the cell cycle of Ad in adult testis.

Leptin-deficient (ob/ob) male mice are morbidly obese and exhibit impaired reproductive function. The objective of this study was to assess the effect of a leptin deficiency on testicular morphology, germ cell development, apoptotic activity within germ cells, and expression levels of apoptosis-related genes in the testis. Sixteen week-old ob/ob male mice (n ϭ 8) and controls (n ϭ 8) were killed, and their reproductive organs were weighed. Testes were processed for either histomorphological analysis (hematoxylin and eosin [H&E] staining), germ cell apoptosis assessment (deoxy-UTPdigoxigenin nick end labeling [TUNEL] method), or apoptosis-related gene expression analysis (microarray). Cross sections of the testes of leptin-deficient animals showed reduced seminiferous tubule area, fewer pachytene spermatocytes, and fewer tubules exhibiting elongated spermatids/mature spermatozoa. Condensation of germ cell nuclei and Sertoli cell vacuolization were evident in the testes of some ob/ob animals. Overall there was an elevation of apoptotic activity in the germ cells of ob/ob mice, particularly within the pachytene spermatocytes. With microarray technology, we identified 9 proapoptosis-related genes that were expressed at a significantly higher level in the testes of ob/ob mice than in the testes of the controls. Among these were members of the tumor necrosis factor receptor super family 1A and 5 (TNFR1 and 5) and peptidoglycan recognition proteins (associated with the extrinsic apoptotic pathway), and granzymes A and B, growth arrest and DNA damage inducible 45 gamma, sphingosine phosphate lyase 1, and caspase 9 (associated with the intrinsic apoptotic pathway). The results of the current study show that a leptin deficiency in mice is associated with impaired spermatogenesis, increased germ cell apoptosis, and upregulated expression of proapoptotic genes within the testes.

The combined effects of transient

The present study was undertaken to examine the antispermatogenic effect of l-CDB-4022 in the adult male cynomolgus monkey. Monkeys (four per group) were dosed via nasogastric tube for 7 d with l-CDB-4022 at 12.5 mg/kg.d or vehicle (d 0=first day of dosing). Plasma levels of l-CDB-4022 and its deesterified metabolite were nondetectable prior to treatment and in all vehicle-treated monkeys. Peak levels of l-CDB-4022 and its metabolite were observed at 4 h after dosing with steady-state levels apparent around d 4. Sperm concentration and total sperm per ejaculate were decreased to levels below 1x10(6) sperm/ml or sperm/ejaculate in l-CDB-4022-treated monkeys by d 17 and remained suppressed through wk 6. Sperm motility also declined to 0% for 6 wk. Testicular volume was reduced in l-CDB-4022-treated monkeys through d 21. The left testis and epididymis were removed from all monkeys on d 24. At this time, the most mature germ cells in the seminiferous tubules of testes from l-CDB-4022-treated monkeys were either spermatocytes or round spermatids. Immature germ cells, but not mature sperm, were found in the efferent ducts and collapsed epididymal lumen of l-CDB-4022-treated monkeys. A steady recovery in sperm motility, concentration, and total sperm per ejaculate was observed in l-CDB-4022-treated monkeys such that these parameters were not different from those of vehicle-treated monkeys by wk 16. Volume of the remaining testis increased in vehicle- and l-CDB-4022-treated monkeys after hemicastration; however, the increase in l-CDB-4022-treated monkeys was delayed compared with that observed in the vehicle-treated monkeys. The morphology of the remaining testis and epididymis, which were removed on wk 17, was normal. Serum inhibin B levels were increased in l-CDB-4022-treated monkeys during the dosing interval; thereafter serum inhibin B levels declined such that there was no difference between the groups by wk 3. l-CDB-4022 treatment did not affect circulating levels of testosterone, LH, FSH, or estradiol. In conclusion, these data indicate that in the cynomolgus monkey, a representative higher primate, l-CDB-4022 exerts a selective antispermatogenic action, which was reversible under the conditions of this study and thus has potential as a nonhormonal oral male contraceptive.