Hum. Reprod. Advance Access published online on March 12, 2009
Human Reproduction, doi:10.1093/humrep/dep051
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A re-examination of proliferation and differentiation of type A spermatogonia in the adult rhesus monkey (Macaca mulatta)
1 Center for Research in Reproductive Physiology, Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA 2 Department of Natural and Physical Sciences, Chatham University, Pittsburgh, PA 15232, USA
3 Correspondence address. Magee Womens Research Institute, 204 Craft Avenue, Room B311, Pittsburgh Pa 15213, USA. E-mail: plant1{at}pitt.edu
BACKGROUND: Companion studies using an experimental non-human primate paradigm known as a testicular clamp indicated that the behavior of undifferentiated type A spermatogonia did not conform fully to earlier classical models. This issue was therefore re-examined in normal monkeys.
METHODS: Adult male rhesus monkeys (n = 4) received an i.v. bolus of 5-bromo-2'-deoxyuridine (BrdU): one testis (first) was removed 3 h later and the remaining testis (second) was removed after 11 days and 3 h. Tissue was fixed in Bouin’s solution, and numbers of A dark (Ad), small A pale (Aps) and large A pale spermatogonia, differentiating B spermatogonia, S-phase-labeled and degenerating cells were enumerated. Data are given as mean ± SEM.
RESULTS: During the early stages of the seminiferous epithelial cycle in the first testis, Ap spermatogonia (1.3 cells/cross section) were predominantly Aps (nuclear dia., 7.1 ± 0.1 µm). Aps were never S-phase labeled. Apl (nuclear dia., 8.8 ± 0.5 µm) appeared in Stages IV–VI and were maximal in Stages VII–X when S-phase labeling of this phenotype at 3 h was greatest. The first generation of B spermatogonia appeared in Stages XI–XII (0.84 cells/cross section). Using cells/cross section, the ratio of Ap (Stages I–V):B1:B2:B3:B4:preleptotene spermatocyte was 1:0.7:1.4:2.8:5.6:11.2. In the second testis, labeled Aps (and Apl) were observed. Ad were not BrdU labeled, and degenerating cells were rarely observed.
CONCLUSIONS: The results are not entirely consistent with earlier models of spermatogonial proliferation and differentiation in the monkey. Most notably, our findings suggest that in any one cycle of the seminiferous epithelium only a fraction of Ap spermatogonia is mitotically active.
Key words: spermatogenesis/primate/undifferentiated spermatogonia/differentiated spermatogonia/testis
Submitted on November 12, 2008; resubmitted on February 3, 2009; accepted on February 6, 2009.
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