de Paiva Camargo, MaríliaCassel, MônicaOliveira de Jesus, Lázaro WenderNóbrega, Rafael Henrique [UNESP]Borella, Maria Inês2018-12-112018-12-112017-07-01Theriogenology, v. 96, p. 97-102.0093-691Xhttp://hdl.handle.net/11449/178788Undifferentiated type A spermatogonia are the foundation of fish spermatogenesis. This cell population includes the spermatogonial stem cell population, which is able to either self-renew or differentiate into cells that will generate the male gamete — the spermatozoa. Spermatogonia stem cells are located in a specific region of the testes known as the spermatogonial niche, which regulates spermatogonial stem cell function. This study characterizes undifferentiated type A spermatogonia and their S-phase label-retaining cell properties in Astyanax altiparanae testes. This is a fish species of substantial commercial, environmental, and academic importance. Two types of undifferentiated spermatogonia have been described in A. altiparanae testis: Aund* and Aund. Among the main differences observed, Aund* spermatogonia have an irregular nuclear envelope, decondensed chromatin, one or two nucleoli, and nuages in the cytoplasm; meanwhile, type Aund have a round nucleus. Aund* is preferentially distributed in areas neighboring the interstitial compartment, whereas Aund is located in the intertubular area. Finally, this study found that undifferentiated type A spermatogonia were able to retain BrdU over a long chase period, suggesting that these cells have a long cell cycle and potential stem cell candidates among them. Based on these findings, undifferentiated type A spermatogonia may be characterized as putative stem cells in A. altiparanae testis. This work will contribute to further studies on the stem cell biology of this promising Neotropical experimental model.97-102engLabel-retaining cellsMorphologyMorphometrySpermatogonial nicheStem cellArtigo10.1016/j.theriogenology.2017.03.027Acesso aberto2-s2.0-850172208762-s2.0-85017220876.pdf05157085852539850000-0001-9796-5076