title: The spermatogonial stem cell niche in the collared peccary (Tayassu tajacu).
abstract: In the seminiferous epithelium, spermatogonial stem cells (SSCs) are located in a particular environment called the "niche" that is controlled by the basement membrane, key testis somatic cells, and factors originating from the vascular network. However, the role of Leydig cells (LCs) as a niche component is not yet clearly elucidated. Recent studies showed that peccaries (Tayassu tajacu) present a peculiar LC cytoarchitecture in which these cells are located around the seminiferous tubule lobes, making the peccary a unique model for investigating the SSC niche. This peculiarity allowed us to subdivide the seminiferous tubule cross-sections in three different testis parenchyma regions (tubule-tubule, tubule-interstitium, and tubule-LC contact). Our aims were to characterize the different spermatogonial cell types and to determine the location and/or distribution of the SSCs along the seminiferous tubules. Compared to differentiating spermatogonia, undifferentiated spermatogonia (A(und)) presented a noticeably higher nuclear volume (P < 0.05), allowing an accurate evaluation of their distribution. Immunostaining analysis demonstrated that approximately 93% of A(und) were GDNF receptor alpha 1 positive (GFRA1(+)), and these cells were preferentially located adjacent to the interstitial compartment without LCs (P < 0.05). The expression of colony-stimulating factor 1 was observed in LCs and peritubular myoid cells (PMCs), whereas its receptor was present in LCs and in GFRA1(+) A(und). Taken together, our findings strongly suggest that LCs, different from PMCs, might play a minor role in the SSC niche and physiology and that these steroidogenic cells are probably involved in the differentiation of A(und) toward type A(1) spermatogonia.
authors.affiliation: Laboratory of Cellular Biology, Department of Morphology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Paulo Henrique A
authors.initials: PH
authors.lastname: Campos-Junior
authors.forename: Guilherme M J
authors.initials: GM
authors.lastname: Costa
authors.forename: Samyra M S N
authors.initials: SM
authors.lastname: Lacerda
authors.forename: José V
authors.initials: JV
authors.lastname: Rezende-Neto
authors.forename: Ana M
authors.initials: AM
authors.lastname: de Paula
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Hofmann
authors.forename: Luiz R
authors.initials: LR
authors.lastname: de França
mesh_terms: D000818:Animals; D001188:Artiodactyla / Q000502:physiology; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors / Q000032:analysis; D007985:Leydig Cells / Q000166:cytology / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000096:biosynthesis; D008297:Male; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000032:analysis; D012671:Seminiferous Tubules / Q000166:cytology; D013091:Spermatogenesis / Q000502:physiology; D013093:Spermatogonia / Q000166:cytology / Q000378:metabolism*; D055153:Stem Cell Niche / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism
chemical_list: D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D016173:Macrophage Colony-Stimulating Factor; D016186:Receptor, Macrophage Colony-Stimulating Factor