Comparison between stem cell renewal and spermatogonial multiplication in humans and mice
Ponente: Dirk de Rooij
Utrecht University [Utrecht, The Netherlands]
Host: Alberto Martín Pendás
Salón de actos del Centro de Investigación del Cáncer
There are large differences in the spermatogenic process between mice (and most other mammals) and humans. Human spermatogenesis at first sight makes a disorganized impression because the cellular associations that compose an epithelial stage are much smaller in the human than in mice leading to multiple cell associations per tubule section in the human. Importantly, the density of the spermatogonia in the human is very much higher than in mice. These differences have made human spermatogenesis difficult to study. Recent immunofluorescence studies and confocal microscopy on organ donor material using several spermatogonial marker proteins and cell cycle markers have led to a better understanding of human spermatogonial (stem cell) behaviour, allowing a closer comparison with mouse spermatogonia. Spermatogonial clonal size and proliferative activity are much smaller/lower in human than in mouse spermatogenesis. Differentiating spermatogonia in the human only go through 3 divisions per epithelial cycle versus 6 in the mouse. This is because in the human almost half of the differentiating spermatogonia are out of the cell cycle while all these cells are actively dividing in the mouse.
While the above study in the human did give some idea about how spermatogonia develop in the human, quite a different kind of data were gathered on human spermatogonia by performing single cell seq studies on mRNA from human and mouse testis material, by several groups. These new data are difficult to relate to the results of the more morphological data described above. These data will be discussed.
Understanding the regulation of human spermatogonial (stem cell) development will be important to interpret problems observed in infertile male patients and will be essential to develop proper treatment protocols.