The mammalian seminiferous epithelium consists of a highly complex yet well
-organized cell population, with germ cells in mitosis and meiosis and post
meiotic cells undergoing transformation to become spermatozoa. To study the
factors which control renewal and differentiation of spermatogonial stem c
ells, animal models are now available which allow for arrest and restart of
spermatogonial differentiation. In addition, marked progress has been made
in understanding the control of apoptosis and its role in spermatogonia. F
or the future, spermatogonial stem cell transplantation may have important
practical applications.