Soluble growth factors stimulate spermatogonial stem cell divisions that maintain a stem cell pool and produce progenitors in vitro.

Spermatogonial stem cells (SSCs) support life-long spermatogenesis by self-renewing and producing spermatogonia committed to differentiation. In vitro, SSCs form three-dimensional spermatogonial aggregates (clusters) when cultured with glial cell line-derived neurotrophic factor (GDNF) and fibroblast growth factor 2 (FGF2); serial passaging of clusters results in long-term SSC maintenance and expansion. However, the role of these growth factors in controlling patterns of SSC division and fate decision has not been understood thoroughly. We report here that in a short-term culture, GDNF and FGF2 increase the number of dividing SSCs, but not the total SSC number, compared to a no-growth-factor condition. Since the total germ cell number increases with growth factors, these results suggest that GDNF and FGF2 promote a SSC division pattern that sustains the size of the stem cell pool while generating committed progenitors. Our data also show that SSC numbers increase when the cluster structure is disintegrated and cell-cell interaction in clusters is disrupted. Collectively, these results suggest that in this culture system, GDNF and FGF2 stimulate SSC divisions that promote self-renewal and differentiation in the SSC population, and imply that the destruction of the cluster structure, a potential in vitro niche, may contribute to SSC expansion.

Ebata KT ，Yeh JR ，Zhang X ，Nagano MC ... -  《-》

Propagation of bovine spermatogonial stem cells in vitro.

Aponte PM ，Soda T ，Teerds KJ ，Mizrak SC ，van de Kant HJ ，de Rooij DG ... -  《-》

Functional differences between GDNF-dependent and FGF2-dependent mouse spermatogonial stem cell self-renewal.

Spermatogonial stem cells (SSCs) are required for spermatogenesis. Earlier studies showed that glial cell line-derived neurotrophic factor (GDNF) was indispensable for SSC self-renewal by binding to the GFRA1/RET receptor. Mice with mutations in these molecules showed impaired spermatogenesis, which was attributed to SSC depletion. Here we show that SSCs undergo GDNF-independent self-renewal. A small number of spermatogonia formed colonies when testis fragments from a Ret mutant mouse strain were transplanted into heterologous recipients. Moreover, fibroblast growth factor 2 (FGF2) supplementation enabled in vitro SSC expansion without GDNF. Although GDNF-mediated self-renewal signaling required both AKT and MAP2K1/2, the latter was dispensable in FGF2-mediated self-renewal. FGF2-depleted testes exhibited increased levels of GDNF and were enriched for SSCs, suggesting that the balance between FGF2 and GDNF levels influences SSC self-renewal in vivo. Our results show that SSCs exhibit at least two modes of self-renewal and suggest complexity of SSC regulation in vivo.

Takashima S ，Kanatsu-Shinohara M ，Tanaka T ，Morimoto H ，Inoue K ，Ogonuki N ，Jijiwa M ，Takahashi M ，Ogura A ，Shinohara T ... -  《Stem Cell Reports》

Basic features of bovine spermatogonial culture and effects of glial cell line-derived neurotrophic factor.

Aponte PM ，Soda T ，van de Kant HJ ，de Rooij DG ... -  《THERIOGENOLOGY》

[Regulatory effect of GDNF on the proliferation and differentiation of mammalian spermatogonial stem cells].

Li XY ，Liu YJ ，Hou LL ，Wang KG ，Guan WJ ，Ma YH ... -  《-》