Spermatogonial Stem Cell Transplantation and Culture - Male Germline Stem Cells Developmental and Regenerative Potential - page 115

Fig. 5.3 Methods of microinjection of testis cells into a donor testis. (a) Cells can be injected
directly into the seminiferous tubules. (b) Cells can be injected into the efferent ducts or (c) the
rete testis. Cells that are injected into either the efferent ducts or the rete testis migrate to the rete
testis and colonize the seminiferous tubules

into seminiferous tubules is inefficient; because of the cell suspension must flow to
the rete to fill tubules other than the injected one.

5.3 Spermatogonial Stem Cell Culture

5.3.1 History

Considerable effort has been directed towards the development of a culture system
for the in vitro maintenance and amplification of spermatogonial stem cells.
Original experiments were conducted shortly after the development of the SSC
transplantation technique; however, SSCs survived only about 4 months in vitro , the
results were highly variable, and increases in SSC numbers were not observed. This
was believed to result from competition by contaminating somatic cells and the lack
of factors within the culture environment that are necessary for SSC survival and
self-renewal. Since the development of a long-term culture system, considerable
progress has been made defining the molecular mechanisms of SSC self-renewal.
It is important to note early in this discussion that SSC cultures are NOT cultures
of pure stem cells and experiments must be designed with this in mind. SSC
cultures are ENRICHED for SSCs, and estimates indicate that approximately 1