To preserve fertility in young boys, a fragment from
one testis can be surgically removed and frozen before cancer therapy starts.
This testis fragment contains Spermatogonial Stem Cells (SSCs) that have the
potential to form sperm later in life. However, clinical treatments that use
SSCs to cure infertility are not yet available.

Several fertility treatments are under development, including SSC transplantation back

into the testis and sperm formation in a dish. Transplantation is not safe for blood cancer patients, since infiltrated cancer cells might stay alive in the frozen testis fragment. Therefore, sperm formation in a dish using the testis fragment is an ideal solution, but this does not work yet for human tissue. In the human body, Sertoli cells help the SSCs in their journey to become sperm, for which maturity of Sertoli cell is crucial. We hypothesized that the failure to produce human sperm in culture is because in a dish Sertoli cells do not mature.

To study this we used lasers to shoot out Sertoli cells from a thin testis tissue slice from both cultured and uncultured tissue, using a technique called Laser Capture Microdissection. We analyzed the gene expression in these Sertoli cells and found that they do attempt to mature, but fail to do so completely. This may be the reason that sperm formation in a dish fails for human tissue. In follow-up studies we need to find out more about the exact order in which Sertoli cells mature in boys at the start of puberty. This knowledge will help us to improve testis fragment tissue culture aiming to produce sperm in a dish.