Testicular endothelial cells (TECs) are a key component of the spermatogonial stem cell (SSC) niche providing factors that are essential for SSC maintenance, according to new research published in Nature Communications. This discovery could aid fertility preservation for prepubertal boys who are diagnosed with cancer by enabling expansion and long-term culture of SSCs from testicular biopsy samples.

Expression of glial cell line-derived neurotrophic factor (Gdnf) mRNA in mouse-derived TECs after fibroblast growth factor 2 (FGF2) treatment was higher than in Sertoli cells. Numerous SSC colonies were observed after 3 weeks of co-culture with TECs, in contrast to SSC co-culture with Sertoli cells and peritubular myeloid cells. In vitro, bulsufan treatment decreased TEC proliferation and increased apoptosis, and testis tissue from bulsufan-treated mice showed reduced TEC populations.

Transplantation of TECs into the testes of bulsufan-treated mice resulted in restoration of spermatogenesis. Furthermore, TEC injection into the testes immediately after bulsufan treatment protected spermatogenesis.

TEC co-culture with SSCs without exogenous GDNF was sufficient for 3D colony formation with typical SSC morphology; colonies were maintained in culture for >3 months and could be serially passaged. Transplantation of SSCs co-cultured with TECs into the testes of infertile mice restored fertility and resulted in the birth of live pups.

Comparison of the secretome of TECs with those of lung endothelial cells and liver endothelial cells showed that, as well as GDNF, insulin-like growth factor-binding protein 2, stromal cell-derived factor 1 and CXC motif chemokine 2 were upregulated in TECs. Addition of these factors along with FGF2 to feeder-cell-free cultures of mouse or human testicular cells was sufficient to maintain long-term SSC colony formation.

Transplantation of TECs into the testes of bulsufan-treated mice resulted in restoration of spermatogenesis

“For many years, scientists have been trying to reproducibly expand SSCs from testicular biopsies harvested from prepubertal boys newly diagnosed with cancer before gonadotoxic cancer treatment,” Sandra Ryeom, corresponding author, tells Nature Reviews Urology. “Our work identifies TECs as a key population in the SSC niche and co-culture of SSCs with TECs enables consistently reproducible long-term expansion and maintenance of these stem cells,” Ryeom continues. “Expansion of sperm stem cells will enable fertility preservation for patients who have no other options. This work is a key first step towards restoring fertility in boys and men who have survived childhood cancer.”