A Role for Exchange of Extracellular Vesicles in Porcine Spermatogonial Co-Culture

Abstract

Spermatogonial stem cells (SSCs) provide the basis for lifelong male fertility through self-renewal and differentiation. Prepubertal male cancer patients may be rendered infertile by gonadotoxic chemotherapy and, unlike sexually mature men, cannot store sperm. Testicular biopsies taken prior to treatment may be used to restore fertility in adulthood. Testicular SSC populations are limited, necessitating in vitro culture systems to increase the numbers of SSCs available for downstream applications. Using the pig as a non-rodent model, we developed spermatogonial culture systems to expand spermatogonia from 1- and 8-week-old porcine testes, comparing feeder layers consisting of populations enriched for Sertoli cells, peritubular myoid cells (PMCs), pig fetal fibroblasts (PFFs), and testicular endothelial cells (TECs). As previously developed porcine spermatogonial culture systems relied exclusively on Sertoli cell feeder layers, we explored whether constituent cells of the SSC niche, such as PMCs and TECs, or fibroblastic cells like PFFs, may also support SSC expansion. Spermatogonia co-cultured with PMCs and PFFs had comparable rates of proliferation and apoptosis to spermatogonia co-cultured with Sertoli cells. To elucidate the mechanism behind the beneficial nature of feeder layers, we investigated the role of extracellular vesicles in the dynamic crosstalk between spermatogonia and feeder cells. Sertoli cell-released exosomes were found to be taken up by spermatogonia, and the inhibition of exosomal release reduced spermatogonial proliferation.