Sertoli cell-mediated differentiation of male germ cell-like cells from human umbilical cord Wharton's jelly-derived mesenchymal stem cells in an in vitro co-culture system

Background: Microenvironment signals play a critical role in directing the differentiation of stem cells. Sertoli cells (SCs) provide a unique microenvironment that is essential for germ cell differentiation. Methods: Our previous study has demonstrated that human umbilical cord Wharton's jelly-derived mesenchymal stem cells (HUMSCs) could differentiate towards male germ cells in vitro, but HUMSC-derived germ-like cells expressed only few germ cell markers. The aim of this study was to investigate the effect of SCs on the differentiation of HUMSCs towards male germ cells using a co-culture system that mimicked the in vivo male germ cell microenvironment. Results: HUMSCs formed clump-like features on SC monolayers after seeding for 3 weeks. Differentiated cells formed round colonies that share the morphological features of spermatogonial colonies. RT-PCR, immunofluorescence, confocal microscopy, and Western blot analyses revealed the expression of early germ cell markers STELLA and VASA and male germ cell-specific marker DAZL in differentiated HUMSCs, confirming the presence of cells with characteristics of male germ cells. Conclusion: The HUMSC-SC co-culture system mimics a native microenvironment for germ cell colonization without any in vitro artificial manipulation and can be used to explore the mechanisms controlling the differentiation of male germ cells from HUMSCs. Male germ cells derived from HUMSCs may be used in the therapy for male infertility.