Valproic acid Promotes the in Vitro Differentiation of Human Pluripotent Stem Cells Into Spermatogonial Stem Cell-like Cells

Abstract

\n Background: Studying human germ cell development and male infertility is heavily relied on mouse models. In vitro differentiation of human pluripotent stem cells into spermatogonial stem cell-like cells (SSCLCs) can be used as a model to study human germ cells and infertility. The current study aimed to develop the SSCLC induction protocol and assess the effects of the developed protocol on the SSCLC induction. Methods: We examined the effects of valproic acid (VPA), vitamin C (VC) and the combination of VPA and VC on the SSCLC induction efficiency and determined the expression of spermatogonial genes of differentiated cells. The percentage of haploid cells and cells expressed meiotic and spermatid genes were also detected. RNA-sequencing analysis was performed to compare the transcriptome between cells at 0 and 12 days of differentiation and differently expressed genes were confirmed by RT-qPCR. We further evaluated the alteration in histone marks (H3K9ac and H3K27me3) at 12 days of differentiation. Moreover, the SSCLC induction efficiency of two hiPSC lines of non-obstructive azoospermia (NOA) patients was assessed using different induction protocols.Results: The combination of low concentrations of VPA and VC in the induction medium was most effective to induce SSCLCs expressing several spermatogonial genes from human pluripotent stem cells at 12 days of differentiation. High concentration of VPA was more effective to induce cells expressing meiotic genes and haploid cells. RNA-sequencing analysis revealed that the induction of SSCLC involved the upregulated genes in Wnt signaling pathway, and cells at 12 days of differentiation showed increased H3K9ac and decreased H3K27me3. Additionally, two hiPSC lines of NOA patients showed low SSCLC induction efficiency and the expression of genes in Wnt signaling pathway. Conclusions: VPA robustly promotes the differentiation of human pluripotent stem cell lines into SSCLCs, which involved the upregulated genes in Wnt signaling pathway and epigenetic changes. hiPSCs from NOA patients showed decreased SSCLC induction efficiency and Wnt signaling pathway gene expression, suggesting that inactivation of Wnt signaling pathway might be a cause of SSC depletion in azoospermia testes. Our developed SSCLC induction protocol provides a reliable tool and model to study human germ cell development and male infertility.