Differentiation of Peritubular Myoid-Like Cells from Human Induced Pluripotent Stem Cells

Infertility affects approximately 15% of couples, and in couples where a male factor is present 15% of these males lack production of any sperm. In order to derive novel regenerative therapies, we must first have an improved understanding of the cell-type-specific function in normal and infertile human testes that regulate spermatogenesis must be achieved. This understanding requires the ability to isolate and functionally characterize each human testis cell type in isolation and in combination within the spermatogenic niche. Similar to other human organ systems, lack of availability to obtain biopsies with viable cells to subsequently, isolate and propagate specific cell types, has stifled human spermatogenesis research. Previous researchers have utilized engineering human induced pluripotent stem cells (hiPSCs) to generate various organ specific cell types for use as in vitro models. In the human testis, previous groups have derived Leydig cells, Sertoli cells, spermatogonial stem cells (SSCs), macrophages and endothelial cells via this method. However, peritubular myoid cells (PTMs) which serve critical roles in human testis cytoarchitecture and spermatogenic regulation, remain to be derived. Therefore, this study set forth to generate hiPSC-derived PTMs to serve as a tool to model and study human PTM function and in vitro spermatogenic modelling by deriving the final missing somatic cell type ofin the human testis. PTMs and Leydig cells arise from a common progenitor, so it was hypothesized that PTMs could be derived by modifying an existing differentiation protocol for Leydig cell differentiation from hiPSCs. These hiPSC-derived cells, or hPTMs, were characterized and compared to hiPSC-derived Leydig cells (hLCs) and primary PTMs. Results show that the substitution of the molecular patterning factor Platelet-Derived Growth Factor Subunit B (PDGFBB) for Platelet-Derived Growth Factor Subunit A (PDGFAA) in a molecule-based differentiation protocol for deriving Leydig-like cells is sufficient to derive cells with peritubular myoid-like transcriptomes and smooth muscle protein expression in an hiPSC line primed for a mesoderm lineage. Results also indicate that maturation of differentiated PTMs between hiPSC lines is variable. Comparison of lineage affiliated gene expression suggests that hiPSC lines with gene expression reflecting a primed state for mesoderm lineage can more efficiently and consistently derive hPTM-like cells. Overall, these hPTMs will allow for in vitro study of their phenotypes and functional role in spermatogenesis. Overall design: We conducted RNAseq experiments on hiPSC-derived peritubular myoid cells. Two hiPSC lines were used: iPS11-10 (Cell Applications) and DL01 (WiCell). Both were differentiated into peritubular myoid cells, and undifferentiated hiPSCs from both were used as negative controls. As a postive control, primary peritubular myoid cells were isolated by magnetic activated sorting and expanded in vitro from testicular tissue obtained from a human patient ("PDGFRA"). In total 5 samples were analyzed: 11-10 hiPSCs, DL01 hiPSCs, 11-10 myoids, DL01 myoids, and PDGFRA+ primaries. Each was completed in technical triplicates.