Human germ cell differentiation from fetal- and adult-derived induced pluripotent stem cells

TLDR

Human germ cell development has been poorly understood because early stages are inaccessible, but pluripotent stem cells provide a system to study it. The study compared the germ cell‑forming potential of adult‑ and fetal‑derived iPSCs to human embryonic stem cells. The authors induced iPSCs with bone morphogenetic proteins to generate primordial germ cells and assessed germ cell markers, comparing the results to embryonic stem cells. About 5 % of iPSCs differentiated into primordial germ cells expressing GFP and germ‑cell proteins, and overexpression of intrinsic regulators produced meiotic cells with synaptonemal complexes and haploid cells with ACROSIN patterns similar to spermatids, showing that adult‑derived iPSCs can generate germline cells and providing a model for research and therapeutic applications.

Abstract

Historically, our understanding of molecular genetic aspects of human germ cell development has been limited, at least in part due to inaccessibility of early stages of human development to experimentation. However, the derivation of pluripotent stem cells may provide the necessary human genetic system to study germ cell development. In this study, we compared the potential of human induced pluripotent stem cells (iPSCs), derived from adult and fetal somatic cells to form primordial and meiotic germ cells, relative to human embryonic stem cells. We found that ∼5% of human iPSCs differentiated to primordial germ cells (PGCs) following induction with bone morphogenetic proteins. Furthermore, we observed that PGCs expressed green fluorescent protein from a germ cell-specific reporter and were enriched for the expression of endogenous germ cell-specific proteins and mRNAs. In response to the overexpression of intrinsic regulators, we also observed that iPSCs formed meiotic cells with extensive synaptonemal complexes and post-meiotic haploid cells with a similar pattern of ACROSIN staining as observed in human spermatids. These results indicate that human iPSCs derived from reprogramming of adult somatic cells can form germline cells. This system may provide a useful model for molecular genetic studies of human germline formation and pathology and a novel platform for clinical studies and potential therapeutical applications.