One of the many causes of male infertility is a failure in germline development, the process by which embryonic cells develop into sperm or eggs. Finding treatments has been challenging because there are no laboratory models that accurately mimic how sperm develop, but a recent study brings us a step closer.

In a recent study published in Cell Stem Cell, scientists presented a recipe for transforming human blood-derived cells into immature primate sperm precursor cells in a mini-testis-like environment.

The researchers started with induced pluripotent stem cells (iPSCs) from humans and rhesus macaques, which are blank-slate cells that can be programmed to become almost any cell type. By exposing them to specific chemical signals, the researchers transformed them into primordial germ cell-like cells (PGCLCs), which are lab-grown versions of the earliest embryonic cells that eventually develop into germline cells, in this case sperm cells.