Researchers at Kyoto University say they have developed a method to create “near-indefinite” volumes of early-stage sperm and egg cells from induced pluripotent stem (iPS) cells, in a step that could potentially lead to new infertility treatments.

In a study published in the journal Nature on Monday, scientists led by Mitinori Saitou at the university’s Institute for the Advanced Study of Human Biology succeeded in using iPS cells — stem cells that can turn into any type of cell — to create early germ cells called “human primordial germ cell-like cells” (hPGCLCs).

The researchers were then able to guide these hPGCLCs to develop into either early-stage sperm cells, called pro-spermatogonia, or early-stage egg cells, called oogonia.