Study summary

Early sperm-forming cells were made from human stem cells

Lab-grown early sperm cells · Laboratory study · Published July 2026, Cell Stem Cell

What was tested

Human and macaque stem cells were turned into cells resembling spermatogonia, the starting point of sperm production, by growing them with mouse testis cells.

What they found

• The cells organized into tube-like structures similar to those in the testis.
• The method still relies on mouse testis cells.
• It does not produce working human sperm.
• A 2026 ASRM ethics opinion says lab-made eggs or sperm should not be used for reproduction until monkey studies are reassuring.

What it means

A real step on a long road. Separately, a startup said in April 2026 that it had grown working human sperm; that claim has not been peer reviewed.