US researchers found a way to develop early-stage sperm cells in mice from human and non-human primate stem cells, providing new hope for fertility challenges. 

Despite major advancements in technology and treatments, fertility remains a major issue in today’s society, affecting female and male patients equally, contrary to popular belief.   

Researchers at the University of Pennsylvania reprogrammed human and rhesus macaque adult cells to form cells that normally develop into sperm. They combined these stem cells with supporting cells from developing mouse testes to create structures resembling the sperm-producing parts of the testis, then transplanted them into live mice. 

After transplantation, the human and macaque cells developed into spermatogonia, an essential early stage in sperm production, and some even began the specialised cell division needed to eventually produce sperm, although full maturation of these cells was still not possible.  

Kotaro Sasaki, from the University of Pennsylvania, and lead author of the study published in Cell Stem Cell, said: “For the first time, we can systematically uncover the molecular mechanisms that build human sperm and begin to understand why sperm development fails in patients with infertility.”  

A potential longer-term goal is to generate functional sperm from a person’s own reprogrammed cells, which would be a major milestone in fertility research.

Sperm cells generated from stem cells. CREDITS: Kotaro Sasaki