Researchers in California hope to become the first in the world to build an artificial testicle that produces human sperm, which could allow infertile men to conceive children.

Unlike the cosmetic, non-sperm-producing prosthesis sometimes given to men missing a testicle, the device will instead be a small cylindrical bag. Dr. Paul Turek, director of the Turek Clinic, a men’s health medical practice in San Francisco, likened the final product to “a transparent, over-sized Tootsie Roll.”

To make the artificial testicle, researchers will first focus on growing cells that normally nurture sperm during their development, including those called Sertoli cells. Then the researchers will add embryonic stem cells, which will be “fortified” with genes so they’ll develop the properties of sperm precursor cells.

In other words, the researchers are hoping to recreate the environment typically found within the seminiferous tubules, the structures in the testes where sperm are formed.

The artificial testicle would likely only last about 70 days — one cycle of sperm production — and would then need to be replaced.

“It’s an ambitious project,” said Kyle Orwig, an associate professor of obstetrics, gynecology and reproductive sciences at the University of Pittsburgh. “But it would be fantastic if it happened. It would be a major impact on the fertility field.”

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