Can Stem Cells be Used to Create People?

Posted on by Paul Turek, MD
Group of sperm going for an egg, 3d illustration.

We’ve known about stem cells for half a century. They are cells that not only make copies of themselves but can also become other types of cells and tissues. This kind of biological feat is unique in science and has the potential to cure disease. So why haven’t we seen more scientific success and stem cell therapies? Where’s the beef?

Jewels Within Jewels

Like good wine, good science takes time to mature and have its potential fully realized. This is exactly the case with stem cell science. Take reproduction. Ten years ago, we published that human sperm precursors, termed spermatogonial stem cells, can create not only sperm, but also other organs in the body. We call this “multipotency” or “pluripotency,” and it suggests that the adult human testicle contains some nifty and powerful stem cells. But neither human sperm nor other organs have been made from these cells over the last decade.

What takes so long is trying to understand how stem cells reproduce themselves or turn into other tissues. This all has to do with getting to know where they live, termed their “niche,” what signals they get, and how they respond to these signals. The science has progressed very quickly in rodents and other mammals, but as you know, humans are…well…different. And figuring out exactly how rodents and men differ has been the Achilles heel of stem cell research.

A Shining Jewel

So, it was nice to see some serious progress in reproductive stem cell science recently published by a large team of researchers. To simulate a potential method of fertility preservation in boys receiving sterilizing cancer treatment, the researchers took testicular spermatogonial stem cells from prepubertal monkeys and then froze them. The monkeys then received sterilizing chemotherapy and recovered. After the monkeys passed through puberty, the researchers thawed the frozen stem cells and implanted them under the skin of the monkeys from which they were taken. The testis tissue grafts made mature sperm which was then harvested and used with IVF-ICSI to make a healthy baby monkey. Years of preparation, four universities, one baby monkey. That’s hard work.

Using stem cells to make sperm outside the testicle. Another advance in stem cell science. Granted, the natural fertility of these monkeys was not restored, monkeys are not humans, and the steps used aren’t that easy to translate into the clinic. But this proof-of-concept study is a cellular leap in right direction.