TORONTO - OK, men, you might have to brace yourself a bit for this one: researchers hope to one day extract stem cells from testicles that could be directed to grow into all kinds of tissues to repair everything from a damaged heart to brains destroyed by Alzheimer's to insulin-producing cells to cure diabetes.
So far, the researchers have found a way to grow different tissues from stem cells isolated from the testes of laboratory mice, but they believe the same technology could work in humans.
"For male patients, it could someday mean a readily available source of stem cells that gets around ethical issues linked to embryonic stem cells,'' said co-author Dr. Shahin Rafii, director of the Stem Cell Center for Regenerative Medicine at Weill Cornell Medical College in New York.
"It also avoids issues linked to tissue transplant rejection, since these autologous stem cells are derived from the patient's own body.''
The Weill Cornell-led research team began by extracting what are known as spermatogonial progenitor cells (SPCs) from the rodents' testicles, which were then induced in the lab to form adult stem cells capable of developing into various tissue types.
These tissues continued to grow both in lab dishes and after being implanted into mice, said co-author Dr. Marco Seandel, a researcher at the Howard Hughes Medical Institute and an oncology fellow at Memorial Sloan-Kettering Cancer Center.
"The first thing that was the most exciting was that in vitro (in lab dishes) even, we've seen these cells become what's very clearly heart tissue because it contracts rhythmically,'' Seandel said Wednesday from New York. "That's one type of tissue that you can't really miss.''
"In terms of blood vessels, we did extensive staining (an identification test) on cells in vitro and after they were implanted to prove not only were they blood vessels but they were also connected with the mouse's blood circulation, to prove that they're actually functional.''
Rafii and Seandel, the principal researchers, had been working more than 10 years on the concept of testicular stem cells, but it was a new method developed by Seandel that allowed their team to efficiently grow large quantities of SPCs _ and hence stem cells.
While acknowledging it's a big leap from mice to men, the researchers believe their findings _ published in Thursday's issue of Nature _ could be applied to human health.
"We don't have any reason to think that it won't work, but it's early days,'' Seandel said with a note of caution. The next step is to try growing stem cells from the testicles of primates, perhaps those of macaques or rhesus monkeys, he said.
Rafii said he's more optimistic than Seandel about how long it would take before the research could move to clinical trials in humans.
"There are no ethical issues attached to this, so we are going to move very fast to implement this technology in humans,'' said Rafii. "I would say five years.''
SPCs lie within a specific area of the testes and their sole function is to generate the precursors to sperm, keeping men fertile well into advanced age. Retrieving the SPCs, which are plentiful, would involve a small biopsy of the testicle, a procedure Rafii said is commonly performed on men undergoing fertility testing.
Not only could tissue generated from testicular stem cells help the individual, but he predicted it could also be transplanted into another man _ or woman _ as long as they were a genetically compatible match, similar to someone receiving a bone marrow transplant.
Besides regenerating organs, brain, skin and other tissues, the scientists say stem cells could also be harnessed as cancer fighters.
"For some reason, tumours love to recruit these cells to their environment because they are very juicy,'' said Rafii. "They go after them, they make blood vessels from them, they provide a lot of good stuff for (tumours).''
He said stem cells conceivably could be loaded with a cancer-killing agent, which could be switched on once they arrive at a tumour.
"So we can take advantage of this unique homing towards the tumour to deliver a toxic load."
