Researchers from the Stanford University School of Medicine and at UC-San Francisco have been able to separate stem cells from human testes which are capable of changing into other body tissues.
The researchers say that the quality of testes stem cells to change into other body tissues suggests that they bear a striking resemblance to embryonic stem cells.
They, however, caution against viewing them as one and the same.
The researchers revealed that the testes stem cells have different patterns of gene expression and regulation, and that they do not proliferate and differentiate as aggressively as human embryonic stem cells.
Their findings are in contrast to a previous study's that concluded that the cells were as pluripotent - meaning they can become any cell in the body - as embryonic stem cells.
''It's time to reinterpret the data, and to accept that we're beginning to discover many different types of stem cells. Although they are all related to each other, they also all have unique therapeutic applications in which they surpass other family members,'' said Renee Reijo-Pera, PhD, professor of obstetrics and gynecology at Stanford.
Working in collaboration with male infertility specialist Dr. Paul Turek, a professor of urology at UCSF and the director of The Turek Clinic in San Francisco, Reijo-Pera observed that the stem cells from the testes seemed to hover in a grey area between true pluripotency and the more limited, tissue-specific multipotency exhibited by many types of adult stem cells.
The researchers termed the cells ''multipotent germline stem cells''. Germ cells are those cells in the body that differentiate to make sperm and eggs.
Reijo-Pera said that playing to these cells' likely ability to differentiate into cells involved in male reproduction might be a wiser choice than trying to pigeonhole them as embryonic-stem-cell-wannabes.
''These cells could potentially treat infertility or other diseases in men,'' Turek said.
Coaxing specialized adult cells to regress back into a more malleable, embryonic-stem-cell-like state (a process called ''induced pluripotency'') would also allow scientists to realize the therapeutic benefits of embryonic cells without the thorny ethical problems that plague cells derived from embryos.
''It's not yet possible to completely re-create human embryonic stem cells from germline cells. These cells differ in gene expression, methylation and in their ability to form teratomas.
But it's the fact that they are different that makes them so interesting. Suggesting otherwise would do a disservice to the research community by overlooking the fact that these cells are a unique cell type that could be really useful in the study of human germ cell formation,'' said Reijo-Pera.
A research article on this work appears in the journal Stem Cells.