Led by Dr. Thomas Skutella, a team of researchers at the University of Tubingen in Germany has reported the creation of “germline stem cells” from the sperm-producing testicular tissue of 22 men, via a culturing process which is similar to that of culturing human embryonic stem cells. Following the standard, global test for pluripotency, the scientists then injected the new “germline stem cells” into immune compromised mice, where the newly created cells formed teratomas and hence are now celebrated for their similarity to embryonic stem cells.
According to Dr. Gerd Hasenfuss of the University of Gottingen in Germany, who has published similar studies involving the transformation of mouse testicular cells into pluripotent cells, “My summary is, it is a nice paper, they made big progress in getting to a pluripotent cell, and they show pluripotency with a teratoma experiment. But I think we are not completely there where we want to be, namely, at pluripotency absolutely comparable to that of embryonic stem cells.” In particular, although the “germline stem cells” were shown to differentiate into most cell types of the body, they did not differentiate into cardiomyocytes, from which heart tissue is formed.
Nevertheless, Dr. Skutella and his colleagues have demonstrated that the transformation and reprogramming of the cells may be accomplished through growth factors in the culture medium rather than through retroviral and oncogenic vectors, as were originally used in the first experiments conducted with iPS (induced pluripotent stem) cells. According to Dr. Dirk de Rooij, professor emeritus of endocrinology at the Utrech University in the Netherlands, “In comparison to the mouse studies that have been done, there is a big leap forward in efficiency with which these people get these germline stem cells.”
Similarly, as Dr. Peter Donovan of the University of California at Irvine explains, “The ability to make a pluripotent stem cell from an individual without the ethical and immunological problems associated with human embryonic stem cells is a big deal.” He adds the following caveat, however: “I suspect people would be much more willing to give up a piece of skin to make an iPS cell than to have a testicular biopsy to give rise to an adult germline stem cell.”