Researchers have successfully derived pluripotent stem cells from macaque oocytes, and their technique could provide researchers and clinicians with a promising alternative to stem cells obtained directly from dissociated embryos.

Stem cell research remains one of the few areas of medical study that one might just as easily read about in a political position paper, religious tract, or legal journal as in a conventional scientific publication. At the center of the raging controversy is the source from which pluripotent stem cells are, according to many researchers, ideally derived: viable human embryos. Although stem cells can be obtained from some adult tissues, such as the bone marrow, these are generally believed to be considerably less versatile than embryonically derived cells.

Parthenogenesis, the activation and subsequent development of an unfertilized oocyte, offers an alternative possibility for obtaining fully functional stem cells. In nature, this process occurs in a wide variety of species but does not exist in placental mammals. Such activation has been achieved experimentally, however, and oocytes activated in vitro (parthenotes) can successfully survive and develop for a number of days or even weeks after transplantation into the womb of a surrogate mother. These growing parthenotes consist entirely of embryonic tissue and are apparently incapable of reaching full maturation.

In an effort to examine this potential alternative to embryonic stem cells, Kent Vrana at the Wake Forest University School of Medicine (Winston-Salem, NC) and his colleagues isolated oocytes from three different cynomolgus monkeys, and chemically treated them to induce activation, resulting in the production of a number of blastocysts. These in turn were dissociated and cultured on feeder cells, leading to the generation of the stable stem cell line Cyno-1 (Proc. Natl. Acad. Sci. USA, 30 September). These cells were karyotypically normal and showed many phenotypic markers typical of embryonic stem (ES) cells—even after two years of maintenance and propagation.

Also like ES cells, the Cyno-1 line proved capable of differentiation into a wide variety of specialized cell types. Several weeks after injection into the peritoneal cavity of SCID mice, the Cyno-1 cells had developed into teratomas containing terminally differentiated skin, cartilage, bone, and muscle cells, among others. Cyno-1 cells could also be cultured under conditions that led them to differentiate into functional dopaminergic neurons, suggesting that these cells could provide potential therapeutic solutions for a variety of neurodegenerative disorders.

Vrana and his colleagues are still in the process of investigating the impact of the Cyno-1 line's uniparental lineage and have not yet determined whether these cells are under any limitations relative to conventional, biparentally derived ES cells. However, their new findings suggest the possibility of a powerful new tool that may allow researchers to conduct stem cell research without quite so much controversy.