"We will not stop testing nuclear transfer, because it is the only means we know for generating embryonic stem cells that are genetically identical to a patient," says Daley, who heads one of two Harvard Stem Cell Institute-associated labs attempting to create human embryonic stem cells with that technique. "However, generating embryonic stem cells from unfertilized eggs is far more efficient than nuclear transfer, and therefore may allow us to move toward human applications sooner."
In the new study, Daley, first author Kitai Kim, PhD, and colleagues at Harvard Medical School, Brigham and Women's Hospital and Massachusetts General Hospital used unfertilized eggs of mice to create so-called parthenogenetic embryonic stem cells. Parthenogenesis is a method of reproduction, common in plants and in some animals, in which the female can generate offspring without the contribution of a male. It doesn't normally occur in mice, but Daley, Kim and colleagues were able to induce unfertilized mouse eggs to develop through a series of chemical treatments, then generated embryonic stem cells.
Next, they used genetic typing to identify those embryonic stem cells that shared with the egg donor the genes responsible for tissue matching, called the major histocompatibility complex (MHC). When they injected these selected embryonic stem cells into MHC-matched mice, a variety of specialized tissues formed, with no rejection and no need to suppress the recipients' immune system.
Daley's laboratory at Children's Hospital Boston is now trying to replicate its results with human eggs.
As Daley noted, there are several potential limitations to embryonic stem cells generated by parthenogenesis. First, since parthenogenetic embryonic stem cells are made from eggs, the technique is only applicable to females. (Methods exist for deriving embryonic stem cells using sperm from men, but these techniques are as technically challenging and inefficient as
Source:Children's Hospital Boston