Chinese Create Hybrid Embryos
Scientists in China have used cloning techniques to create hybrid embryos that contain a mix of DNA from humans and rabbits, according to a report in a scientific journal.
More than 100 of the hybrids, made by fusing human skin cells with rabbit eggs, were allowed to develop in laboratory dishes for several days before the scientists destroyed them to retrieve embryonic stem cells from their interiors.
Although scientists in Massachusetts had previously mixed human cells and cow eggs in a similar attempt to make hybrid embryos as a source of stem cells, those experiments were not successful.
Researchers said Wednesday that they were hopeful that the rabbit work would lead to a new and plentiful source of embryonic stem cells for research and, eventually, for medical use.
But theologians and others decried the work as unethical. Some wondered aloud what, exactly, such a creature would be if it were transferred to a womb to develop to term.
The vast majority of the DNA in the embryos is human, with a small percentage of genetic material -- called mitochondrial DNA -- contributed by the rabbit egg. No one knows if such an embryo could develop into a viable fetus, though some experiments with other species suggest that it would not.
The new work, led by Huizhen Sheng of Shanghai Second Medical University, appears in the latest issue of Cell Research, and was highlighted in a news report in the journal Nature. Cell Research is a peer-reviewed scientific journal affiliated with the Shanghai Institute of Cell Biology and the Chinese Academy of Sciences.
Some researchers said Wednesday that they were frustrated by the lack of details in the paper.
Researchers said the paper stops short of proving beyond a doubt that the stem cells retrieved from the hybrid embryos are capable of growing for long periods of time in lab dishes, or could turn into every known kind of cell like ordinary stem cells.
Douglas Melton, a Harvard cell biologist and cloning expert, noted that although this is the first creation of a human “chimeric” embryo -- a reference to the fabulous chimera of Greek mythology, which had a lion’s head, a goat’s body and a serpent’s tail -- it is not the first time scientists have blended human cells into certain lab animals. Some mice, for example, have been endowed with human brain cells or portions of the human immune system for research.
