Human Cloning Advance Raises Personalized Medicine Hopes: Embryonic Stem Cells Made with Nuclear Transfer Method

By Rosen, Meghan | Science News, June 15, 2013 | Go to article overview

Human Cloning Advance Raises Personalized Medicine Hopes: Embryonic Stem Cells Made with Nuclear Transfer Method


Rosen, Meghan, Science News


For the first time, scientists have created human embryonic stern cells by transferring the nucleus of a mature cell into an egg. The cloning technique could nudge the dream of personalized medicine closer to reality, researchers suggest May 15 in Cell.

"It's a huge, landmark achievement," says stem cell biologist George Daley of Children's Hospital Boston and Harvard University. Creating embryonic stem cells by nuclear transfer in humans, he says, is "the next major technological advance since Dolly."

The famous sheep was the first mammal cloned by the nuclear transfer technique, which inserts the nucleus of a cell from one adult animal into the egg of another. Since Dolly's birth in 1996, scientists around the world have tried to duplicate the technique in human cells.

If cloned human cells could be made to grow into normal embryos, the technique could supply fresh stocks of embryonic stem cells.

Unlike adult cells, which have already followed a path to become, say, heart cells or neurons, embryonic stem cells are uniquely poised to become any cell in the body. By making these stem cells from a patient's own tissues, once-untreatable conditions might be cured by replacing damaged cells with healthy ones.

Until now, the only way to get embryonic stem cells was from leftover embryos made through in vitro fertilization. These cells are useless for personalized medicine because they are not genetically matched to a patient, but they are extremely valuable for laboratory experiments. In 2001, however, President George W. Bush set new regulations that choked off federal funding for embryonic stem cell research. Scientists could use only discarded embryos created for reproductive purposes, and all embryos discarded after 9 p.m. August 9, 2001, were off limits. The rules sent researchers racing to find alternative ways to make embryonic stem cells.

In 2007, one new technique to create the cells dazzled scientists in the field. By dosing human cells with a small cocktail of molecules, researchers pushed a reset button that turned adult cells back into embryonic-like ones called induced pluripotent stem cells, or iPS cells.

"For the last six or seven years, virtually all of us have ended our nuclear transfer efforts and switched over to iPS cells," Daley says.

But a team led by Shoukhrat Mitalipov of the Oregon National Primate Research Center in Beaverton kept plugging away at nuclear transfer, first using rhesus macaques, and then human cells.

Using cloning to create embryonic stem cells in humans has proven tricky, says Kathrin Plath, a stem cell biologist at UCLA. No one knew why the technique worked in some other mammals but not humans.

Researchers had to figure out the best way to ease out an egg's DNA, slip in a new nucleus and then cue the egg to divide and grow. In 2011, scientists came close, but the egg stalled out after three divisions, producing just eight cells.

A key change to the protocol was adding caffeine to the eggs before DNA transfer, says stem cell biologist James Byrne of UCLA, who was not involved in the new work. Caffeine acts like a set of chemical reins, holding back the egg's development until researchers inject a new nucleus. The new protocol also features other tweaks such as examining the eggs under polarized instead of ultraviolet light, which can be more damaging to the egg. …

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