Cloned Embryos Created to Match Stem Cells, Patients
South Korean scientists have surmounted a key hurdle in stem cell research, reporting Thursday that they have produced 11 human embryo clones of injured or sick patients and harvested individualized stem cells -- a template for creating therapeutic cells for anyone.
The experiment involved male and female patients ranging in age from 2 to 56 and produced stem cells much more efficiently than before, validating the technology’s medical feasibility.
The findings were reported by the same team that produced the first human embryo clones last year.
If the process can be replicated in other labs, scientists said they could create individualized lines of stem cells to produce tissues suitable for transplants without running the risk of rejection.
Patient-specific lines of embryonic stem cells could be created to produce new heart muscle to repair the damage from a heart attack, for instance, or fresh brain tissue to treat stroke victims.
Researchers could also develop stem cell lines to study different types of cancer and genetic diseases, such as Alzheimer’s, Parkinson’s and juvenile diabetes.
“It just opens a floodgate of possibilities,” said Fred H. Gage, a professor of genetics at the Salk Institute in La Jolla.
The researchers, who published their work in the online edition of the journal Science, insisted that their progress in cloning human embryos would not make things easier for anyone attempting to create a cloned baby, which they believe is impossible in any event.
“Reproductive cloning is not our goal,” said Woo Suk Hwang, the lead researcher from Seoul National University. “Reproductive cloning is unsafe and unethical, and so it shouldn’t be done in any country.”
Hwang created human embryo clones last year using eggs and DNA from the same donors, all healthy women. This time, the donor eggs were mixed and matched with unrelated DNA from patients.
The researchers collected 185 eggs from 18 healthy women and removed the genetic material from the nucleus. They then took skin samples -- about the size of a small button -- from 11 patients with spinal cord injuries, juvenile diabetes and a form of severe combined immunodeficiency disease, the so-called bubble boy disease.
The researchers took DNA from the skin samples and inserted it into the eggs.
The procedure resulted in 31 embryos. When they were five days old, the embryos were transferred to culture dishes, where 11 of them from nine patients developed into stem cells.
Tests verified that the stem cells were able to multiply as well as differentiate into neurons, muscle, bone, cartilage, respiratory and islet cells, among others.
The researchers were able to produce a cell line using an average of 16.8 eggs. In their previous paper, they required 242 eggs to create a single line of stem cells.
Ian Wilmut, the Scottish scientist who led the team that cloned Dolly the sheep in 1996, called it a “remarkable improvement in efficiency” that marked “a very significant step forward.”
Scientists said it was significant that the South Koreans were able to largely overcome a persistent problem with contamination that plagued stem cell lines.
A study this year by Gage and others found that human stem cells nourished by tissue from mice, calves and other animals had incorporated a type of acid that would trigger a harmful immune response if transplanted into humans.
Each of the advances reported in the paper is considered crucial to achieving the ultimate goal of customizing stem cells to treat individual patients, said Gerald Schatten, a biomedical researcher at the University of Pittsburgh and a coauthor of the study.
Researchers strongly suspect that tissues made from stem cells containing a patient’s own genetic material are most likely to succeed in a transplant because there would be little danger of tissue rejection or other complications.
“This may be nature’s best repair kit,” said Schatten, who leads the Pittsburgh Development Center, a biology research institute.
But there is a range of genetic diseases that cannot be solved by simply growing new tissue from stem cells because they would contain the same defects that caused the disease.
Scientists, however, believe stem cells could be used to research other cures by illuminating “the cellular mechanisms that cause these diseases to occur,” Gage said.
For instance, Gage envisions creating a line of stem cells using the DNA of a patient with pancreatic cancer.
“The embryonic stem cells don’t have cancer, but they have the capacity for it,” he said. “You could differentiate the cells into pancreatic cells and watch as the cancer develops.”
Scientists could use the information to develop a treatment that might prevent cancerous tumors from forming. When they were ready to test it, they could apply it to the cells and “see if we can interfere with the progress of the disease,” Gage said.
Wilmut and Dr. Christopher Shaw, a neurologist at the Institute of Psychiatry in London, are already making plans to collaborate with Hwang’s research group to produce embryonic stem cells cloned from patients with motor neuron disease. They hope the cells will allow them to zero in on causes of the disease and to test drugs that might provide cures.
Schatten said Hwang was also collaborating with researchers at Memorial Sloan-Kettering Cancer Center in New York who focused on degenerative diseases such as Parkinson’s.
“This work is powerful evidence that stem cell research can unlock the keys to understanding and eventually treating conditions from spinal cord injuries to diabetes,” said Daniel Perry, president of the Coalition for the Advancement of Medical Research.
Although 60% of Americans support embryonic stem cell research, according to a Gallup poll conducted this month, they remain uncomfortable with the idea of human cloning, with 87% of respondents calling it “morally wrong.”
David Magnus, director of the Stanford Center for Biomedical Ethics, who wrote an article accompanying the Science study, said Hwang’s approach largely avoided serious ethical complications.
Scientists say the cloned embryos are incapable of growing into healthy babies because they don’t go through all the steps that normally follow fertilization of an egg by a sperm.
“There’s no reason to think any of these things could become a human being even if somebody wanted to,” Magnus said.
He said that embryos produced through cloning had fewer ethical strings attached than embryos discarded from in vitro fertilization clinics, which have the potential to become babies.
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