Cloned Embryos Created to Match Stem Cells, Patients
By Karen Kaplan, Times Staff Writer
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.
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
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
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.