Progress in Therapeutic Cloning of Stem Cells

Using new cloning techniques, scientists have taken a significant step toward the successful therapeutic cloning of nonhuman primate embryos. Their progress was reported in the December 1, 2004, issue of Developmental Biology.

Researchers at the University of Pittsburgh (PA, USA) used newer cloning techniques developed by South Korean researchers, which included the "gentle squeeze” method they used to create the first cloned human embryonic stem cell line earlier in 2004.
It is the first time researchers have applied methods developed in South Korea to nonhuman primate eggs. The resulting cloned embryos progressed to the blastocyst stage, in which the embryo resembles a hollow, fluid-filled cavity surrounded by a single layer of cells. Called the inner cell mass, this layer contains embryonic stem cells. Growth of a cloned nonhuman primate egg to the blastocyst stage is further along the developmental spectrum than ever before, according to the researchers.

In a 2003 study, researchers using the techniques of nuclear transfer that had resulted in the cloning of Dolly, the sheep, found basic molecular obstacles that blocked normal cell development, such as absent or deficient proteins, chaotic mitotic spindle structures, and misaligned chromosomes. The most recent study appears to have broken that impasse. On the other hand, reproductive cloning remains elusive, and the Pittsburgh team indicates that the possibility of successful cloning of primates is even more remote than previously believed.

"What this shows is that the Korean method for efficient human somatic cell nuclear transfer is equally effective for nonhuman primates, allowing the further progress toward development of an animal model which parallels human biology,” remarked Dr. Gerald Schatten, Ph.D., director of the Pittsburgh Development Center at Magee-Womens Research Institute. "This approach does not violate federal or state laws, and allows for preclinical investigations that would not be ethically feasible in humans.”




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