By Jonny Lupsha, Wondrium Staff Writer
Stem cell research has found new controversy of hybrid human-monkey embryos. Scientists lab created the embryos by using human and monkey cells, with future hope of providing organs for transplant patients. Stem cells are carefully manipulated by geneticists.
For the second time in as many months, stem cell research has entered the spotlight with some controversy. In March, stem cell therapy that repaired damaged spinal cords raised ethical questions after being fast-tracked in Japan to reach the experimental phase. Now, geneticists have grown embryos in a lab that are a mixture of human and monkey cells.
Why do this in the first place? Conductors of the experiment say that the demand for organ transplants in humans far outweighs the supply and they hope to find fertile ground to grow new organs. In recent years, scientists have injected human stem cells into sheep and pig embryos in attempts to grow organs, but those attempts have failed.
In his video series Understanding Genetics: DNA, Genes, and Their Real-World Applications, Dr. David Sadava, Adjunct Professor of Cancer Cell Biology at the City of Hope Medical Center in Duarte, California, said that stem cells must be carefully manipulated by geneticists.
Tricking the Cell
Dr. Sadava said that the cell’s nucleus is the location of genetic material, so stem cell scientists brainstormed how to approach experimenting with it.
“The idea was, ‘Let’s surround not the whole cell with some chemical signals, but let’s surround the cell nucleus with the chemical environment that says, ‘You’re in a fertilized egg now; you’re not in a skin cell,'” he said. “This can be done by a little surgery here. We can replace the nucleus of the egg with the nucleus of a specialized cell; and thereby, we’ll give that nucleus of the specialized cell the ‘eggy’ environment.”
Incredibly, this can be done with pipettes, or incredibly small straw-like instruments. The pipettes literally suck the nucleus out of an egg cell and replace it with the nucleus of a specialized cell. The specialized nucleus in the egg cell then receives signals around it that tell it to stop acting like, for example, a skin cell, and to act like a fertilized egg cell since that’s its environment, and the nucleus and its egg cell may take that up.
The Model Organism
“The first experiments in this regard were done on frogs,” Dr. Sadava said. “Why do it on frogs? Scientists use organisms they can manipulate to show what they need to show experimentally. The frog lays its eggs in the water; the eggs are very large, and they’re easy to obtain, so the experiments were done on frogs.”
In all these ways, frogs made the ideal organism on which geneticists could conduct early stem cell research in the 1950s. According to Dr. Sadava, scientists removed the nucleus in the way he described and replaced it with another. Then they used methods to coax the egg into developing into a tadpole and an adult frog. Different nuclei provided different results.
“If the donor nucleus that went into this empty egg was from an early embryo, it always worked—you always got a tadpole and you always got a brand-new frog,” he said. “Later in the embryo, if you were an embryo that was a little bit before the tadpole time, they would work usually. If the nucleus donor was from a tadpole, it sometimes worked.”
In the 1960s, scientists tested donor nuclei from adult frogs and found that they would take and the cells would grow, but only very rarely.
In the 60 years since then, stem cell research has continued to develop, sometimes at a rapid pace.