Researchers in America have produced the world's first primate stem cell clones in a move that could ultimately see patient-specific stem cells on offer in the clinic.
Oregon-based researcher Shoukhrat Mitalipov and his colleagues successfully transferred the genetic material from the mature skin cells of a nine year old male rhesus monkey into egg cells collected from 14 "donor" female monkeys. The egg cells used in the experiment first had their own genetic material removed, and then the adult skin cell nucleus was delicately re-injected into the egg.
After a short incubation period drugs were added to chemically kickstart cell division in the injected eggs. A small number (0.7%) subsequently began to divide, yielding embryonic stem cells (ES cells) that the researchers were able to grow in the dish. The technique works because eggs contain a cocktail of chemicals that re-programme DNA by switching on the correct combination of genes that are required for embryonic development. But despite huge effort, until now, scientists had not succeeded in making cloning technology work with primate cells - Dolly the sheep and Snuppy the dog were the farthest that they had progressed along the mammalian cloning path.
Exactly why the technique should be so difficult in primate cells is a mystery, but Mitalipov and his team think that they key to their success was a more gentle approach to handling the egg. They avoided using ultraviolet light when removing the egg's own genetic material, and kept the concentrations of calcium and magnesium very low in the culture medium used to handle the cells. The results, they say, prove that the technique can work in primates (and hence humans) and it should theoretically be possible in the future to produce stem cells tailor-made to an individual to repair damaged tissues and organs but without the risk of immune rejection.