Significant Advances Are Being Made in Stem Cell Therapy

Associate Professor Tamer Önder and his team at Koç University conducted research on stem cells and found that the time required to obtain stem cells from skin cells has been shortened, and the conversion rate of skin cells to stem cells has increased by 1,000 times. Associate Professor Dr. Tamer Önder, Faculty of Medicine at Koç University, developed a method in his study published in the 8 April issue of Nature Chemical Biology, advancing the technique called "Cellular Reprogramming" discovered by Professor Shinya Yamanaka, who previously won the Nobel Prize in Physiology or Medicine. Associate Professor Dr. Tamer Önder's new method enabled results to be obtained in a shorter time and at a much higher success rate.

In the Yamanaka method, four genes that are highly active in embryonic stem cells but inactive in skin cells are transferred to skin cells. These genes, called "Yamanaka factors," are OCT4, SOX2, KLF4 and MYC.

Reactivating these genes converts the skin cell into pluripotent stem cells just as they exist in the embryonic stage; however, since these are obtained through the conversion of other cells, they are called induced pluripotent stem cells, or iPS for short.   Although this method worked well, it required improvement, particularly in two areas. First, this conversion took a long time of 3-4 weeks, and additionally the reprogramming rate was quite low: one in one hundred thousand. However, Associate Professor Dr. Tamer Önder from Koç University Faculty of Medicine, working with doctoral students Ayyub Ebrahimi and Kenan Sevinç and in collaboration with Professor Udo Oppermann from Oxford University, found that both this waiting period was shortened and the success rate increased. The viruses used to deliver the Yamanaka factors to skin cells sometimes acted independently and could insert these genes anywhere on the chromosome. For this reason, Associate Professor Önder, who considered using certain chemicals instead of viruses, decided to collaborate with Udo Oppermann from Oxford University. Professor Oppermann and Associate Professor Önder calculated in their research that if they could produce a chemical that would fit precisely to a protein whose structure was known, they could eliminate the possibility of binding to another gene as occurs with viruses. Subsequently, conducting targeted experiments, Professor Oppermann and Associate Professor Önder observed that two chemicals produced the desired results in converting skin cells to stem cells. Determining that this actually meant two of the four Yamanaka factors were now unnecessary, Oppermann and Yamanaka accomplished the process with two factors instead of four, thereby reducing the waiting time to nearly one week. The more important contribution was reported to be raising the success rate to 1 percent.