Are mature cells better than stem cells for cloning?

by Gayatri on  October 3, 2006 at 5:11 PM Genetics & Stem Cells News   - G J E 4
Are mature cells better than stem cells for cloning?
According to scientists in the U.S. cloning can be performed without the stem cells and other mature cells seem to perform better.

Two baby mice were created from fully matured blood cell that cannot produce more of its kind, by a team at the Pittsburgh University. This is contrary to the general notion that only immature stem cells that can differentiate in to several different types of cells are capable of doing it.

Somatic cell nuclear transfer (SCNT) is a method of cloning in which, an embryo is generated by transferring the nucleus or the genetic material of the cell to an unfertilized egg whose own genetic material has been removed. The embryo generated is an exact replica of the donor of the genetic material.

Scientists had pinned their hopes on stem cells as they are still at an early stage of development and have the capacity to differentiate into different types of cells forming tissues and organs. Hence, they were hopeful of treating several genetic disorders. However, the rate of success was only 1-5% in studies using adult stem cells from mature tissue to generate early stage embryo.

Dr Tao Cheng and colleagues conducted studies to detect if granulocytes, fully matured white blood cells, could be used to generate early embryos. The success rate was high and in fact, it performed better than stem cells destined to become granulocytes.

Early stage embryos called blastocysts were generated from 35-39% of the mature granulocytes. However, only 4% of the immature stem cells could generate blastocysts. Two live cloned mice pups could be generated only by the differentiated granulocytes, though they died a couple of hours after birth.

To confirm their findings, the scientists performed cloning using embryonic stem cells, cells derived from blastocysts. Almost 50% yielded blastocysts and 18 cloned pups were born. However, the use of embryonic stem cells is controversial. Thus, scientists are looking for successful substitutes for embryonic stem cells.

Dr Cheng said, "The results clearly show there is no advantage in using adult stem cells over mature fully differentiated cells. We can say with near certainty that a fully differentiated cell such as a granulocyte retains the genetic capacity for becoming like a seed that can give rise to all cell types necessary for the development of an entire organism."

Stem cell expert Dr Stephen Minger, from King's College London, said: "The findings are quite surprising. "Up until this [point], the conventional wisdom was that the less mature a cell, the more likely it is to be reprogrammed. This work suggests the contrary. "Certain types of mature cells could be much easier to reprogramme than expected.

"But of course this has only been done in mice and there could be a big difference when it comes to humans. It would be interesting to see whether the same is found with human cells."

Source: Medindia

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