Cell reprogramming: the next successes
Two news about cell reprogramming: good and good :)
Dmitry Tselikov, Compulenta
A safer method for obtaining pluripotent cells has been developed(based on the materials of PhysOrg: Researchers develop a safer way to make induced pluripotent stem cells).
Researchers from Johns Hopkins University (USA) have found a safer way to create induced pluripotent stem cells (iPSCs) (mature cells that have acquired the properties of embryonic stem cells as a result of reprogramming) from a small blood sample.
"These cells are much safer, because their production is not associated with the integration of foreign viruses that can lead to uncontrolled growth of cancerous tumors," emphasizes the head of the group Linzhao Cheng.
This means that such iPSCs will become more reliable material for scientific research, since there is no longer any need to worry about genetic changes caused by outside interference.
The necessary genetic components were delivered to the cells via cyclic DNA. Unlike viral methods, ring DNA was not combined with the genome of the host cell. After the formation of iPSCs, the ring DNA gradually resorbed.
The researchers took about a tablespoon of adult blood or umbilical cord blood, after which the cells were grown for 8-9 days. 14 days elapsed between the introduction of ring DNA and the appearance of induced pluripotent stem cells.
Tests on the ability to convert iPSCs into various types of cells – bone, muscle, nerve – were successful.
The results of the study are published in the journal Nature Cell Research (Bin-Kuan Chou et al., Efficient human iPS cell derivation by a non-integrating plasmid from blood cells with unique epigenetic and gene expression signatures).
Without detracting from the merits of American scientists, it should nevertheless be noted that they were a little late: their colleagues learned how to turn some mature cells into others directly – bypassing the IPC stage. However, the safety of this approach has not yet been confirmed.
For the first time, heart cells were directly obtained from skin cells
(based on the materials of PhysOrg: Scientists convert skin cells to beating heart cells).
Scientists from the Scripps Research Institute (USA) effectively turned the skin cells of an adult mouse directly into contracting heart cells, bypassing the laborious process of creating stem cells.
A powerful technology platform developed by researchers could lead to new ways to treat a number of diseases and injuries with loss or damage to cells, including heart disease, Parkinson's and Alzheimer's. "This is a new paradigm of stem cell reprogramming," emphasizes the head of the group, Sheng Ding. "We hope it will help overcome the safety problem and other technical barriers associated with certain types of therapy using stem cells."
During the development of the body, stem cells multiply and turn into more mature types. It is this process, called differentiation, that is responsible for the creation of all kinds of cells and tissues. Unfortunately, having emerged from its infancy, the human body has limited capacity to create new cells to replace those that have been lost or damaged. Therefore, scientists are trying to develop ways to "reprogram" adult human cells to return them to an embryonic, or pluripotent, state.
In 2006, Japanese researchers were the first to report that they were able to reprogram mouse skin cells – simply by adding four genes to them. Since then, the technology of creating induced pluripotent cells (IPCs) has stepped far forward, but several unresolved problems remain: the generation of IPCs and their subsequent differentiation takes a long time, it is a tedious process, and the cells themselves are not always perfect. So, it takes two to four weeks to create a PKI from skin cells, and only one cell out of several thousand is capable of complete transformation. It is extremely difficult to make the PKI turn into the desired cell type, this procedure also takes two to four weeks.
In addition, the actual cultivation of cells from IPC remains unclear. When, for example, scientists try to make IPCs become heart cells, they get a mixture of heart cells and IPCs. Their implantation (together with IPC) can be dangerous: in experiments on mice, this led to the appearance of crustacean growths.
In connection with the above, Mr. Dean and his colleagues decided to try to completely bypass the IPC stage and directly move from one type of mature cell to another. The scientists used the same four genes, but instead of allowing them to remain constantly active, they turned off the genes a few days later – long before the cells were supposed to turn into IPCs. Immediately after the genes were turned off, scientists gave a signal for the transformation of skin fibroblasts into heart cells. Just eleven days later, the desired cells were beating in the Petri dish.
"It's like launching a rocket," says Mr. Dean. "Until now, people thought that it was necessary to first send a rocket to the moon, and only from there you can fly to other planets. We have shown that it is possible to go to another celestial body immediately after launching from Earth. This is a completely new approach."
It is possible that in this way it will be possible to avoid the development of cancer, because the genes associated with it remain active for a very short time.
The results of the study are published in the journal Nature Cell Biology: Jem A. Efe et al., Conversion of mouse fibroblasts into cardiomyocytes using a direct reprogramming strategy.
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03.02.2011