Embryonic stem cells were obtained without embryos
Since the discovery of human embryonic stem cells (ESCs) capable of differentiating into almost all types of cells in the body, experts hope that over time they can be used to treat a wide range of diseases.
However, the isolation of cells from the embryo implies its destruction, which is a serious problem from an ethical point of view. In 2006, researchers proposed an alternative to embryonic stem cells – the so-called induced pluripotent stem cells (iPSCs), obtained by returning adult cells to a pluripotent state. This is achieved by introducing genetic material into cells using viral vectors, which changes the initial state of cells and can cause their malignancy.
In order to avoid these difficulties, some researchers prefer to work with adult stem cells, but the possibilities of their use are limited, since due to partial differentiation they can give rise only to cells of a certain type.
A recent study conducted by scientists at Boston's Brigham and Women's Hospital together with Japanese colleagues from the RIKEN Center for Developmental Biology demonstrated that any mature cells of an adult organism can be reprogrammed into cells that are analogues of embryonic stem cells. The reprogramming protocol they developed was called STAP (from the English stimulus-triggered acquisition of pluripotency – the acquisition of pluripotency triggered by a stimulus). The most important feature of this protocol is that it does not require the introduction of foreign DNA into cells.
The authors suggested that, like a callus – a cluster of cells formed by plants at the site of injury in order to release a new shoot – any mature cell of an adult organism under the influence of stress can naturally de-differentiate.
To test the hypothesis, they multiplied mouse lymphocytes in laboratory conditions and subjected them to sublethal exposure to various damaging factors, such as physical injury, low oxygen levels and high acidity of the medium. A half-hour placement of cells in an acidic environment (pH 5.7) turned out to be optimal. Experiments have shown that in a normal nutrient medium, the surviving cells recovered from stress for several days by naturally transitioning to a state equivalent to the pluripotency of embryonic stem cells.
Acid-exposed lymphocytes express the pluripotency marker Oct4.
To assess the potential of these cells, the scientists used lymphocytes of GFP+ mice, whose cells emit a green glow when illuminated with light of a certain wavelength. Such luminous lymphocytes were placed in an acidic environment, after which their transformation into pluripotent cells forming spherical clusters was observed for several days. These clusters were injected into the developing embryo of an ordinary mouse to create a so-called chimera. Subsequent analysis of the embryo showed that the implanted cells formed glowing GFP+ tissues in all organs. This is a confirmation of their pluripotence.
A mouse embryo with STAP cells present in all its tissues.
The researchers suggest that currently unknown cell functions activated by external stress "release" mature cells from previously acquired "obligations" and allow them to return to a state of pluripotency. They plan to continue studying this process on the cells of more complex mammals, including humans.
Reproducing the results obtained on human cells will open up huge unprecedented opportunities in the field of regenerative medicine.
Articles by Haruko Obokata et al. Stimulus-triggered fate conversion of somatic cells into pluripotency and Bidirectional developmental potential in reprogrammed cells with acquired pluripotency are published in the journal Nature.
Evgeniya Ryabtseva
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Researchers create embryonic stem cells without embryo.
30.01.2014