Girl cells: what they are and what they are for

To talk about stem cellsa simple but very evocative metaphor is often used, that of “girls” cells. These are not yet specialized cells, which are in an early phase of development and which still retain the ability to transform into different types of cells, depending on the instructions they receive from the surrounding environment. Some may become blood cells, others of the liver, skin or brain, depending on the path of maturation they undertake. A path determined by external molecular signalsas growth factors and genes activated in precise sequences, which guide the differentiation process.

The presence of cells with these potential is characteristic of first phases of embryonic developmentbut less immature forms of stem cells are also found in adult tissues. In the laboratory, the research on this front continues hardly: the possibility of reprogramming adult cells, bringing them back to a state similar to the initial one, could in fact be the keystone of a long and healthy life. But there is more. Since the 90s, the experiments have shown that it is possible to “reset” the cell identity of an adult cell, and then guide it towards a new function. But how many types of “girls” cells exist?

• Embryonic stem: they are found in the very first stages of embryo development and are characterized by a great plasticity. They are totipotent cells (they can give rise to an entire organism) and pluripotent (can generate all cell types, including germ cells). They represent the most complete model of Staminale.
• Adult stem: are progenitor cells present in many tissues of the adult organism. They have already embarked on a path to specialization and are therefore defined as multipotent: they can only differentiate themselves in some types of cells, linked to the tissue of origin.
• Induced pluripotent stems (IPS): Obtained in 2006, they are “reprogrammed” adult cells to return to a state similar to that of embryonic stem. The reprogramming takes place by introducing a set of specific genes in the cell, through an inactive viral carrier. This technique initially aroused great enthusiasm, but subsequent studies have highlighted risks of genetic instability and potential carcinogenicity.

However, more recent experiments have managed to transform directly one adult cell in another mature, without going through the embryonic stage, which further expands the field of potential applications.