The reasoning is simple : if an organism with more than 200 different types of cells is formed from a group of embryonic cells without specialisation, then manipulating the division of these original cells called stem cells should make it possible to generate all the human tissues and even produce auto transplants with minimal risk. Let's know about cellular division and mechanism of stem cells.

Cellular division 

All the cells of higher organisms divide and multiply through mitosis, with the exception of the reproductive gametes. Mitosis is the process through which a cell divides to form two identical cells. For this to happen, the first cell copies its genetic material inside the nucleus, and later it slowly partitions until it fully divides, producing two cells with the same genetic material. An adult cell divides on average 20 times before dying; a stem cells does it indefinitely.

Mechanism of stem cells 

A. Obtaining 

Because the stem cells are the first that form after fertilization occurs, they are abundant in the placenta and especially in the umbilical cord. Geneticists obtain them from the cord once the baby has been born, and it is possible to freeze the cord to harvest the stem cells later.

B. Multiplication

Once isolated, stem cells are cultivated in vitro under special conditions. It is common to resort to a substrate of irradiated cells, which serves as support without competing for space. Later, every seven days, they need to be separated to keep them from dying and to be able to reproduce them.

C. Differentiation

The stem cells are pluripotent, which is to say that they have the power to create any of the more than 200 different cells of the body. This process happens as the embryo grows. If the optimal conditions could be created in vitro, it would be possible to form in a laboratory all the cells of the body using the genetic program of the cells. In practice, this technique is possible only with a few type of cells, in particular blood cells.

D. Implantation

Doctors and geneticists hope to be able to provide new pluripotent cells to damage tissue and provoke its regeneration. To date, they have been able to introduce a umbilical cord haematopoietic stem cells into patients with dysfunctional formation of red blood cells. This is equivalent to a bone marrow transplant without surgical intervention.

16 cells is the limit for cultivation. This limitation guarantees the absence of a human embryo.

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