Physiological features of development and options for technology for obtaining pluripotent stem cells

Topical issues related to the technology of isolation and mechanisms of development of pluripotent stem cells and their application in medicine are considered. The isolation, as well as the subsequent use of stem cells, still remains an unsolved problem both from a scientific point of view and especially in practical health care. There are three ways to produce pluripotent stem cells. First, they can be obtained in vitro from cell culture of the inner layer of early eggs. These are embryonic stem cells. Second, they can be obtained from somatic cells, as a result of the introduction of a group of genes that induce pluripotency. These are induced pluripotent stem cells. Finally, they can be obtained by transplanting the nucleus of somatic cells into an enucleated secondary egg. The microenvironment of the egg contributes to the reprogramming of the nucleus to a state close to the zygote. Mouse embryonic stem cells have many embryonic markers on their surface: carbohydrate receptors — CD15, alkaline phosphatase, factor 4 like Kruppel, estrogen-bound receptor, transcription factor CP2 like 1, T-box transcription factor and gastrulation homeobox brain 2. Embryonic mouse stem cells differentiate from the internal mass of cells at the stage of preimplantation, epiblast. This is established by comparing gene expression profiles and directly isolating embryonic stem cells from epiblasts of 4.5-day-old fertilized eggs. Embryonic stem cells derived from mouse embryos of later stages of development lose markers of pluripotency. Approximately 3 days after the elimination of the leukemia inhibition factor, the expression of the Oct4 gene leads to the loss of specificity markers by cells of the early embryo. Currently, the reprogramming of pluripotency is an active area of research in which significant technological progress has been made. So, the original gene cocktail consisting of four genes is used: Oct4, Sox2, Klf4 and cMyc. The obtained types of embryonic stem cells of mouse and human, from fertilized blastocysts, induced pluripotent stem cells undoubtedly exist. However, this does not apply to pluripotent stem cells derived from postnatal animals, humans, or from extraembryonic sources such as amniotic fluid or cord blood. Despite the fact that many laboratories are working to obtain stem cells from these objects, unfortunately, there is little reproducibility in this work, and the properties of the resulting cells and even their existence are still the subject of controversy.