[Stem cells: properties and perspectives of therapeutic use]

In the present work, we review the properties of some stem cell types, namely embryonic, hematopoietic and mesenchymal stem cells, which present the most significant interest for use in medicine. Stem cells are undifferentiated cells capable of both self-maintenance and differentiation into mature specialized cells. According to their origin, stem cells can be classified as embryonic and somatic ones. The first ones can be indefinitely maintained in culture, and possess the ability to differentiate into all cells of the adult organism. The second ones possess the limited capacity to differentiate and, probably, a limited proliferative potential. For therapeutic use, important but hotly debated is the plasticity of somatic stem cells, i.e. context-dependent differentiation into "non-related" cell types. It is assumed that the differentiation of the majority of stem cell types proceeds according to the principle of stepwise hierarchical maturation through the stage of intermediate rapidly proliferating progenitor cells. The use of stem cells in medicine is mostly at the preclinical stage now. Despite the fact that embryonic stem cells are highly promising as therapeutic agents, a number of circumstances substantially limits their therapeutic use in the near future. At the same time, approaches involving autotransplantation of hematopoietic or mesenchymal stem cells are beginning to be applied successfully in the clinical trials for treatment of limb ischaemia and myocardial infarction. It is clear that despite a large number of problems and unsolved questions, the use of stem cells in medicine promises a dramatic progress in the treatment of many severe diseases.