Pechersky A V
North-West State Medical University named after I.I. Mechnicov, St. Petersburg, Russia.
J Stem Cells. 2016;11(2):63-67.
The majority of populations of differentiated cells are subject to renewal. Progenitor cells (cells-predecessors) and differentiated cells, having started the differentiation pathway or having finished it, can divide a limited number of times and are not capable of ensuring tissue regeneration during the whole period of ontogenesis. Renewal of tissues over such a long period is impossible without the participation of a specialized system which is responsible for regeneration. The given system is represented by pluripotent stem cells. Pluripotent stem cells, which conduct regeneration of all body tissues during ontogeny, are formed during implementation of the development program of the fertilized ovum, along with the formation of tissues and organs of the new organism. Being a separate direction of differentiation of embryonic cells, pluripotent stem cells are not embryonic cells. The immune system takes part in the formation of tissue-specific receptors among pluripotent stem cells. The latter remain pluripotent until the formation of tissue-specific receptors in them, and become committed (tissue-specific stem cells) after the formation of such receptors. Committed stem cells (tissue-specific stem cells) that migrate through the extracellular matrix replenish the progenitor cells of all tissues. Mesenchymal stem cells are the precursors of fibroblasts, and they only create conditions in the extracellular matrix for the migration and differentiation of committed (tissue-specific) stem cells in the places of cell death.
大多数分化细胞群体都需要更新。祖细胞（细胞前体）和已开始或完成分化途径的分化细胞只能进行有限次数的分裂，并且在个体发育的整个过程中无法确保组织再生。如果没有负责再生的专门系统的参与，在如此长的时间内组织更新是不可能的。该系统由多能干细胞代表。在个体发育过程中进行所有身体组织再生的多能干细胞，是在受精卵发育程序实施过程中，随着新生物体组织和器官的形成而形成的。作为胚胎细胞分化的一个独立方向，多能干细胞不是胚胎细胞。免疫系统参与多能干细胞中组织特异性受体的形成。在它们形成组织特异性受体之前，后者一直保持多能性，而在形成此类受体后则成为定向（组织特异性干细胞）。通过细胞外基质迁移的定向干细胞（组织特异性干细胞）补充所有组织的祖细胞。间充质干细胞是成纤维细胞的前体，它们仅在细胞外基质中为定向（组织特异性）干细胞在细胞死亡部位的迁移和分化创造条件。
