Types of Human Stem Cells and Their Therapeutic Applications

Abstract

The present review\rexamines in the first place various kinds of naturally occurring stem cells,\rincluding germ cells and embryonic stem cells (ES cells), as well as\rhaemopoietic stem cells, which are historically the first to be used for\rmedical treatment. Attention is also given to cancer stem cells, as a source of\rperseverant malignant disease. The main interest is now represented by the\rvariety of somatic cells, which can be re-programmed to different types of\rdifferentiated cells, the so-called induced pluripotent stem cells (IPSC’s).\rFocus is now directed not only to the factors which make such events possible\rlike de-differentiation and reconversion but also to the stages involved in\rthis process. It is actually postulated that the transition from differentiated\rcells to pluripotent cells follows a definite sequence with evidence of two\rwaves of gene regulations. Main applications of stem cell therapy are reviewed,\rfrom the established use of haemopoietic stem cells for clinical\rtransplantation in a variety of haematological disorders to the initial\rattempts to employ stem cells for the treatment of other disparate conditions.\rProblems related to stem cell treatment with both ES and IPS cells, like the\rnecessity of a large in vitro expansion to provide sufficient\ramounts of cells and the related risk of genomic abnormalities are illustrated.\rThe necessity of safe procedures for the development of this venture is also\routlined.