Types and Origin of Stem Cells

The main characteristics of stem cells are related to their undifferentiated state and their ability to self-renew and to differentiate. They may be referred to as embryonic or adult stem cells according to their appearance either in the inner cell mass of the embryo or in specific tissues throughout the fetal and postnatal life. They may also be characterized according to their developmental potency as totipotent, pluripotent, multipotent, or unipotent cells. Also, they may be obtained from their natural niche (the specific microenvironment where they reside) or may be engineered ex vivo by reprogramming somatic cells, then referred to as induced pluripotent stem cells. Based on the concept that stem cells are the organizing principle for tissue formation and homeostasis, their clinical application was a matter of time. This chapter describes the types and origin of stem cells and discusses their potential for cell therapy for vascular diseases.