Adult Stem Cells: Overview

About 65 years ago, a team of researchers discovered that red bone marrow was composed of two types of stem cells: hematopoietic stem cells (HSCs) described as mesoderm-derived blood cells, and stromal stem cells. Cells of the mesoderm form one of the three primary germ cell layers of an embryo in its early stages of development, and give rise to other blood cells. Stromal stem cells, on the other hand, constitute the so-called skeletal or mesenchymal layer. The role of these stem cells, which only make up a fraction of all stromal cells, is to generate cartilage, bone, and fat cells able to support the formation of fibrous connective tissue and blood.

Despite these findings, most scientists remained convinced for a long time that the adult ...