Are All Adult Stem Cells The Same?

Abstract

Abstract: Every adult tissue has its own resident committed progenitor or stem cell. In addition, there exists a class of adult stem cells that are multipotent and/or have injury-specific functions. Mesenchymal stem cells (MSCs) are quite different in comparison with neural stem cells (NSCs) when focusing on the range of different differentiated cell types that can develop from their progeny. These striking differences aside, MSCs, NSCs, and hematopoietic stem cells (HSC) have a very striking number of similarities. They are all dominant cells, multipotent, have a well-defined niche on or in contact with blood vessels, they all actively sense and respond to their local environment, they are all paracrine secretors, they are all immune-modulatory and trophic, and they all have a profound effect on site-specific regeneration following injury. These similarities, especially their unique interactions and association with vasculature, distinguish these adult cells from their embryonic progenitors and by virtue of these similarities define these unique adult stem cells. Lay Summary: The adult body has many stem cells, at least one for every major tissue. These stem cells provide the basis for the maintenance, repair, and regeneration of these tissues. These stem cells can divide and differentiate into a specialized tissue like muscle or liver. However, stem cells from different tissues have a common core of properties that are similar in function. For example, the hematopoietic stem cell (HSC) produces all the cells in blood. The mesenchymal stem cell (MSC) can produce fat or bone. The HSC and MSC function at tissue sites of injury to cause the tissue to regenerate. Thus, the HSC and MSC do the same injury function although they are uniquely different. Moreover, each stem cell establishes a unique habitat next to or in contact with blood vessels.