Mesenchymal Stem Cells – An Oversimplified Nomenclature for Extremely Heterogeneous Progenitors

Abstract

Mesenchymal stem cells (MSC) are plastic-adherent fi broblast-like cells that can readily be isolated from various tissues and expanded in vitro. Per de fi nitionem , they are able to differentiate into bone, cartilage and adipose tissue. In the last 15 years, a huge number of different preparative protocols have been developed to yield MSC-like cell lines from starting materials as diverse as bone marrow, fat tissue, umbilical cord blood and peripheral blood. However, these protocols as well as the resulting cell populations are heterogeneous. Furthermore, the composition of the cell products and their differentiation potential changes in the course of long-term culture expansion. There is an urgent need for the development of molecular markers and universal criteria for quality control of the starting cell populations as well as for the cell products after expansion. Nevertheless, MSC have already found their way into a huge number of clinical studies addressing a broad variety of diseases. Even though there is no convincing evidence that MSC are involved in the process of tissue repair by transdifferentiation, they probably contribute to the repair process by immunomodulatory effects and interaction with other cell types.