Human mesenchymal stem cells (hMSCs) have attracted much attention for tissue repair and wound healing because of their self-renewal capacity and multipotentiality. In order to mediate an effective therapy, substantial numbers of cells are required, which necessitates extensive sub-culturing and expansion of hMSCs. Throughout ex vivo expansion, the cells undergo telomere shortening, and critically short telomeres can trigger loss of cell viability. Telomeres are nucleoprotein structures that cap the ends of chromosomes, and serve to protect the DNA from the degradation which occurs due to the end-replication problem in all eukaryotes. As hMSCs have only a finite ability for self-renewal like most somatic cells, assaying for telomere length in hMSCs provides critical information on the replicative capacity of the cells, an important criterion in the selection of hMSCs for therapy. Telomere length is generally quantified by Southern blotting and fluorescence in situ hybridization, and more recently by PCR-based methods. Here we describe the quantification of hMSC telomere length by real-time PCR; our results demonstrate the effect of telomere shortening on the proliferation and clonogenicity of hMSCs. Thus, this assay constitutes a useful tool for the determination of relative telomere length in hMSCs. (C) 2013 Elsevier B.V. All rights reserved.