Original Research Report Age-Related Changes in the Frequency of Mesenchymal Stem Cells in the Bone Marrow of Rats

SERGEY V. TOKALOV, SUSANNE GRUNER, SEBASTIAN SCHINDLER, GUNTER WOLF,MICHAEL BAUMANN, and NASREDDIN ABOLMAALIABSTRACTMesenchymal stem cells (MSCs) are pluripotent cells that can differentiate into endothelial, osteogenic,adipogenic, and other lineages. In spite of the broad interest, little is known about the variation of MSCnumber in relation to the age of the donor. The aim of this study was to investigate the age-associatedvariations of bone marrow (BM) MSCs using a rat model. Cell populations were characterized by flowcytometry using light-scattering parameters, DNA content and a set of monoclonal antibodies and de-tected by magnetic resonance imaging (MRI). Single-cell analysis was performed by conventional fluo-rescent microscopy. BM mononucleated cells (MNCs) were isolated, in vitro culture of MSCs was es-tablished, and endothelial cells differentiation and intracellular magnetic labeling was shown. The amountof BM tissue obtainable from femurs and tibiae increased with age and reached a maximum in 8- to 12-week-old rats. At the same time, the proportional number of MNCs containing MSCs decreased. As aresult, after 2 weeks of culture, the maximum yield of MSC number was registered from the youngestage group (4 weeks). MSCs were differentiated into endothelial cells by administration of vascular en-dothelial growth factor (VEGF) and subsequently revealed immunocytochemical and morphologicalcharacteristics of endothelial cells. The results of our study are the basis for further experiments withMSCs and their endothelial descendants, which may be labeled with different agents for cell trackingand detection experiments, but age-related changes in MSCs number should be taken into account when-ever these cells are considered for practical applications.