Cellular Aging of Mesenchymal Stem Cells (miRNA)

To determine miRNA expression changes during in vitro senescence of mesenchymal stem cells (MSC) we have analyzed differential expression of the corresponding early passage (P2) and senescent passage (PX). Keywords: miRNA, senescence, mesenchymal stromal cells, mesenchymal stem cells, MSC Mesenchymal Stem Cells (MSC) were isolated from human bone marrow (BM) as described before (Wagner et al., 2005, Exp Hematol, 33, 1402-1416; Wagner et al., Exp Hematol, 34, 536-548). Cells were always replated when grown to about 70% confluency. A sample for RNA isolation was taken at every passage until the cells finally became senescent: they became much larger with irregular and flat shape. The nucleus became more circumscribed in phase contrast microscopy. The cytoplasm began to be granular with many inclusions and there was more cell debris. Global gene expression profiles were analyzed to determine molecular changes between corresponding early passage (P2) and senescent passage (PX) in three donor samples. In addition we have analyzed different passages of donor 1 (P2, P3, P4, P5, P6, P7, P8, P9, P10, and P11) to determine changes in the course of cellular aging. The medians of four background-corrected replicas for each miRNA capture probe were used for further analysis. Data of each hybridization was median normalized (each value was divided by the median of values). Differential expression was compared between P2 and later passages of the corresponding donor sample.