[PMC free article] [PubMed] [CrossRef] [Google Scholar] 29. miR-17/92 cluster, involved in cell cycle regulation, aging and also development of immune system, were down-regulated specifically in cells from old donors. Rabbit Polyclonal to MUC7 The role of this cluster in MSC functionality is worth future studies since it links expansion, aging and immune system together. and . Several miRNA molecules (including members of miR-17/92 cluster, miR-181 and miR-155) have been shown to be key regulators of various immune responses, such as T-cell development . Mesenchymal stromal cells can be isolated from virtually any tissue . In therapeutic applications, bone marrow (BM), adipose tissue (AT) and cord blood (CB) are the most relevant sources. Although the different origins have been shown to produce MSCs with different immunomodulatory properties , the results from various studies are contradictory . Since miRNA regulation is thought to be one of the key players in MSC differentiation and functionality, it has been proposed that MSCs may have a typical miRNA expression pattern which varies only slightly according to the tissue origin . The age of MSC donors and the required expansion of the therapeutic MSCs are considered to be factors that may affect the properties and functionality of MSCs and eventually have a negative effect on the therapeutic outcome [12, 13]. The age-dependent changes in miRNA expression may be one possible explanation for the observed differences between the old and younger donors. Although miRNA expression is relatively stable in the MSCs, some age-dependent changes in miRNA expression have been previously identified . Interestingly, the miRNA expression of hBM-MSCs and hAT-MSCs is differently affected by the donor age . Previous reports also indicate that the replicative senescence is at least partly driven by miRNA regulation [16, 17]. The Nilvadipine (ARC029) results are, however, contradictory and the influence of the donor age on the senescence remains unclear. In this study, we investigated the age-related changes in miRNA regulation in human BM- MSCs by analyzing age-induced changes in miRNA expression profiles together with mRNA expression. We were able to show that, as opposed to mRNA expression levels, miRNA levels underwent only minor changes during continuous passaging. Interestingly, the age of the donor had even less effect on miRNA expression. Therefore, this study shows that miRNA expression is rather robust and BM-MSCs have a distinct miRNA expression pattern that could provide new identifiers for MSCs. RESULTS MiRNA expression is changed during expansion MSCs were collected and characterized from five young adult donors (mean age 22.3) and four elderly donors (mean age 76) as previously described . The miRNA expression profiles of BM-MSCs collected from three young adult donors and three old donors were analyzed using Agilent Human miRNA 860K microarray (release 16.0), which contains probes for 1,205 human miRNA molecules, 294 of which were expressed in studied samples (Table S1). Let-7a, let 7b, let 7c, let-7e, let-7f, let 7i, miR-100, miR-125b, miR-199 ad miR-21 were the 10 most highly expressed Nilvadipine (ARC029) miRNAs in all the samples studied, and all of them are included in the distinct miRNA signature of MSCs . From among the 308 miRNAs, we were able to identify 63 differentially expressed miRNAs (Fig. ?(Fig.1).1). Interestingly, the miRNA profiles of the young Nilvadipine (ARC029) and elderly donors were relatively similar in the early passages. The most prominent changes in miRNA expression were seen towards the late passages. During the expansion of BM-MSCs derived from young donors, the expression of 39 miRNAs was changed, whereas 36 miRNAs were differently expressed in old donors. BM-MSCs from young donors behaved differently during passaging compared to BM-MSCs from the old donors, as both groups shared only 12 differentially regulated miRNAs (Fig. ?(Fig.1).1). The direction of expression change was also opposite. Our results demonstrate predominant down-regulation of miRNA expression in.