br Experimental Procedures br Author Contributions br Introd

Experimental Procedures
Author Contributions
Introduction Bone-marrow-derived mesenchymal stromal order (RS)-CPP (BM-MSCs) have been reported to secrete neurotrophic cytokines as well as a range of pro-inflammatory cytokines, chemokines, and other soluble growth factors (Nakano et al., 2010; Ma et al., 2013). Because of these properties, their feasibility and safety of administration were assessed in clinical trials for the treatment of multiple sclerosis (MS), with results suggesting they can modulate the immune response, protect neurons from degeneration, and improve disease progression (Bonab et al., 2012; Connick et al., 2012). MSCs have been isolated from a range of tissues including bone marrow, adipose, pancreas, skin, muscle, tendon, umbilical cord, skin, and dental pulp (Hass et al., 2011; Wang et al., 2013). We have recently isolated MSCs from the lamina propria of human olfactory mucosa (OM) (termed OM-MSCs; Lindsay et al., 2013); a tissue of fundamental interest in the context of neuroprotection and repair because of its ability to continually support neurogenesis throughout life (Graziadei and Monti Graziadei, 1985). Our previous studies have demonstrated that OM-MSCs have a similar antigenic profile and differentiation properties to BM-MSCs (Lindsay et al., 2013). However, the entire OM-MSC population expressed nestin, while conversely around 50% of BM-MSCs were nestin-positive, despite being isolated using identical methodology (Johnstone et al., 2015). Importantly, there was a major difference in the ability of OM-MSCs to promote CNS myelination in vitro via a secreted factor(s) (Lindsay et al., 2013). Since these properties can be explained by a vast number of genes, we decided to use a microRNA (miRNA) array approach to identify differences and similarities between the two MSCs. miRNAs are an abundantly expressed family of small post-transcriptional regulators (18–24 nucleotides). They control gene expression by modulating the translation (usually by repression), stability, and localization of specific mRNA targets (Ambros, 2001). They regulate numerous functions ranging from cell differentiation, proliferation, and apoptosis to fat metabolism (Skalnikova et al., 2011). miRNAs are thought to act as regulatory signals for maintaining stemness, self-renewal, and differentiation in adult stem cells and are therefore important in controlling classic stem cell properties (Collino et al., 2011; Tomé et al., 2011). Characterization of miRNAs from MSCs of different tissue sources could be relevant not only as a marker of the cell but also to fully understand their biological activities and give an insight into what makes them different (Collino et al., 2011). Recent work has described nestin-positive MSCs as a subpopulation (Tondreau et al., 2004; Wiese et al., 2004) that originates not from the mesoderm but from the neural crest giving nestin-positive MSCs specialized niche functions over nestin-negative MSCs (Isern and Méndez-Ferrer, 2011; Isern et al., 2014). Therefore, in this investigation, we have compared the miRNA profile of nestin-positive OM-MSCs with classical BM-MSCs to determine any important biological differences that, in particular, may be relevant to their role in cell transplantation therapies for the treatment of demyelinating conditions, such as MS.
Results
Discussion In this investigation, miRNA-based fingerprinting demonstrated that OM- and BM-MSCs were 64% homologous, suggesting they have related regulatory miRNA patterns. Others have shown that MSCs derived from different tissue niches share expression of a core set of miRNAs that regulate associated target genes, although miRNA similarity between the two MSC types here was greater than that reported for other MSCs (Lazzarini et al., 2014). We identified 26 DE miRNAs, which could explain their different biological properties. We focused on miRNAs associated with chemokine production and myelination. and therefore examined miR-146a-5p, and miR-140-5p in more detail due to their reported association (Nicolas et al., 2008; Suzuki et al., 2010; Göttle et al., 2010; Hsieh et al., 2013).