is strongly and significantly increased at time points three, six and nine days after stimulation. Likewise the degree of MBP-expressing OPCs was elevated with significant changes on gene Scutellarein web expression levels at every time-point, and after six and nine days of treatment for protein levels Mesenchymal and Oligodendroglial Cell Interaction Hepatocyte Growth Factor as a Secreted MSC-CM Factor is not the Critical Component for OPC Differentiation The composition of mesenchymal stem cell secreted factors and their molecular interactions are still poorly understood. Among the few identified molecules is hepatocyte growth factor, which has been shown to mediate mesenchymal stem cell-induced recovery in animal MS models. We therefore evaluated whether HGF is also a key regulator of the described MSC-CM effect exerted on immature OPCs. To this end, we determined HGF content using enzyme linked immunosorbent assay revealing a significant enrichment of HGF in MSC-CM after a three days incubation of MSCs with a-MEM containing either 10% or 1% 19219009 FBS. To clarify, whether HGF exerts an oligodendroglial differentiation effect, we quantified CNPasepositive cells in a-MEM supplemented with 50 ng/ml recombinant HGF. Importantly, we did not observe any significant differences between a-MEM cultured with or without HGF whereas both conditions induced significantly lower CNPase expression levels compared to MSC-CM. Moreover, GFAP expression levels of cells grown in a-MEM plus HGF were similar to those kept in a-MEM. Likewise, Id2/4 transcript levels were also not down-regulated by HFG, as compared to a-MEM grown cells, and were even further increased after three and six days in culture. We also analyzed gene expression levels after neutralizing HGF with a functionblocking antibody based on previously published conditions. We analyzed GFAP, Id2, Id4, CGT, MBP and CNPase gene expression levels at time-point nine days of stimulation. Importantly, we did not detect any differences between media without and media with anti-HGF antibodies, further supporting that HGF is not involved in the MSC-CM dependent fate and differentiation effect. Discussion Oligodendroglial cell maturation is coordinated by different factors either stimulating or inhibiting differentiation processes. Here, 
we demonstrate that mesenchymal stem cell secreted factors of yet unknown identity support and enforce cell fate decisions and promote differentiation and maturation towards oligodendrocytes. Furthermore, a slight MSC-CM mediated increase in OPC proliferation was observed which is in line with previous data on the control of neural stem cell proliferation. The observation that OPCs did not develop astrocytic features and morphologies in the presence of mesenchymal stem cellsecreted components leads to the assumption that cell fate decisions are regulated. Although currently unidentified, this mixture of factors apparently influences glial transcription patterns some of the regulated genes being dependent on Olig2 and Idmodulated bHLH transcriptional activities. In this regard, the regulation of Id2 and Id4 is most noteworthy as, for the first time, it demonstrates a glial cell regulatory effect based on mesenchymal stem cells independent of FBS concentration in the medium used for conditioning. Since adding as well as neutralizing HGF 20573509 turned out to be ineffective in either reversing the fate of fetal bovine serum containing medium instructed cells or in supporting oligodendroglial differenti
