Iranian Red Crescent Medical Journal Iran Red Crescent Med J 2011; 13(10):726-734 ©Iranian Red Crescent Medical Journal ORIGINAL ARTICLE Differentiation MicroRNAs Affect Stemness Status of

Background: MicroRNAs are endogenous non-coding RNAs with important regulatory and cell fate functions. Many studies have shown that several microRNAs are obviously up-regulated during stem cell differentiation. The question rises here is weather inhibiting differentiation will affect the stemness and self renewal status of stem cells. Methods: miRCURY ™LNA microRNA inhibitor (anti-miR-145 and anti-let7g) are a sequence-specific and chem-ically modified oligonucleotide that specifically target and knockdown miR-145 and let7g miRNA molecules. Unrestricted somatic stem cells (USSCs) were isolated from umbilical cord blood and treated with LNAs. The effect of anti-miRNA transfection was assessed by quantitative real-time PCR. Results: Real-time PCR showed that LNA was efficiently introduced into the cells and reduced miR145 and Let7g expression levels to 40 % and 10 % in relation to corresponding scramble control, respectively. Gene ex-pression analysis as to self renewal and expansion showed more than 3.5 fold up regulation in Oct4 in cells treated with mir145 inhibition. Similarly a significant up to 2.5 fold up-regulation in Oct4 and cMyc expression was observed in samples treated with anti-let7g. Conclusion: Suppression in differentiation inducing microRNAs (miR-145 and let7g) can enhance the self re-newal and stemness status of USSCs at transcriptional level