Inhibition of micro RNA 210 biological activity with an anti-miR-210 peptide nucleic acid

Peptide nucleic acids (PNAs) are DNA mimics extensively used for pharmacological regulation of gene expression in a variety of cellular and molecular systems, being described as excellent candidates for antisense and anti-gene therapies. At present, very few data are available on the use of PNAs as molecules targeting micro RNAs. MicroRNAs (miRs) are a family of small (19 to 25 nucleotide in length) noncoding RNAs that regulate gene expression by sequence-selective targeting of mRNAs, leading to a translational repression or mRNA degradation, depending on the degree of complementarity between miRNAs and the target sequences. Micro RNAs are deeply involved in the control of highly regulated biological functions, such as differentiation, cell cycle and apoptosis. Low expression of a given miRNA is expected to be linked with a potential for accumulation of targets mRNAs; conversely, high expression of miRNAs is expected to be causative to low expression of the target mRNAs. The aim of the present study was to determine the activity of a PNA targeting micro-RNA 210. Micro-RNA 210 is of great interest because it has been firmly associated to hypoxia and is modulated during erythroid differentiation. The major conclusion of our study is that a PNA against miR-210 and conjugated with polyarginine peptide (R-pep-PNA-a210) (a) is effciently internalized within target cells; (b) strongly inhibits miR-210 activity; (c) deeply alters the expression of raptor and -globin genes. Unlike commercially available antagomiRs, which need continous administrations, a single administration of R-pep-PNA-a210 is sufficient to obtain the biological effects. Interestingly, vehiculation within the cells is necessary to obtain biological activity, since the PNA lacking of the arginine tail (PNA-a210), despite being able to hybridize to target nucleotide sequences displays very low activity on cells. Our data demonstrate that efficient delivery strategies are necessary. Rpep-PNA-a210 does not need of transfection reagents (i.e. lipofectin, lipofectamine and similar reagents) which, on the contrary, are required when RNA- or DNA based analogues are used. Our results allow to propose PNA-based molecules are very promising reagents to modulate the biological activity of micro RNAs.