RESUMO
Engineering of Chinese Hamster Ovary cells by manipulating microRNA (miRNA) expression levels has been shown to induce advantageous, desired phenotypes. Most of these studies so far were concerned with increasing productivity or reducing growth rate (with the implied intention of thus freeing cellular resources to also increase productivity). Here we evaluated the ability of growth correlating miRNAs to increase the growth rate of CHO-K1 cells by transient overexpression or knock down, respectively. Candidates were selected based on the correlation between growth rate and miRNA expression levels as observed in previous studies. These candidates were then up- or downregulated initially by transfection of mimics or inhibitors and subsequently by transfection of plasmids bearing the corresponding miRNAs or sponges. None of the 40 selected candidates was able to induce a better growth phenotype under these conditions. Overlap between miRNAs identified to correlate to growth in published miRNA expression studies and those identified to actively increase growth rate in a functional screen is minimal, indicating that the here selected approach of traditional overexpression/knock down engineering of miRNAs may not be a suitable strategy for the purpose of increasing growth rate.
