MicroRNAs as Engineering Targets: Pathway Manipulation to Impact Bioprocess Phenotypes

Abstract

Chinese hamster ovary (CHO) cells are the primary mammalian culture system used for recombinant protein production; therefore there are continuous research and development efforts to improve cell production capabilities by both genetic modification and process optimization strategies. The genetic modifications are used to increase specific growth rate, to reduce apoptosis and to improve nutrients utilization. Since altering the expression of a single gene or even a single pathway may not be sufficient to produce desirable phenotypes, regulation of global gene expression may be a better approach for pathway engineering in CHO cells. miRNA(s) were found to be global regulators of gene expression with the ability to simultaneously alter multiple cellular pathways such as cell growth, apoptosis, stress resistance, metabolism and protein secretion. Therefore, modifications of miRNA expression profiles may facilitate the design of high-producing CHO cells. Recent advances in transfection techniques allow the insertion of miRNA mimics or inhibitors into CHO cells at specific stages of the bioprocess. Unlike traditional engineering approaches, manipulation of miRNA expression profiles does not burden the translational machinery of the cell and therefore, cellular metabolic resources are allocated to recombinant protein production. In this chapter we highlight the industrially-relevant pathways, report on miRNA involvement in their regulation, discuss how these miRNAs can be used to improve performance of CHO cells for industrial applications and propose specific miRNA candidates for CHO cell engineering.