The microRNomes of Chinese Hamster Ovary (CHO) cells and their extracellular vesicles, and how they respond to osmotic and ammonia stress

A new area of focus in Chinese Hamster Ovary (CHO) biotechnology is the role of small (exosomes) and large (microvesicles or microparticles) extracellular vesicles (EVs). CHO cells in culture exchange large quantities of proteins and RNA through these EVs, yet the content and role of these EVs remain elusive. MicroRNAs (miRs) are central to adaptive responses to stress and more broadly to changes in culture conditions. Given that EVs are highly enriched in miRs, and that EVs release large quantities of miRs both in vivo and in vitro , EVs and their miR content likely play an important role in adaptive responses. Here we report the miRNA landscape of CHO cells and their EVs under normal culture conditions and under ammonia and osmotic stress. We show that both cells and EVs are highly enriched in five miRs (among over 600 miRs) that make up about half of their total miR content, and that these highly enriched miRs differ significantly between normal and stress culture conditions. Notable is the high enrichment in mir-92a and miR-23a under normal culture conditions, in contrast to the high enrichment in let-7 family miRs (let-7c, let-7b and let-7a) under both stress conditions. The latter suggests a preserved stress-responsive function of the let-7 miR family, one of the most highly preserved miR families across species, where among other functions, let-7 miRs regulate core oncogenes, which, depending on the biological context, may tip the balance between cell cycle arrest and apoptosis. While the expected –based on their profound enrichment – important role of these highly enriched miRs remains to be dissected, our data and analysis constitute an important resource for exploring the role of miRs in cell adaptation as well as for synthetic applications.