Separation and Purification of CHO Secretome and Extracellular Vesicles for Proteome Analysis.

For decades, host cell proteins (HCPs) have been investigated as putative contaminants in downstream processing of biopharmaceutical products of Chinese hamster ovary (CHO) cells. However, little is still known about the composition of the entire protein and vesicle environment in CHO cultivations. Ever evolving mass spectrometry techniques allow more and more insights into cell-cell communication processes and the composition of extracellular matrix, proteases, and further actively segregated compounds such as extracellular vesicles (EVs). EVs themselves are a heterologous group consisting of exosomes, ectosomes, and apoptotic vesicles. To specifically analyze these subsets of the secretome and determine beneficial and detrimental factors for a production process, targeted separation and purification techniques are necessary.In this chapter, we present our optimized workflows for a clear differentiation between directly secreted proteins and the vesicular protein content of different fractions (especially exosomal small EVs) from CHO cell supernatant for proteomic analysis by NanoLC ESI-MS.