Updated project metadata. Chinese Hamster ovary (CHO) cells are the main platform used to produce recombinant proteins in the biopharmaceutical industry and are commonly cultured in either fed-batch or perfusion mode. However, the optimization of the complex biological systems used in such processes is extremely challenging. Omics approaches can reveal otherwise unknown characteristics of these systems and identify culture parameters that can be manipulated to optimize the cultivation process. Here we have applied proteomic profiling to a monoclonal antibody (mAb) production operated in perfusion mode to explore how cell biology and reactor environment change as the cell density reaches ≥ 200 x 106 cells/mL. The proteomics data show an increase of structural proteins as cell density increase, signs of oxidative stress and changes in glutathione metabolism at very high cell densities. Additionally, metabolomic profiling was carried out. See article “High cell density culture has a maintained exoproteome and metabolome” for more information.