Mass Spectrometry Measurement of Albumin-Alpha Fetoprotein Ratio as an Indicator of iPSC-Derived Hepatocyte Differentiation.

During the process of differentiation from induced pluripotent stem cells (iPSCs) to hepatocytes it is crucial to monitor the levels of cellular maturation. We present a new method to evaluate the stage of differentiation based on the monitoring of the ratio between two plasma proteins typically secreted by hepatocytes， that is， albumin and alpha-fetoprotein. This ratio is particularly useful for the direct comparison of cells grown in different conditions， avoiding typical processes of standardization for the cell number (i.e.， variation of cell quantity due to the use of different seeding densities and different growth vessels/supports or difficulties in establishing the effective cell viability due to the use of bioreactors or other 3D devices). Our analysis is performed via liquid chromatography-tandem mass spectrometry which allows a precise， selective， and reproducible quantitation of low-abundance proteins.