Embryonic stem cell differentiation studied in situ by FT-IR spectroscopy.

We propose, here, an FT-IR method to monitor the spontaneous differentiation of murine embryonic stem (ES) cells in their early development. Principal component analysis and subsequent linear discriminant analysis enabled us to segregate stem cell spectra into separate clusters – corresponding to different differentiation times – and to identify the most significant spectral changes during differentiation. Between days 4 to 7 of differentiation, these spectral changes in the protein amide I band (1700–1600 cm−1) and in the nucleic acid absorption region (1050–850 cm−1) indicated that mRNA translation was taking place and that specific proteins were produced, reflecting the appearance of a new phenotype. The DNA/ RNA hybrid bands (954 cm−1 and 899 cm−1) were also observed, suggesting that the transcriptional switch of the genome started at this stage of differentiation. As confirmed by cytochemical assays, the FT-IR approach presented here allows to detect at molecular level the biological events of ES cell differentiation as they take place and to monitor in a rapid way the temporal evolution of the ES cell culture.