Fourier transform infrared microspectroscopy reveals that tissue culture conditions affect the macromolecular phenotype of human embryonic stem cells.

We employed Fourier transform infrared (FTIR) microspectroscopy to investigate the effects of different tissue culture environments on the FTIR spectra of undifferentiated human embryonic stem cells (hESCs) and their differentiated progeny. First we tested whether there were any possible spectral artifacts resulting from the use of transflectance measurements by comparing them with transmission measurements and found no evidence of these concluding that the lack of any differences resulted from the homogeneity of the dried cytospun cellular monolayers. We found that hESCs that were enzymatically passaged onto mouse embryonic fibroblasts (MEFs) in KOSR based hESC medium, hESCs enzymatically passaged onto Matrigel in mTESR medium and hESCs mechanically passaged onto MEFs in KOSR-based hESC medium, possessed unique FTIR spectroscopic signatures that reflect differences in their macromolecular chemistry. Further, these spectroscopic differences persisted even upon differentiation towards mesendodermal lineages. Our results suggest that FTIR microspectroscopy is a powerful, objective, measurement modality that complements existing methods for studying the phenotype of hESCs and their progeny, particularly changes induced by the cellular environment.