Tracing the fate of stem cells

Coherent anti-Stokes Raman scattering (CARS) has recently emerged as a new multiphoton microscopy technique that directly addresses endogenous biomolecules with high chemical specificity. This imaging technology is ideal for non-invasively following living stem cells during differentiation in real time. The EU-funded CARSFORSTEM project aimed to develop and adopt CARS technology for tracing the fate of living stem cells during differentiation.

Researchers developed a method of quantitative chemical imaging going from data acquisition using hyperspectral CARS to unsupervised analysis and visualisation of the spatially resolved absolute concentrations of chemical components. The developed method has been proved to analyse CARS hyperspectral images for quantitative chemical information of the samples over a range of different investigations. In particular, the method has been used to study the uptake of saturated and unsaturated lipids by stem cell-derived adipocytes.

The hyperspectral image analysis method has proven to be a key factor for the study of CARS markers for the differentiation of mouse embryonic stem (mES) cells. Researchers found that in mES cells undergoing differentiation into adipocytes, CARS hyperspectral imaging reveals the presence of sub-cellular structures that are chemically different from the cytosol. They concluded that such structures contain the fatty acid binding protein 4, which facilitates the transfer of fatty acids between extra- and intracellular membranes in adipocytes. This result represents a first step in identification of the differentiation pathway of a stem cell, even before a change in morphology occurs, using a label-free microscopy technique.

In conclusion, project work resulted in development of a fast method enabling real-time chemical imaging and high-throughput, high-content label-free microscopy. The study has important implications for the applicability of stem cell technology as treatment for a series of diseases. In addition, it might help to understand the fundamental mechanisms of lipid metabolism in cells.