Researchers in Germany have used infrared spectroscopy to spot stem cells as they change into new cell types.

Christoph Krafft, at the Dresden University of Technology, and colleagues wanted to develop a spectroscopic technique that would tell if stem cells were differentiating, a process in which they become a specialised type of cell, such as a skin cell or a white blood cell.

Stem cells are used in medicine to restore damaged tissues and are being investigated to find new treatments. Krafft explained: 'A frequent problem in stem cell research is to determine the type and differentiation state of the cells. The standard techniques depend on antibodies, which recognise cell-specific antigens. However, antibodies are not available for each cell type or differentiation state and the antigen-antibody binding is sometimes weak or not specific enough.'

In a computer image non-stimulated stem cells (left) appear red when their IR spectra (centre) are analysed (right); stimulated cells appear blue.

Krafft and his team coupled an infrared (IR) spectrometer with a microscope so they could locate stem cells and measure their IR spectra. They grew some of the cells in a medium designed to stimulate them to turn into bone-forming cells, called osteoblasts. The IR spectra from these cells were different from those of non-stimulated cells. Both sets of spectra were used to train a computer model to distinguish between the cell groups.

The team used the IR microscope and computer model to produce images of stem cells; stimulated and non-stimulated cells appeared as different colours, showing whether they had differentiated. The technique also showed stimulated cells that had started to produce calcium phosphate salts for bone formation. Krafft explained that he hopes to develop the research to find out more about how stem cells form new bone.

Rachel Warfield