German scientists have used a non-invasive technique to provide detailed 3D images of human sperm cells, which could be developed into a high-throughput fertility test.

Low numbers of normal, mobile sperm are associated with male infertility, but there is still very little knowledge about the movement of normal sperm. Current methods used to investigate sperm such as electron microscopy or x-ray imaging, damage the cells and cannot provide both structural and chemical composition information. Now, Erik Bründermann, Konrad Meister and colleagues at Ruhr University Bochum have used confocal Raman spectroscopy to produce images of the individual sperm. 

In sperm, different subcells or organelles, such as the nucleus and mitochondria, have different roles that can control sperm functions and movement. Until now it has only been possible to image the whole cell but Bründermann's team were able to produce images that clearly show the different organelles. 'Since the sperm count of men around the world has dropped to 50 per cent of what it was more than 50 years ago, there is an urgency to investigate organelles,' says Bründermann. 

The team also found that Raman spectroscopy provides a different signal when sperm are damaged so it could be used to distinguish between fertile and infertile sperm.  

'Spontaneous Raman microspectroscopy and imaging is a very exciting and novel method for a wide range of cell biological questions,' says Cees Otto, an expert in non-invasive imaging of live cells at the University of Twente, the Netherlands. He adds that the team has 'discovered that the chemical characteristics of different areas in the cells could be clearly distinguished using the Raman spectra'.

Bründermann concludes that 'this technique offers new insights into the understanding of motility and may improve the current standards for testing male fertility'. 

Harriet Brewerton

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