Ageing research gets under the skin

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Researchers in Taiwan are using laser microscopy to measure natural age-related changes in the sizes of skin cells.

The technique can be used to study skin ageing and may help provide an index for measuring the effectiveness of anti-ageing skin products.  In the study Chi-Kuang Sun, a professor at National Taiwan University and chief director of the university’s Molecular Imaging Center, evaluated 52 subjects ranging in age from 19 to 79 years old.

Researchers focused a brief burst of infrared laser light into the skin of the subjects’ inner forearms, an area that is generally protected from sun damage. The beam penetrated to a depth of about 300 millionths of a metre, or approximately where the epidermis (the upper layer of skin) and the dermis (the lower layer) meet.

They used a technique known as harmonic generation microscopy (HGM). In the procedure, a concentrated beam of photons is sent into a material. The photons naturally oscillate at a particular frequency, and as they interact with the material, they generate 'harmonics' – vibrations that are multiples of the original frequency,  which are characteristic of the material structure and properties.

In an imaging system, harmonics can reveal different structures at very high resolution.  In their study, the team scanned for reflected second and third harmonic photons – and, from those measurements, produced a 3D map of the tissue that revealed structures within the skin cells.

Natural ageing, the scanning showed, caused a significant increase in the overall size of cells known as basal keratinocytes – the most common cells in the outermost layer of skin – as well as in the sizes of their nuclei. However, other types of skin cells, known as granular cells, did not show a similar pattern.

Thus, says Sun, the relative changes in the two types of cells can serve as an index for scoring natural or “intrinsic” skin ageing –the ageing of skin caused by programmed developmental or genetic factors. The results were published in December in the Optical Society’s (OSA) open-access journal Biomedical Optics Express.