Using a specialized microscope scientists are able to peer harmlessly beneath the skin surface to measure natural age-related changes in the sizes of skin cells.
National Taiwan University professor Chi-Kuang Sun and medical researcher Yi-Hua Liao evaluated 52 subjects ranging in age from 19 to 79 years old, focusing a brief burst of infrared laser light into the skin of the subjects' inner forearms; as it is an area that is generally protected from sun damage, which accelerates natural aging.
From this they were then able to produce an image of the skin cell structure.
Skin index
"No one has ever seen through a person's skin to determine his or her age," says Sun. "This could provide an index for someone who cares about the health of their skin and might also provide a test-bed for measuring the effectiveness of 'anti-aging' skin products.”
A skin age index would provide a standardized, quantitative scale that could be used to rate the true "age" of skin, from young (less age-related damage) to old (more age-related damage).
For the industry this could mean being able to test how effective anti-aging treatments are at slowing the rate of skin aging.
Study in detail
In carrying out the study, the beam penetrated to a depth of about 300 millionths of a meter, or approximately where the epidermis (the upper layer of skin) and the dermis (the lower layer) meet.
The researchers used a technique known as harmonic generation microscopy (HGM), which has previously been used to study developing embryos.
They scanned for reflected second and third harmonic photons, and from those measurements, produced a high-resolution 3D map of the tissue that revealed structures within the skin cells.
Natural aging, the scanning showed, caused a significant increase in the overall size of cells known as basal keratinocytes, 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 aging.
Intrinsic - extrinsic
This is different from extrinsic aging, which is caused primarily by sun exposure.
"There are a lot of extrinsic factors that can accelerate the aging process, such as smoking, ultraviolet light, and stress," says Sun.
The researchers found that the extent of extrinsic skin aging in their study subjects varied depending on occupation, personal habits, and skin type, but because the researchers looked at skin on the sun-protected inner forearm, their findings provide a measure of the primarily genetically-based intrinsic skin aging.
The results were published in the Optical Society's (OSA) journal Biomedical Optics Express.